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The general flow pattern of an open channel flow, downstream of a width restriction by two artificial dams, is analysed. A physical Froude-scaled model, under hydraulic rough conditions, with a significant large Reynolds number is used to ensure turbulent flow. Upstream of the dams the flow is uniform in transverse direction, in between and downstream of the narrow part a jet is formed. On both sides of the jet large eddies are formed bounded by the wall, the jet and the dams. Due to the large velocity gradient in transverse direction a mixing layer develops at both sides of the jet. The width of the mixing layer, as expected, grows with the downstream distance and exceeds the water depth. 2D structures are clearly visible by injecting dye. In the mixing layer besides the macro time and spatial scales, the small Taylor and Kolmogorov scales are present. Whereas the macro scales are well represented in the measured data, the small scales are impossible to mark due to limitations of the Doppler device. When there is initial no net momentum in transverse direction present the jet is expected to appear symmetrical. However the jet is aligned to one of the sides every time the model starts to run. The preference for one or the other side seems to be random and cannot be related to momentum in transverse direction in between the dams. During measurements the position of the jet is stationary. The fixed position of the jet during measurements can be related to the Coandă effect. When the flow is disturbed and transverse momentum is added to the upstream flow, the jet can be deflected. The position of the jet and the evolving mixing layers can be related very well to the measured velocities upstream. Due to the limitations of the used momentum balance equation and use of the mean velocity in the bottom friction calculation the measured head loss is large compared to the calculated dissipative terms (bottom friction and Carnot loss).

Flowforms zijn relatief nieuwe waterlopen en zijn niet heel bekend. In flowforms kan er een bijzondere stroming opgewekt worden. Ze zijn puur experimenteel ontworpen en er zit geen theorie achter het ontwerp. Het doel is om deze bijzondere stroming toe te passen bij vistrappen. Het probleem is dat de flowforms kleinschalig zijn in vergelijking tot vistrappen. Daarnaast is er geen theorie bekend over de stroming. Daarom wordt voor het onderzoek de flowform als eerst gemodelleerd en de daar bijbehorend theorie wordt opgesteld. Het model met theorie wordt getoetst aan de hand van experimenten die gedaan worden aan een flowformcascade die in Rotterdam saan. Hieruit blijkt dat het gekozen model klopt en met deze theorie kan verder gewerkt worden. De bijzondere stroming in de flowform kan plaatsvinden door de vorm en afmetingen van de flowform, en ontstaat door een verstoring waardoor het systeem in eigentrilling raakt. Voor het opschalen is het daarom van belang om elke geometrisch eigenschap met een lineaire verhouding op te schalen. Uit een extra experiment dat door middel van plexiglazen bakken is uitgevoerd volgt, zoals eerder theoretisch is verondersteld, dat de schaling van de hydrodynamische eigenschappen plaatsvindt volgens Froude.  Verder is er gekeken wanneer de gezochte beweging in resonantie raakt en wanneer deze beweging nog wel kan bestaan ondanks da de stroming niet zo aansprekend is wanneer het in resonantie is.    Voor c=1 geldt dat resonantie optreedt. Voor c>1 treedt er geen resonantie op maar blijft de beweging in minder mooie vorm bestaan. En voor c=0,5 vindt er demping van het systeem plaats. De toepasbaarheid kan onderzocht worden nu het duidelijk is hoe de stroming werkt en hoe het geheel is op te schalen. Volgens bovenstaande verhouding is de diepte uitgezet tegen de snelheid. Dit is in een Excel‐document gedaan. Uit deze data volgt dat de bijzondere stroming alleen kan plaatsvinden in het minder diepe water in de orde van enkele decimetrs. Hieruit blijkt dat het opschalen voor de toepassing van vistrappen vooral geldt voor de kleinere sterkere vis.

Oblique dunes have an important influence on the direction of the bed-load sediment in rivers. However, not much is known about these effects, and about what affects the angle of oblique dunes. Therefore tests have been carried out to look into this effect of oblique dunes on sediment transport. Based on these tests, formulae for bed-load transport direction which take the dune angle into account have been derived. Application of these formulae shows a large effect of the dune angle on the transport direction, but the formulae have not been validated yet. Based on the hypothesis that dune angles are related to the dune migration rate along the crest, a formula to calculate the dune angle has been derived. The formula has not been compared to laboratory tests or field measurements, but the validity of the formula is questionable as in the test cases very large angles are found. Formulae for the dune angle and the bed-load transport have been implemented in a numerical model. For the dune angle formula an iterative scheme is needed to solve it. Three methods have been tested. Out of these three the bisection method is the most promising scheme.

The flow of water through a river bend can be characterized as a turbulent open-channel flow that is dominated by streamline curvature. In order to adequately manage the planimetry of meandering rivers and the according safety aspects, the features of the flow and the associated turbulence have to be understood well. This thesis presents results of detailed numerical simulations of curved open-channel flows on a laboratory scale. These flows can basically be considered as downscaled river bend flows. The presented results provide a broad image of the behavior of curved open-channel flows in general and their characteristics with respect to the secondary flow, the bed shear stresses and turbulence in particular. Hereby, these results also facilitate further development of parameterizations of these key bend flow features for lower-dimensional modeling tools that are used in the engineering practice.

The Ph.D. thesis “Large-scale turbulence structures in shallow separating flows” by Harmen Talstra is the result of a Ph.D. research project on large-scale shallow-flow turbulence, which has been performed in the Environmental Fluid Mechanics Laboratory at Delft University of Technology. The dynamics of quasi two-dimensional turbulence structures in shallow separating flows have been studied both experimentally and numerically. The research work contained three parts: respectively laboratory experiments, three-dimensional simulations and two-dimensional simulations. A number of schematized flow cases have been investigated in a large-scale shallow laboratory flume, using the free-surface measurement technique of Particle Image Velocimetry (PIV). Subsequently, detailed three-dimensional Large Eddy Simulations (LES) have been performed on a parallel cluster, providing useful 3D data on the flow cases studied experimentally as well as on additional flow geometries. The conclusions drawn are useful for e.g. design purposes in engineering practice. Finally, the flow cases studied before have been revisited by means of 2D depth-averaged computations, testing a new approach to accurately resolve large-scale shallow-flow turbulence in a 2D schematization. The new approach has been coined Depth-Averaged Navier-Stokes with Large Eddy Stimulation (DANSLES). The thesis offers a rather complete picture of the turbulent flow cases that have been studied, both in terms of physical behavior and numerical modeling aspects.

Two experiments are performed in order to investigate suspended sediment transport in a turbulent open channel flow. The first experiment used particle image velocimetry (PIV) to measure the fluid velocity with a high spatial resolution, while particle tracking velocimetry (PTV) was used to measure the velocity of individual sediment particles. The sediment particles were injected in the flume close to the free surface at different distances from the measurement section. In this way, the development of a sediment plume towards an equilibrium situation could be studied. The results were compared with direct numerical simulations, in which the particle equation of motion was used to calculate the movement of individual sediment particles. The second experiment used refractive index matching, in order to make the sediment particle invisible. In this way, a PIV experiment could be performed in order to determine changes in the flow and turbulence structure due to high sediment concentrations.

In this study the focus is on modelling turbulence anisotropy in open channel flows with the SWASH model. Turbulence anisotropy significantly influences the flow features of: channel flows with heterogeneous roughness conditions, curved open channel flows, compound channel flows with different floodplain depths, etc. The SWASH model is a non-hydrostatic wave-flow model, mainly used to predict the transformation of surface waves from offshore to the beach. For this study, adaptations were made to this SWASH model, in order to model turbulence anisotropy. Two different modelling approaches were used: RANS modelling and Large Eddy Simulation (LES). The SWASH model is extended with a non-linear k-ε closure to the RANS equations, since the standard linear closure does not take turbulence anisotropy into account. A 3D subgrid model is implemented to perform LES. The performance of the LES code and the RANS model with the non-linear k-ε closure is tested on two flow geometries: an open channel flow with homogeneous bottom roughness conditions and an open channel flow with parallel smooth to rough bed sections. Results of the RANS computations, for both horizontal homogeneous and non-homogeneous open channel flow, show good agreement with laboratory measurements of Muller and Studerus [13], Nezu and Rodi [17] and Wang and Cheng [32]. Although there is a number of closure constants involved with the non-linear k-ε model, additional tuning of these coefficients was not necessary for this study: both the homogeneous and non-homogenous test case were simulated successfully using the standard values proposed by Speziale [25]. With its low computational costs and robustness, the non-linear k-ε model appears to be a useful extension to the SWASH wave-flow model. LES results for horizontal uniform flow are validated with DNS data of Moser, Kim and Mansour [12]. Especially near the bed the LES results deviate from the DNS data. The mean velocity, as well as the transverse and vertical turbulence intensities, is seriously underestimated. The deviation from the DNS data is related to the use of non- periodic boundary conditions, the coarse grid resolution, the size of the computational domain and the amount of numerical dissipation that is involved. Since it is the bottom region where secondary currents are generated, the use of the present LES code for problems involving heterogeneous roughness is not appropriate.

Hydrodynamic processes largely determine the efficacy of drinking water treatment systems, in particular disinfection systems. A lack of understanding of the hydrodynamics has resulted in suboptimal designs of these systems. The formation of unwanted disinfection-by-products and the energy consumption or use of chemicals is therefore higher than necessary. In drinking water engineering, computational fluid dynamics (CFD) is therefore increasingly applied to predict the performance of treatment installations and to optimise these installations. CFD uses advanced numerical models to predict flow, mixing and (bio)-chemical reactions. In this thesis, the hydrodynamics and (bio)-chemistry in ozone and UV systems are studied by means of CFD models combined with experimental techniques. This combination leads to further development of CFD modelling as a tool to evaluate the performance of drinking water treatment installations. If the CFD model is applied properly, accounting for the complex turbulent motions and validated by experiments, this tool leads to a better design of UV reactors, ozone systems and other systems dictated by hydrodynamics. This work resulted in new insights in the applicability of models in ozone and UV installations, and new insights in design aspects of these installations.

It has been widely recognized that ongoing climate change, most likely due to human interference with nature, may accelerate sea level rise and increase storm intensity. It is therefore urgent to design countermeasures to alleviate the impact of climate change on coastal regions. Apart from the view point of coastal protection, it is also very important for coastal engineers to keep an eye on environmental issues in the coastal region. In this context, vegetation fields such as salt marshes, sea grasses and mangrove forests in coastal regions have started to attract the attention of coastal engineers due to their function as wave attenuator. However, the wave attenuation function of a vegetated field is not well understood yet. To utilize coastal vegetation fields as a part of coastal management in practice, it is crucial to accumulate more knowledge about the physical processes, especially the hydraulic processes, and these need to be modeled in a practical sense. Hence, this thesis is intended as an investigation of the process of wave dissipation over vegetation fields through various approaches, specifically theoretical, physical and numerical studies.

Aquatic plants –or macrophytes- are an important part of coastal, estuarine and freshwater ecosystems worldwide, both from an ecological and an engineering viewpoint. Their meadows provide a wide range of ecosystem services: forming a physical protection of the shoreline, enhancing water quality and harbouring many other organisms. Unfortunately, these vegetations such as salt marshes, seagrasses or mangroves have been on the decline as a result of anthropogenic pressure and climate change, despite costly conservation and restoration efforts. The low success rate of these efforts might partially be due to a lack of understanding of the complex bio-physical interactions between plant properties, plant growth, hydro- and morphodynamics and water quality. The capability of plants to alter their abiotic environment via these interactions is referred to as ‘ecosystem engineering’. Many experimental studies, both in the field and in laboratory flumes, have been performed to unravel these interactions. Since such experiments are always hampered by practical limitations such as flume dimensions, available time, or uncontrolled conditions, this knowledge cannot always be generically applied. Therefore, the primary objective of this study is to develop a generically applicable model for feedbacks between flexible macrophytes and their physical environment. To warrant this general applicability under the various circumstances occurring in estuaries, the model development follows a process based approach; a data-orientated approach is merely applicable to known conditions. Modelling starts out on the scale of one plant to finish at the scale of a meadow. The focus is on seagrass, as seagrasses are well studied, highly flexible, have a relatively simple shape and are among the most productive as well as threatened ecosystems. The first step was to create the numerical model called ‘Dynveg’, by combining a novel dynamic plant bending model based on a Lagrangian force balance to an existing 1DV k-ε turbulence model (Chapter 2). The plant bending model is based on measurable biomechanical properties of plants: length, width, thickness, volumetric density and the elasticity modulus. Because very flexible plants can assume a position almost parallel to the flow direction, friction too needed to be incorporated rather than pressure drag alone. Flume measurements on strips of eelgrass-like proportions provided the actual values for drag- and friction coefficients, as well as validation data for predicted strip positions and forces. The effect of multiple plants on hydrodynamics was incorporated by assuming that all plants in a meadow do the same, and by defining two turbulence length scales: One for internally generated turbulence, related to the wakes behind individual stems, and one for larger eddies created in the shear layer above, penetrating the canopy depending on the space between the stems. Dynveg compared favourably with the measurements of hydrodynamic characteristics in mimicked eelgrass by Nepf & Vivoni [2000]. Next, Dynveg was combined with the large-scale hydro- and morphodynamic model Delft3D to simulate two-dimensional spatial processes in and around meadows of flexible macrophytes (Chapter 3). The leading principle for this integration is the conditional similarity between flow characteristics in flexible vegetation and those in rigid vegetation: If the rigid vegetation has i) the same height as the deflected vegetation, ii) its plant volume redistributed over the vertical accordingly and iii) a drag coefficient representative of the streamlined shape, the flow is practically analogous for a range of plant properties and hydrodynamic conditions. This modelling method was validated by comparing model results with flume experiments on two seagrass species, showing good agreement for canopy height, flow velocity profile and flow adaptation length. A field measurement campaign in a French macrotidal bay bordered by an eelgrass meadow provided validation data for application to real meadows (Chapter 5). Along with a detailed bathymetry survey by jetski, time-series of flow velocity and sediment dynamics inside a meadow and over a bare adjacent area were measured over two tidal periods. The applied sediment transport formula [van Rijn, 1993] deals with vegetation effects on sediment pick-up and transport via the effects of plants on hydrodynamics. Vegetation-specific interactions such as particle trapping by blades or flow intensification directly around shoots were not taken into account. Nevertheless, the three-dimensional numerical model was able to reproduce the main features of the observations, indicating that the processes of vegetation bending in non-stationary flow and sediment transport through vegetated areas are incorporated correctly. Thus, the objective of making a model for feedbacks between flexible macrophytes and their physical environment has been met. The model can be applied as a tool in conservation and restoration studies or in long-term biogeomorphological feedback studies. Recommended extensions are the incorporation of plant-wave interactions, more intricate plant morphologies and a vegetation-specific transport formula. The second objective of this thesis was to use the developed model(s) as a tool to learn more about biophysical interactions under different conditions. In Chapter 4, Dynveg and the two-dimensional model were used to assess the ecosystem engineering capacities of three plant species that partly co-occur in temperate intertidal areas: the stiff Spartina anglica, the short flexible seagrass Zostera noltii and the tall flexible seagrass Zostera marina. The flow velocity inside the canopy, the canopy flux and the bed shear stress were used as proxies for the species’ ability to respectively absorb hydrodynamic energy, the supply of nutrients or sediment and the ability to prevent erosion. This analysis showed that a species’ eco-engineering capacities depend on its spatial density, its size, its structural rigidity and its buoyancy, but also on environmental conditions. Therefore, biomass, leaf area index or other lumped parameters that neglect structural properties are no good generic indicators of ecosystem engineering capacities. Rigid plants have more potential to trap sediment due to a higher canopy flux than flexible plants. This canopy flux showed to be inversely related to spatial density along the entire natural range. For flexible plants, the canopy flux is only related to density in relatively sparse meadows; in denser meadows the canopy flux is constant with increasing density. Flexible plants are better at preventing erosion because they are more efficient in reducing bed shear stresses than rigid plants. For very thin plants, buoyancy is the most important determinant of position in given flow conditions. For intermediate flexible plants, the structural rigidity is the most influential parameter, whereas for (nearly) rigid plants, the spatial density is dominant. In Chapter 6, the three-dimensional model of the macrotidal bay was used to study the effects of different types of macrophytes on (residual) sediment transport and light availability. The effects of the real, relatively sparse eelgrass meadow were compared to those of a meadow with rigid plants of the same spatial density, with a dense eelgrass meadow, and with a bare bed. Though the differences between these four vegetation scenarios were small –only a few percent- the consequences on long timescales can be considerable. In deep water, sparse flexible vegetation kept more sediment inside the bay than rigid or denser plants. When vegetation only occupies a small part of the water column, plants prevent erosion rather than promote deposition and they have more effect on bed-load transport than on the transport of suspended sediment. Stiff and denser plants affect the bed-load more than sparse flexible vegetation, thereby blocking the transport from outside to inside. The presence of dense or stiff macrophytes increased the light availability at the bed over a tidal cycle up to 7% with respect to a bare bed. The increase of light availability was less pronounced for the relatively open eelgrass meadow: up to 3%. Overall, this study has resulted in a widely applicable model for the interactions between flexible aquatic plants, flow and sediment transport and in more insight in some of these interactions. Other researchers are encouraged to use this tool complementary to fieldwork and laboratory experiments, and to extend it with other functionalities, e.g. for wave attenuation or vegetation development.

In 2000 the Dutch government chose a new point of view for the Dutch rivers: “Room for the River”. This viewpoint is the basis for a new approach of high water protection in the Netherlands. Instead of strengthening and raising the dikes, solutions must be based on space and spatial quality. One of the suggested measures is the addition of secondary channels. The purpose of these channels is enlarging the conveyance area and the ecological role of the river. Maintaining the profile of these channels involves substantial financial consequences. Finding a sustainable solution for undesired erosion or sedimentation is the main focus of this study. The research question is stated as follows: “How can the undesired erosion or sedimentation in secondary channels be corrected with a temporary but sustainable solution in the form of surface screens?”. The main part of this study is an experimental study on the effects of surface screens on a mobile bed. The design of the physical experiments requires choices about the geometry of the flume. The experiments were carried out with a straight flume and with a dividing wall. Preparing the experiments requires information about the flume facility. The experiments have been carried out in the Environmental Fluid Mechanics Laboratory of DUT. The upstream boundary conditions are discharge and velocity distribution. The downstream boundary condition consisted of a fixed water level. The water level was kept constant along the natural slope of the surface. The experiments consist of taking velocity and bed level. The angle of attack and the penetration depth were chosen to be variable. The angle of attack was varied between 15 and 25 degrees. With these relatively small angles the screen acts as guidance for the flow, instead of an obstruction. The penetration depth was varied between 20% and 60% of the water column. The initial test run determined the optimal measurement duration and the initial equilibrium. Four representative cases have been described in detail, giving support to the general conclusions. The flow pattern changes under influence of the surface screen. The main flow direction is guided by the screen, introducing a transverse velocity at the surface. As flow continuity in the flume has to be maintained, the water near the bottom is forced to have a transverse velocity in opposite direction. Redistribution of the suspended transport and the bottom transport was induced. This generated locations were the actual transport did not meet the transport capacity, which gives rise to morphological changes. Next to the spiral motion the screen had an effect on the longitudinal flow velocities. The attacked side of the flume experiences a higher velocity, thereby having a higher transport capacity. This higher capacity gives rise to local erosion of the bed. At the unattacked side, sedimentation occurs, thereby rising the bed level. In the B-series of the experiment a dividing wall was added. The screen in front of the bifurcation gave rise to the same two processes, but the wall introduced an extra effect. The screen influenced the bifurcation relationship. The bed level adapted to the new conditions. The upstream effect of the bifurcation is explained by changes in water level topography, thereby influencing the backwater curve. In general the wall amplified the morphological development of the bed. Finally some suggestions have been made for the practical application of surface screens. In general the screens can be applied in a (secondary) channel or in front of a bifurcation. The use of a screen inside a channel has an advantage not to interfere with the navigation channel. The advantage of a screen in front of a bifurcation is influencing two channels simultaneously. One of the main disadvantages of the latter is the possibility of disturbing the delicate bifurcation relationship. When carefully implemented this effect can simultaneously be the main advantage of this screen layout, as the morphological response increases.

Sharks require a certain current condition in their basin for survival. The shark basin of Blijdorp zoo (Rotterdam) has been modeled in order to provide information regarding the currents in the basin and to optimize the physical environment for the sharks in the basin

The objective of the present work is to see whether the transport of sediment in a turbulent free surface flow can be studied with a new method of video image analysis, called the Two-Dimensional Particle Tracking Velocimetry. A slice of a two-dimensional turbulent flow in a laboratory flume is illuminated and particles are injected. After the recording of the illuminated particles, the video images are digitised and a software package called DigImage is used to analyse them, in order to give for each image the number of particles and their two dimensional positions and velocities. Four parameters are varied in the experiments: the diameter of the particles, the depth-averaged flow velocity, the distance between the injection and the point of observation, and the height of the injection. An analysis is then carried out in order to see the influence of these parameters on the concentration profiles and on the particles velocities. This analysis compares the measurements and the model of suspension ofparticIes by coherent structures ofturbulence (bursting phenomena). This work concludes on one hand that the Two-Dimensional Particle Tracking Velocimetry by DigImage is reliable for the study of sediment transport as long as the video recordings are of good quality. It confirms on the other hand that the concentration profiles are not described well by a diffusion model. Finally, it concludes that some measurements agree with the bursting phenomena, in particular the observation of larger downward velocities and that some other measurements are more difficult to interpret, in particular downward velocities larger than the settling velocity when the injection is near the surface and near the point of observation.

For a proper management of rivers and river bends in particular, it is important to have good models to predict the flows through bends. It is important that those developed models are well validated with measurements to demonstrate the usefulness of the models. This research is a validation of the Delft3D-FLOW model which is a model that is often used in practice. For the validation, detailed measurements of flows through a sharp bend (radius/width < 2 a 3) flume, performed at the EPFL (Lausanne, Switzerland) and Large Eddy Simulations (LES) conducted at the TU Delft are used. The objective of this study is to analyze to what extent Delft3D-FLOW is able to predict the hydrodynamic processes in sharp open channel bends. This study contains the comparison of several important quantities of Delt3D-FLOW simulations, measurements and LES

A cobble sea defence appears to be an easy constructible protection, with relatively low total costs of ownership. Flume tests show that sand under such single layered constructions is stable. However, it is not exactly known how the hydraulic loading of a breaking wave is reducing in the filter. Two datasets containing pressure measurements in a revetment were available for identification of this reduction: 1) A dataset of a test performed in the Großer Wellenkanal (Hannover), for improvement of the understanding of all relevant processes in Elastocoast revetments (obtained from the Braunschweig University of Technology). 2) A dataset of tests in the Delta Flume, for the verification and optimization of the cobble shore design of the ‘Maasvlakte 2’ (obtained from PUMA). The dataset of the Großer Wellenkanal test was analysed to increase the insight in the behaviour of pressures in a filter resulting from (breaking) waves and to explain processes and test results of the Delta Flume model tests. Hydraulic loading at the top of a revetment exist out of two types of loads; impact and non-impact loads. The impact load, resulting from plunging waves, can be distinguished in an impact peak and a quasi-static part. The impact peak is very high (>10 kPa), last for only a fraction of time (<0.2s) and reduces completely in the filter. The non-impact load and the quasi-static part of the impact load reduce less and are responsible for the hydraulic loading at the interface of sand underlying a thick, single filter layer. Although large influence was expected for turbulence generated by breaking waves it does not have an important role in the hydraulic loading that eventually reaches the interface. The parallel gradients at the interface are only the result of pressures in- and decreasing with the wave period. The maximal destabilizing perpendicular gradients are frequently accompanied by a maximal parallel gradient. The main loading mechanism at the interface results from the run-down; during run-down the largest parallel and perpendicular gradients are generated. Predicted gradients acting on the interface between gravel and sand in the Delta Flume models are higher than traditional stability criteria. Therefore, an erosion process of the sandy embankment would be expected for the tested Delta Flume models. However, erosion was not observed. The stable interface in the Delta Flume tests can thus not be explained from the pressure reduction resulting from the analysis of the measurements in the Delta Flume models itself. The damping observed in the Großer Wellenkanal and the non-distorted interface in the Delta Flume models give strong indications that the reduction observed in the gravel material of the Delta Flume models is not representative for the performance of the gravel layer, resulting in a conservative prediction of gradients at the interface of gravel and sand. Several factors could have been influencing the pressures in the revetments of the Delta Flume models and the reduction found in the analysis of the measurements.

Construction of breakwaters is performed consecutively from core layer, filter layer, up to the armour layer. During construction, excessive damage is often encountered on core layers due to environmental conditions. The damage behaviour of core layers is similar to berm breakwater structures, where the initial profile is reshaped into a more stable S-shaped profile in response to environmental loads. In addition, when breakwaters are exposed to oblique waves, longshore transport occurs due to wave force components parallel to the structure alignment. Many researchers have studied the behaviour of profile reshaping and longshore transport on berm breakwaters. Nevertheless, very little information is available about the behaviour of core materials. Most of the studies also focused on investigating the behaviour of breakwater trunks (the straight part of breakwaters), and not much is known about the behaviour of breakwater roundheads. To investigate the behaviour of berm breakwater roundheads that consist of core materials, a physical model was performed in the Hydraulic Laboratory at Delft University of Technology. The model is exposed to two different wave loads (H_s=8 cm;10 cm); two different stones grading, which is narrow (D_n85⁄(D_n15=1.3)), and wide grading (D_n85⁄(D_n15=6)); and three different wave obliquities (0°, 30°, and 45°). In total, twelve tests were performed based on a combination of the above mentioned parameters. During the tests, the data and profile changes were measured using laser profiling, video recording, and manual measurements. The result of laser profiling is then processed using MATLAB software to obtain 3-Dimensional plots that represent the breakwater models. Based on the 3-dimensional plots, the analysis of profile reshaping and longshore transport could be performed. Several profile reshaping parameters, such as crest recession length (Rec), crest length (l_c), step length (l_s), crest height (h_c), step height (h_s), and slope below crest (θ_3) were measured and then compared with the calculated values using existing design formulas. The measured values in roundheads were also compared to the measured values in trunk sections. The effect of stone grading, wave loads, and wave obliquity were also investigated. Finally, a model to calculate the longshore transport on berm breakwater roundheads is proposed.

During the construction of breakwaters contractors often encounter undesired reshaping of exposed core material. This reshaping is comparable to the deformation process of berm breakwaters in which the outer profile reshapes into a more stable s-curve. In the case of oblique waves this deformation is enhanced by a longshore transport of stones leading to even more loss of material and damage. Throughout the years few formulas were derived for both processes which describe the behaviour of berm breakwaters as well as gravel beaches reasonably well. These formulas however turned out to be inadequate when it comes to describing the behaviour of core material. In particular the influence of the wide grading of quarry run, commonly used as core material, is to a large extent unknown and generally not described in the available relations. To investigate this influence of the stone grading on both the two-dimensional deformation and longshore transport new physical model tests were carried out in the wave basin at Delft University of Technology. In total 12 tests were executed in which two different gradings, three different angles of wave attack and two different wave spectra were tested. Data collected from the tests included wave and profile measurements together with the displacements of stones, originating from two colour beams which were applied in the middle of the trunk. These data along with visual observations eventually led to a conceptual model describing stone movements in both transverse and longshore direction. Using Matlab three-dimensional profile and erosion models were generated from which the different profile parameters were determined. With respect to the distance from origin, for each test an exponential relation was derived to describe the stone displacements. After determination of the area of uniform transport these exponential relations were used to calculate the total longshore transport by means of extrapolation and multiple integrations. Subsequently all parameters found were compared to the formulas currently available for both processes. Regarding the deformation parameters the test results produced the best fit with the formulas derived in [MERLI 2009]. Still on several occasions a deviant relation was found concerning the influence of wave obliquity. In addition, the formulas became less accurate for the narrow grading used in the tests, which fell outside the range tested by Merli. However, for the crest height of the deformed profile test results deviated completely from the available formula as no influence was found whatsoever for all tested parameters. Here the deviation was contributed to a higher instability of the part above the initial deformation, partly due to the steepness of the slope. On the subject of the longshore transport clear trends were found describing the influence of the varying parameters. Both a higher wave load and wider grading lead to an increase of the longshore transport. For the wider grading, however, this increase gave a rather distorted image, as not all fractions in the mixture were transported evenly. Due to segregation the coarsest fractions were mostly transported in the transverse direction while the finer fractions were transported further away in the longitudinal direction. Alternatively, computation of the longshore volume transport proved to be more representative. Regarding the effect of wave obliquity an increase in angle of wave attack of 30 to 45 degrees was accompanied by a decrease in longshore transport; though this decrease was less than already available formulas indicated. However despite the fact that it describes a completely different trend concerning this particular influence, the best fit was found after multiplying the relation derived by [ALIKHANI 1996] with a factor 100.

During the winter 2009, beach and dune nourishments have been executed at Vlugtenburg (Holland coast) in order to reinforce the coastal defense. Natural processes such as wind and waves are expected to take care of effective and efficient redistribution of the sand throughout the system. The present study is part of the sub-project Monitoring Program Delfland Coast which main goal is to provide measurement data for process-based modeling of the interactions between the foreshore and the dunes. Based on field measurement realized in November 2009, this MSc thesis aims to find an efficient procedure to monitor the aeolian transport (transport by the wind) of sediment over a beach. These measurements involved innovative devices and methods. Four saltiphones were deployed at different locations on the beach. A forced deposition area was build up and the deposited volumes were monitored using a laser scanner. An analysis of the problems to use formulas derived from wind tunnel experiments in the modeling of transport on the field is carried out. It is followed by the derivation of a model describing the relation between the transport measured with saltiphones and the wind speed for specific conditions. However, no relation is derived between the transport measured with saltiphones and volumes transported and an extrapolation of the model to the whole beach remains incomplete. Finally, the existences of a fetch effect and a cross-shore decrease of the transport are measured, though not accurately quantified.

Due to the planned construction of Maasvlakte 2 the E.ON power plant on the Maasvlakte will not discharge its heated water into the North Sea anymore, but in the harbour basins itself. This together with a planned increase of the total amount of thermal discharges in the Maasvlakte area (power plants of EnecoGen and Electrabel, chemical industry etc.) will most probably lead to an increase of the water temperature within the harbour basins, which can lead to economical, legal and ecological consequences. In cooperation with the Port of Rotterdam and Deltares, this master thesis aimed to give an answer to the amount of increase of water temperature due to the planned thermal discharges, its consequences and measures to reduce this increase of temperature. With the use of some first estimates and a heat-balance there could be concluded that the increase of temperature is significant and that the movement of the tide together with the freshwater flux is the main mechanism for the netto heat flux out of the Maasvlakte area. Stratification has an important influence on the spreading of the heat plumes in the harbours. To give a more accurate prediction of the increase of water temperature at the mixing zone borders and at the intake locations (recirculation), the numerical hydrostatic model Delft3D-FLOW and the near-field model CORMIX are used. It is shown that the regulations will not be exceeded if the borders of the mixing zones are chosen close to the Beerkanaal. The predicted increase of temperature at the E.ON-intake will cause some economical losses. Replacing the intake at a greater depth or (even better) a variable intake near the water surface and bottom could be effective measures to reduce these losses. For a more drastic reduction of the increase of temperature in the harbour basins, relative expensive measures are needed. It is recommended to the Port of Rotterdam to place future thermal discharges as close as possible near the Beerkanaal or North Sea, and to study the ecological effects of the temperature rise in the Eastern Yangtzehaven.

The overtopping empirical formulas calculate the discharge only at the top of the crest of a coastal protection structure. On the other hand, the tolerable overtopping discharges are defined at certain points behind the crest where the total overtopping is reduced. The scope of this thesis is to find an empirical formula to describe the distribution of overtopping at the space behind the crest. This thesis comes as a further investigation on the work conducted by v.Kester [2009] for regular waves. In this research, a physical model was developed on which irregular waves are tested. Because of the duration of the tests and the amount of collected water (significant lose of water during the test), a completely new measuring system was designed. Five influencing parameters (variables) are considered on this research: wave height, wave period/steepness, slope angle, crest freeboard and crest permeability. The entire overtopping process is analysed separately for the total overtopping discharge, the overtopping discharge directly behind the crest and the distribution of overtopping behind the structure. In the analysis of the data collected from the measurements, the impact of the varying parameters is investigated leading to useful conclusions and better understanding of the entire process. Additionally, the experimental findings are analysed and compared to the relative existing methods. Based on the TAW [2002] method which is proposed by the EurOtop Manual [2007], a prediction formula is developed. This formula is a generic version of TAW [2002] formula in which a new reduction factor γc is introduced in order to describe the decay of the overtopping and thus predict the discharge at any certain distance behind the crest. Other relevant methods are also analysed (Juul Jensen [1984], Steenaard [2002], Besley [1999] and v.Kester [2009]) and conclusions for their applicability are drawn leading to suggested improvements or corrections. Apart from the distribution of overtopping, on this thesis the determination of crest freeboard (which is an ambiguous issue) is also investigated. Finally, suggestions of further research on this topic are discussed. The entire work has been perfomed in close cooperation with van Oord.