A variation study is conducted in which the tunnel width and depth are varied to envisage the effect on the required propulsion power and the longitudinal position of buoyancy. The propulsion power is calculated using a combined RANS - BEM model. Furthermore, the propeller is evaluated using different design difficulty indices.

Engineering has become more and more optimisation and simulation based. This causes an increase in the use of optimisation methods for complex problems. This thesis focuses on the implementation of a surrogate-assisted optimisation method for propeller optimisation, to design a better propeller in a shorter timespan. Therewith reducing both: computational expenses, and fuel consumption when a propeller has been built. This thesis tries to reach two objectives: The first goal is to implement a surrogate-assisted method for propeller optimisation. The other objective is to design a propeller for both propulsive as well as for regenerative operations. To succeed, this thesis has been limited to the testing and coupling of SAMO-COBRA (A Fast Surrogate Assisted Constrained Multi-objective Optimization Algorithm) with PropArt. The testing has been based on benchmark tests where SAMO-COBRA was tested against CMOPSO and NSGA-II (the two algorithms that MARIN currently uses for propeller optimisation). Here, SAMO-COBRA outperformed NSGA-II and CMOPSO on over half of the test cases and is therefore considered for the rest of the research. The thesis evaluates propellers using a Boundary Element Momentum theory, which is a mathematical method that is the basis of MARINs in-house propeller tool PROCAL. To be able to model propellers that operate at high J values correctly certain improvements regarding the wake expansion and alignment have been made. For the wake expansion three methods are proposed. After comparing the open water diagram of a F4-63-0.6 propeller, that is evaluated by PROCAL, and the one that was made after physical testing. It can be concluded that the disk theory is the most versatile implementation for propellers that operate at a range of advance ratio. Results show that from the two proposed methods, the method where the wake pitch is prescribed by the advance ratio results in the best wake alignment. The test case optimises 3 configurations, two separate designs, one for propulsion and one for regeneration. A normal CPP that is loaded under a negative angle of attack for regeneration and a propeller that can be fully reversed for regenerative operations (the propeller is loaded from the trailing edge in regeneration). The propeller is optimised to reach a maximum regenerative power whilst minimising the propulsive power. The optimum propeller has to satisfy multiple constraints based on cavitational-, geometrical- and separation of flow constraints. The optimisation using SAMO-COBRA did not yield feasible results for any of the three cases. After removing the cavitational constraints a new analysis of the results has been done, it is found that a propeller that is rotated 180 degrees can provide the highest regenerative power. This thesis proposes multiple hypotheses that cause the lack of feasible results of the test case. The proposed causes are: errors in the PropArt model, problems in the compiled PropArt version or a too low convergence level of COBYLA.

The awareness of the impact of air pollution on global climate change is more and more growing in society. The urgency to make ships more eco-friendly captures the interest of shipowners and naval architects. Hull designs of a ship, with regard to minimum fuel consumption have been optimized in the last decades and it has been proven difficult to improve current hull forms. Another strategy is to reduce fuel consumption by using external wind power combined with engine power, so called 'wind-assisted propulsion' or 'motor-sailing'. The potential of an extraordinary high lifting device of a mechanical sail using aspiration power, known as a 'Turbosail' introduced by Jacques Cousteau [1], has been selected as wind propulsion for an existing cargo ship. This foil can generate about 3 times higher lift compared to conventional foils, which do not use active suction of the boundary layer. Similar to the concept of a velocity prediction program for sailing yachts, a fuel prediction program (FPP) is set up to visualize the fuel savings for all wind directions relative to the vessel. For a wind force 7 Beaufort, the fuel savings for optimal wind angle can reach up to 40%, which are enormous. The working mechanism of the Turbosail is further explored and examined with CFD using ReFRESCO [38], to see if the performance of the Turbosail is as high as reported by Cousteau. Steady and unsteady RANS simulations are conducted for infinite span Turbosail using the k-ω SST turbulence model of Menter [32]. As a verification study, an expansion of two other turbulence models are included, which are the  k-ω SST-LCTM model of Langtry et al [30] and the EARSM model for a more anisotropic flow accounting for Reynolds stresses. The difference between all turbulence models appeared to be small, and a fair agreement is found with the lift and drag coefficients found by experiments of Cousteau. A steady RANS simulation has been conducted at model scale for a finite Turbosail to calculate the lift, drag and aspiration power. The distribution of air suction along the span of the foil is visualized, which gives insight for the real experiments. During this study, a Turbosail at model scale 1:2 is built with a span height of 5.5 metres and a chord length of 1 metre. The comparison with CFD is therefore very useful for validation. As a final step, the lift and drag coefficients found from the numerical result are implemented in the FPP. The fuel savings from the FPP are analysed by placing four full scale Turbosails on an existing cargo ship. In this model, there has been accounted for aspiration power needed for the boundary layer suction. Hydrodynamic forces due to leeway of the hull and rudder, propeller efficiency and specific fuel oil consumption of the engine.

Tip vortex cavitation around the marine propeller is the primary source of the underwater noises emitted by ships. Investigating the tip vortex inception is important to understand the aforementioned side effect. The water quality, highly related to the bubbles population, surrounding the tip vortex is crucial to the tip vortex cavitation inception. This research explores how bubble moves around the tip vortex and investigates its background mechanisms. A one-way coupled Lagrangian bubble tracking model is applied to the Lamb-Oseen vortex and the hydrofoil tip vortex flow field, where the tip vortex is simulated with an open-usage CFD software, ReFRESCO. A series of capture time models have been developed by exploiting the bubble force (acceleration) balance in the Lamb-Oseen vortex to identify the crucial parameters. The other aspect of the acceleration analysis reflects the role of the lift force as the system's stabilizer, which has long been ignored. In the CFD tip vortex flow simulation, the bubble population evolution is investigated from upstream to downstream. Several kinds of bubble behaviors around the tip vortex flow have been identified via the numerical simulation, and simplified models based on the bubble force analysis have been proposed in order to explain them. Mainly due to the stagnation bubble events, clustering of large bubbles has been discovered a short distance downstream of the foil tip, implying that this may be a possible hotspot for tip vortex cavitation inception. The stagnation bubble phenomenon still needs to be further investigated, particularly in terms of quantifying its dependence on various flow parameters. The results also need to be rigorously validated which has not been possible as of yet due to insufficient measurement data. Still, this research manages to explore the bubble motion around the tip vortex and their fundamental mechanism.

While the awareness of global warming rises, transport over sea remains a large contributor to green house gas emissions. New regulations imposed by the International Maritime Organization (IMO) aim to reduce the emission of green house gasses. Consequently, ship owners turn to technological solutions in order to achieve this. The Ventifoil from Econowind is a promising device in the field of Wind Assisted Ship Propulsion (WASP). By applying boundary layer suction, this airfoil shaped profile can generate large aerodynamic forces, which are used as additional propulsion to reduce fuel consumption. Often multiple devices are installed on the deck of a vessel. Literature shows that the aerodynamic interaction between multiple airfoils can significantly influence the local flow conditions in which each individual device operates. Nonetheless, literature agrees that it is possible to mitigate detrimental effects by adapting to the local conditions. The operational guideline of the Ventifoils are based on the far-field wind conditions. Consequently, aerodynamic interaction between Ventifoils is not considered. This leads to the main research question: "To what extend does aerodynamic interaction between two Ventifoils mutually affect aerodynamic performance?". This thesis aims to analyse aerodynamic interaction using a numerical Lifting Line Model (LLM). This method has the potential of evaluating a broad range of operational and environmental conditions in limited computational time. Aerodynamic interaction between two Ventifoils will be evaluated over a range of apparent wind angles between 0◦ and 180◦, for two different absolute distances. The results fromthe LLM will be validated by means of three dimensional, steady Reynolds Averaged Navier Stokes (RANS) simulations. Five different interaction components will be analysed, being; changes in flow angle, changes in flow velocity, viscous interaction, pressure field interaction, and boundary layer suction interaction. The results reveal that aerodynamic interaction can reduce the lift and drag coefficients by multiple tens of percentages. It is found that the reduction ratio of the thrust force coefficient, CX, varies between −16% and −1% relative to a single isolated Ventifoil. The magnitude is mainly depending on the relative position of the devices. It is concluded that the interaction is most significant if the devices are positioned closely near each other and parallel to the flow direction. Both methods show good qualitative agreement. It is concluded that discrepancies in the magnitude of reduction ratios can be attributed to modelling differences in terms of viscosity, pressure fields and boundary layer suction. Better quantitative agreement is found for larger absolute distances. The LLM is furthermore used to maximize CX by optimizing the angle of attack of each Ventifoil independently. The resulting increase in CX showed to be between +5% and +11% added to the non-optimized reduction ratio.

The main goal of this master thesis is to reproduce by CFD computations the characteristic cavitation dynamics in a venturi which were experimentally discovered at TU Delft by Jahangir and al. The different cavitation regimes were obtained by modifying the global static pressure and flow velocity in the flow loop. Based on this, three different cloud cavitation shedding regimes were identified. One of the mechanisms appears at high cavitation number and can be attributed to the presence of a re-entrant liquid jet. Another dominant shedding mechanism was found at lower cavitation number, with the presence of propagating bubbly shock waves. A transition regime was also observed where both mechanisms seem to coexist. A two phases flow model is implemented in the open-source software OpenFOAM. The transition regime from the bubbly shock to the re-entrant jet dominated regime will be identified and compared to experimental findings. The three cavitation shedding regimes will be investigated by using different cavitation numbers. The simulations will mostly be conducted using an inviscid and incompressible solver.

The shipping industry is forced to reduce its emissions and underwater radiated noise in order to decrease the impact on the environment and limit global warming. Moreover, a low acoustic signature can be lifesaving for a navy ship, especially during submarine on mine threats. To be able to operate as flexible as possible under these threats, a flexible propulsion plant is required. A diesel engine with a controllable pitch propeller (CPP) is contributing to this. A method to reduce the emissions and noise of such a plant is to improve the control strategy. Often this is tested with numerical models. However, frequently they contain many simplifications of reality, for example, the neglection of several hydrodynamic effects. Hardware In the Loop (HIL) takes these effects into account by replacing a software part of the model with a hardware component. In this research, the CPP is the scaled hardware part. A feasibility study is performed to determine whether a propeller open water HIL setup can be used to simulate the dynamic behaviour of the propulsion plant. Therefore, a comparison is made between full and model scale numerical simulation of a diesel engine with a CPP controlled by adaptive pitch control (APC). To reduce the pitch actuations with the APC strategy a Kalman filterwith deadband is implemented. Full-scale simulations with irregular waves demonstrated that the pitch actuations could be reduced during acceleration and at a constant speed. The validated full-scale model is Froude scaled and implemented in a model of the open water HIL setup. The results of the full and model scale simulations are very similar. Thus, the HIL setup can be used to simulate the dynamic behaviour of a propulsion plant. However, the hardware limitations such as the backlash in the CPP blades, the low sample rate of the actual pitch and the Froude dissimilarity of the acceleration of the towing tank need to be resolved to ensure the scaled simulations are representative for the actual, full scale, vessel. Due to these limitations, it is not possible to use the setup at this moment to perform experiments and improve novel control strategies. If these physical limitations of the current HIL setup are overcome, the effect of the propeller and the pitch control strategy during turns can be investigated by performing experiments with oblique inflow.

The Royal Netherlands Navy (RNN) operates four diesel-electric submarines, the Walrus class. The submarines sail submerged on electric engines and periodically recharge the batteries with diesel engines at periscope depth. The exhaust gases are dispelled at the back of the sail below water level. During the sea trials it was observed that the rising exhaust gases elevated the surface locally with a height of 1 to 2 m. This elevation limited visibility through the periscope, water flooded the air intake and the submarines could be easily detected. To remedy this problem model tests were performed. To enable evaluating several exhaust configurations for a replacement of the Walrus class a numerical model is studied to predict the surface elevation. To model this situation a numerical method is used. The method applied in this work is the Volume of Fluid code ReFRESCO, which is a Reynolds Averaged Navier-Stokes (RANS) solver. Three test cases are studied, a rising bubble, a buoyant jet and an exhaust plume from a submarine sail. The simulations for the buoyant jet show that the momentum in the jet is dominated by buoyancy rather than by the initial inflow momentum. The influence of different turbulence models on the width of the jet and the corresponding surface elevation are investigated. The choice of turbulence model influences the distribution of air in the domain, but does little to the surface elevation. It is concluded that the KSKL model yields the most physical results where the air spreads out in the domain. This model also has a satisfactory convergence behavior. It is concluded that both the density of the exhaust gas and the velocity profile at the nozzle have little influence on the final result. A parabolic velocity profile instead of a uniform outflow does improve the convergence. The dominant numerical error is the discretization error, which is in the order of 12% for the surface elevation. To this end the L∞ norm of the iterative error must be reduced to a satisfactory value, in the order of 10^-3 or smaller. Comparing the results with experiments is difficult due to a lack of proper experimental data, however it is concluded that the results are in a similar order of magnitude. Finally the exhaust gases on a submarine sail are modeled. For the modeling three simplifications are made: only the flow surrounding the sail is modeled (the hull of the submarine is not modeled), the control planes on the sail are not modeled, and no incoming waves on the free surface are taken into account. Both in the experiments and in the simulations a pulsating behavior can be observed in the rising air. L∞ norms for the submarine modeling are generally in the order 10^-3, but occasionally less. The numerical results are validated against the experimental results. It is concluded that the use of the RANS code ReFRESCO is possible for the modeling of a submerged exhaust of a submarine. The estimated uncertainty for the result is in the order of 15%.

Tip vortex cavitation was previously identified as a source of the broadband noise emitted by ships underwater. This leads to unwanted noise and vibrations on board, which reduces passenger comfort, and increases the underwater signature of naval ships. The influence of different cavitation regimes on propellers and boundary layer transition on wings, has led to studies that isolate the cavitating tip vortex. This is done by using a converging-diverging nozzle (Venturi tube) geometry, combined with a suitable inflow condition to simulate a cavitating line vortex. The currently available computational power allowed for a comparative study of SRS methods (i.e. the IDDES model) and RANS models (i.e. the k − ω SST and EARSM) in wetted and cavitating vortex conditions. Both the general flow field, as well as the dynamics of the cavity deformations in the vortex were analyzed in this thesis. The geometry was selected based on the available experimental validation data for the wetted flow case, whereby preliminary studies determined the inflow and outflow lengths of the domain. A Lamb-Oseen tangential velocity profile was specified at the inlet. The vortex strength and viscous core size were tuned to obtain similar inflow conditions as in the experimental measurements, which used a fixed-blade swirl generator to generate the line vortex. The flow field in the wetted vortex case demonstrated an excessive amount of viscous diffusion of the vortex for both RANS models.This was caused by the overproduction of modeled turbulent kinetic energy at the viscous core edge. EARSM resuls were verified in a grid- and time step refinement study, however the large modeling error in the viscous core prevented the validation of the results. The IDDES model results were closer to the experimental reference, but were obtained with an almost laminar flow field. Modeled turbulence was mostly dissipated and no resolved velocity fluctuations were present in the flow at the measurement section. In the cavitating vortex simulations, numerical diffusion of the EARSM led to a more diffuse vapor core interface and a more downstream development of the vortex cavity compared to IDDES, where the flow field remained predominantly laminar at the measurement section. Both EARSM and IDDES predicted a solid-body rotation of the vapor core, combined with an increase of radial velocity towards the vapor core edge. The non-negligible radial velocity resulted in a conical cavity shape. The velocity profile of the simulated line vortex therefore did not correspond to that of a cavitating Lamb-Oseen vortex (which assumes no radial velocity components), such that the simulated line vortex was not representative of a cavitating tip vortex. he sheet cavities originating from sharp edges at the front and end of the Venturi throat strongly influenced the flow field and cavity dynamics. The developed front sheet cavity determined the streamwise inception of the vapor core of the vortex. Periodic shedding and collapse of the irregular downstream sheet cavity caused axial and radial contractions of the vapor core as well as a noncircular deformation of the cavity cross-section. No traveling or standing Kelvin waves could be identified on the cavity interface using the developed post-processing and spectral analysis tool. The identified cross-sectional deformation did not correspond to cavity deformation modes defined in previous research and none of the other deformation modes were found to occur. Grid-dependent solutions, numerical noise and large wavenumber resolution indicated that a finer grid is required and that the analyzed length of the cavity should increase to improve the quality of numerical analyses of simulated cavity dynamics.

In recent years the awareness and the effort to reduce air pollution and global warming have increased. Many new ideas are being developed to reduce harmful emissions. Despite this, the shipping industry is still a large contributor to air pollution worldwide. To reduce the environmental impact of shipping, the use of sustainable energy sources such as wind energy on-board ships is being explored. Wind energy is widely available at sea, the challenge is to harness this energy. The relatively unknown wind propulsion device called the Turbosail is a vertical wing shaped device which uses wind energy to provide thrust. This propulsion technology was invented in the 1980’s by the Frenchman Jacques-Yves Cousteau. This report describes the investigation into the similar wind propulsion device called the VentiFoil. Two retractable VentiFoils are fitted inside a 40 foot container, this ship propulsion device is called the eConowind unit. Multiple eConowind units can be installed on the hatch covers of general cargo vessels. If successful, this wind propulsion device can be applied on many different ships. The VentiFoil concept will be investigated and improved using Computational Fluid Dynamics (CFD) research tools. These tools are used to simulate the flow around different VentiFoil geometries. The result of this project will be a better understanding of the working principles of the VentiFoil, sensitivity information for the variation of different characteristic design parameters and an evaluation of the generated forces and performance of VentiFoil propulsion.

There is increasing attention for the effects of anthropogenic underwater radiated noise (URN) on marine fauna. This is expected to lead to regulations with respect to the maximum permitted sound emissions of ships. It is known that cavitating tip vortices, generated by ship propellers, are some of the key contributors to URN. Consequently, there is a need to evaluate propeller designs with respect to noise generation in a design stage. Computational fluid dynamics (CFD) has the potential to offer detailed insights into cavitating vortex dynamics and noise sources, at a reasonable cost. URN can be efficiently estimated using CFD in combination with an acoustic analogy. In order to use such predictions in a design process, it is essential to understand and quantify the errors associated with the numerical predictions of noise sources. This thesis investigates the reliability of such evaluations and aims to reduce occurring modelling errors. To compute noise sources, it is necessary to simulate cavitation dynamics using scale-resolving simulations (SRS). Here, part of the turbulence kinetic energy spectrum is resolved in space and time, as opposed to being modelled using Reynolds averaged Navier-Stokes (RANS). The SRS method of choice in this work is the partially averaged Navier-Stokes (PANS) method. Bridging models, such as PANS, exhibit a smooth transition and absence of commutation errors between RANS and large eddy simulation (LES) zones, in contrast to hybrid models such as detached eddy simulation (DES). The formulation allows for a theoretical decoupling of the discretisation and modelling errors, thereby enabling verification and validation processes. PANS allows the user to select the ratios of resolved-to-total turbulence kinetic energy and dissipation (rate). Appropriate settings and methods to estimate these settings a priori are investigated. Furthermore, a new PANS closure is developed, which offers improved convergence behaviour compared to more commonly used models, and is better suited to application for multiphase flows. It has been shown repeatedly in literature that SRS should be accompanied by physical inflow boundary conditions, where time-varying fluctuations, resembling turbulence, should be inserted upstream of the object of interest, to prevent laminar solutions. However, from literature it is clear that for maritime applications this is often neglected. To the knowledge of the author, there is no previous application of such an inflow in combination with cavitation. In this PhD thesis, a synthetic inflow turbulence generator (ITG) is implemented, and tested for several test cases in wetted and cavitating conditions. For these cases, the numerical errors, consisting of discretisation, iterative and statistical errors are evaluated. Firstly, the results when using the ITG are compared against recycling flow results for a turbulent channel flow, using different SRS methods. It was shown that the ITG can deliver a resolved turbulent inflow at lower computational cost. Secondly, the effect of neglecting such an inflow was tested for the Delft Twist 11 hydrofoil, where it was shown that simulating such a flow with a low ratio of resolved-to-total turbulence kinetic energy can lead to flow separation at the wing leading edge. This is in contrast to experimentally observed behaviour. The inclusion of the ITG can reduce this modelling error, although the sheet cavity dynamics remain largely unaffected. Finally, an elliptical wing with a cavitating tip vortex is simulated. The observed vortex dynamics are compared against a semi-analytical model from literature. To obtain vortex dynamics, the ITG was shown to be necessary. The far-field noise generated by the vortex is quantified and related to the cavity dynamics. Some of the main contributions of this research are improved insight in the use of SRS in cavitating conditions, in simulating cavity dynamics and in using an ITG to obtain flow fields representative of experimental conditions. In this way it has enhanced our understanding of the ability and limitations in the prediction of acoustic sources due to cavitation. To improve predictions of cavitation dynamics it is recommended to address the cavitation model and the method which describes the cavity interface, to reduce the discrepancy in average cavity size between simulations and experimental observations.@en

This research focuses on identifying the most important stern shape aspects, with regard to resistance and propulsion power, of inland ships. Such information should help designers to determine which hull form aspect to adjust in case design requirements need them to do so. The information is obtained by firstly conducting a large series of CFD calculations, using the PARNASSOS code, for systematically varied inland ships. Next, response surface technologies are used to identify the most important aspects. This is done by sequentially adding and/or removing parameters from the response surface in order to find the combination of parameters that explains the majority of the variance in the performance data for the tested hull forms. Finally, an optimization algorithm is used to determine the optimal hull forms for varying displacement, showing which parameters should be adjusted preferably in order to increase (or decrease) ship displacement. This, specifically, should aid designers in making the trade-off between displacement (or cargo capacity) and energy consumption. @en

In response to the leading narrative of increasing sustainability in the yachting sector, a research collaboration is started between the Delft University of Technology and Dykstra Naval Architects to examine the potential use of hydro generation on board sailing superyachts. By harvesting energy from the water flow when under sail, diesel generator use can be limited, reducing overall emissions. Currently, it is not yet possible to quantify the impact of a chosen hydro generation system on the overall design during the early stages of yacht design. To assess the correct balance between the inevitable increase in system weight and size relative to, for example, emission reduction. To allow for this, a novel method is developed, presenting the designer with the opportunity to explore various hydro generation systems quickly. With the ability to complete this in an early design stage, more opportunities for hydro generation remain, and the need for a feasibility study for hydro generation is removed. In this thesis, the developed method is described, and results are presented that provide insight into its applicability. The design method considers the impact of six variables that influence hydro generation. The first three variations concern size and include the propeller diameter, battery capacity, and sail area. The remaining considerations relate to operational and design choices and include decisions on energy consumption, fixed or controllable pitch propellers, and generation in the first or third quadrant. A scenario for an ocean crossing with a sailing yacht aiming to limit fuel consumption demonstrates the influence of these considerations. The results presented in the thesis show that the method provides the basis for a later detailed design stage when an actual hydro generation system is implemented.

An accurate prediction of propeller hull interaction is an important step in the design of a new vessel. The prediction of full-scale flow phenomena, which eliminates scale effects, is becoming available due to increasing computational power. However, the complexity of full-scale CFD calculations combined with a lack of validation data results in unknown uncertainties. This study contributes to the uncertainty estimation for full-scale calculations by answering the question With what uncertainty can we currently numerically predict resistance and propeller power on full-scale Reynolds numbers?. The resistance and propeller flow predictions are done for the general cargo vessel MV-regal for three cases; a double body, a free surface resistance simulation and an open water propeller simulation. The simulations are performed for the design speed of 14 knots, resulting in a full-scale Reynolds number of 푅푒 = 1.12 ⋅ 10ዃ. The discretization error is determined by the grid refinement study as presented by Eça and Hoekstra for the propulsion parameters; resistance coefficients and the wake factor. For each case the flow field is analysed, an uncertainty assessment is made and the results are compared to a group of numerical results for the same simulation performed by 20 participants of a case study organised by Lloyd’s register on the same vessel as is considered in this thesis. Modelling the boundary layer of a flat plate on model and full-scale Reynolds numbers encourages the use of unstructured grids for full-scale Reynolds numbers. The uncertainties as predicted by the grid refinement study, vary between 0.6 and 24.5 percent for the friction coefficient. For the 푅푒 = 10^7 the values are compared to a structured grid study, which had a better trend over the grid refinement series. Comparison to theoretical friction coefficient calculations confirmed the absolute friction result. The double body simulation, performed on the full-scale number 푅푒 = 1.12 ⋅ 10^9, demonstrated the use of the unstructured grids on the full-scale Reynolds numbers. The iterative error had to be closely monitored in order to get a stable solution. While the iterative errors had the same order of magnitude, the uncertainties as predicted by the grid refinement study for the propulsion parameters varied between 1.5 and 140 percent. This is an unacceptable large scatter in uncertainty which calls for another method to determine the uncertainty. The free surface simulation added complexity, by modelling the free surface resistance of the vessel. The order of convergence is lower for the free surface simulation, which creates a higher iterative error in the uncertainty assessment. The discretization uncertainty prediction varies between 2.7 and 23.5 percent. The open water simulation, which is based on a hybrid grid of structured and unstructured grids, showed for the monitored parameters a sufficiently low iterative error and a low discretization uncertainty (between 0.1 and 3.4 percent) for the thrust and torque coefficients. Although all different cases showed mixed results for the discretization error, the absolute values are well within the range of results from the test group of 20 participants. This is a good starting point of the repeatability of the flow parameters. It is noted that the current uncertainty estimation is larger than the difference between two grids.

During berthing operations of ships, the horizontal thrusters cause a hydraulic load on the quay wall and bed. This could eventually lead to scour holes in the bed, which may affect the structural integrity of the quay wall. This thesis is about a numerical simulation of a bowthruster jet which is deflected by a quay wall and the focus of this study will be on the resulting bottom velocities. In 2019, field measurements were executed with an inland vessel and the measured bottom velocities were low compared to the design guidelines. The goal of this study is to simulate the field measurements in a numerical model to gather more knowledge about the flow field induced by bowthrusters next to quay walls. The obtained numerical results are compared to the field measurement and to the design guidelines of PIANC. As it turns out, the velocity sensors probably did not measure the maximum bottom velocity during the field measurements, since they are located slightly above the highest velocities at the bottom, as predicted by the numerical simulations. The maximum bottom velocities from the numerical simulation are similar to the expected near-bed bottom velocities by PIANC. However, there is room for improvement in these design guidelines, e.g., adjusting the efflux velocity for tunnel thrusters to account for the variation in cross-sectional area between propeller and tunnel exit.

A fairly recent development in the maritime industry is the rising interest in composites, as they have great potential to outperform conventional metallics. They offer good corrosion resistance, fatigue resistance, a low magnetic signature, and a high strength to stiffness ratio. In case of a propeller, the latter may be utilized by adapting the geometry passively to suit the loading condition more optimal. A possible is to mitigate cavitation by utilizing the relatively large deformations when subjected to loads. The hydrodynamic response of a flexible propeller in a flow field can be predicted by the use of Fluid-Structure Interaction (FSI) software, which is currently being developed at MARIN. The project is called ComPropApp, and combines existing fluid and structural solvers. As the ComPropApp is still under development it needed to be verified and validated, which is the main objective of this thesis. As an initial step in the verificatio, a falsification study was applied on the procedures followed in the ComPropApp. This led to the discovery of several errors, to which corrections have been applied to improve the program. With an updated version, computations with a number of different materials were performed to finalize the verification. Then, a model size polyurethane propeller has been manufactured at MARIN to be used in the experimental validation. Experiments were performed in the cavitation tunnel testing facility at MARIN. Here the propeller was tested in several operating conditions, which was then compared with ComPropApp simulations. Lastly, it was investigated whether the application of a composite can reduce cavitation. This was for theoretical research only, since the testing propeller would fail far before reaching cavitating conditions. With the fluid solver, a requirement for twist deformation was set up. Based on these requirements, a range of composite materials was defined, and with it, ComPropApp computations were performed. The resulting displacements and pressure distributions were then compared for rigid and composite propellers. With the presented verification study, it can be concluded that the FSI software is capable of providing realistic computation results. The validation study has led to conclude that the unsteady FSI module is capable of qualitatively predicting the bend deformations in open water conditions. However, due to the large uncertainties arising from the testing material properties and questionable machining quality, the measurements cannot be utilized to define the accuracy of the FSI software. In wakefield conditions the additional uncertainty of the wake velocity distribution meant that these measurements are inconclusive, hence the validation was only performed for open water conditions. The material study with the purpose of mitigating cavitation has shown potential in the application of anisotropic materials. Composites with a specific ply orientation sequence have the possibility of realizing bend twist coupling motions, such that the propeller would unload itself in the vicinity of the ship hull, with reduced cavitation as an expected result.