Human activities, particularly fossil fuel consumption, are accelerating global warming. Allseas, in collaboration with the report’s author, is interested in the installation procedures for Floating Offshore Wind Turbines (FOWT) to mitigate this global warming. This research focuses on Tension Leg Platforms (TLPs), a structure that has more buoyancy forces than gravitational forces and thus uses tendons for stability when installed. There is potential in TLPs due to their motion stability, minimal seabed impact, and cost efficiency when installed, however, installation is a challenge because a TLP relies on its tendons for stability. The installation should be safe, reliable, and cost-effective. Current installation methods are inefficient and not used on a commercial scale. Allseas has designed a concept ship
to install FOWT TLPs cost-effectively, potentially reducing emissions. Research performed with free-body diagrams and a literature study into hydrodynamic behaviour during installation reveals several challenges and knowledge gaps. Most papers about the behaviour of TLPs are about the moment that they are already installed. The papers that are found about the installation and include time-domain simulations are on TLPs used for the oil and gas industry. These do not have a flexible tower structure on top of them, while in the wind industry the accelerations of the flexible structure might be one of the key limiters of the operation. Next steps need to be taken in understanding what is necessary to model the installation of tension moored structures; in particular, tension-moored structures for FOWT in the process of going from slack to taut. The safety of the installation of FOWT TLPs would improve when their behaviour during installation is known. To study this gap in the existing literature, the following research objective is proposed: To find the minimal viable method to investigate the feasibility of the tendon tensioning phase of a FOWT TLP in different sea states.

What makes the TLP installation studied in this paper state of the art, is that a unique installation method is applied. For installation, an external ballast deck will be used, which is connected to the installation vessel with an installation system. This research will be performed on the test case of a 20𝑀W TLP that is brought to its design draught starting the moment that the tendons are connected. For the case study, the maximum nacelle acceleration that may happen during installation is 3.0𝑚/𝑠2 (Taboada et al., 2020). The maximum tendon tension may be 25𝑀𝑁; this is a criterion for a 20𝑀𝑊 TLP and can change for other wind turbines. The following steps have been taken to successfully fulfil this research. First, the method of numerical modelling of a TLP had to be validated. To do this, an
experiment of a 5𝑀𝑊 TLP was remodelled. After this was validated, a 20𝑀𝑊 model could be made following the same procedure. When the behaviour of an already installed TLP was validated, the installation model could be built. For the installation, only the installation deck was modelled at first to build on the complexity of the model. When this was done, the ship’s presence could be taken into account. To research the implications of simplifications, the ship first responded to displacement RAOs before load RAOs were used to model the hydrodynamic interaction between both bodies. When the model was finished, different sea states could be modelled. Because every spectrum has different seeds that all correspond to the spectrum, a statistical analysis had to be performed on the results.

The results of the installation without the ship present show that with a perfect motion compensation the installation of a TLP would be possible. The influence of waves is significant during the installation. When there is a slight disturbance at the moment when the tendons go from slack to taut, peaks in the nacelle accelerations and tendon tensions arise. The tendon loads peak with the same frequency as the wave period, which means that they are directly generated by wave loads. The higher the waves, the higher the peak loads.

The influence of the installation ship on the results is that the maximum nacelle acceleration and tendon tension during installation get higher. This holds for the model with the displacement RAOs and the model with load RAOs. The model with the load RAOs is the most realistic: the ship’s movements influence the TLP motions and the TLP impacts the ship.

Adding a sea state to the simulation can increase the movements compared to when a regular
wave is used. If the sea state includes periods closer to the natural frequencies, the response is
higher. This can also be due to the second order wave drift and sum frequency loads that are included on the TLP. A randomly generated wave time series can also include lower and higher waves during the simulation. To account for this randomness, the simulations of a chosen set of sea states are run with 20 different seeds. Four of them have the same significant wave height and differ in average wave period, three of them have the same average wave period and differ in significant wave height.

The research has shown that when the response is higher, the spreading of the maximum nacelle acceleration and maximum tendon tension observed per simulation is also higher. This means that near the installation criteria, the most seeds have to be run to make sure that the operation is feasible. With the results obtained during the 20 seeds, the change of the P90 remains below 5% after 11 runs, this would thus be the recommended amount of seeds. The sensitivity study also found that the tensioning phase, where the tendons go from slack to taut till the moment that the deballasting is finished, is the normative phase for installation. The taut phase is the phase where the deballasting is finished till the end of the simulation. For the nacelle accelerations a maximum factor of 2.0 is found between the two phases. For the tendon loads a maximum amplification factor of 1.2 is found. The study also established that the tendon loads were not governing for the design of the TLP. It can be concluded that the current method for modelling can be used to find the limit of workability. With other designs for the turbine or TLP, one could still implement the method used.

The main limitation of this study was the concept nature of the installation method, and thus, not every part of the design is known yet. Additionally, the model simplifies reality. In spite of its limitations, the study gives insight into the minimum model necessary for a safe TLP installation.

The Paris Agreement of 2015 has increased the demand for renewable energy sources. The Dutch government plans to exploit the North Sea as its green power plant by implementing 3 GW of offshore solar (OS) energy in existing wind parks. The complementary nature of wind and solar results in more clean energy at a constant power rate. By pooling the power infrastructure of the offshore wind farms (OWF), only a short power export cable (PEC) from the OS system to an OWF transformer is needed to plug in the OS system.

This study aimed to address a research gap in operational conditions for OS systems by exploring how to perform a PEC pull-in on an OS farm. Power cable pull-in operations are normally performed on monopiles of OWTs and, more recently, on floating OWT foundations. However, pull-in operations at sea-surface level, directly at the ocean surface, are not common, especially on systems that act like enormous blankets on the ocean surface. The Oceans of Energy OS farm was used as a case study, representing a novel floating system that behaves like a large blanket and moves directly with the waves at sea-surface level.

The need for an integrated pull-in equipment design was addressed by applying a double diamond design cycle. According to the design methodology, the research first focused on mapping the limits of the OS system. Firstly, a large-scale OS system description was given to understand the relevant aspects of the OS system. This resulted in the hang-off floater location, at which the PEC is pulled in and terminated. Secondly, the hang-off floater was described from a more local perspective to define the requirements.

The requirements were found by analysing and calculating the OS system boundaries and by consulting experts in marine operations. Calculations were done to determine the submerge limits of the hang-off floater, resulting in a limiting external force. The analysis identified the critical steps in the pull-in procedure, which were applied to a force analysis on the relevant PEC segment. This force analysis led to the limiting forces needed for the design of equipment. Together with the advice from experts, this effort resulted in a statement of requirements.

By applying the second part of the design methodology, the design of the equipment resulted in an A-frame. It proved to be a feasible design, as it is commonly used in offshore marine operations. By performing internal force calculations, multiple design choices were addressed and validated. The design proved to be ideal for integration with the OS system; therefore, future iterations towards a final design were provided.

The integration of the A-frame proved to be feasible based on the force analysis. To find out whether the operational challenges of the OS system could be tackled, the offshore operations were considered. By design, the A-frame consists of multiple 20kg pieces, which can be carried to the hang-off floater from a boat landing. In order to verify the design, the equipment installation and the PEC pull-in procedure were described.

In conclusion, this research addressed the unique challenges of power export cable (PEC) pull-in operations at sea-surface-level offshore solar (OS) systems. Unlike fixed or stable floating offshore wind turbines (FOWTs), OS systems require lightweight, modular equipment for safe deployment and retrieval in dynamic conditions. The study demonstrated that A-frames, widely used in offshore operations, can also be adapted for PEC pull-ins on large-scale OS systems in shallow waters. Clear design boundaries and requirements were established to guide future equipment development. The applied design methodology clarified operational limits and provided a starting point for refining pull-in equipment for OS systems.

For future work, it was advised to address the detailed design of the equipment integration to the floater. Also, the material choice was addressed to create weight savings for a more efficient operation. Further recommendations suggest inputs for a model that links parameters to requirements, to address future projects in environments other than the North Sea.

This thesis investigates a floating truss structure’s local and global response to breaking waves slamming loads. The case study of interest is the supporting structure of SolarDuck’s (SD) platform FPV. Their design consists of different triangular modules, with the solar panels at a safe height from wave impacts. In future designs, the truss supporting structure underneath them, made of non-circular aluminum braces, may be exposed to slamming events.

The literature research concluded that the current state-of-the-art lacks methods to estimate local and global load on truss structures accurately, and the most relevant physical aspects to correctly represent such phenomena are uncertain. Among them, hydroelasticity, in particular, may play a role. Consequently, the research is structured into three parts, and, in each of them, two cross-sections are considered for the structure, SD’s one and an equivalent circular hollow tube (HT) one.

In the first one, the local analysis on individual braces is performed and four methods are applied to compare the relevance of different assumptions. The structure is expected to show a hydroelastic response at the local level according to the Bereznitsky criterion. Faltinsen’s method takes hydroelasticity takes into account, and provides lower values for the response, being the best method to calculate the actual deformation of the structure. Nevertheless, good estimations of the deflections were offered also by the General Wagner Method and Modified Logvinovich Method for the asymmetric loading, assuming the brace as rigid.

These two methods are included in the global analysis: one triangular module is modeled in ANSYS, and a transient analysis is performed. The structure shows mainly a local behavior, and the non-circular cross-section geometry shows double values for the deformation. The local analysis can be used to approximate the global one, even though additional proof is needed.

A CFD simulation is performed to verify the analytical models through COMFlow, and the MLM applied to the symmetric load case offers the closest response to the numerical calculations. From this analysis, the local slamming coefficient is also derived to be equal to 4.78 for the circular cross-section and 10.38 for the square one.

Shipping is one of the most cost-effective and environmentally sustainable modes of transportation. Given that approximately 60% of a typical ship’s propulsive power is used to overcome frictional drag, implementing practices to reduce this resistance stands to yield substantial economic and environmental benefits, (Larsson & Raven, 2010). A promising drag reduction technique for a ship is air lubrication. Damen Shipyards Group is currently making this technology commercially available as the Damen Air Cavity System (DACS). The system reduces the frictional resistance of a ship by creating stable air cavities on the bottom hull of a ship. The air cavities cause a reduction in friction drag by decreasing the wetted area of a ship’s bottom. During the development of the DACS system, it was observed that air cavities also change the inflow into the propeller. Both the changed inflow and the frictional drag reduction affect the propulsive efficiency and required propulsive power of the vessel. This thesis aims to provide a better understanding of how the propulsive performance of a ship is affected by air cavities. Additionally, a key application for air lubrication systems is on inland waterway vessels, which frequently operate in shallow waters. However, the impact of shallow water conditions on the performance of the air cavity system is currently unknown. The research goals of this thesis are investigated with the help of computational fluid dynamics (CFD). A literature review identified the most feasible method to model a ship with air cavities i.e. representing the cavities as surfaces with a slip boundary condition. The influence of the air cavities on propulsive performance is investigated by studying the change in nominal wake field, thrust deduction, and propeller efficiency. Three ships were investigated: a cargo ship, a cruise ship, and an inland ship. The CFD results of the cargo ship were compared to sea trial data. Model test data was available for comparison of the cruise ship results. First, a grid convergence study and a sensitivity analysis were performed to investigate the accuracy of the numerical simulations and the power predictions. The biggest source of numerical uncertainty arose from the pressure drag. From the sensitivity analysis, it was found that the uncertainty of the power prediction is mainly affected by the uncertainty of the thrust prediction, followed by the uncertain propeller geometry for the cargo ship. For the cargo ship, it was found that the air cavities cause a significant frictional drag reduction. It was also found that the air cavities caused a decrease in pressure drag because they decreased flow separation at the stern. Furthermore, a strong decrease of the nominal wake fraction was observed for this ship, because the air cavities change the boundary layer on the bottom of the ship. A change in propeller efficiency was also observed because the propeller working point changes. The magnitude of the change was larger than for the other ships because this ship has a controllable pitch propeller running at a fixed rpm. When comparing sea trial data to the CFD results, it was found that CFD underpredicts the power, especially at higher speeds. Next to this, CFD predicted a larger reduction in power than measured during the trials. The prediction of the cavity length was identified as the most likely cause for the difference. A good comparison between model tests and CFD results was found for the cruise ship. It was found that the drag reduction and change in propulsive performance could be predicted reasonably accurately by modeling the air cavities as surfaces with a slip boundary condition. Furthermore, it was observed that the air cavities caused little change in propulsive efficiency on this ship. This is because the propellers of the cruise ship are located further away from the boundary layer of the ship and the wake field is therefore only slightly affected by the air cavities. On the inland ship, it was observed that the pressure drag and flow separation at the stern were influenced due to the air cavities. However, no comprehensive conclusions could be made due to scatter in the data. This is most likely due to the uncertainty present when modeling flow separation. Furthermore also for this ship, a decrease in propulsive efficiency was found because the air cavities decreased the wake fraction of the ship. Additionally, CFD simulations were conducted for the inland ship at varying water depths to assess how shallow water conditions impact the performance of the air cavity system. Since the ship’s frictional drag increased in shallow water, the total drag reduction from the air cavities also increased. Next to this, a change between pressure and flow separation when comparing air on and air off was observed. Also here, no strong conclusion could be made due to scatter in the data. Lastly, it was found that the change in wake field caused by the air cavities is larger in shallow water than in deep water. ii Based on the results of the three ships studied it can be concluded that an air cavity system affects the propulsive performance of a ship. It was found that an air cavity system reduces the wake fraction of a ship because it limits the growth of the boundary layer on the bottom of a ship. The reduction increases for ships with a high block coefficient and a large air-covered area. For a twin screw ship, the change of the wake field is less significant. The change in propeller efficiency depends on the resistance reduction, possible change of the wake field, and the original working point of the propeller. Furthermore, it was found that the thrust deduction effect is not affected by the air cavity system. It can also be concluded from the results of the cruise ship that the flow around a ship with air cavities can modeled reasonably accurately provided that the shape of the air layer under the ship is known. More research is recommended on how air cavities change the flow separation and pressure drag of a ship.

Offshore wind stands as a crucial contributor to generating clean, renewable energy, but the limited availability of shallow water locations restrains the potential of bottom-fixed wind. To unlock the vast wind energy potential in deeper waters, a substantial reduction in the Levelized cost of energy (LCOE) of floating wind technology is necessary. Tension leg platform (TLP) floating offshore wind turbines (FOWTs) offer significant cost-saving potential, positioning them as a promising solution. However, achieving cost-effective installation of TLP FOWTs poses significant challenges. In the existing literature, this remains relatively undressed with only two studies focusing on this subject, providing partial solutions

The overachieving goal of the thesis is to address this challenge by conducting an in-depth design space exploration (DSE) of an innovative special-purpose installation vessel along with a robust installation method, offering a cost-effective solution. Floating wind represents a yet-to-be-explored market, presenting design challenges associated with managing uncertainties in operational conditions and TLP designs it intends to commission. The research is conducted within the framework of systems engineering.

During the literature phase, a needs analysis is performed to establish design requirements. The installation vessel must be capable of transporting future fully assembled TLP FOWTs. These include 20 MW wind turbines, three-legged TLPs, and an innovative TLP design with one foldable leg for efficient stacking onboard. The DSE model comprises a two-step design approach and a design evaluation based on scenario modeling. The first design step explores radically different designs using an exploration approach integrated with morphological mapping. A trade-off analysis led to the Windchanger concept featuring an installation deck (ID) integrated with the stern design, employing a winch system for FOWT lowering and recovery. In the second design step, this concept is subjected to further exploration through a parametric model, including generating the hull surface for extensive stability calculations. The key factors for scenario modeling comprise the distance to the port, the operational area, and the TLP design. By evaluating the cost-effectiveness and installation duration in each scenario, the goal is to gain insights into the optimal design ranges. This serves as the basis for establishing a design decision framework to manage the considered uncertainties.

The results of this research offer valuable insights into both the technical feasibility and the cost-effectiveness of the Windchanger concept, facilitating optimal design decisions. The model enables evaluation across diverse scenarios to identify the most suitable design within predefined parameters. This is showcased by assessing performance in two operational areas: the North Sea and the U.S. East Coast. The optimal design ranges derived from these analyses can guide further development of the Windchanger Concept, highlighting that a transport capacity of 2 emerges as the most cost-effective option based on the scenarios evaluated.

Introducing a new installation solution necessitates benchmarking against existing methods to ensure cost-effectiveness and feasibility. The results reveal that TLP foundation costs are approximately 40 percent lower than other floating foundations, confirming the anticipated cost-saving potential. Installation costs represent only a fraction, ranging from 0.5% to 1% of foundation costs, emphasizing the importance of robustness and installation time in cost-effectiveness. The model demonstrates that the Windchanger concept outperforms other TLP installation methods, with lower installation costs per FOWT and a significantly higher number of yearly installations. These findings underscore the Windchanger concept's robustness and cost-effectiveness, potentially leading to a substantial reduction in the LCOE of floating wind.

Current service and installation activities for offshore wind turbines are carried out by jack-up vessels, which eliminate wave disturbances to a large extent. The use of these vessels imposes several disadvantages, including high operational costs and the limitation of operating in restricted water depths. An alternative is a crane mounted on a floating vessel (monohull), which is quicker in operation and multi-deployable. With these vessels, however, a motion compensator is needed to eliminate most of the hydrodynamic disturbances. The purpose of this graduation assignment is to develop a concept design for a passive motion compensator (PMC) to isolate the vessel motion from the payload.

This goal is achieved by the implementation of a multi-objective optimization algorithm based on genetic programming (GP) that constructs a two-dimensional PMC based on the principle of quasi-zero stiffness. The GP employs a set of genetic operators to explore the design space in terms of topology and design variables, which effectively mimics Darwin’s Theory of Evolution. The better a mechanism performs, the higher the fitness, and thus the higher the chance this design appear in future generations.

Each design is a composition of cylinders and nodes that are assembled into a mechanism. During the fitness evaluation, all mechanisms are examined by a nonlinear finite element method to extract the force-displacement relations. The arc-length control method is used due to the large displacements and rotations of the members in the mechanism, whereby both the nodal displacement vector and external load vector are varied to follow an equilibrium path in an incremental-iterative way. To provide sufficient support to the payload, the mechanism is prestressed, which is applied by using the arc-length procedure as well.

Static and dynamic results show that the GP is suitable for constructing a high-level planar QZS mechanism for the intended application in various sea states. From multiple runs, it can be concluded that the optimizer generally produces designs with the same topology. Dynamic analyses in the time domain show that motions are effectively mitigated in the horizontal and vertical directions for the chosen designs. In addition, analysis in the frequency domain shows that the mechanisms effectively attenuate motions in the frequencies of interest.

Drop-on-Demand Inkjet Printing requires jetting ink particles at 100kHz at velocities of 10m/s from sub-millimeter-scale printhead assemblies, and represents a physics-rich engineering problem. CFD simulations have been used to study the jetting process. From meniscus deformation at the nozzle, to the presence of entrained particles in the jet, modelling contact line dynamics is very important.
Color-Gradient Lattice Boltzmann (CG-LBM) simulations can capture surface tension between fluids. Contact angles with solids are often imposed on geometrical grounds as boundary conditions. Alternative energy-based wetting, based on solid-liquid surface tension/energy arguments, is investigated for its applicability in the inkjet printing regime.
CG-LBM fluid-fluid interfaces are diffuse, despite modelling macroscopically sharp interfaces. This requires interpolation of viscosity in the interface region: new arguments are given to support the idea that this interpolation is free, and can be chosen, for example, on the basis of validation results.
New theory on CG-LBM for any number N of fluids is developed, and broadens the applicability of known N-fluid algorithms, allowing the use of in-simulation phase definitions that are more suitable for large density ratios among fluids.
The use of superviscous particles is investigated, where an N-fluid CG-LBM implementation is leveraged by using very viscous fluids to model solids. Wetting would then be mediated by the CG-LBM fluid-fluid interaction framework. The way CG-LBM maintains fluid-fluid interfaces is now also extended to the solid-fluid interfaces, and can lead to catastrophic spurious smearing of physical features.
Separately, recognizing the fundamental physical similarity of surface-tension across fluid-fluid and fluid-solid interfaces, wetting phenomena were simulated with additional fluid-fluid-like interactions near walls. This solid-phase perturbation approach was consistently formulated thanks to the new N-fluid CG-LBM theory developed earlier. Inaccuracies arise when these interactions are not paired with a diffuse fluid-solid interface, similar to those maintained between fluids in CG-LBM.
Sufficient results are obtained to motivate future development of solid-phase perturbation, which indeed describes solid-fluid and fluid-fluid surface-tensile interaction in a unified framework.

Huisman has introduced the Windfarm Installation Vessel as a complete solution to assemble and install offshore wind turbines at sea.
Installing a floating wind turbine at sea brings two main challenges, the relative motions between the floating structures and the load transfer of the wind turbine.
The proposed installation procedure considers a connection between the installation vessel and a semi-submersible floating support structure to reduce the relative motions and facilitate the load transfer.
This research investigates how the connection's structural configuration affects the system's relative motions and loads during five defined installation stages.
The different installation stages cover varying amounts of ballast transfer, as well as the mating phase of the wind turbine.
A two-dimensional multi-body model has been formulated considering a rigid link between the installation vessel and the floating support structure.
The hydrodynamics of the floating structures and the regular wave loads on the structures are calculated using Ansys AQWA.
A system analysis is performed to investigate the effect of adding stiffness in one or combined directions of motion of the connection.
The change in dynamic effects during the installation stages are minimal, the ballast transfer mainly changes the static load on the connection.
Overall, it can be concluded that a combination of stiffness in the different connection directions will provide the most favourable results.
To limit the relative heave motions, coupled surge or pitch and heave stiffness is required.
A different stiffness on both sides of the connection is also shown to improve the system’s behaviour.
Fixing the rotation of the connection on one side improves the relative pitch motions between the wind turbine and the support structure.
More research is required to investigate favourable combinations of limiting motions on each side of the connection.
The presented model could be used for a future optimization study to find optimal stiffness values for the connection.

The main aim of the research presented in this report is investigating analytical methods to model fluid-structure interaction in large-scale offshore floating photovoltaics. The model that was attempted to be solved analytically is based on a model presented by Pengpeng Xu (2022).
The dimensions in the equations were removed. Applying a perturbation method yielded hierarchic partial differential equations by introducing the wave amplitude divided by the depth of the ocean as a small perturbation parameter. The analytical solution of the first order problem was found by applying separation of variables and by using a Fourier transform. For certain classes of problems it is shown in this report that it is possible to analytically solve a model for fluid-structure interaction in offshore solar farms for various initial conditions.

The development of an Active Reflection Compensation (ARC) algorithm for a wave generator is challenging. Water behaves in a strong nonlinear way and the time available for the computation of the compensating segment displacements is short. Especially for the case where the wave height sensors are mounted on the surface of the segments. The current ARC algorithm of Bosch Rexroth is based on an approximation of the Biésel transfer function. Although this method gives fair results, it lacks performance regarding the absorption of oblique waves. This report introduces a wave model identification method based on the Discrete Fourier Transform (DFT) and Extended Kalman Filter (EKF). With the EKF having the ability to include measurement noise and determine model uncertainty, this leads to reasonable estimates of complex second order waves. This report does not only cover the identification part of the algorithm but the full ARC algorithm from wave height measurements to a time series for the segment displacements. Although the results are based on simulations, the algorithm shows a much improved absorption performance for a wide range of propagation directions. It shows decent results for tests with several different sets of wave characteristics. The identification process needs time to mature, which leads to a decrease in absorption performance in the early stage of the free-surface elevation time series. A hybrid method is designed, in which the short-term absorption is based on the current algorithm and, after a certain time interval, the model based algorithm will take over.

Trim optimization is an approach considered by the industry to improve the energy efficiency of ships, having a potential in both reducing operational costs and to decrease the emissions of the ship. Potential fuel consumption reduction by trim optimization is 0.5 to 3 % and to up to 7% in extreme cases. Stolt Tankers, a shipping company active in the chemical tanker market, wants to increase the energy efficiency of their ships in operation by trim optimization. For a limited number of ships, trim tables from model scale towing tests are available, but these are not used and the accuracy of these tables are unknown. The objective of this research was to develop a method to decrease fuel consumption by trim optimization, by a dynamic fuel consumption estimation model based on available operational data, that can be integrated in the voyage management system of Stolt Tankers. A dynamic fuel consumption estimation model has been developed, using mainly the noon report data of the C-38 ship class, consisting of six sister vessels of 38 000 DWT chemical tankers. Quality of noon report data is an issue: human error in observing and recording data causes noise and a mismatch exists between the snapshot of conditions on one hand, and the 24 hr averaged sailing speed and recorded shaft power or fuel consumption on the other hand. A data pre-processing framework has been developed and applied to integrate and transform the data, clean and filter the data. The model is able to extract the effects of speed through water, mean draft, trim, sea water temperature, wind force, sea state and swell state and their relative direction to the ship and days since last hull cleaning and propeller polishing. The model has shown to perform optimal using the regression model of Lutzen and Kristensen (2013), combined with a multiple layer feed-forward neural network, consisting of 1 hidden layer with 15 neurons. The model is able to estimate the shaft power with an average accuracy of 6.58 % for a random test set of the noon report data. It is able to extract the effect of trim on shaft power and to consider the effect of weather and fouling conditions. Model results show that about 1 to 2% of shaft power per 0.50 m can be saved, with trim by bow being the optimal trim. Based on sea trial results, it is concluded that the model performs most accurate for conditions that are represented by a high quantity of historical data. The model can be applied for speeds between 12 and 14 knots and for mean draft conditions of 9.5 m and more. Within this range, the effect of trim and weather conditions are followed with reasonable accuracy. It is confirmed by the sea trial that trim by bow is the optimal trim, with a much stronger magnitude of the effect of trim on shaft power. A difference of 6 to 8% in shaft power was found for a change in trim of 0.50 m.

The awareness of the climate change is increasing and the effect of air-pollution is irrefutable. To decrease the emissions of large ships the required amount of fuel has to be minimized. This is done by increasing the efficiency of the engine, decreasing the hull resistance or by lowering the cruise speed. Another interesting way of decreasing the emission is by using Wind Assisted Ship Propulsion (WASP). The Turbosail is a promising type of wind propulsion for this purpose introduced by Jacques Cousteau[4]. The Turbosail is an aspirated wing which is able to generate up to 3 times more lift compared to a non aspirated wing. A lot of research has been done in order to increase the performance of the Turbosail. But this research has mainly been done on the outside of the Turbosail and the suction area is often modelled as an area with a uniform flow. In this research a model has been made in order to give insight in the behaviour and sensitivity of the suction system of the Turbosail. First the model foundation is described. A lumped parameter approach is chosen and the structure of the model is described. The model of the fan is described and after this the total model is made using Matlab Simulink. This model is made such that the number of elements (the amount of parts that the Turbosail is divided in) can be easily varied. This is done in order to perform a convergence study. Followed by a mathematical verification with carefully chosen tests the model is considered as verified. To understand the sensitivity of different parameters of the system a parameter variation is performed. Different parameters are varied and their effects are simulated. This yields insight in the sensitivity of the system and can be used in order to optimize the energy efficiency of the total suction system. Finally two possible improved designs are simulated combined with their decrease in power consumption. These results can be used for future simulations and designs with the main purpose to decrease the energy consumption of the shipping industry.

Inefficiency in trucking has both economical and ecological consequences. In literature, horizontal collaboration is identified as one of the most promising solutions to this problem. However, collaboration is not often encountered in trucking industry, since carriers are hesitant to join collaborations. This is caused by a fear of sharing information and an uneven distribution of requests between carriers. Furthermore, the amount of collaborative gain remains still unclear when dealing with a dynamically changing environment, which is often present. This work aims to fill this knowledge gap. Firstly by developing a vehicle routing problem (VRP) model, which includes dynamic requests, horizontal collaboration and customer satisfaction. Next to that, a solution method is developed which is based on Adaptive Large Neighborhood Search (ALNS). The performance of the implemented method is evaluated with a computational study of 10 instances. The performance is compared with a full information (FI) method and another dynamic method (SI). The FI method evaluates the same instances, with all information known beforehand, thereby acting as a lower bound. The newly developed solution method has shown to perform 39% worse compared to full information, while being able to deal with dynamic requests. The SI method shows an increase of 60% in routing costs when compared with FI.
Next the development of the model and solution method, the implemented method is used to investigate the collaborative gain for four levels of collaboration in a dynamic environment. The level of collaboration is expressed by the number of requests that is reassigned between carriers. The results show that up to 23% collaborative gain can be realized in the dynamic setting.

To improve the submerged time of diesel-electric submarines (SSK), air independent power (AIP) systems have been developed in the past. So far only submarines with AIP systemsin combination with one or more diesel generator (DG) sets are designed and built. The increased technological readiness level of modern fuel cells (FC) and the energy density of modern lithium-ion (li-ion) batteries trigger the possibility of a fully electric submarine. This concept of hybrid FC-battery energy storage and generation could eliminate the requirement for DG sets and a snort system to charge the batteries. The operational advantages in terms of improved indiscretion rate, reduced maintenance and smaller crew, silent energy conversion and reduced complexity of the ship systems design could have a great impact on conventional submarine design. In this thesis the design changes due to a switch to a fully AIP plant are described and a submarine concept design is created. The design should have the same submerged displacement and sprint capacity as a set reference design. The selected AIP plant uses a proton exchange membrane fuel cell (PEMFC), lithium iron phosphate (LFP) batteries and hydrogen stored in high pressure bottles. The design is based on a reference design from which the diesel related systems and batteries were removed. Since the new power plant requires less maintenance also the crew size was reduced, which resulted in a smaller accommodation. The removal of systems and the smaller accommodation resulted in a freed up volume for the new power plant. Using a matlab program that systematically generates power plant configurations within the available volume an ideal power plant is selected. The selection criteria is set to maximum
range, while still satifying the speed requirements. Subsequently, this power plant is integrated in the design. Other aspect that are considered during the design are the electric load balance, the heat balance, air quality and the type
of main electric motor. Also the trim and stability are considered. This results in a concept submarine design. Finally, the new concept design is compared with the reference design on the aspects mentioned earlier. For the range and endurance a fully battery powered submarine is also included in the comparison. The results show that the reference design has a three times higher maximum range and endurance than the concept design. However, when the indiscretion rate (IR) was taken into account the full potential of the concept design became clear. The IR of the concept design is 0%, which means it can operated underwater for the entire range and endurance. This is a large improvement over the reference design, which has to snort on regular intervals. When the concept is compared with the fully battery power submarine the maximum range and endurance are approximately doubled. As always, it all depends on the desired operational profile of the user whether the design is the most suitable option; however, it is expected that for most navies the created design is a significant
improvement over the diesel-electric alternatives. Considering all aspects above it can be concluded that the concept design with PEMFC, LFP batteries and compressed hydrogen is capable to perform short to middle long missions, while provided their operating navies with significant operational advantages like 0% IR, lower acoustic signature and smaller crews.

This work simulates the impact of horizontal motion on the Symphony wave power device. To that end the existing time domain simulation is expanded with a module that simulates horizontal motion in the 2d plane. This extension is coupled with the existing operational modelling. the extension is based on a mathematical motion model based on rigid body dynamics and linear wave theory. Simple cases are compared to analytical solutions in order to test the model. The model is then used to calculate expected motions, mooring loads and differences in energy production between a Symphony that can move freely and a restrained Symphony.

The demand for renewable energy is growing, due to a growing awareness among people about the effect of burning fossil fuels on the environment. Governments have signed climate agreements and are obliged to decrease their level of exhaust gasses. This change in attitude regarding the environment led to an upcoming market for renewables. A significant part of the demand for renewable energy is covered by the wind industry, both on- and offshore. Especially the offshore wind market holds huge potential, due to stable wind conditions and growth opportunities. A side effect of the evolving industry is that turbines are increasing in size and are being installed in deeper water depths. It is expected that the methods of installation, currently used in the offshore wind market, will no longer be suitable for the installation of new generation turbines. In this research, installation of offshore wind turbine towers using a heavy lift vessel (HLV) is opted as an alternative to the current installation methods (jack-up installation). The major benefits of floating installation, when compared to jack-up installation, are the independency on both soil conditions and jacking operations. A challenge of floating installation, however, is the introduction of vessel motions resulting in excitation of the tower. The main objective of this research is to find the most efficient way to control the motions of the tower during installation using a HLV. To fulfill this objective, first, a conceptual design study has been conducted, which focused on developing concepts for the safe installation of offshore wind turbine towers using a HLV. Safe installation was assumed if the displacements of the tower bottom maintain within limits, as specified in a list of design requirements and criteria. Before examining any concept in more detail, the response of the tower and the effect of applying a form of motion compensation has been examined in a general way. To test the response of the tower in the crane in a general way, with and without motion compensation, the tower in the crane has been represented by a double pendulum system with a moving support point. Then, using the numeric model, the response of the tower in the crane has been computed for certain sea-states in both frequency- and time domain and for both the free hanging- and the motion compensated case. The motion compensation system has been represented by a virtual spring damper system, of which, by changing the simulation parameters, the optimal configuration (position, stiffness and damping) has been determined that minimizes the tower response. From the results, it can be concluded that a significant reduction of the tower bottom displacements can be achieved under the application of an active motion compensation system, the requirements for safe installation, however, are not yet fulfilled.

Offshore operations are increasingly executed by vessels operating on dynamic positioning (DP) due to advantages it has for short operations, such as maintenance and crew transfer but also for track keeping operations and projects in deeper water. Currently, DP capability plots are used to indicate whether an operation can be performed, but this is based on static calculations and it does not consider the offsets that are found due to motions of the vessel, while the offsets can be critical in case a structure is present or if a certain accuracy of a station keeping operation is necessary. Currently, to determine the offsets of a vessel on DP, the system is modelled using a time domain approach. Multiple simulation runs are carried out to calculate the expected extreme offsets in a given time interval, which is known as the most probable maximum offset (MPM offset). This is a complex and time consuming process and therefore it is not always done in practice before an operation starts. In this research, a method is developed to estimate the surge MPM offsets of a vessel on DP due to the wave drift forces using a frequency domain approach, as this can lead to faster estimates. But two problems are faced: The first is that there is no mathematical model available describing a vessel on DP which can be used to accurately calculate the offsets in the frequency domain. The second problem is that there is no known relation between the offsets and the extreme behaviour, which leads to the MPM offsets. To find the MPM offsets, first of all a one-dimensional time domain model of a vessel on DP is made, considering only the surge degree of freedom. Next, to determine the surge offset response using a frequency domain approach, the differential equations of the system are linearised, which gives the transfer functions from the environmental forces to the surge offsets. This is used to estimate the surge offset response in the frequency domain. The accuracy of this method is determined by comparing the root mean square value (RMS) and the zero up crossing period to that of the time domain results. Then, two alternative methods are developed to calculate the MPM offsets from the surge offset response characteristics directly. The methods use the RMS and zero up crossing period of the surge offsets calculated in the frequency domain, to determine the extreme behaviour statistically without the use of multiple simulation runs. Using the linearised model of the vessel on DP, it is found that the surge offset response can be calculated within an accuracy of 4% of the results generated by the time domain simulations, based on the root mean square value and the zero crossing period. Therefore, an accurate estimate of the surge offsets is found using a frequency domain approach. Both alternative MPM offset calculation methods, using the surge offset results of the linearised model, give MPM offset estimates within approximately 10% of the results of the time domain simulation approach. Taking into account the strong variability found in the MPM offsets calculated by the time domain approach, the estimates from the frequency domain approach are regarded as good estimates.
It is concluded that the methods developed in this research can lead to faster and therefore timely MPM offset estimates to use for the safety and accuracy of operations. This can improve the way of working for many offshore operations where often no use is made of MPM offset estimates due to the disadvantages of the methods currently used in practice. It is recommended to extend the method developed in this research to three degrees of freedom, such that it can be implemented in practice.

Five naval support vessels are being replaced. For this replacement two focus points are important. The first one concerns creating more unity within the fleet, achieved by using the hull geometry as a monolithic part. The second one concerns the aim to reduce harmful emissions by reducing the effects of the energy transition by minimising the resistance of the vessels. The current design approach at DMO has deficiencies which limit the ability to vary hull forms and to analyse a large set of design options. Also propulsion power is predicted by regression lines only, which makes it difficult to evaluate novel hull forms. Motion predictions are only used in a later design phase. These deficiencies need to be resolved. The technological opportunities which will be used to address these deficiencies are incorporating CAESES and RAPID in the concept exploration phase. CAESES is a CAD method with integrated optimisation algorithms which makes it useful to make hull form variations by using parametric optimisation. RAPID is a potential flow solver which can be used to predict the wave resistance on the geometry. The total resistance will be predicted by using Holtrop and Mennen for the viscous resistance components. The seakeeping capabilities are predicted by a simplified version of the linear strip theory. The main objective can be formulated as: How can the unity and the energy transition be analysed in the concept exploration phase for the new generation naval support vessels with a hull geometry point of view using RAPID/Holtrop/seakeeping integrated with CAESES Four validation studies have been performed. The test case studies are analysed on the differences in effective power and vertical displacement. The first conclusion is that the effective power will increase for a family design strategy in comparison to a single ship design strategy. The second conclusion is that the vertical displacement can be decreased when using a family design in comparison to the single design strategy. But only when the Logistic Support vessel is left out of the family of vessels, because of its restricted length. The design speed can be used as a design variable, but only when a more sophisticated power usage objective is used. The new approach can be very useful in the concept exploration phase at DMO. The new approach uses a more advanced resistance objective in combination with hull variation. It can also predict the seakeeping capabilities in the concept exploration phase already. The integration of a potential flow solver and prediction on vertical displacement at the bow can be done within one optimisation and a study is possible within reasonable time (under six hours). This makes the new approach practical in the concept exploration phase.

A stinger is a steel space frame structure, used on pipe-lay vessels, to support the weight of a suspended pipeline. A stinger is highly fatigue loaded due to environmental loads, vessel motions and variable pipe loads. In the design phase, predictions for the structural behaviour of the stinger were made. However, inspection history showed discrepancies between the design phase and reality. A stinger monitoring system was proposed to provide a solution for this problem. The goal of the thesis was formulated as follows: Design of an optimised sensor placement method for a stinger monitoring system to localise and quantify damage. A method based on the vibration characteristics of a stinger model was chosen for damage localisation and quantification. This method correlates the measured modal property changes with analytical modal property changes to identify damaged members and to estimate the damage extent in these members. A sequential sensor placement method was applied to determine the sensor locations contributing most to the modes of vibration of the stinger model. The proposed method can accurately localise damage for damage situations with one damaged member. For damage situations with multiple damaged members, the method is able to correctly identify one of the damaged members. To identify the other damaged members, a modification of the method was proposed. On the condition of a damage threshold, this modified method is able to localise multiple damaged members in a selected number of damage situations. The damage quantification method was able to give a good estimate of the damage extent.

The development of renewable energy applications has become increasingly important in the past couple of years due to a growing global energy demand and increasing consciousness of global warming. A recent development in renewable energy is the application of offshore floating solar systems. A prototype design for this application, as developed by the company ’Oceans of Energy’, consists of multiple floating platforms (floaters), moored to the sea bed. One of the challenges for offshore floating solar systems is the continuous wave induced force acting on the floater that can become significant in severe weather conditions. Numerical simulations are often used to analyse and predict these forces. Combined frequency-time domain solvers are the most promising tool for this design to obtain reliable results within reasonable computational time. However, it is unknown what the capabilities of this solver is for the novel offshore floating solar system. The goal of this study is therefore to determine to what extend the frequency-time domain solver is able to accurately simulate the behavior of the multi-body, offshore floating solar system. A numerical model was developed in the simulation tool ’aNySIM’. Experiments conducted in the offshore basin at MARIN were used for the model structure development and validation. Additionally, viscous damping effects were implemented from empirical data based on the experiments. Decay tests were used for damping determination. This resulted in inaccurately determined forces and motion amplitudes for regular and irregular wave tests. A new damping determination method was introduced, using regular wave results as input. The accuracy of the model improved with 4% using this method. Nonetheless, inaccuracies in mooring line forces, oscillating behaviour and motion amplitudes are present. These inaccuracies have been addressed with an uncertainty analysis and sensitivity studies. Trends within the accuracy of the simulation model were linked to physical phenomena that occurred during the experiments. Analysis showed that several effects, related to the novel design characteristics, influence the model accuracy. Multi-body (e.g. shielding of floaters) and mooring system aspects (e.g. hydrodynamic loads on mooring lines) have been identified, influencing the viscous damping of the system. Additionally, nonlinear effects due to, amongst others, breaking waves have been identified. For regular wave tests and lower irregular wave tests, the simulation model gives reliable results with errors in the mooring line forces below 10%. These errors are mainly ascribed to viscous damping effects. For higher sea states the simulation behaviour shows discrepancies and errors in the mooring line forces increase. In these tests, nonlinear effects due to breaking waves become more relevant. For future work, different uncertainty causes must be further isolated in the simulation model. This can be done by obtaining more experimental data. To quantify the effects, studies in other numerical tools can be performed (e.g. CFD calculations) and more extended sensitivity studies must be executed in aNySIM. We present a structured