Accurately predicting wave-induced forces plays an important role in ship design. Currently, pressure integration is the standard method for calculating wave-induced forces from panel methods. For Computational Fluid Dynamics (CFD) and experiments, it is not even possible to separate the wave-induced forces from the viscous forces. Pressure integration is limited by discretization, which can compromise the accuracy of the results. Wave pattern analysis offers an alternative by calculating wave-induced forces from the far-field wave elevation, thereby reducing the influence of discretization.

The transverse wave cut method (TWC) uses wave elevation measured along a single line perpendicular to the ship's path. Previous research has demonstrated that wave resistance can be determined using this method. Since only wave elevation data is necessary, wave resistance could even be calculated from experimental data.

No effort has been made yet to extend this method to calculate wave-induced side forces. This research investigates whether side forces can be accurately determined using the TWC method and evaluates its performance against conventional pressure integration in panel methods and CFD simulations.

The TWC method is derived from the conservation of momentum around the ship hull. The method applies a Fourier transform to the measured wave elevation to determine the free wave spectrum, which describes the wave field as a superposition of individual wave components. By reformulating the final expression, it is shown that the same spectral coefficients used to calculate the wave resistance can also be used to determine the wave-induced side force, without requiring any additional measurements or calculations.

The TWC method was compared with pressure integration results for a submerged spheroid using a panel method. Multiple test cases were considered, all of which showed good agreement between the two approaches. The TWC method was therefore successfully validated for calculating wave-induced side forces.

By plotting the free wave spectrum, the contributions of individual wave components at different propagation angles can be observed. As expected, the wave resistance was found to be dominated by the transverse wave components, while the side force was caused almost entirely by the diverging wave system.

In CFD simulations, the cell size strongly influences the quality of the simulated wave pattern. Coarser meshes introduce more numerical damping, causing the wave pattern to decay faster than physically expected. This was confirmed by evaluating the TWC method at multiple longitudinal locations, where the decay rate was extracted and compared across refinement levels. The numerical damping prevented accurate force predictions. However, the TWC method proved to be a useful diagnostic tool, providing a quantitative measure of wave decay and indicating the quality of the simulation.

Overall, the TWC method can accurately predict wave-induced side forces from a simulated wave field, showing good agreement with pressure integration for panel method results. In CFD simulations, its accuracy is limited by mesh resolution and numerical dissipation, but it can still be used as a diagnostic tool. ... Read more

The expansion of floating offshore wind energy into deeper waters requires suitable anchoring solutions, for which IQIP has developed a specialized 170 t subsea piling rig. A critical phase in deploying this system is the lowering operation through the water column to the seabed, which introduces significant operational risks, most notably damaging snap loads resulting from temporary line slack. This occurs when the installation vessel's downward motion exceeds the rig's descent speed. The hydrodynamic behavior of the rig's large mudmat (foundation plate) is complex and creates substantial resistance.
The objective of this thesis was to quantify how the rig's specific shape affects its vertical oscillatory motion and to identify slack-inducing conditions in a given sea state. The hydrodynamic response of the rig and resulting line tensions were investigated using time-domain simulations in OrcaFlex, focusing on the deep submergence and positioning/landing phases. A representative Service Operation Vessel (SOV) was modeled using Response Amplitude Operators (RAOs), and the mudmat was treated using a heave-plate analogy with coefficients derived for low oscillation movements.
Three distinct operational scenarios were analyzed to capture the varying physics of the descent:
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Unbounded Deep-Water Region (Mid-water Transit): In this regime, where the mudmat is sufficiently far from both the surface and the seabed, the rig behaved with stable hydrodynamic forces. Simulations showed that slack events were present but infrequent.
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Near-Seabed Region: The rig's response when positioned close to the seabed was drastically different. Flow confinement amplified both added mass and damping significantly. This caused the slack probability to increase drastically compared to the unbounded case, consistent with the confinement-dominated regime.
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Passive Suction Release: Uncontrolled suction release at the maximum upward vessel movement (heave crest) was found to trigger an immediate, full slack event. The sudden release of stored elastic energy in the lifting line caused the mudmat to shoot upward, leading to a complete loss of line tension even before the vessel began its downward motion.
Based on these findings, operational conclusions emphasize the need for caution. The increased hydrodynamic resistance near the seabed makes the system prone to slack, indicating that the rig should be lifted far away from the seabed before horizontal repositioning. Furthermore, controlled or gradual suction venting is essential, preferably timed near a point of neutral vertical vessel movement, to prevent the severe dynamic snap loads associated with sudden suction failure. Future modeling should incorporate porous boundary conditions using suitable open source potential flow solvers and dedicated experiments to better capture complex flow interactions. ... Read more

There is a lack of knowledge on the hydrodynamic behaviour of an AdBm Noise Mitigation System (NMS) designed to reduce sound during monopile piling, which is relevant for improving design and safety. The NMS contains panels designed to mitigate underwater noise. Model tests were performed on both an actual AdBm panel and geometry-based perforated panels, and hydrodynamic coefficients in the form of added mass (C_a), drag (C_d), and linear damping (C_b) were determined for the heave and surge directions, improving the understanding of hydrodynamic loads on the NMS.

Experiments were conducted in the Towing Tank No. 2 at TU Delft, where both forced oscillation and wave tests were performed with test conditions based on regular environmental waves. The hydrodynamic coefficients in heave and surge have been determined and show that the nondimensional Keulegan-Carpenter number (KC) is the most dominant parameter, which leads to the coefficients being expressed as functions of KC. Tests were performed with a single panel and three panels in series to study interaction effects. The main findings showed a significant decrease in C_d and C_b up to 70% within the tested KC range using panels in series, resulting in lower hydrodynamic loads compared to using a single panel. Furthermore, the results of the forced oscillation and wave tests were compared. The hydrodynamic coefficients were found to be similar for low KC values, but the forced oscillation results increasingly overestimated the hydrodynamic coefficient values as KC increased. However, the range of comparison was constrained due to limitations in the wave maker capabilities. The findings contribute to a better understanding of the hydrodynamic loads on the perforated models that reduce the knowledge gap of the hydrodynamic behaviour of the NMS, providing a basis for improving the design parameters for the deployment system.
... Read more

Over the past years tugs are evolving to more compact designs equipped with large power installations. This inherently increases the risk of accidents, demanding a more reliable prediction of the tug’s dynamical behaviour in critical situations. To capture the dynamic behaviour of a tug, a time domain simulation tool has been developed and used to evaluate the tug’s safety in those critical situations. Multiple methods derived from recent studies are combined and used to establish a reliable description of the involved hydrodynamic forces and moments. Besides a sensitivity study is performed to investigate the impact of inaccurate approximations of those forces and moments. Furthermore, the sensitivity to a change in more design and operation related parameters has been investigated. Finally, the research includes a step by step validation and an evaluation of the current regulations. ... Read more

This work is focusing on the 2020 IMO sulphur regulation and its impact on the shipping industry and more particularly Fednav’s activity. The thesis report presents a holistic approach starting with IMO emission regulations including current and future. The thesis is then moving on to Fednav business characteristic followed by the possible solutions to successfully implement the 2020 IMO sulphur regulation and stay competitive. These solutions are shortlisted to LNG and scrubber as they are the only mature technologies already implemented in the industry. They are then analyzed using both a private and welfare cost & benefit analysis to evaluate LNF and scrubber systems economic feasibility from a business and society perspective. LNG is discarded based on low bunker availability worldwide in combination with Fednav’s fleet tramping sailing patterns. For the scrubber, the opened loop solution is selected as the one offering the best return on invest- ment. After the welfare cost & benefit analysis, all scrubber solutions are also discarded because of the low pH washwater dump in the ocean. The strategy for Fednav is to make sure Canada is strict on sulphur regulation, mitigate bunker sensibility risk as well as bunker quality risk. ... Read more

In dredging there are a lot of opportunities to improve the production processes and to make the production cycle more efficient, especially the excavation process of the draghead. The aim of this research is to determine the trailing forces and to estimate the production of the draghead. Besides that, the goal is to get more insight into how the draghead behaves, depending on the trailing velocities. The variations in the trailing velocities, soil characteristics, control settings and draghead and suction pipe geometries that can occur do not make it easy to determine the trailing forces on the draghead and suction pipe. Because of this complexity, it is also hard to define how to estimate the production. Therefore, the scope of this research is limited to just one sand type with specific soil characteristics.

An analysis of the draghead and the suction pipe, with a freely suspended visor, showed the physical processes in and around the whole suction pipe system. Because the draghead is fixed to the suction pipe, the influence of suction pipe on the draghead is analysed first. After that, the draghead is divided into two parts, the visor and the visor house. With the use of force and moment balances the trailing forces are determined for every trailing velocity. In addition, the production and its production limits are defined.

The calculations show that the increase of the trailing velocity results in higher trailing forces on the suction pipe and draghead. For a velocity of around 2 m/s the draghead, for a Damen SLK600 used in the case study, will lift of from the bed. It should be notified that, among other variables, the dredging depth has an effect on this ‘floating’ point. Moreover, the results showed that the drag forces at common trailing velocities of 1-2 m/s are relatively low compared to the soil excavation forces and therefore have a small share in the total trailing forces. When the suction pipe system is trailed against the current the dragforce becomes more significant.

The interaction of the draghead with the bed causes several processes to take place. The resulting relevant trailing forces are mapped and determined. The settlement of the draghead causes a hump of sand to be pushed forwards which result in a sled force and a friction force. Besides that, the flow through the pipes will cause impulse forces in the bends and at the end of the jet pipe out of the nozzle. The jets fluidize the sand which results in the largest production contribution. Furthermore, it can be seen that the penetration depth and cavity width of the jets depend on the trailing velocity and determine the amount of sand that is loosened. The cavities can overlap at low trailing velocities, resulting in a jet production limit.

The jets have a significant influence on the behaviour of the visor. The freely suspended visor will drop until a solid bed layer is reached. The cutting force and vacuum force are the dominant forces working on the visor. Application of the equilibrium-moment method showed that the visor is slowly moving upwards when the trailing velocity is increased. However, the cutting layer thickness remains almost constant for an increasing trailing velocity which results in a linear increase of the cutting production. The cutting production contributes, 20-25%, to the total situ production. The total jet and cutting production lead, together with the jet water inserted and ambient water flow, to the total production and mixture density. When the capacity of the dredging pump is insufficient, spillage will occur.

This research shows the best possible estimate of the draghead production and corresponding trailing forces. It should be kept in mind that the calculations are based on a simplification of the suction pipe system and the geometries of the suction pipe system of Damen. Nevertheless, a lot of research can be performed into the processes that occur, to improve the results of the calculations. Suggestions for further research would be to determine the magnitude of the vacuum force, the erosion production which is not considered in this research or the on velocity depending cavity width. Validations of the results is another point of consideration. Thus, to determine trailing forces and production, the new approach used in this study contributes to a better understanding of the draghead.
... Read more

Spliethoff is a ship-operating company with around 120 cargo vessels under management.
The vessels of Spliethoff are generating a lot of operational data as they sail around the globe. To make better decisions based on this data, a system is required that takes operational data and translates it to useful information, accessible in the offce and on the ship through online dashboards. Ultimately, better informed decision making should lead to cost minimisation in the areas of fuel consumption and maintenance. In this research a Ship Performance Monitoring System (SPM System) for operational data of Spliethoff's vessels was developed, after which data analysis was performed with the goal to minimise
operational cost of the vessels.
The SPM System was developed using a Rapid Prototyping methodology. By conducting decision support analysis, data requirements analysis and user requirements analysis, Key Performance Indicators (KPIs) for the system were established and coupled to endusers.
In general, one can state that when developing new information systems, end-user involvement is key. If end-users are not involved from the start, interest will be low, resulting in limited added value.
Using the SPM System, data analysis was performed targeting a number of key questions with regards to fuel efficiency, maintenance and ship operation.
Firstly, from the data analysis it can be concluded that for a Spliethoff S-Type vessel the most fuel efficient speed is 14 knots, both in laden and unladen condition. It is recommended to implement this speed for all voyages where the schedule allows it. Accurate implementation of this speed optimum could result in bunker cost savings of up to 10% over a voyage.
Regarding engine efficiency, the specific fuel consumption (SFC) of the main engines of all three vessels is worse than the specifications given by the engine manufacturer. This is according to expectation, given the fact that manufacturers specifications are attained at different conditions. The development of SFC over time showed that the main engine
maintenance schedule currently employed is working effectively, so it is advised to continue in the same manner.
Hull and propeller fouling negatively in uence fuel consumption and speed of a ship. In the data analysis different trends are found regarding fouling. Therefore is is recommended to prolong the measuring period to at least a year before drawing any conclusions. If after a year a fuel consumption increase in the region of 5% is measured, it is advised to increase hull cleaning frequency to once every year. Regardless of any measured fouling increase, it is recommended to inspect the hull of all vessels at least twice a year to increase knowledge of fouling.
A ship's crew is of large in uence on the operational cost of a ship. Consequently,
more intensive collaboration between office and ship on the vessel's operation is suggested, using data in a supporting role. Training crew for correct use of onboard decision support systems and giving feedback on performance will build awareness among crew and increase fuel efficiency.
The SPM System can be improved by installing thrust sensors on the vessels. Implementing a newer correction method for wave added resistance will also enhance the system significantly. Thirdly, it is recommended to reduce dependence on manually entered data to a minimum, due to the inherent inaccuracy of manual input. Finally, matching data quality of all different data sources will increase the precision of the system. In general, the biggest challenge for Spliethoff is to create a company culture where decision making
is data-driven. This will yield the biggest benefits. ... Read more

In the last couple of decades, Arctic Engineering has become a topic of interest. There are still plenty rooms of research to understand the unique characteristic of sea ice, especially in relation to offshore engineering. This includes the most fundamental problem in floating body motion analysis: the radiation-diffraction problem. A powerful mathematical concept, - so called Greens Function – is one of the favourable tools to be used for solving this mathematical problem. This is because the radiation-diffraction problem can be formulated as a boundary value problem expressed by partial differential equations. Although the application is already quite advanced for the open water case, the same cannot be said for the vessel operating in ice infested waters. The integral solution of 3D Greens Function for ice-infested waters which has not been studied before, was derived in this thesis. The open water case is also studied to gain more insight in the implementation of an arbitrary floating body thoroughly. As a closure, interpretation about the difference between open and ice-infested waters is discussed.

For Greens Function in the open water case, numerical evaluation of the principal value integral is not straightforward due to the hyperbolic term inside the integrand. This term makes the integrand exceed the limit of floating point number (in MATLAB) and cannot be evaluated into infinity. On the other hand, a numerical integration is quite time consuming (whereas the analytical solution, as far as the writer’s concern, is not found yet). A well-known alternative form of the solution which formulated as an infinite series might improve the computation speed. The rate of convergence depends solely on the ratio of horizontal distance between source and field point (R) and water depth (H). Another numerical issue arises in the deep water case. A finite water depth causes a catastrophic cancellation, both for the integral and the infinite series solution, due to the extremely small difference of the wave number between deep water and infinite water depth. This is where the infinite depth solution needs to be used.

In numerical implementation, an influence function at a panel can be approximated by multiplying the potential with panel's surface area. Due to the singularity of the Rankine source term in the integral or the modified Bessel function in the series, this approach fails and the solution need to be integrated over the panel. Although the analytical solution is available, a numerical approach is chosen to simplify the problem. The surface integration procedure can be done by transforming the global arbitrary panel orientation into the local element coordinate system, and subsequently, perform a bilinear mapping to reshape the quadrilateral panel into the desired rectangular panel. This transformation procedure is needed since MATLAB is only capable to handle double numerical integration of a function bounded between four lines perpendicularly each other. This encloses the whole challenge that needs to be addressed and might be re-occur in the ice-infested waters as well.

From the derivation of the Greens Function for ice-infested waters, it is shown that the hyperbolic term inside the integrand is present. This discloses that the obtained solutions cannot be used instantaneously. Another effort to rewrite them in the exponential term might be useful. Moreover, the radiation condition is not satisfied yet in this thesis. However, the suggested approach of the derivation by introducing an imaginary line to represent the source depth location avoids the use of a singular term. Generally speaking, this thesis initiates a promising foundation for further research in the hydromechanics analysis of sea ice. ... Read more

The suitability of the MoorMasterTM system by Cavotec MSL in inland shipping is researched. It is an innovative mooring system using vacuum pads with active motion control, utilising a PID controller. A case study of a 110m Large Rhine vessel moored directly beside the Amsterdam-Rijnkanaal (ARK) is performed. In order for the system to be suitable, the ship motions have to remain within certain mooring criteria, while passing vessels should not have to reduce speed. The forces on the moored vessel caused by the passing vessels are simulated using ROPES, a numerical method based on a 3D flow model, using the panel method. Three different passing vessels at three different passing distances are simulated. All passing vessels are simulated to sail at the maximum allowed speed in the ARK. Next, the manoeuvring model is used to set up the equations of motion of the moored vessel. The external force consists of the forces calculated in the Ropes simulations and the modelled forces of the MoorMasterTM units. Solving these equations results in the ship motions. ... Read more

In this thesis I present a novel discretization procedure which combines two relatively new technologies for solving partial di_erential equations (PDE's): IsoGeometric Analysis (IGA) is a new paradigm which provides an exact geometry description and tight integration of Computer Aided Design (CAD) and Finite Element Analysis (FEA) by using the same basis for representation of the unknown _eld variables as is used for describing the geometry in CAD. Mimetic Discretization Methods on the other hand combine concepts from the Finite Element Method (FEM) and the Finite Volume Method (FVM) and provide a uni_ed and straightforward approach to model any physical _eld problem. Mimetic Methods aim at preserving as much as possible the structure of a PDE by 'mimicking' at the discrete level, important properties of the continuous realm, such that symmetries and conserved quantities are preserved. Central in this framework is the relation between physics and geometry. The Mimetic Discretization approach developed in this thesis is based upon B-splines1 for representing the unknown _eld variables. Besides inheriting all advantages from the IsoGeometric Analysis framework, B-splines appear as a natural basis for Mimetic Discretization Methods. They can be seen as higher order Whitney forms and provide vector spaces which are discretely conservative by construction. The resulting discretization approach resembles a Finite Volume Method on a staggered grid for the representation of the conservation laws and a Finite Element Method for the representation of the constitutive equations. In short, the scheme features the following advantages, - exact geometry description and tight integration with CAD; - fundamentally a higher order approach, featuring spectral like convergence. In practice though, IGA is con_ned to low or medium order due to bad conditioning of inner product mass matrices as a function of the polynomial order; - increased continuity resulting in continuous representations of _eld variables and derivatives; - a strong indication exists that these methods automatically meet the inf-sup conditions, leading to naturally stable discretizations of any physical problem; - local conservation of primal variables (strong) and secondary variables (weak); - in contrast to FVM and FEM which describe variables only locally, the Mimetic discretization is induced with a global topology which makes it possible to make useful decompositions of _eld variables. ... Read more