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Calibri 83ffff̙̙3f3fff3f3f33333f33333.TU Delft Repositoryg uuidrepository linktitleauthorcontributorpublication yearabstract
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departmentresearch group programmeprojectcoordinates)uuid:403708f3b359439b8a6cfe8a83781707Dhttp://resolver.tudelft.nl/uuid:403708f3b359439b8a6cfe8a83781707Crosssectional stability of tidal inlets using a processbased model: Application of a processbased model to compute the equilibrium crosssectional areas of the Frisian inlethvan den Berg, Jelle Jacobus (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)Wang, Zheng Bing (graduation committee); van de Kreeke, J. (mentor); Zitman, Tjerk (graduation committee); van Prooijen, Bram (graduation committee); Delft University of Technology (degree granting institution)
In this thesis the equilibrium crosssectional areas of a tidal inlet are investigated. The most common used methods to study crosssectional stability are the Escoffier method (Escoffier, 1940) and the Modified Escoffier method (Van de Kreeke, 2004). The Escoffier methods are mainly empirical and lack physical justification. Therefore, in this thesis a processbased model, as proposed by Hinwood et al. (2012), is used to show that in the longterm the inlet crosssectional area approaches a stable equilibrium or closes. Additionally, the influence of higher harmonics on the equilibrium crosssectional areas is studied. The stable equilibrium crosssectional area of the Frisian inlet in the Dutch Wadden Sea is computed and the results are compared to earlier findings.~tidal inlet; stability; crosssection; escoffier; equilibrium; stable; unstable; frisian inlet; processbased; numerical modelen
master thesis53.474767, 6.091948)uuid:8c7f10809add4f2aa4996a67ce93561bDhttp://resolver.tudelft.nl/uuid:8c7f10809add4f2aa4996a67ce93561bIMonohull versus Semisubmersible for offshore heavy lift crane operationszSchouten, Ewout (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Ship Design, Production and Operations)Hekkenberg, Robert (mentor); Bot, Sander (mentor); Akkerman, Ido (graduation committee); Vrijdag, Arthur (graduation committee); Delft University of Technology (degree granting institution)In this thesis the differences between the monohull and semisubmersible are investigated. For a general heavy lift crane operation and its operational profile, the difference is performance and total cost are calculated. These are used to determine the turning point, the point where the semisubmersible is more favourable for a heavy lift crane operation. The monohull has relatively low capital and operational costs, but also a lower workability. There is thus a balance that has to be investigated and compared between the two vessel types. This is done for the North Sea and West Africa, which have significantly different sea conditions.Monohull; Semisubmersible; resistance; dynamic positioning; propulsion; comparison; opex; capex; workability; motions; hydrodynamics; stability; concept design; general arrangement; NPV; turning point; crane capacity; heavy lift vessel
20230704)uuid:c9492ef892544ba483b38b0ad46149c5Dhttp://resolver.tudelft.nl/uuid:c9492ef892544ba483b38b0ad46149c5Towards Practical Hybrid Laminar Flow Control: Boundary Layer Stability with Suction and Scalability of Pressure Losses across Perforated Sheets0Hemmen, Patrick (TU Delft Aerospace Engineering)Kotsonis, Marios (mentor); Rius Vidales, Alberto (mentor); van Oudheusden, Bas (graduation committee); Ragni, Daniele (graduation committee); Cosin, Renato (graduation committee); Delft University of Technology (degree granting institution)7Hybrid laminar flow control (HLFC) reduces skin friction drag, by combining boundary layer suction with pressure gradient tailoring to delay boundary layer transition. This research addresses two key developments required to perform the aerodynamic design of suctiontype HLFC components. First, an existing numerical transition < prediction tool was made compatible with boundary layer suction, by incorporating suction in its boundary layer solver and by ensuring that an appropriate grid of disturbance frequencies is evaluated with linear stability theory. Second, the scalability of the pressure losses associated to the perpendicular flow through largescale and actualscale perforated sheets was investigated experimentally. This development is required to predict the pressure losses of generic HLFC surfaces. It was found that the scalability of these pressure losses is limited, because the frictional losses inside holes decrease continually with decreasing hole diameter. In contrast, the inertial losses across holes reach a steady value with sufficiently many holes.Vhybrid laminar flow control; HLFC; suction; stability; pressure loss; perforated sheet)uuid:89b8545488334f05ab54a0f7ad751f20Dhttp://resolver.tudelft.nl/uuid:89b8545488334f05ab54a0f7ad751f20CGuidance & Stability of Parachute Systems for Planetary Descent5Trovarelli, Federico (TU Delft Aerospace Engineering)SMooij, Erwin (mentor); Delft University of Technology (degree granting institution)A key requirement for enabling Mars manned mission is the capability to land a payload within 100 m from its nominal target. State of the art technology, however, is still far from reaching this objective. A possible solution for improving the landing accuracy on Mars is the development of a guidance system that exploits thrusters installed on the backshell of the descent vehicle to control its position during the parachute flight. The research aims at evaluating how the stability properties of the parachutepayload spacecraft are influenced by the control action and what performance the resulting closedloop system can achieve. To do this, first the dynamics of the spacecraft, modelled as a rigid body, has been investigated analytically. Second, its response in different mission scenarios was simulated by means of a multibody model. The results are encouraging and prove that the parachute descent guidance system could efficiently contribute to improving the landing accuracy on Mars.)parachute; guidance; stability; multibody
20190329Astrodynamics & Space Missions)uuid:227503b2ff6d4e679c29041843a3222fDhttp://resolver.tudelft.nl/uuid:227503b2ff6d4e679c29041843a3222fEvaluation of frequency and transient stability indicators in future power systems with high levels of wind power generationWMola Jimenez, Jorge (TU Delft Electrical Engineering, Mathematics and Computer Science)Rueda Torres, Jose (mentor); Palensky, Peter (graduation committee); Ghaffarian Niasar, Mohamad (graduation committee); Delft University of Technology (degree granting institution)This master thesis analyses different ways to perform assessment in frequency and transient (rotorangle) stability when high penetration of renewables exists in the grid, based on researches done in the academic world and in industries. The goal of this research focuses on assess the distance to frequency and transient instability in power systems with high penetration levels of RES by exposing the related parameters in the grid that might play an important role to detect and prevent these hazards. The proximity to instability (a quantifiable value to determine how far the system is to unstable operating condition) is an indication that can be greatly used by operators in the control room, and therefore, it is investigated exhaustively.frequency; rotorangle; stability; indicators
20180827
MIGRATE H2020)uuid:dd61dbae67ea4a67b5f2b9691240f729Dhttp://resolver.tudelft.nl/uuid:dd61dbae67ea4a67b5f2b9691240f729kExploration into the mechanisms that govern the stability of an Xbloc<sup>+</sup> <sup>v1</sup> armour unitWVos, Amber (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)Aarninkhof, Stefan (mentor); Verhagen, Henk Jan (mentor); Hofland, Bas (mentor); Reedijk, B (mentor); Jacobs, R (mentor); Delft University of Technology (degree granting institution)In this MSc thesis it is investigated how the f< irst version of concrete armour unit Xbloc<sup>+</sup>, Xbloc<sup>+ v1</sup>, acquires its stability. The stability mechanisms are investigated by conducting two type of physical model tests. First, 23 dry pullout tests are done to obtain insights into the aspects and mechanisms that influence the armour layer stability. At 8 locations per slope, blocks are pulled out to determine the force needed to extract an armour unit. Tests are done on a 3:4 slope with 2 pulldirections; under an angle of 45 degrees with respect to the slope and perpendicular to the slope. Concrete as well as plastic armour units are tested, both having a different surface roughness. The conclusions of the pullout tests are verified by means of the second type of model tests; small scale physical hydraulic model tests in a 2D wave flume. In total, 10 tests are conducted; 6 tests with plastic armour units and 4 tests with concrete armour units. Each test starts with a run with a small significant wave height which is increased stepwise in each run until failure occurs. All test sections have a 3:4 slope and are subjected to waves with a 4% steepness. Additionally, the influence of the significant wave height step size for successive runs is investigated. The combination of both physical model tests results in recommendations for a change in design which is expected to lead to a higher stability of an armour layer with Xbloc<sup>+</sup> armour units.qbreakwater; concrete armour unit; Xbloc+; Xbloc+ v1; uniform; stability; extraction; pullout test; 2D model test)uuid:fa4596e83c3d495e83e3c1cdccdd6f75Dhttp://resolver.tudelft.nl/uuid:fa4596e83c3d495e83e3c1cdccdd6f75`A Geotechnical Working Plan for a Thorough but Quick Assessment of Existing Slopes in Clay Mines]Bloem, Hugo (TU Delft Civil Engineering and Geosciences; TU Delft Geoscience and Engineering)zNganTillard, Dominique (mentor); Schmitz, Robrecht (mentor); Delft University of Technology (degree granting institution)tIn the Westerwald area clay quarries are in production. In order to assess the stability of the slopes the geotechnical characterisation of these quarries needs to be improved. This report provides the justification for a working plan for a thorough but quick assessment of existing slopes in clay mines. Literature is consulted for the information for the types of measuring and monitoring equipment for slopes, what instabilities look like in the field, how the safety factor are calculated, what information can be gathered outside the mine and what a field investigation should concern. To come to a working plan a field investigation was conducted to try out the different measurement equipment. For field testing, the needle penetrometer and hand vane shear came out as useful tools for correlating undrained shear strengths parameters of different layers. For thorough correlations, between layers and a dataset of geotechnical parameters, Atterberg limits are used to minimise the number of geotechnical parameters that have to be tested. The parameters are tested with different machines based on the timespan over which the slope has to be stable. Shortterm slopes with insitu conditions are best tested with triaxial tests, but UCS and a theoretical strong shear box can provide useful data as well. Longterm slopes are better tested with either a shear box or ring shear because remoulded or weathered properties are needed. Monitoring is found to be done best by using InSAR monitoring provided a suggestion is added to increase the number of data points inside the mine. The working plan is presented as a flowchart for a good overview.&clay mines; geoengineering; stabilitybachelor thesis)uuid:fbe797ef59444bc19d25e7448dce3d1bDhttp://resolver.tudelft.nl/uuid:fbe797ef59444bc19d25e7448dce3d1b*Hydraulic Performance of Xbloc+ Armor Unit]Rada Mora, Belen (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)Aarninkhof, Stefan (mentor); Hofland, Bas (mentor); Smith, Greg (mentor); Reedijk, B (mentor); Eggeling, T (mentor); Delft University of Technology (degree granti< ng institution)
In recent years, the use of Xbloc units has increased exponentially. However, the placement of this unit is not always done as randomly as it should be and consequently, the stability of the armor is affected. In order to overcome this problem, Delta Marine Consultants is developing a new armor unit called Xbloc+ that has a regular placement. In this research, the hydraulic performance of version 1 and 2 of this block are analyzed. Small scale tests were performed in a 2D wave flume in order to analyze the damage, rocking and the (partially and fully) displacement of units. In total, 1 series of tests were performed with Xbloc+v1 and 6 series with Xbloc+v2. To analyze the influence of the wave steepness and the slope angle, three wave steepness were tested (Sop = 2%, 4% and 6%) and tests were conducted in two different slope angles (1:2 and 3:4). Each series is formed by several sub tests conducted with increasing wave heights (and wave period in order to maintain a constant wave steepness). Tests were carried out until the failure of the armor slope was reached in order to completely define the failure mechanism. Furthermore, tests after failure where also executed to further investigate the stability of the armor after the damage has started.<br/>Results obtained from the laboratory tests provided an overall understanding of how the Xbloc+ performs under certain conditions. It was perceived that the permeability of the armor layer is low as it happens often with single layer units. Thus, the pressure gradient between the underlayer and armor layer is significantly high creating an uplift pressure that leads to a revetmentlike failure mechanism.<br/>Although the failure mechanism can be related to both slopes used during the laboratory tests, (3:4 and 1:2), the behavior of the armor layer differed completely between slopes. On a steeper slope, the armor layer remained undamaged for wave heights significantly higher than the design wave. However, once one unit was fully displaced, the damage was quite destructive.<br/>In contrast, on a milder slope, failure occurred much faster but the damage was not as aggressive. Moreover, after the failure was reached, the structure gained a new level of stability in which remained to provide shelter without reflecting significant damage.<br/>Furthermore, the wave height variation did not have much influence as the wave steepness. There was a noticeable difference between the performance of the structure during swell and wind waves. During swell waves, it could be seen that not only failure was achieved faster but it caused much more damage to the structure, while during wind waves the structure had a higher stability.HCoMEM; Breakwater; Xbloc+; Physical modelling; concrete units; stability5CoMEM  Coastal and Marine Engineering and Management)uuid:dd7b993358104585b1fea9db8b90dbd4Dhttp://resolver.tudelft.nl/uuid:dd7b993358104585b1fea9db8b90dbd4QOptimising the Input Filter of Traction Installations in DC Railway Power SystemsnJongeling, Alexander (Electrical Engineering, Mathematics and Computer Science; Electrical Sustainable Energy)Winterling, Max (mentor); Bauer, Pavol (mentor); Gagic, Mladen (mentor); Shri, Aniel (mentor); Dong, Jianning (graduation committee); Cvetkovic, Milos (graduation committee); Delft University of Technology (degree granting institution) In the world of DC railway trains nowadays, asynchronoustraction machine with traction controllers, i.e. an inverter with variable output frequency, is implemented. This controller changes the incoming DC voltage into an AC voltage of a variable frequency and RMS amplitude. The disadvantages of switching inverters, compared to a pure sine wave source, are the harmonics they inject in both the output as in the input of the inverters connection. At the incoming power line, it is necessary to damp these harmonics, in order to avoid resonance issues or issues regarding other systems, for instance, train detection. For this purpose of harmonic and transient filtering, generated within as well as outside the train,< an LC filter is utilised. <br/>However, this LCfilter has also influence on stability. Due to the resulting impedance to current variation in the inductance of the LCfilter, the power flow dynamics towards the train are decreased. When applying a certain amount of power, the voltage over the capacitance can become unstable very quickly. In this thesis, a graphical user interface simulation model is made to simulate these stability phenomena in Simulink in order to find the optimum size of the LCfilter in a train on the Dutch DC railway. <br/><br/>The simulations are achieved with a model representing a generalised train. The model is simple to modify, and consists of the important parts for determining the stability of the system. <br/><br/>Different simulations have been carried out, in order to examine the effect certain parameter variations have on the stability. Two systems have been considered, a constant power controlled system and a system where the motors had no controlling regime. An important factor is the value of the capacitance and inductance. A larger filter inductor results in an unstable system. Likewise, implementing a higher value capacitance will cause the system to be more stable.<br/>Simulations have shown that a motor controller with a simple constant power control regime is unstable with normal values for the inductance and capacitance. However a damping branch can solve this problem up to an extent. A system without any controlling regime has proven to be more stable with smaller capacitance.<br/><br/>By utilising the model presented in this thesis, the stability of the system, consisting purely of a controlled constant power load or as a noncontrolled load, can be investigated, and the impact of the LCfilter can be determined.<brdDC; railway; traction; power; stability; input; filter; LC; RC; resonance; train; ProRail; NS; Dutch'DC Systems, Energy Conversion & Storage)uuid:cadd8f1bcafb473b9849d7f723a33e95Dhttp://resolver.tudelft.nl/uuid:cadd8f1bcafb473b9849d7f723a33e954Stability of block mattresses under nonuniform flowbArrieta Ortubay, Xabi (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)Uijttewaal, Wim (mentor); Kuiper, Coen (graduation committee); Verhagen, Henk Jan (graduation committee); Delft University of Technology (degree granting institution)Block mattresses are widely used bed protection elements under nonuniform flows. Previous studies show that the turbulence of the flow plays a key role on the instability of the mattress. However, in the available design equations, the turbulence intensity is included as a magnification factor roughly and qualitatively defined. Consequently, the design equations are often used as a rule of thumb, where the engineering criteria of the designer is critical and large safety factor are used. In turbulent nonuniform flows, the available design equations were developed for uniforms flow and the turbulent intensity is included as a magnification factor, usually poorly defined. The stability reduction due to turbulence has been proved by several authors. However, there is not any study in previous literature that investigate the role of velocity fluctuations on block mattress failure. Nevertheless, the literature review showed that an innovative approach, which combines the mean velocity and the turbulence intensity to quantify the flow forces, has been largely study for loose rock by several authors. Following this trend, the option of applying this structure (u +"k) as a flow quantification on Pilarczyk equation was decided to study. For this purpose, a series of test were done under four different configurations. Two weir heights were used (15 and 18.5cm) and the distances corresponding to 3h and 4h were checked. Four failures were recorded for each configuration for a total of 16 failures. Additionally, a data base was recorded for each configuration where the flow discharge was related to mean velocity and the turbulence intensity. An analysis of the failure mechanism was done by synchronizing the velocity time ser< ies with the displacement of the blocks. The results showed that an episode of peak streamwise velocity and downwards (sweep) was present at the failure. However, the analysis of the velocity showed that higher combinations of streamwise velocity and shear stress were present before the failure on almost all the records. Therefore, the streamwise velocity and the induced shear stress cannot solely explain the failure of the block mattress. This conclusion is in line with the work done by Hofland (2005). However, the recorded data did not allow to describe completely the failure mechanism. <br/>The turbulence magnification factor () at the stability equation was derived by two different approaches. The first approach was based on the peaks of velocity associated to failure while the second one was described as a fitting parameter. The analysis concluded that the values were close to 3 for both cases, in line with the expected value from previous studies. Finally, the new developed equation was compared with the original Pilarczyk equation and the modification proposed by the Rock Manual (2007). The comparison shows that the new developed equation described the required thickness of the block more accurately than the available equations. Thus, the results show that the proposed approach described the effect of turbulence accurately on a design equation. Additionally, all the relevant derived conclusions for design propose were summarized in a design guideline.Bstability; Bed protection; Block mattress; NonUniform; Turbulence
20180703)uuid:920e49c1fd4c4299a68643c9403e6a68Dhttp://resolver.tudelft.nl/uuid:920e49c1fd4c4299a68643c9403e6a68<A method for actuator comparison for a stable humanoid robotXKlop, Wouter (Mechanical, Maritime and Materials Engineering; Biomechanical Engineering)van der Weijde, Joost (mentor); Wisse, Martijn (mentor); van Ostayen, Ron (mentor); Delft University of Technology (degree granting institution) A humanoid robot is being developed, intended to operate robustly in a typical daytoday human environment. Its ability to react quickly to stochastic disturbances, especially its ability to avoid falling, termed stability in this context, is of prime importance. The choosing of a suitable actuator that affords such stability is seen as a challenge in the current stage of the humanoid project. A novel method for comparing various actuators in terms of humanoid stability is investigated, to aid with this choice.<br/>A common method for comparing actuators is the use of lowlevel actuator parameters, e.g. power density. With a lowlevel parameter, a specific actuator property can be compared between multiple actuators. To incorporate relevant properties of all actuators, a large set of actuator parameters is required. This becomes even more challenging when comparing a heterogeneous collection of actuators, e.g. muscle and hydraulics. Besides subjectiveness in parameter definitions and comparisons, the multidimensional set of actuator parameters needs to be related to a onedimensional measure of humanoid stability. As lowlevel parameters and highlevel humanoid stability are not directly relatable, subjective weighting factors are traditionally employed to reduce dimensionality.<br/>Step time is introduced as a onedimensional criterion for comparing different actuators. The ability to make fast movements is a critical component in defining humanoid stability. Therefore, by comparing step times of different actuators in a fixed test case, a measure of humanoid stability is obtained. The step movement represents a simplified motion of the lifting of a foot, in which essential elements of humanoid motion are incorporated.<br/>A framework is developed, with which step times of Human Muscle (HM), ElectroMechanical Actuators (EMAs) and Hydraulic Actuators (HAs) are computed. While EMAs are often thought to have limited potential for humanoid applications, step times are similar to those of muscle. Supplemented with recent examples of successful EMA implementations, step time demonstrates the potential of< EMAs. Furthermore, HA capability is also demonstrated, as step times can obtain lower values than those of HM and EMA.<br/>Step time as developed in this thesis appears to be a powerful tool for comparing vastly different actuators. It provides a onedimensional measure related to humanoid stability, evaluated directly for each specific actuator.<br$humanoid; actuator; stability; robot)uuid:76f67586ab154c859841544259b3be82Dhttp://resolver.tudelft.nl/uuid:76f67586ab154c859841544259b3be825Rear Wheel Steer Bikes: Unconventional stable bicycle
De Jong, P.H.Schwab, A.L. (mentor)`The design of the ordinary bicycle has barely changed since the end of the 19th century. Until then it evolved to a well ridable machine with no need for further drastic modifications. However, around 2011 it was shown that, just like an ordinary bicycle, strange appearing designs could also be stable. One of these designs was a bicycle that steers with the rear wheel instead of the conventional front wheel steering. This was contrary to the popular believe that such a bicycle is inherently unstable. Although it was seen that such a bicycle could be stable, both from a theoretical as well as an experimental point of view, it was not yet revealed why and how this occurs. Now, a thorough study on the stability of rear wheel steered bicycles is conducted to fill up this knowledge gap. The history of research on rear wheel steered bicycles varying from simple trialanderror studies, to theoretical researches based on models, is researched and documented. This makes clear where the knowledge on the subject can still be increased and which methods could be used to do that. Subsequently, these deficiencies in the knowledge on rear wheel steering for bicycles are investigated. With the Whipple bicycle model, a quantitative kinematic steerside definition is found and rear wheel steering is dynamically compared to front wheel steering on bicycles. In this process differences and similarities between the lateral dynamics of different vehicles like bicycles, cars or unicycles are mentioned. Finally, the process of modeling, designing, constructing and validating a selfstable rear wheel steered bicycle is revealed.Qbicycle; bike; rear; steer; kinematics; dynamics; lateral; stability; selfstable
20220224.Mechanical, Maritime and Materials EngineeringBioMechanical Engineering)uuid:261dc0b9dc534234b66df32b7adf1d1dDhttp://resolver.tudelft.nl/uuid:261dc0b9dc534234b66df32b7adf1d1dStability of block mats under flow conditionsSmyrnis, A.Verhagen, H.J. (mentor)Block mattresses or block mats are, nowadays, very commonly applied as protection in a large range of applications either against flow or wave loads. Specifically, this large range of applications contains offshore pipeline protection and stabilization, erosion and scour protection, protection of embankments and river banks (slope protection). The reason why block mattresses are increasingly used in many applications as protection system is due to the following advantages compared to discreteunit armour systems such as quarry stone or individuallyplaced blocks which are the enhanced stability that block mats have because of the virtue of connection between adjacent blocks and their properties of being able to be laid quickly and efficiently even under water.EBlock mats; Block mattresses; stability; nonuniform flow; turbulence
20180125!Civil Engineering and GeosciencesHydraulic Engineering)uuid:7396890ccab04114822364a198193b57Dhttp://resolver.tudelft.nl/uuid:7396890ccab04114822364a198193b57>Control Loop Design for a Helicopter Tactile Cue Trim Actuator
Noordam, N.M.Voskuijl, M. (mentor)Force feedback in helicopters can improve the performance of the pilot, decrease direct maintenance costs and increase the safety of every flight. Traditional force feedback is done with the use of a force sensor. In this thesis the use of a position based, feedforward control loop to achieve the same purpose is investigated. The limits of stability and passivity of the control loop are shown t< o be highly dependent on the characteristics of the digital control loop and the mechanical aspects of the flight control kinematics. Additionally it is researched whether the control loop can be used for autopilot control and if a manual intervention by the pilot can be detected.<helicopter; haptic feedback; autopilot; passivity; stability
20260620Aerospace Engineering!Flight Performance and Propulsion)uuid:3f903786381a47a4a7a593cfd370361aDhttp://resolver.tudelft.nl/uuid:3f903786381a47a4a7a593cfd370361aFlexible Power Transfer Network
Purgat, P.Bauer, P. (mentor)pThe flexible power transfer network is a conceptual transfer network for residential areas. The main advantage of the proposed concept is the increased safety and flexibility compared to currently used AC network. The core idea is to incorporate wireless power transfer into the network which leads to inherently safer and more flexible network compared to 50 Hz AC network. The networkmust be able to supply enough power to several loads without any means of communication between the source and the load side. Furthermore, with introduction of distributed energy sources (eg. PV), the network must also be able to operate several sources at one time. Themain challenge tackled in this thesis was a design of a controller that is able to control several sources simultaneously, independently and efficiently. The controller is the same for each source, which means that there is nomaster and no slave source and each source has the same priority. The solution provided in this thesis is based on the sliding mode control theory and the physics of series loaded resonant converter. The proposed controller is suitable to be used in applications like PV clusters, or other applications with distributed sources. The derivation of the controller proposed in this thesis starts with the energybalance equation. However, it is realized that in order to control multiple sources with possibly different voltage levels it is important to utilize the reactive power. Therefore, the controller proposed emphasizes the powerbalance equation. The dynamic stability of the powerbalance controller is studied in the framework of sliding mode control theory.series loaded resonant converter; energybalance; sliding mode control; wireless power transfer; stability; equivalent control; averaged model
201612248Electrical Engineering, Mathematics and Computer Science'DC systems, Energy conversion & Storage)uuid:2e95ed99d6c445b7892012341f6d9f98Dhttp://resolver.tudelft.nl/uuid:2e95ed99d6c445b7892012341f6d9f98PFeasibility of increasing the pedestal height on the Jclass vessel by 10 metersLee, M.WMetrikine, A.V. (mentor); De Oliveira Barbosa, J. (mentor); Van der Heiden, K. (mentor)aIn order for Jumbo to stay competitive in the offshore market, it's heavy lift vessels should be able to take on a wide range of lifting purposes. This can range from installation of transition pieces for wind turbines to installing modules of fpso's and platforms. One of the demands from the offshore market requires large lifting heights. It is proposed to increase the lifting height on existing mast cranes by increasing the pedestal by 10 meters. In this thesis it is tried to answer the question whether this is feasible. The pedestal should be increased such that it complies with geometric constraints, stability, vessel motions and structural integrity. This feasibility study is divided in two parts. In the first part it is investigated how the enhanced pedestal influences the vessel with regards to hydrostatic characteristics and vessel motions. This information is used to obtain the changed workability of the vessel. Stability characteristics were slightly worse compared to the original vessel layout. As a result of this the maximum offshore lifting capacity decreased from 648 ton to 580 ton at an outreach of 36.5m as measured from the centerline of the vessel. For three crane configurations the hydrostatic values were obtained and served as input for the vessel motion analysis. Since the Jumbo Javelin he< avy lift vessel is equipped with a DP2 system, only first order motions needed to be taken into account. The motions or Response Amplitude Operators (RAO's) express the ratio of the vessel motion amplitudes with the amplitudes of the incoming waves. In all crane configurations, the natural period shifted upwards. From all six degrees of freedom, the roll motion was the largest which is explained by the fact that roll has very little potential damping (energy transfer from ship motion to fluid motion). The final evaluation consisted of a workability study, expressed by the percentage of time that the vessel is able to operate in different sea states. Workability remained similar to the workability of the original vessel in cases where Jumbo performed operations before. A check for North sea circumstances led to an increased workability. This is due to the fact that the natural frequency of the enhanced vessel went further away from the most common sea states. In the second part of this study the pedestal is evaluated structurally. A pedestal geometry is chosen such that it resists normal bending stresses by using the least amount of material. The Fatigue limit stress was taken as the limiting value. In this way an optimal tapered pedestal shape was chosen with varying wall thicknesses ranging from 6.25cm till 4.85cm along the height of the pedestal. The obtained shape is further processed by studying the natural frequencies of the pedestal including the mast and jib. Ship motions should not interfere with natural frequencies of the crane structure due to the effects of resonance which could lead to disproportionate stresses. To study this a finite element model is created using MATLAB that can include the effects of pedestal taper, crane components and DOF's for different jib angles. Planar motions for a plane frame are considered. 6 DOF's for each element are considered and hence represent elements that take both bending and compression. Natural frequencies for two operating conditions and one stowed condition with tip mass are investigated. The lowest observed frequency has a value of 1.39 rad/s. While the lowest natural frequency of vessel motions considered in the workability study is 1.25 rad/s. This led to the conclusion that the improved pedestal geometry and stiffness are sufficient and hence workable.offshore; heavy; lift; stability; motions; pedestal; crane; natural; frequencies; vessel; structural; workability; feasibility; jib; boom
20210519Offshore & Dredging Engineering)uuid:1a0c5a194cbb49c896bc236d0a40d278Dhttp://resolver.tudelft.nl/uuid:1a0c5a194cbb49c896bc236d0a40d2789Stability of Single Layer Cubes on Breakwater Rear SlopesHellinga, L.B.Uijttewaal, W.S.J. (mentor); Verhagen, H.J. (mentor); Kuiper, C. (mentor); Van den Berg, B. (mentor); Van Gent, M.R.A. (mentor)sBreakwaters with single layer concrete armour are very commonly applied nowadays. Much research is available on the stability of single layer armour units on the seaward slope. However, rear slopes design methods for single layer armour units are rare. On rear side slopes usually similar sized units as on the seaward slope are applied. Limited design methods are available for the stability of concrete armour units on the rear side of a breakwater. To obtain stability information on single layer cubes on the rear side, scale model tests have been performed in the wave flume of the University of Technology Delft. The purpose of the model tests is to obtain a relation between the overtopping wave characteristics (overtopping volume of an individual wave event and the overtopping wave front velocity) and the stability of the cubes at the rear slope of low crested breakwaters. This relation can lead to a more optimal rear side breakwater design. The test programme consists of different configurations, in which the following parameters have been varied:  Wave steepness: three typical values for steepness have been tested s_op=0.015, 0.027 and 0.039;  Relative crest width: relative crest width ranges were W_c/H_s= 1.1 6.3;  Relative free board: r< elative free board ranges were R_c/H_s= 0.4 1.3;  Rear slope angle: two slope angles of 1:2 and 1:1.5 have been tested;  Packing density; packing densities of 73% and 69% have been tested A total of 11 breakwater configurations have been tested. Each configuration was tested with a sequence of waves with increasing wave height until failure of the armour layer occurred. The focus was on the determination of start of damage of the rear armour cubes, but also on filter material wash out. Together with the stability tests, wave overtopping volume tests have been performed. The overtopping volume per wave was measured in a special designed box. The overtopping wave front velocity at the crest is measured by correlating the signals of two wave gauges. The number of displaced cubes in the rear slope armour layer has been determined with image analyses and expressed in the damage number N_od. The influences of the various parameters and overtopping characteristics on the rear slope damage are presented in stability graphs. Due to lack of sufficient data points, no trend line could be established. However, the graphs can be used as a guideline for conceptual breakwater design. The critical overtopping characteristics are in a wide range. Therefore, the quantitative influence of the overtopping velocity and volume on the rear slope damage is unclear. This suggest that other aspects may influence the stability of the rear slope, for example the transmission through the breakwater or the shape of the overtopping flow around the rear slope. The analysis of the test data shows that damage on the single layer cubes on breakwater rear sides occurs later than expected. The expected cube dimensions were calculated for various configurations. First, the armour dimension of randomly placed rock is calculated with the formula of van Gent and Pozueta [2004]. Secondly, the difference in stability of randomly placed rocks and regular placed cubes was estimated applying a factor obtained from the known stability numbers on seaward slopes of both armour layers. The estimated cube dimension was used in a first test series. During this test series (almost) no damage was observed. Therefore, the remainder of the experiment was carried out with a 37% smaller cube diameter. The damage seems to be limited to first rows below the water level, which may indicate that cubes on the rear side below this level could be lighter..breakwater; rear slope; stability; overtopping)uuid:d9f03d2803ff4fb7992c053908f87243Dhttp://resolver.tudelft.nl/uuid:d9f03d2803ff4fb7992c053908f87243=The stability region of the tubing performance relation curveGromotka, Z.J.G.4Dubbeldam, J.L.A. (mentor); Egberts, P.J.P. (mentor)The tubing performance relation curve is a measure of well performance in gas well engineering. It describes the twophase flow inside a well and as such is modeled as a twophase one dimensional pipe flow. Convention claims that production points on the TPR curve to the right of its minimum are stable. There also exist claims about the region slightly to the left of the minimum of the TPR curve being stable. To find the stability criteria the time behaviour of a small perturbation from the steady state conditions is modeled and studied. In the end the first claim was indeed verified but further research is suggested to determine if the stable region might be slightly larger.Itwophase flow; pipe flow; nonlinear; stability; gas well; liquid loadingApplied mathematicsMathematical Physics)uuid:b3c23f27259a44a49e16598740232b3eDhttp://resolver.tudelft.nl/uuid:b3c23f27259a44a49e16598740232b3eVOffshore stabilization pontoon for a heavy lift vessel: Concept design and workabilityTen Klooster, A.M.jHuijsmans, R.H.M. (mentor); Den Haan, J. (mentor); Hekkenberg, R.G. (mentor); Van der Heijden, K. (mentor)workability; stability; pontoon!Offshore and Dredging Engineering)uuid:8f90e72809a346fd84fb030d769db42aDhttp://resolver.tudelft.nl/uuid:8f90e72809a346fd84fb030d769db42aBThe stabilization and destabilization of Brouwer's Rotating VesselVan H< eumen, D.J.Van Horssen, W. (mentor)We beschouwen Brouwers roterende lichaam, een voorbeeld van een mechanisch systeem met het volgende paradoxale gedrag; zonder demping is er stabiliteit, met demping is er sprake van instabiliteit. Met modulatie van de hoeksnelheid wordt er een model afgeleid waarbij we pogen de instabiele gevallen te stabiliseren, hierbij is het meenemen van de hoekversnelling cruciaal. De differentiaalvergelijkingen die gevonden worden bevatten niet constante termen die langzaam in de tijd variren met parameter ?. We gebruiken de methode van middelen om een benadering te krijgen van de oplossing die op lange tijd geldig is. Met O(?) demping treedt er instabiliteit op ten gevolgen van demping voor alle resonanties. Met O(?) demping kan er zowel stabiliteit en instabiliteit optreden afhankelijk van de amplitude van de modulatie voor n specifiek combinatie resonantie. Voor alle andere resonanties treedt er alleen instabiliteit ten gevolgen van O(?) demping op. Brouwers roterende lichaam is dus zowel te stabiliseren als te destabiliseren.Sstability; damping; frequency modulation; Method of Averaging; pertubation; BrouwernlBachelor Applied Mathematics)uuid:05dde2aa8c214fcba531d541a60bc751Dhttp://resolver.tudelft.nl/uuid:05dde2aa8c214fcba531d541a60bc751GDynamic Assessment of the Bolivar Roads Navigational Barge Gate BarrierSmulders, J.Jonkman, S.N. (mentor); Vrouwenvelder, A.C.W.M. (mentor); Van der Toorn, A. (mentor); Metrikine, A. (mentor); Willems, A. (mentor)The devastation caused by Hurricane Ike in the Galveston Bay area (Texas, United States of America) proved the necessity of an improved water defense. Multiple flood risk reduction studies were undertaken. The Texas A&M University of Galveston proposed the Ike Dike, a fortification of the coastal spine to prevent a storm surge from entering the Galveston Bay. It includes construction of a storm surge barrier at the Bolivar Roads inlet (3 km) consisting of a navigational section to close of the Houston Ship Channel and a wide shallow environmental section. For the environmental section a preliminary design was made by De Vries (2014). For the navigational section (span of 220 m) the project group (IVinfra, DUT and Royal HaskoningDHV) concluded that a barge gate with a length of 240 m, width of 40 m and height of 20 m seems a suitable solution. The barge is stored parallel to the channel and connected to the shore by a hinge. Approximately 30 hours before landfall of a hurricane, the barge is set afloat and swings 90 degrees around a hinge to two concrete abutments and is immersed. The barge will now act as a simple supported beam and a 1 m high gap is present below the barge. Once the hurricane has passed the barge is set afloat and returned to the storage area. A structural design with static loads has been developed by IVinfra. The dynamic behavior and response to wave and current excitation is not included in this structural design, which is essential information to determine the technical feasibility of this design. This dynamic behavior is investigated in this report. To do so the following phases of a complete closing cycle are distinguished which are assessed separately: Swing operation, immersion operation, landing, closed position and occurrence of a negative head (a bayside water level exceeding the seaside water level). Next to these phases it is assessed if a concrete or steel barge is preferable. First a wave study was completed to determine the governing closing wave conditions and hurricane wave conditions. Swing operation: The barge is closed in one hour with anchor lines connected to the abutment and storage area. During the swing operation the roll motion is governing. But can be reduced by introducing ballast water in the outer compartments of the barge or a different configuration of the anchor lines. Immersion operation and landing: The barge is immersed with pumps and valves in one hour. During the immersion operation the stick slip mechanism will occur but the duration will be limited and will not result in problems.< For increasing drafts the heave, sway and roll response will increase slightly but stay within acceptable limits. Closed position: The overall motion of the simple supported barge will consist of a combined torsion, vertical bending and horizontal bending motion. Due to the high underflow velocity the barge is prone to selfexcitation in vertical, horizontal and torsion direction. The impact is expected to be limited due to outflow of water in the longitudinal direction and the influence of turbulence but substantial research is required into this topic. The first natural frequency in vertical bending is close to the peak of the wave spectrum. The bayside water level may exceed the seaside water level, a stop block is required to ensure the barge does not slide off the abutment. A concrete barge has been compared to a steel barge. For a first estimate the dynamic response of a concrete barge is slightly better. For future research it is recommended assess the selfexcitation in closed position with a scale model.dynamic; barge; gate; stability; hydrodynamic; Bolivar; roads; ike; dike; immersion; swing; operation; hydraulic; engineering; civil29.20496356, 94.4644214)uuid:3427179458ea495cb0f935cd6f102614Dhttp://resolver.tudelft.nl/uuid:3427179458ea495cb0f935cd6f1026143Bioinspired locomotion of a rotating cylinder pair
Novati, G.Westerweel, J. (mentor)tWe developed bioinspired reducedorder models of swimmers, consisting of a selfpropelling pair of rotating cylinders. The aim of the project is twofold. First, simplified and nondeforming geometries can more easily be employed in smallscale robotic applications to solve relevant engineering problems. Second, they can serve as reduced physics models to efficiently simulate fluidmediated interactions in schools of swimmers and perform learning studies involving multiple swimmers. In the first half of the thesis, we investigate the selfpropulsion regimes of a pair of counterrotating cylinders. For low rotation rates, the cylinders behave like a vortex dipole and the flow is characterized by an elliptical closed streamline surrounding the cylinders. For intermediate rotation rates, the cylinders move in the opposite direction and each has a different set of closed streamlines. Further increasing the rotation rate, the motion of the pair becomes unstable. We systematically explore the phase space defined by the nondimensional centretocentre distance and the rotational Reynolds number, and find inverted exponential correlations that describe the transition between states. In the second half, we design three different locomotory modes of the cylinder pair, with few degrees of freedom, inspired by the movement of undulatory fish and jellyfish. The parameter spaces were explored with the CMAES stochastic optimization algorithm in order to find the best solutions in terms of maximum speed and efficiency. The undulatory fishinspired motion achieves propulsion by shedding vorticity in a sequence of alternating sign vortices, similarly to its biologic counterpart. The jellyfishinspired motion during each period sheds a vortex dipole, which generates a strong momentum flux in its wake and thus a large thrust, the definition of the swimming mode of jetpropelled oblate medusae.zvortex method; evolutionary strategy; counter rotating; cylinder; stability; bioinspired locomotion; reduced order modelsProcess and EnergySolid and Fluid Mechanics)uuid:e9552a63df4049e5bb80add4cfa300f7Dhttp://resolver.tudelft.nl/uuid:e9552a63df4049e5bb80add4cfa300f71Damping of wind waves in the IJmuiden breakwatersLavies, H.G.dUijttewaal, W.S.J. (mentor); Verhagen, H.J. (mentor); Van den Bos, J. (mentor); Reedijk, B. (mentor)The breakwaters of IJmuiden are of a unique design; a riprap core is covered with a thick impermeable asphalt slab. During construction and after completion, slope instability caused extensive damage. Placement of a concrete cube armour layer prevented further damage to the asphalt, but proved to be unstable and required a significant amount of maintenance. Rijks< waterstaat (RWS), which is responsible for the maintenance, contracted a number of companies to investigate the strength and loading of the breakwaters. Lifting of the asphalt slab as a result of overpressure in the breakwater core was found to be the decisive failure mechanism. To determine the amount of overpressure, measurements were performed in both breakwater heads. A bigger favourable damping of wind waves was measured in the southern breakwater. Based on these measurements and other research outcomes RWS decided to change the maintenance strategy; armour units above the NPA 2 m line will not be maintained in the future. The new strategy is based on the reasoning that the damping of wind waves reduces lifting forces and makes the weight of the armour layer redundant to prevent lifting. The mechanism(s) causing the larger damping in the southern breakwater are however unknown, this makes it hard to predict the amount of damping and therefore the magnitude of the loading of the asphalt during storm conditions. Aim of this thesis is to get insight in the stability of the asphalt slab during design storm conditions, and the necessity of an armour layer. Therefore the damping mechanism and the amount of damping during storm conditions need to be determined. Numerical modelling is performed to describe wave transmission through the breakwater and to evaluate the influence of different damping mechanisms. Most important mechanism causing additional damping is siltation of the toe structure of the southern breakwater. Along the Dutch coast the net longshore sediment transport is directed northwards. Therefore sediment passes the southern breakwater, part of the sand might settle in the toe and core of the breakwater. A sand layer with a height of 3.3 m reduces the flow of water enough to cause the measured damping. The stability of the sand during storm conditions is checked using open filter sediment transport formula. Erosion of the sand layer is expected, however the erosion is expected to be in the order of centimetres which is insignificant. The damping mechanism causing the measured damping in the southern breakwater is determined; hence loading of the asphalt slab during design storm conditions can be determined. The thickness and quality of the asphalt slab is uncertain and might vary significantly over the length of the breakwaters. In order to get insight in the quality of the asphalt two cores were drilled in 2004. One showed high quality cohesive asphalt, the other showed low quality with low cohesion. Lifting of the asphalt cannot be ruled out. The dead weight of the designed asphalt slab in combination with a partial armour layer is not sufficient to resist the upward pressures during a design storm. The additional resistance needed against lifting can be provided by the weight of a complete armour layer or bending strength of the asphalt slab. The bending strength of the asphalt slab depends on the quantity and quality of the asphalt present. In order for the asphalt slab to have sufficient bending strength a top layer of high quality cohesive asphalt is required. Concluding, without additional information concerning the asphalt quality and thickness lifting of the asphalt slab and thereby failure of the breakwaters cannot be ruled out in case the armour layer erodes above a level of NAP 2 m.@IJmuiden; VOF; wave damping; stability; porous flow; breakwaters52.464778, 4.544884)uuid:b47a9ec6cde745999bd8ec4edb81c8ffDhttp://resolver.tudelft.nl/uuid:b47a9ec6cde745999bd8ec4edb81c8ff4Stability analysis in a model of the human inner earWijchers, M.S..Vuik, C. (mentor); Van Hengel, P.W.J. (mentor)/In this thesis a special kind of differential equation will be analysed, namely the delay differential equation. For test equations the stability behaviour is analysed and there's checked whether there is a method to prove stability. Also, a full description is given, for the model submitted by INCAS3.&stability; delay differential equation
20140416Numerical AnalysisTechnische Wiskunde)uuid:c381d952a2d045d3b801e< 4f262105ffbDhttp://resolver.tudelft.nl/uuid:c381d952a2d045d3b801e4f262105ffbMStability of slope material affected by bow thrusters at open quay structuresRoelse, F.P.}Vellinga, T. (mentor); Verheij, H.J. (mentor); Verhagen, H.J. (mentor); Blokland, T. (mentor); Van den Elzen, M.G.A. (mentor)In the last decades shipping has increased significantly, resulting in larger ships with an increasing power in bow thrusters. Due to this increasing power, the hydraulic loads at bottom protection near quay structures has also increased, making a traditional bed protection more expensive. Therefore an alternative design method is suggested in which the bottom is not fully protected. As a result, scour could occur. The designer of the super structure should adapt his design on this scour. Consequently the total structure (bed protection and superstructure) could be designed more cost effective compared with the current design method of full bed protection. However, at this moment a method to predict scour at a sloping bed with piles affected by a bow thruster is not available, so it is impossible to apply the alternative design method. The objective of this master thesis is to set up a method to predict the equilibrium scour depth. In order to set up such a prediction method, a literature study was conducted. This literature study focused on the available knowledge of bow thruster induced currents and the effect of these currents on the instability and erosion of the bed material. The stability and mobility of the bed material depend on the ratio between flow forcing (flow velocities and turbulences) and the bed strength (particle size and density). When this ratio exceeds a critical value the bed is not stable anymore and transport will occur, leading to scour holes. Not only the thruster jet itself could induce scour formation, also the presence of a pile at the slope could lead to additional scouring. This is caused by the fact that a pile in a flow field causes differences in the flow field (local higher velocities and turbulence intensities). Consequently, extra scour is induced. This scour mechanism is called the pile obstruction mechanism. The total proposed equation consists of both the pile obstruction mechanism and the jet diffusion mechanism. The equation is validated for a horizontal bed. Due to absence of data for the sloping bed case the equation is not validated for the case of a slope yet. It is recommended to validate the proposed equation for the case of a slope with piles by conducting lab experiments.?scour; bow thrusters; stability; quay structure; bed protection
20140312)uuid:115fbcac5a694c2e867466f8c4098ebcDhttp://resolver.tudelft.nl/uuid:115fbcac5a694c2e867466f8c4098ebc^The influence of core permeability on the stability of interlocking, single layer armour units
Verdegaal, I.oUijttewaal, W.S.J. (mentor); Van den Bos, J.P. (mentor); Van den Berg, A. (mentor); Van Zwicht, B.N.M. (mentor)The permeability of a breakwater is of great importance for the stability of the armour layer. The influence of the structural permeability on the stability of rock armour units was already researched by Van der Meer using the 'notional' permeabiltiy. However, for single layer interlocking armour units the influence core permeability is rather unfamiliar. The goal of this research is to extend the knowledge on the failure mechanism of the armour layer for different structural permeability. To achieve this goal, model tests are conducted in the permeameter of the Technical University of Delft and in the wave flume of Delta Marine Consultants, Utrecht. The tests show that the stability of the armour layer decreases with increasing and decreasing core permeability.?breakwater; armour; interlocking; core; permeability; stability
20130604Coastal engineering)uuid:d42b233438864d75aa2971a417d24311Dhttp://resolver.tudelft.nl/uuid:d42b233438864d75aa2971a417d24311Stabiliteit van een dragendeleuning brug uitgevoerd in beton. Stability of a concrete pedestrain bridge with load bearing railings
Weidema, V.M.fWalraven, < J.C. (mentor); Van der Veen, C. (mentor); Blom, C.B.M. (mentor); Hoogenboom, P.C.J. (mentor)Usually, concrete bridges contain a thick bridge deck. For various reasons, bridges are constructed with railings. This thesis discusses the stability problem of concrete bridges, which are designed with integrated railings into the carrying construction. The most important advantage, using load bearing railings, is a thinner bridge deck. This was also one of the requests of Public Works Rotterdam. The load bearing railings have to endure buckling. This phenomena is not very common in massive concrete bridges. Since the request for to alternative bridges with a thinner bridge deck, like this one, is becoming larger and larger, there is need for a simple rule of thumb. This indication is necessary for estimating the dimensions of this kind of bridge without a complicated calculation. For this thesis, the stability of a concrete pedestrian bridge with load bearing railings, has been checked in three ways. There has been focussed at the compression zone of the bridge, the handrails. 1. First the buckling force is calculated. Using the buckling force and the actual normal force in the handrails, it is possible to calculate the second order effects. 2. The total resisting moment in the handrails must be large enough to withstand the external first and second order moments. The resisting moment is based on uncracked concrete, therefore no tension stresses in the handrails are aloud. 3. If stability isn t the problem, strength is. Hence the external normal force in the handrails most be lower than the normal force resisted. The problem has been analysed. The three checking s are visualized in graphs over various dimensions. These graphs were used as a starting point of a parameter study to get a rule of thumb, which can be used for concrete pedestrian bridges with load bearing railings. There is also concluded that bridges with load bearing railings are more sensitive to local forces (on bridge deck and railings), than plate bridges are. The rule of thumb is applicable for bridges larger than 14 meter and smaller than 23 meter, depending on the applied concrete strength. Using this indications gives a correct estimation of the dimensions of a concrete pedestrian bridge with load bearing railings.stability; pedestrain bridge; load baring railings; dragende leuning; concrete bridge; kip; buckling; Engesser; Formula of TU Munchen; EulerDesign and Construction)uuid:ffdd9505e341437392bd0a8704a28026Dhttp://resolver.tudelft.nl/uuid:ffdd9505e341437392bd0a8704a28026MA timber bearing structure for 'Concept House': A design to solve bottlenecksVan Wijngaarden, A.D.Ravenshorst, G.J.P. (mentor); Van de Kuilen, J.W.G. (mentor); Gard, W.F. (mentor); Van Kemenade, J. (mentor); Wirtz, R.R.A. (mentor)This research focus on the solving of important bottlenecks which hinder a timber bearing structure for the new appartment building system of concept house.xtimber frame; multistorey; sound insulation; vibrations; stability; sustainable; environmental score; structural design#structural and building engineeringbuilding engineering)uuid:5663ca3e89054d1c92293f516a132003Dhttp://resolver.tudelft.nl/uuid:5663ca3e89054d1c92293f516a132003TLinear Stability Analysis of a Supercritical Water Loop driven by Natural ConvectionKoren, G.B.+Rohde, M. (mentor); T'Joen, C.G.A. (mentor)The HPLWR (High Performance Light Water Reactor) is the European version of the SCWR (Supercritical Water Reactor) and is one of the Generation IV concepts that have enhanced safety, improved efficiency and less nuclear waste compared to current nuclear reactors. A possible way to enhance the safety is by using natural convection as the driving mechanism for the coolant flow. Natural convection is especially interesting because of the large differences in density occurring under supercritical conditions. This is safer because of its independence of mechanical systems (i.e. pumps, which are used in forced convection loops). The goal of this project was to investigate the lin< ear stability of a onedimensional, simplified version of the HPLWR (without the powerdensity feedback, but with constant power) around the steadystate solution for a range of operational conditions. A code was written based on onedimensional equations for mass, energy and momentum transport. The code successfully predicted the steadystate behaviour of a system. The results were benchmarked with data from literature. The code works for natural convection loops as well as forced convection systems. The stability plots do not agree with literature and are therefore considered to be incorrect.:nuclear energy; SCWR; HPLWR; stability; natural convectionApplied Sciences(Radiation, Radionuclides & Reactors (R3)BSc Technische Natuurkunde)uuid:dba12197ca854ad3b3569b71376df635Dhttp://resolver.tudelft.nl/uuid:dba12197ca854ad3b3569b71376df635XStability analysis of Embankments located within A8 interstate motorway Wroc?aw bypassWoldeyohannes, S.Y.*Pytel, W. (mentor); De Ruiter, H. (mentor)Roads support our daily life, and play crucial role in supporting the infrastructure for economic activities. However, road disaster can be caused by different natural conditions of slope failures such as rainfall, steep topography, brittle geology, etc. Road disaster occurrences do not only cause the primary disaster from the infrastructure point of view; but also the secondary disaster, hindrance to the society and the economic activity by traffic stops. In order to prevent or mitigate such road disasters caused by diverse reasons; measures should be taken in every phases of road engineering practices, usually mainly thorough investigation about the surface geology, the subsurface conditions of the foundation and the careful testing of the construction materials principally. Hence detailed investigation about the site is compulsory before commencing the design and construction phases. In addition, post construction phases mainly regular monitoring and maintenance must be undertaken to give the intended service of the highway. Limit equilibrium method is one of the most widely used stability analysis in practice due to its reliability for most practical cases. Its simplified approach can be used in the preliminary assessment only while more complex analysis that gives more accurate results can be carried out with computer programs. This research presents results of stability analysis of A8 motorway Wroclaw bypass on selected embankments under construction founded on heterogeneous soft soil layers. Different methods of limit equilibrium analysis adopted in computer analysis program SLIDE 2D was used to calculate the Factor of Safety of each embankment. The discussion was based on the results of the computation carried out for crosssections of A8 motorway characterized by variability of height and reinforcement conditions. The limit equilibrium method which satisfies both force and moment equilibrium give better prediction on the stability of the slope. In addition to that the method whose assumption mimics the slope condition is preferred. The assessment was executed by referring to the slope stability requirement by Polish regulations.(stability; embankment; Wroclaw; motorwayApplied Earth SciencesGeoEngineering)uuid:0c792bebf1a04e27ad45d37ab4d45887Dhttp://resolver.tudelft.nl/uuid:0c792bebf1a04e27ad45d37ab4d45887/Process and stability of slow moving landslidesSloof, E.J._Hicks, M.A. (mentor); Molenkamp, F. (mentor); Brinkgreve, R.B.J. (mentor); Kringos, N. (mentor) The stability of the slow moving Big Rock Mesa (BRM) landslide located in California (USA) was analysed. A detailed description of its geometry and soil structure is presented. For the stability vital shear zone and unsaturated zone were identified. The strength and permeability of the different layers that exist in the BRM were determined using computational methods and from literature data. The stability of landslides is susceptible to rainfall and changes to the groundwater level. The corresponding pressure changes cause slopes to become unstable. In dry peri< ods the landslide is stable and in wet periods displacements by deformations occur. For the BRM landslide the rainfall data and displacements recorded with inclinometers were analysed. A water balance was made for a critical and stable period to evaluate the hydraulic flow. Besides rainwater it is likely that also water from adjacent areas flows into the BRM mass. Most of the rainwater is stored in the unsaturated zone of the BRM, which has an average thickness of about 42.5 m. Only a part of this water disappears by runoff and dewatering. The water pulse in the unsaturated zone is slowly drained by the evapotranspiration. The groundwater level profile of BRM was determined from measurements and computed with a statistical program called Surfer. The infiltration of water into the unsaturated zone reduces the suction. This suction is smallest over the vertical infiltration length of the water pulse. The water pulse propagates deeper into the unsaturated zone when rainfall increases. The reduction suction weakens the soil. Consequently, the stability of a slide increases with evapotranspiration and decreases with water infiltration. The stability of the BRM and the flow through the unsaturated zone was analysed with the finite element program Plaxis. However, due to the size of the BRM a full coupled analysis of deformations and hydraulic flow was not possible. Instead steady state calculations were performed. The flow through the unsaturated zone was compared with results from the onedimensional flow program called SWAP. For the conditions of steady state calculation with suction the BRM is stable with a safety factor of 1.17. The safety factor of the BRM decreases slightly with increasing head on the hill side of the geometry. Suction in the unsaturated zone increases the safety factor by only 0.01. This suction decreases when water infiltrates. The calculated small influence of increasing groundwater table corresponds with inclinometer readings.stability; landslides
Geotechnology)uuid:9bdda53179254e52aa58281314117dd9Dhttp://resolver.tudelft.nl/uuid:9bdda53179254e52aa58281314117dd9?Stability of morphological cells to dredgingdumping activitiesZimmermann, N.qWang, Z.B. (mentor); Van Prooijen, B. (mentor); Ranasinghe, R. (mentor); Eelkema, M. (mentor); Stive, M. (mentor)The Westerschelde estuary in the SouthWest of the Netherlands displays two meandering flood and ebb channels separated by shoals. The system of flood, ebb channel and shoal between two channel crossings form a morphological cell. The stability of the serial cell system formed by the Westerschelde is important for the navigation route to the port of Antwerp. Wang and Winterwerp (2001) proposed a simplified model to predict the evolution of the flood and ebb channel. They suggest that the cell will remain stable if dredgingdumping activities do not exceed a certain limit. Hibma et al. (2003) modelled successfully morphological cells with the processbased model Delft3D. This report investigates the stability of morphological cells in estuaries by comparing stability results of the processbased model Delft3D to the simplified model of Wang and Winterwerp (2001). Settings of Hibma et al. (2003) are used to generate an equilibrium state suitable for stability analysis. Sediment is then dumped continuously in the flood or ebb channel at various rates to assess stability. The cell geometry, flow and sediment transport characteristics are used to review the applicability of assumptions underlying the simplified model. Results of the two models are confronted to gain further insight into the cell behaviour. Results are applied to the Westerschelde estuary to discuss the safety of the current dredgingdumping strategy. The study shows that the behaviour of the cell can be described in terms of channel dominance. It suggests that the current dredgingdumping strategy in the Westerschelde is generally safe. It also highlights the need for more understanding and control of the outcome of a Delft3D simulation.hWesterschelde; estuary; morphological; cell; channel; s< tability; bifurcation; dredging; dumping; Delft3D)uuid:8e598f604f274fedb5ab16327e0c516bDhttp://resolver.tudelft.nl/uuid:8e598f604f274fedb5ab16327e0c516b3Oscillations and stability of a massvarying system
De Gier, J.M.Van Horssen, W.T. (mentor)In this paper the stability properties of the vibrations of a singular degree of freedom oscillator with a periodically and multistepwise timevarying mass are studied. The free vibrations and the vibrations due to two types of forcing are investigated.stability; massvarying
20110701)uuid:6fef6b2558c242d48271b00b5ddb00b4Dhttp://resolver.tudelft.nl/uuid:6fef6b2558c242d48271b00b5ddb00b4xConnection of largescale wind power generation to the Dutch electrical power system and its impact on dynamic behaviour Bos, J.A.qKling, W.L. (mentor); Hendriks, R.L. (mentor); Kamp, L.M. (mentor); Paap, G.C. (mentor); Spaan, F.J.C.M. (mentor)Installed wind power world wide is increasing rapidly. The increase in wind power in the European electricity grid is expected to have its impact on the system behaviour. A European study, European Wind Integration Study (EWIS), was thus set up to study the impact of wind power. This thesis was carried out in parallel with EWIS and overlaps at some points. The impact of large scale wind power integration on transient stability in the Dutch grid was studied. For the simulations the Dutch part of the UCTE interconnected system load flow model was used. Speed controls and excitation controls were added to the thermal power plants, and at the interconnections equivalent generators were placed to represent the external grids. Nine connection points were defined and all installed wind power was aggregated in wind parks at those nine connection points. The distribution of wind power amongst turbine type and location was determined to get a realistic distribution. Several simulation cases were then taken into account, first a comparison was made between the dynamic grid behaviour of the year 2008 and the year 2015, when no changes in the current regulations regarding faultridethrough capabilities are made, i.e. all wind power will be disconnected from the grid on a voltage drop below 0.8 p.u.. Secondly a comparison of the dynamic grid behaviour of 2008 and the year 2015 was made, with no wind included in this case. As a third case, different connection requirements were applied, so the wind turbines had to stay connected to the grid in case of a fault. These `new' regulations were applied to the 2015 grid situation. From the calculations it followed that the 2015 grid without wind power installed shows a less stable behaviour than the 2008 grid. In the 2008 situation a short circuit in the centre of the grid may cause the disconnection of up to 1258 MW of wind power. For the 2015 situation this can become over 5000 MW. A disconnection of such a large amount of wind power is leading to voltage oscillations and oscillations at interconnection power flows. These oscillations however damp out fast and do not increase in amplitude. The voltage recovery time increases enormously between these years. Applying new regulations, where all variable speed wind turbines will have to stay connected to the grid during a short circuit, reduces the oscillations. As can be concluded from the calculations, a rather stable grid situation is created. This is mainly caused by the fact that the external grids are not taken into account, but modelled as an equivalent. When a larger part of the surrounding UCTE grid will be implemented the results will be different and most probably show a less stable behaviour. This thesis also looked into the large differences in wind power penetration in Europe. Several countries have a leading position in installed wind power, whilst a country like the Netherlands stays behind. Governments in Germany and Spain are very supportive and show a stable position towards renewable energy. Furthermore social acceptance is high in Germany and Spain, and both have a large local wind turbine production. These are important explaining factors for the < differences in local selection environment and increase in installed wind power.stability; dynamics; wind power; power system\TU Delft, Electrical Engineering, Mathematics and Computer Science, Electrical Power Systems)uuid:b3d35f24c0724bef8b115872da7a72afDhttp://resolver.tudelft.nl/uuid:b3d35f24c0724bef8b115872da7a72af1The stability of a facetted glass shell structureAanhaanen, J.A.M.dVambersky, J.N.J.A. (mentor); Rots, J.G. (mentor); Borgart, A. (mentor); Hoogenboom, P.C.J. (mentor)yThe Master s thesis has focussed on the stability of a facetted shell structure. The research contributes to a Ph.D. research currently carried out at the Technical University of Denmark (DTU), which investigates the possibilities to design and build a shell structure from flat glass panels. The structure is a socalled plate (facetted) structure, which is a relatively unknown, though very efficient structure type. By combining this structural typology with laminated float glass, a very transparent structure becomes possible. Since smooth shell structures are prone to buckling, it is very important to assess the behaviour of the glass facetted structure in this respect. During the research different aspects that are important for the stability of the structure have been investigated using a finite element model. Important was for instance the sensitivity of the structure to imperfections. Furthermore, the influence of the stiffness of the joints between the glass facets turns out to play an important role in the behaviour of the structure. Especially the normal stiffness (k_n) is vital, while the bending stiffness (k_m) is less important. Other aspects that have been considered are the robustness of the structure and the influence of the stiffness of the panels. The research has shown that the structural system and its combination with laminated float glass looks very promising.Sfacetted structures; plate structure; structural glass; shell structures; stability)uuid:ee1dae45df5d4e799769960cfe1ead2bDhttp://resolver.tudelft.nl/uuid:ee1dae45df5d4e799769960cfe1ead2b+The stability of synthetic gabions in wavesOosthoek, J.Stive, M.J.F. (mentor); Uijttewaal, W.S.J. (mentor); Verhagen, H.J. (mentor); De Meerleer, F. (mentor); Texion Geosynthetics (contributor)Gabion mattresses consist out of a steel wire grid in which fill material is retained. The advantage of these constructions is that the individual particle stability is no longer of importance. The containing function of the grid results in the effect that the fill material starts to behave as a group. Next to that the mattresses are all interconnected to each other. Loads are divided over the length of the revetment. The grid is protected with zinc to prevent corrosion. The problem is that when gabions are applied in waves, vibration of the particles can damage the protective layer. Next to that, zinc gives an environmental objective, due to slow dissolving of particles. By applying a synthetic geogrid these problemes are eliminated. From the material demands it comes forward that certain types of geogrid are suitable. The general fear of applying synthetics in gabions is the sensitivity to deformation. Scale model experiments are performed in a wave flume to study the process of deformation. From these tests it came forward that the development of deformation depends on the filling degree of the compartment. The material will always settle in a bulging shape, which results in tension on the grid. Therefore it is recommended to close compartments under tension in the bulging shape. Second objective is the improvement of the stability relation. Aspects as mattress length, friction and permeability are not taken into account in the current design formula. Scale model experiments are performed to determine the stability relation of different revetment designs. With the results a start is made for an improved stability relation. Based on a ratio that represents the tension force absorbation capacity and a relative length parameter, influence of these parameters are implemented. The p< ermeability is implemented by creating three different filter groups, which have a different mutual relation. Further research is necessary to confirm and improve the stability relation./gabion; mattress; stability; stability; geogridBTU Delft, Civil Engineering and Geosciences, Hydraulic Engineering)uuid:97eebc0a460f465e95d91cc9a98bab39Dhttp://resolver.tudelft.nl/uuid:97eebc0a460f465e95d91cc9a98bab39*Stability of Iceland type berm breakwatersSveinbjornsson, P.I.Stive, M.J.F. (mentor); Verhagen, H.J. (mentor); Uijttewaal, W.S. (mentor); Caljouw, M. (mentor); Icelandic Maritime Administration (contributor)bA major part of the breakwaters constructed in the world are the socalled conventional rouble mound breakwaters, which consist of a core, a filter layer and a heavy armour layer. An alternative to the conventional rouble mound breakwater is a berm breakwater. Berm breakwaters have mainly developed in two directions over the last couple of decades. On the one hand a dynamically stable structure, where reshaping is allowed. And on the other hand a more stable multi layered structure often referred to as Icelandic type berm breakwater. When there is a rock quarry, relatively close to the construction site, which is dedicated to the breakwater project, the Icelandic type has proven to be very attractive economically. The basic reason for that is that unlike the other types the Icelandic type utilizes the quarry 100%. This M.Sc. thesis focuses on the Icelandic type berm breakwater. Before an Icelandic type berm breakwater is constructed the stones are divided into classes depending on their size. The smaller armour stones are then placed rather deep where the influence of the wave attack is less, as well as on the rear end of the structure, while the largest stones are placed where the largest wave attack is expected. The goals of the project are the following: a) Design rules for the transaction of stone classes with depth have not yet evolved and the main goal of this project was to develop a stability criterion for the stones in that area (Primary goal). b) Stones on berm. Since the total amount of the largest stones (Class I) is usually limited, the combination of the amount of large stones on the berm and down the berm is important (Secondary goal). c) Recession. Recession will be measured in each test and thereby a large database on the subject will be made available for further research on the subject (Secondary goal). d) The location of the transition of the original and the reshaped profiles as the berm height changes as well as for different stone setups. This is also closely related to the primary goal of the project (Secondary goal). Numbers of model tests were performed in order to reach those goals.*breakwater; berm; armour; layer; stability)uuid:a1848eea754e4e8e8dd9f592d385d8bcDhttp://resolver.tudelft.nl/uuid:a1848eea754e4e8e8dd9f592d385d8bc3Armour layer stability on a bermed slope breakwaterDijkstra, O.P.J.Stive, M.J.F. (mentor); Verhagen, H.J. (mentor); Uijttewaal, W.S.J. (mentor); Spaan, G.B.H. (mentor); Van Gent, M.R.A. (mentor); Van Oord (contributor)
In coastal regions where the land is sensitive to erosion, but also for harbours and ports, numerous types of defensive structures have been developed to protect it from the effects of incident waves. More recently breakwaters have been constructed which combine the stability characteristics of a conventional twolayered uniform sloped breakwater with the wave energy dispersive character of a berm breakwater. This type is referred to as a 'breakwater with a bermed slope' or a 'bermed sloped breakwater' In order to develop more insight in the development of damage on bermed sloped breakwaters, smallscale experiments have been performed in which the two most important parameters related to a berm were tested. These governing parameters were the relative berm length and the relative water level with a range of respectively 0.00 < B/Lm1,0 < 0.35 and 0.8 < Rc/Hm0 < 0.7. It is concluded that the development of damage on a bermed slope has a similar< , but more stable, trajectory as predicted for a uniform slope with the stability formula of Van Gent (2003). The increase in stability can be indicated with a constant factor rD. Also the damage level parameters for 'start of damage' and 'failure' on a bermed slope are independent of the governing parameters and correspond to the values of a uniform sloped breakwater. The influence of the governing parameters on the stability of the lower slope for 'start of damage' is shown in Figure 1. Conceivable trendlines are drawn for constant values of Rc/Hm0 and B/Lm1,0. It can be concluded that when regarding constant values of Rc/Hm0 the test results show, for initial values of the relative berm length, an increase in stability as B/Lm1,0 increases. As the relative berm length gets increasingly larger, the increase in stability indicates a horizontal limit. Also the range for which the relative berm length has a positive contribution on the increase in stability is strongly related to the relative water level. For Rc/Hm0 < 0 this range is small but it widens quickly as the water level approaches the berm level. As the water level on the berm increases, it gradually becomes smaller again. A research by WLDelft Hydraulics (Vermeer (1986)), which performed similar tests but for Rc/Hm0 > 0.9, showed different results. The development of the increase in stability for constant values of the relative berm length showed a peak at B/L0 = 0.15. This peak seemed to flatten out as the water level on the berm became smaller. This process could possible link the findings of this study to the findings of Vermeer (1986), however, more research has to be done to confirm this hypothesis. Finally the two design principles, which in practice are used as indication of the increase in stability, were validated with the results of this study. The first principle applies stability formulae for uniform slopes on the average slope of a bermed profile. The second principle adopts the characteristics of lowcrested structures on the bermed profile. The correlation between the predicted increase in stability and the results of the test series was very low. Apparently the complexity of the processes related to the (in)stability of armour layers on a bermed slope can not be overcome by means of the design principles. This is most probably caused by the influence of the return current, which has large impact on the stability, is not accounted for. Therefore both principles are not well suited to predict the increase in stability of armour layers on bermed slopes.)uuid:00654c23ac524e2da3348cb4ab132e03Dhttp://resolver.tudelft.nl/uuid:00654c23ac524e2da3348cb4ab132e03;Breakwater stability with damaged single layer armour unitsDe Rover, R.A.hStive, M.J.F. (mentor); Verhagen, H.J. (mentor); Uijttewaal, W.S.J. (mentor); Van den Berge, A. (mentor)WAt breakwater and seawall projects at Port St Francis and Scarborough breakage of single layer interlocking armour units was observed. It is generally assumed that breakage of single layer armour units has a significant negative effect on the hydraulic stability of a rubble mound breakwater. The significant decrease of interlocking capacity and mass of the broken units would lead to displacement of these units and surrounding units. The broken parts of the damaged units would act like projectiles. The waves would "throw" these broken parts back and forth to the armour layer. More armour units would break due to the impact of these broken parts leading to rapid damage progression of the armour layer and finally to failure of the total construction. This damage behaviour has however never been confirmed. The main objective of this research is to determine the effect of single layer armour unit breakage on the hydraulic armour layer stability and potential damage progression. A 2dimensional model of a rubble mound breakwater with typical cross section was tested with individual and clustered positioned broken Xbloc armour units around the still water line. The residual stability of the armour layer was determined. The armour< unit displacement and damage progression was assessed. It is concluded that breakage of single layer armour units has a significant negative effect on start of damage of the armour layer. Breakage of single layer armour units has no significant effect on failure of the armour layer. This damage behaviour leads to a long and gradual damage progression. This type of damage progression looks more like the damage progression of an armour layer consisting of riprap rock. The majority of the broken parts show little to no movement. It is therefore unlikely that rapid damage progression occurs due to broken parts damaging other units.breakwater; stability; damaged; armour; units)uuid:0528aadb341543d0876eb0f399395030Dhttp://resolver.tudelft.nl/uuid:0528aadb341543d0876eb0f3993950309The impact of placement method on Antiferblock stabilityFrens, A.B.Stive, M.J.F. (mentor); van Gent, M.R.A. (mentor); Uijttewaal, W.S.J. (mentor); Olthof, J. (mentor); Verhagen, H.J. (mentor)
The main objective of this research was to assess the impact of different placement methods, with different packing densities, on the stability of double layered Antiferblock armour layers. This was done by experimental research in the waveflume of the Fluid mechanics laboratory of the Faculty of Civil Engineering and Geosciences at Delft University of Technology. 17 experiments were performed with packing densities between 44.8 and 61.1 percent. For every experiment the under layer, toe and armour layer were rebuilt. The placed Antifer layer was tested with eight irregular wave series with increasing significant wave heights from 9cm up to 20cm. From these experiments followed that regular placement methods behave more stable than irregular placement methods with a similar packing density. Also the more irregular (less accurate) positioning of blocks within a regular placement method caused a decrease in stability. Higher packing densities for equal placement methods lead to higher stabilities and higher reflection coefficients. The resulting values were between 4.0 and 23.7. If the reflection coefficients during the first wave series were high, this resulted in more overtopping during the latest wave series, which indicates that there is a positive correlation between the reflection and the overtopping. Overall it could be concluded that, when the under layer and the toe are smooth and the blocks can be placed accurately, the best performing placement methods are the closed pyramid placement method for packing densities around 45% and 50% and the double pyramid placement method for packing densities around 55% and 60%. The size of the openings to the under layer, of the double pyramid placement method, influenced the reflection coefficients. When the second layer was shifted half a nominal diameter upwards the reflection coefficients were minimal. It is recommended to investigate the possible negative influence of oblique incoming waves on the stability of the double pyramid placement method. The eventual choice of the placement method and packing density depends on the allowed reflection and/or overtopping and the construction costs. The construction costs can be divided into the production costs, the placement costs and the constant costs. For equal constant costs and equal or small differences in placement costs the placement with the higher packing density and accompanying stability value is cheaper for high design wave heights. When the placement costs decrease for both placements or only for the placement with the higher packing density, then the placement with the higher packing density becomes also cheaper for lower wave heights.antifer; placement; stability)uuid:9f5463f11aa749919c9bfa1fb8bf146aDhttp://resolver.tudelft.nl/uuid:9f5463f11aa749919c9bfa1fb8bf146azStability of rock on slopes under wave attack: Comparison and analysis of datasets Van der Meer [1988] and Van Gent [2003]Mertens, M.`Stive, M.J.F. (mentor); Verhagen, H.J. (mentor); van der Meer, J.W. (mentor); Booij, R. (mentor)In VAN GENT [2004] graphs were presented in which < the datasets of VAN DER MEER [1988] and VAN GENT ET AL. [2003] were compared, but in this comparison a number of parameters were not correctly transformed into a comparable format. In this M.Sc. thesis after an extensive analysis to the datasets all parameters of the datasets of Van der Meer were transformed into the same format as the parameters used by Van Gent. In the same way the dataset of THOMPSON & SHUTTLER [1975], which formed the basis of the work of Van der Meer, was treated. The inclusion of correction factors for the effects of stone roundness from LATHAM ET AL. [1988] gave remarkable effects on a certain part of the dataset of Van der Meer which showed more damage than average. After this still differences could be seen between the datasets of Van der Meer and Van Gent. Using the statistical Ttest these differences are approved. Explanations for the differences found between the datasets of Van der Meer and Van Gent can be found in the fact that most of the tests of Van Gent. were done with shallow foreshores where Van der Meer did most tests with deep water conditions. Tests by a number of M.Sc. students at Delft University of Technology showed that tests with identical spectra, but with different foreshore slope angles show different damage patterns. In the dataset of Van Gent also the 1:30 foreshore slopes on average show more damage than the 1:100 slopes. In further research the influence of the foreshore should be incorporated in the stability formulae by a foreshore Iribarren parameter. Also a detailed investigation to the effects of wave breaking on shallow foreshores is needed. For this the complete dataset of Van Gent needs to be available and accessible.&Meer; Gent; stability; foreshore; rock)uuid:8a91005b31a148c78f611fa9077ea295Dhttp://resolver.tudelft.nl/uuid:8a91005b31a148c78f611fa9077ea295Gabion stabilityBeekx, R.H.P.A.Vrijling, J.K. (mentor) South Korea is reclaiming land by constructing dams and polders. The large tidal differences along the Korean coast make building these dams a challenging job. One of the solutions in South Korea to cope with the high flow velocities in closure projects is to apply sack gabions. These are steel nets with rocks inside them that weigh up to 3 tons. It is not clear how stable these sack gabions are exactly. The objective of this report is to make a preliminary study on the stability of sack gabions. In 2006, the Saemangeum estuary in South Korea was closed with a dam. During the closure sack gabions were used in the bed protection, sill construction and dam heads. In a field trip to the Saemangeum project useful data was collected on the stability of gabions. Experimental data of RRI on model tests on the stability of gabions was also obtained. In addition model tests were done in Delft. All data are compared to come up with an advice for calculating the stability of gabions. To calculate the depth averaged critical velocity for 3t  5t rock with 3t sack gabions mixtures, formula [15] proves to be useful. ucM = 2.513*x+5.4 [15 Where: ucM = critical velocity of a mixture of 50% rocks of 3.0 to 5.0 t and 50% 3.0 gabions x = the proportion of gabions in the mixture 0.2 < x < 0.5 For the calculation of the local critical velocity for a bed of sack gabions, it is advised to use Izbash' formula with a gabion stability factor (Gamma in formula [10]) while calculating the nominal diameter of a sack gabion as in formula [1] (a mass based approach): Delta Dn = (Beta*Uc2)/(Gamma*2*g) [10] Dn = (M/Rs)^1/3 [1] Where Gamma = 1.26 for sack gabions (while for loose rocks Gamma = 1) Also a qualitative analysis of the Delft model tests is made that leads to several considerations for the design of gabion bed protections: When applying gabions one has to take into account the difference in behavior between gabions and loose rocks. Another behavior that needs to be investigated further is the effect of applied pressure on a gabion bed. There is still much unknown about the stability of gabions and the report mentions several things that should be further investigated. Also it is< advised to use sluices in the Netherlands or in South Korea as flumes for extensive prototype tests on the stability of gabions.gabion; stability; South KoreaJTU Delft, Civil Engineering and Geosciences, Hydraulic Engineering Section)uuid:e0998d8d497a4720b393803c207dcb16Dhttp://resolver.tudelft.nl/uuid:e0998d8d497a4720b393803c207dcb16Turbulence structures affecting stone stability in backwardfacing step flow: Experiments by means of Particle Image Velocimetryde Ruijter, R.YBattjes, J.A. (mentor); Booij, R. (mentor); Hofland, B. (mentor); Verhagen, H.J. (mentor)Downstream of manmade hydraulic structures, bed protections made of granular material are often used to prevent erosion of the bottom. The stones in the top layer of such granular filters must be able to withstand the hydraulic forces. Probably the bestknown formula that is used to determine the stability of granular bed material is the design criterion by Shields (1936). However, this criterion is only valid for uniform flows. Little is known about the influence of turbulence on the stability of stones. In this thesis the influence of turbulence structures on the stability of stones in the top layer of a granular filter in one type of nonuniform flow that is often encountered near hydraulic structures, namely backwardfacing step (BFS) flow, was investigated.2turbulence; stone; stability; step flow; structure)uuid:ab1b820eed76432880d71eeafb6ac09fDhttp://resolver.tudelft.nl/uuid:ab1b820eed76432880d71eeafb6ac09f^The influence of structural permeability on armour layer stability of rubble mound breakwatersDe Heij, J.The first one who studied the problem of armour layer stability was Iribarren (1938). Iribarren derived stability criteria that were based on the acting physical processes on the slope of a structure. In the stability criteria of Iribarren only the influence of a few structural and hydraulic parameters were taken into account. In 1988 Van der Meer derived a stability relation in which the stability of armour layers was depending on several hydraulic and structural parameters. Van der Meer concluded that the stability of armour layers is strongly influenced by the composition of a structure. He implemented the influence of the composition of the structure in a permeability coefficient, P. This permeability coefficient is defined for four different structures. Van der Meer is a good tool for the design of armour layers, it has little physical background. The empirical character of the stability relation is found back in the definition of the permeability coefficient. If a different structure is designed than tested by Van der Meer, an estimation of this permeability coefficient has to be made. Since the permeability has large influence on the stability, new methods should be developed to calculate armour layer stability. Due to the irregularity of armour stones it would take a lot of effort to obtain a full analytical solution for the problem of armour layer stability. However, a good attempt into the direction of an analytical solution can be made, since good models are available that describe the water motion on and in coastal structures. An example of such a model is the model ODIFLOCS. ODIFLOCS stands for Qne dimensional flow Qn and in foastal structures. With ODIFLOCS it is possible to calculate the velocities on a coastal structure for certain hydraulic and structural parameters. With these velocities the hydrodynamic forces on the stones in the armour layer can be calculated. Iribarren (1938) proposed a model for armour layer stability. He assumed a hydrodynamic drag force that act on a stone, which is caused by the runup or rundown, parallel to the slope of the structure. Two stability criteria for the stability of rock on a slope can be distinguished, which are upward and downward stability respectively. The drag force can be written as a function of the velocity on the slope of a breakwater. Iribarren was not able to calculate these velocities, since no models were available to calculate them, and estimated them by wave celerit< y in shallow water. Van den Berk (1999) was able to proceed the approach of Iribarren and calculated the velocities with the numerical model ODIFLOCS. He modelled homogeneous structures and calculated the armour layer stability for homogeneous structures for several hydraulic and structural conditions. He found that his results and the results ofVan der Meer were strongly correlated. In this research a next step will be made to see whether physical background can be given to the influence of structural permeability on armour layer stability. Structures with different permeabilities will be modelled and the velocities on the slope will be calculated for different hydraulic conditions. With the use of these velocities, which will be calculated with the numerical model ODIFLOCS, the stability can be determined. The test showed that the strongest increase in stability was found for gentle slopes in combination with low and high wave steepness. The test with steep slopes gave significant lower influence of structural permeability, compared with gentle slopes, on armour layer stability. This is contradicting with the findings of Van der Meer, who found a strong influence ofpenneability on the stability for high values of the surf similarity parameter. This shows that the penneabilities that are modelled in this research do not correspond to those tested by Van der Meer.&numerical model; breakwater; stability)uuid:83968ad069f442b1990b7700304a59c4Dhttp://resolver.tudelft.nl/uuid:83968ad069f442b1990b7700304a59c4%Tidal inlets on littoral drift shores
De Haas, M.J.bVan de Graaff, J. (mentor); Roelvink, J.A. (mentor); Huisman, P. (mentor); Kamphuis, J.W. (mentor)After consulting the "Department of Environment" in Australia it was suggested that an extensive generic study about Tidal Inlets on Littoral drift shores gives them an insight in the processes at work and also the possibilities to improve the stability in order to make tidal inlets suitable for safe navigation. This report describes the most important issues related to tidal inlets on littoral drift shores in general. It is written with the intention to provide some general information to readers who are interested in tidal inlets in general. However this report also provides some specific information to be able to study the stabilisation of the Nerang River Entrance, Queensland Australia..tidal inlets; littoral drift shores; stability)uuid:d4ba530aeebe456e8d612a3300380f45Dhttp://resolver.tudelft.nl/uuid:d4ba530aeebe456e8d612a3300380f45fHoofdstroming contra menglaag: De invloed van een menglaag op het begin van bewegen van bodemmateriaalZuurveld, J.D' Angremond, K. (mentor); Fontijn, H.L. (mentor); Uijttewaal, W.S.J. (mentor); Van der Meulen, T. (mentor); Schiereck, G.J. (mentor)Experimental research on the stability of bed material behind a backward facing step. Measured is the stability as a function of the local velocity and the local turbulence (turbulence intensity) due to the eddy formation.,stability; turbulence; backwards facing step)uuid:e9b76cf817c24b4f8e1b6206f4fa26e5Dhttp://resolver.tudelft.nl/uuid:e9b76cf817c24b4f8e1b6206f4fa26e58Transport van stenen van een granulaire bodemverdediging
De Boer, G.M.D' Angremond, K.D. (mentor); Fontijn, H.L. (mentor); Schiereck, G.J. (mentor); Van der Meulen, T. (mentor); Olthof, J. (mentor)Experimental research on the stability of bed protection and transport of stones on such a bottom protection. Investigated were the effects of duration and magnitude of the load, the shape, and placing density of the stones."bed protection; stability; shields)uuid:98e5d9c031af46b0ac061a527ede7c64Dhttp://resolver.tudelft.nl/uuid:98e5d9c031af46b0ac061a527ede7c64#Rock Behaviour near the Tunnel Face
Nuijten, G.A.AVerruijt, A. (mentor); Stille, H. (mentor); Isaksson, T. (mentor)QFor tunnels it is not only important, how the tunnel and the surrounding rock behave during the life time of the tunnel. It is also very meaningful to understand how the tunnel is behaving, while it is under construction. The basis for < this thesis is to understand, how the tunnel behaviour, concerning deformation and stability, is for different rock conditions during the excavation process and what its influence is on the tunnel in final state. Additionally a case study is made of a praxisexample in Switzerland, in which it is pointed out, how difficult circumstances can be during the excavation and what measurements had to be done to cope with all the problems of excavating the tunnel. This example emphasises once more, how important a good understanding of rock behaviour during the excavation is. The report is built up in three more or less different sections: Chapters 2 to 4, chapters 5 and 6, and chapter 7. Chapters 2 to 4 form the first part, that is functioning as a basis for the calculations and analysis made in chapters 5 to 7. An analytical analysis about stressdeformation relations together with basic rock mechanic principles is worked out in chapter 2. Due to the complexity of the rock many rock classifications have been made to qualify different rock classes with their corresponding behaviour. One of these rock classes is used to obtain basic rock parameters, with which calculations are performed. This is, together with an description of different types a specific rock behaviour, outlined in chapter 3. An analytical approach for face stability problems is presented and further worked out in chapter 4. Chapters 5 to 6 are the main part with the calculations and the analysis, in which chapter 5 deals about the aspects, concerning the tunnel ring, and chapter 6 deals about the aspects, concerning the tunnel face. Basic rock calculation is given, about how the rock responds to the excavation of a tunnel. This calculating formed the basic for further calculations and research. The influence of different tunnel constructing aspects have been computed and compared with the basic rockbehaviour. In this way a good impression is obtained about how different constructing aspects, such as lining constructed far away and close to the face, pretunnelling, sequential excavation and rock improvement are performing in respect to stability and deformation of both the tunnel face and the tunnel lining. Chapter 7 is the case study of the Adler tunnel in Switzerland. Rock mechanical problems are analysed and described. It is also recapitulated, what measurements have been carried out to deal with the risen problems and how successful they were. The result of all these calculations for behaviour of the tunnel ring is, that lining gives an extensive reduction of the radial inward movement. The performance of the lining is at its most in the weakest rock and when the lining is constructed close to the face. The addition of a pretunnelled construction improves the performance in weaker rock. The deformation is further reduced. This is however not the case in good rock. In those cases pretunnelling should not be used, as it is a waste of time and money. An extra aspect of these performances is, that by reducing the lining the pressure on the lining is increased. The lining has to be dimensioned on these higher pressures. The most important aspect for the tunnel face is stability. Pretunnelling is not an option to stabilise the tunnel face. Grouting may introduce inadmissible tension stresses in the grouted area, which nullify the desired stabilisation. A good option for making the face more stabile is to excavate in sequences, because decreasing the diameter means a high reduction of the risk for face collapse. A stabile tunnel face is very much depending on the diameter of the tunnel, there where the depth of the tunnel determines the amount of plasticity around the tunnel face. Readers who are interested in typical geohydrological aspects of rock tunnelling, shield tunnelling, such as EPB and Slurry Shields, with counter pressures on the tunnel face, typical lining aspects, such as differences between different linings or the improvement of the lining strength in time, or time dependent behaviour of the rock are kindly requested to read other papers or reports. Those a< spects, although very interesting and highly important, are not a part of this report."excavation; stability; deformation)uuid:b47d80339f164ed6b98011e4c14a98afDhttp://resolver.tudelft.nl/uuid:b47d80339f164ed6b98011e4c14a98af&Transport van tunnelelementen over zeeCoopmann, S.W.M.`Vrijling, J.K. (mentor); Bezuyen, K.G. (mentor); Journ, J.M.J. (mentor); De Leeuw, W. (mentor)
In Nederland wordt het steeds moeilijker om bouwdokken, voor het vervaardigen van afzinkelementen van een afzinktunnel, aan te leggen. Daarom wordt uitgeweken naar reeds bestaande bouwdokken, en worden de tunnelelementen over langere afstanden en ook over zee vervoerd. De krachten en momenten die door de golfbelasting, tijdens transport over zee, in de elementen worden opgewekt zullen door middel van voorspanning moeten worden opgenomen. Dit afstudeeronderzoek omvat een studie naar de optredende krachten en momenten in tunnelelementen als gevolg van golfbelastingen en de optimalisatie van de benodigde voorspanning alsmede de lengte van tunnelelementen. Bij het onderzoek is uitgegaan van het transport van de elementen van de Wijkertunnel, dat plaatsvindt over de Noordzee tussen de Nieuwe Waterweg en het Noordzeekanaal. De langetermijn verdeling van golven op de Noordzee is bepaald met behulp van 3uurlijkse waarnemingen, van twee meetstations op de Noordzee over een periode van 13 jaar voor de zomermaanden mei tot en met augustus, van de significante golfhoogte Hs, de piekperiode Tp en de invalshoek </> van de golven. Uit de waarnemingen blijkt dat de piekperiode, de pieksteilheid en de hoek van inval onafhankelijk zijn van elkaar, zodat de kans op voorkomen van een karakteristieke golf wordt verkregen door vermenigvuldiging van de verdelingsfuncties van deze variabelen. De piekperiode en pieksteilheid zijn normaal verdeeld met respectievelijk j1 = 5,326 ,~ = 1,034 seconde voor de periode en j1 = 1,9 %, ~ = 0,9 % voor de steilheid. De invalshoek is uniform verdeeld. Voor de deining is een significante hoogte van 0,5 m. met een piekperiode van 10 sec. aangehouden. Uit de beschrijving van golven met behulp van verdelingsfuncties volgt een probabilistische aanpak van het probleem. Om de krachten en momenten in de elementen te kunnen bepalen wordt, met behulp van spectraalanalyse, een karakteristieke golf vertaald naar een golfspectrum; door middel van overdrachtsfuncties worden dan de krachten en momentenspectra bepaald. De overdrachtsfuncties zijn bepaald met een dynamisch rekenprogramma dat gebruikt maakt van de lineaire striptheorie, en zijn gecontroleerd aan de hand van overdrachtsfuncties bepaald met modelproeven voor de Wijkertunnel. Hieruit blijkt dat de berekende overdrachtsfuncties zeer goed voldoen aan de werkelijkheid. Met de momentenspectra zijn de significante buigende momenten bepaald, waaruit de significante benodigde voorspanning voor elke karakteristieke golf is berekend. De kans op falen van het tunnelelement tijdens zeetransport als functie van de voorspanning is gelijk aan de kans op overschrijden van de significante voorspanning tijdens transport over zee (extreme Rayleigh verdeling) vermenigvuldigd met de kans op voorkomen van een karakteristieke golf (Iangetermijn verdeling) gesommeerd over alle voorkomende golven. Met behulp van deze faalkans als functie van de voorspanning en eisen ten aanzien van de faalkans voor de gebruiks en bezwijkfase van het transport is bepaald dat de benodigde voorspanning gelijk is aan Fp = 74000 kN. De gebruiksfase is hierbij maatgevend. De optimalisatie van de voorspanning is gedaan naar de kosten van bezwijken van een element tijdens transport. Het blijkt dat de optimale voorspanning lager Iigt dan de toegepaste voorspanning, echter omdat de gebruiksfase maatgevend is wordt de werkbaarheid, bij een lagere, optimale' voorspanning te klein. Kostenoptimalisatie van de voorspanning moet dus geschieden aan de hand van wachttijden voor de gebruiksfase.+immersed tunnel; tunnel elements; stability)uuid:51af1788de9f4ef38115ffefb2e26f76Dhttp://resolver.tudelft.nl/uuid:51af1788de9f4ef38115ffefb2e26f76<V3Toe structure stability of rubble mound breakwatersGerding, E.5D'Angremond, K. (mentor); van der Meer, J.W. (mentor)In this report an analysis of data from a series of tests is presented on the stability of the toe structure of rubble mound breakwaters. The existing knowledge on toe stability and the influence of all governing parameters in the existing knowledge is reviewed. The tests which were performed for the present research are treated extensively. The main governing parameters, which determine toe stability in rubble mound breakwaters, are: Significant wave height : Hs Nominal stone diameter : Dn50 Stone mass density : s Depth above the toe : ht Damage level : Nod Parameters investigated which appeared to have no significant influence are: the fictitious wave steepness sop and the width of the toe structure bt. The choice of the governing parameters, the definition of damage levels for the design of the toe structure and the way they are made dimensionless are motivated. The results from the present tests are compared with existing design formula. With the selected parameters two formulas have been derived from the available test data. One describes toe stability using the shallow water significant wave height Hs the other uses the shallow water 2% wave height H2%. The formulas are compared with existing test results and their range of application is given.3toe structure; breakwaters; rubblemound; stability)uuid:cc85154f51834df4b64900f380a3f175Dhttp://resolver.tudelft.nl/uuid:cc85154f51834df4b64900f380a3f175Modelling of tidal inlets  Preliminary design of the configuration of the harbour layout of the proposed harbour at the Boca Vieja at La Ceiba
Bogers, P.Id' Angremond, K. (mentor); Noppen, J.P. (mentor); Roelvink, J.A. (mentor)At present no computer model is available that can determine the stability of an inlet or what will happen to the stability after some adjustment of the inlet. This study has the objective to develop a simple model th at combines all major parameters in order to determine the stability of an inlet and the effects of adjustments on the stability of an inlet. A computer model has been developed that incorporates these two basic elements. Stability is defined as the situation in which the ebb delta does not move. The effects of the tidal currents and longshore currents on the bottom profile are calculated separately. The effects of the longshore current are determined by using the theory of Pelnard Considere. The effects of the tidal currents are calculated by using a river sediment transport formula. The tidal currents are determined by applying a one dimensional long wave theory to the inlet bay system. The most important restrictions of the model are: Widening or closing of the access channel is not possible. The neglect of interaction between longshore current and tidal currents The effect of wave action on the sediment transport is neglected during the tidal cycle. It is th us likely that the sediment transport calculated in the tidal module is to low.0inlet; stability; computer model; bottom profile
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