The increased consciousness of the negative impact of human-induced climate change has resulted in rapid developments within the offshore wind industry. With Wind Turbine Generators (WTGs) becoming increasingly larger and available shallow water sites becoming scarcer, new offshore wind solutions must be developed to accomplish the goals set by today’s policymakers. The new deep water sites available for offshore wind are not applicable for the current benchmark of monopiles and jack-up vessels. New state-of-the-art applications, such as Floating Offshore Wind (FOW), come into play in the global offshore wind market. To meet this demand, Heerema is developing installation methodologies for floating to floating installation applications. One of these methodologies is the RNA+ method (Rotor Nacelle Assembly + Tower), lifting a fully assembled WTG module in one lift from the vessel deck on top of its foundation to limit the number of critical lifts. Operability studies are required to examine whether such operation is feasible. As the FOW industry is the new kid on the block, little is known about FOW’s configuration and other influences. Therefore, this research aims to determine the effect of design parameters of the three key components of an offshore floating to floating installation on its operability. These key components are the WTG, floater, and installation vessel. For this research, the IEA 15 MW reference turbine with an altered tower, a Tension Leg Platform (TLP) provided by Intecsea, and Heerema’s Semi-Submersible Crane Vessel (SSCV) Sleipnir were used as WTG, floater, and installation vessel respectively. A numerical base case model containing these key parameters was built to address the influence of the design parameters. This base case models the free-hanging stage of a complete WTG module suspended in the SSCV’s crane 3 m above the TLP in a water depth of 150 m. The numerical model was analyzed in the Frequency Domain (FD), considering only first-order effects. With respect to this base case, all parameter variations were compared. A mean JONSWAP spectrum was used as wave spectrum. The results show that this installation method is sensitive to long wave periods ( > 8 s). The clearance between the nacelle and crane-boom is deemed the most governing limiting criterion. The relative vertical Z-tip motion between the tower bottom and TLP top and the side-lead angle of the crane hoist wire are the secondary governing limits. Design parameters that influence the static clearance between the nacelle and crane-boom have the most impact on the total operability. With the current design parameters world’s largest SSCV has a limited operability for installing the modified version of the IEA 15 MW reference turbine with a single crane lift. Alterations to increase its crane boom reach and clearance are needed to perform this single lift installation. The hub height and nacelle casing size of the WTG limit the operability significantly. Furthermore, due to its relatively small size, stability and stiffness in heave direction, the TLP hardly affected the operability.

Over the last few decades, the bypass ratio and nacelle diameter of modern turbofans have been increasing to achieve higher efficiencies. This trend has forced the underwing-mounted engines to be coupled more closely to the wing surface and the flap system, which significantly enhances the low-frequency noise, known as jet installation noise (JIN). In this project, lobed nozzles are proposed and tested as a passive flow control technique for the reduction of the JIN. Measurements were performed using hot-wire anemometry and a linear array of microphones to investigate the effects of lobed nozzles on the near-field structure of a jet. The lobed nozzles were found to alter the convection velocities of the pressure fluctuations and the transition to turbulence of the jet. Moreover, far-field pressure measurements were performed inside the anechoic wind tunnel to examine the effects of the near-field structure on the perceived far-field noise. These findings can be used to assess the effectiveness of lobed nozzles for the reduction of the JIN in specific jet installation configurations.

The offshore wind industry is increasingly constructing wind turbines farther from the coast, in deeper water, and under more extreme conditions. This requires larger (monopile) foundations and necessitates new installation methods. An important factor affecting workability is the dynamic behavior of the monopile during installation. The objective of this thesis is to develop a method for determining the hydrodynamic loads caused by internal sloshing in an open-ended monopile (MP) as it transitions from a horizontal to a vertical position in the splash zone. First, the resonance frequencies of the internal water column are predicted with analytical approximations based on linear theory. Distinction is made between piston mode and sloshing. Two numerical methods, linear potential flow (LPF), and computational fluid dynamics (CFD) are used to verify the resonance frequencies. Since the CFD analysis is done in 2D, a 2D representation of the open-ended monopile is considered. Due to the presence of viscous effects in CFD, the resonance observed with CFD consistently occurs at a lower frequency than for the analytical and LPF methods. Also it is found that an decrease in inclination angle of the monopile with respect to the horizontal, while maintaining the same submerged length, results in lower resonance frequency for both piston mode and sloshing in both LPF and CFD. To assess the accuracy of LPF in describing the motion of the internal water column, it is compared to the CFD model. Input excitation in the CFD model is low enough to avoid non-linear sloshing modes and other non-linear behaviour of the free-surface. The ComFLOW 2D CFD model has been validated against various works from the literature for the accurate representation of gap resonance frequencies. For both the piston mode and sloshing resonance, discrepancies between the two numerical methods are found, which can be attributed to viscous effects. At resonance viscous effects are nonnegligible, therefore the LPF method over-predicts the severity of the piston mode and sloshing. The influence of both the submergence of the monopile and its inclination angle with respect to the horizontal is considered. The hydrodynamic coefficients for added mass and damping are found with forced oscillation for both upright and inclined geometries. While good agreement is found between the LPF and CFD results away from resonance, the CFD results in the vicinity of the resonance frequency are used to tune the LPF model, by way of additional linear damping, to achieve more accurate results. It can be concluded from the present work that the resonance of the internal water column near the first sloshing mode significantly affects the overall hydrodynamic force and must be taken into account. At the peak hydrodynamic force observed during the first sloshing mode, the sloshing induces forces 5.59 times higher (submergence of 5 meters), 3.62 times higher (submergence of 10 meters), and 2.33 times higher (submergence of 15 meters) compared to cases where sloshing is not considered. Looking forward, it is strongly advised to conduct forced oscillation tests with larger amplitudes, as this explores the effect of non-linear chaotic sloshing. Additionally, expanding the CFD analyses to 3D, where more non-linear sloshing effects are expected, such as swirling, is recommended. Furthermore, given the differences in results between LPF and CFD, it is valuable to validate the findings through model experiments.

The offshore wind market is growing rapidly, and new offshore wind projects are being launched more than ever. To keep up with demand, parts for these wind turbines are being produced all over the world. To get all the parts needed to their destination on time, they must be transported on heavy transport vessels (HTVs). Today, business cases focused on maximizing profits dictate the design of these vessels. Despite the upcoming energy transition, the environmental impact of these vessels is usually neglected. Therefore, there is a need for a method to evaluate the economic and environmental performance of HTVs. One basis for such a method is Blended Design. This method is able to cope with market uncertainties in the early stages of ship design by expanding knowledge when design freedom is still high by combining market forecasts for offshore wind farms with multiple vessel designs. An uncertainty model then evaluates the financial performance of the vessels in the market, allowing designers to explore the performance on basic main dimensions of an offshore wind installation vessel. The main limitations of this method are that it is not able to optimize on environmental performance and evaluate the financial impact of alternative fuels. Due to growing concerns about climate change, Ulstein has seen an increase in requests for the use of alternative fuels in ship designs. For this research, methanol, ammonia and liquid hydrogen are being investigated as these alternative fuels are considered future-proof. The use of alternative fuels in ship design involves some adjustments to the Blended Design method. Due to the different gravimetric and volumetric densities of these alternative fuels, this has implications for the endurance of the ship design and the amount of cargo the ship can carry. Changing system and installation requirements and varying fuel costs also drastically alter the financial performance of alternative fuels on ship designs. The proposed methodology accounts for these changes and quantifies alternative fuel emissions by converting them to CO2-equivalent emissions. In this way, other greenhouse gases such as CH4 and N2O are also included in this metric. The environmental performance is then expressed in the EEXI-equivalent: the amount of CO2-e emitted by the ship design per tonmile. The EEXI-e index makes it possible to compare the various alternative fuels in terms of their environmental performance on the same basis. In this work the EEXI-e method is combined with the original Blended Design method and the method is adapted to include alternative fuels. This makes it possible to evaluate the environmental performance and associated financial impacts of different alternative fuels. Because financial and environmental performance are now linked, it is possible to examine the impact of different ranges of carbon taxes. The case study results presented in this thesis show that the carbon tax has a large impact on the financial performance of the ship when it is applied. When enforced, the choice of an alternative fuel system becomes more attractive. The proposed method has provided a guide to ship designers to make better decisions about the main dimensions of a ship at an early stage of ship design. In addition, the method can provide much-needed insight in the selection of alternative fuels by evaluating the financial and environmental performance of alternative fuel systems.

Introduction - Hydrofoils are often used for high-performance craft. They enable the hull to rise out of the water and reduce drag. A recurring problem is ventilation, this is the presence of a cavity filled with ambient air on the lifting surface. Ventilation causes the lift of the hydrofoil to decrease drastically. A lot of research has been done on ventilation behaviour. Ventilation remains a stochastic phenomenon to this day. The same operational conditions do not yield the same flow behaviour, a correlation between the pressure on the lifting surface and ventilation behaviour might exist. This research is an intermediate step towards finding a correlation between pressure on the surface of a foil and ventilation, making ventilation repeatable. The main goal of this research is to find out if a full surface pressure reconstruction can aid the search for a correlation between pressure and ventilation. Method - The test geometry is a NACA0012 surface-piercing hydrofoil with pressure measured using 2 rows of 15 pressure tappings. Extension pieces are used to obtain the span-wise pressure distribution while keeping the submerged span constant. The test program has three sets: all vertical runs (Set 1), high roll angle runs (Set 2), and runs with ventilation (Set 3). During the experiment, the loads are measured with force transducers on a frame that measures forces in 6 degrees of freedom. The calibration of the force transducers is performed prior to the experiment. The calibration of the pressure sensors is done first using a 9 meter water column before the experiment and during the experiment in the towing tank, extra re-calibration (stepped runs) data is collected. The collected force measurement data is processed to attain the lift and drag coefficients. The pressure measurements are translated to the pressure coefficient and placed in a matrix on the right location of the lifting surface. Results - Based on repeated experimental runs the percentage differences are obtained on sensor and array levels. 30% of the sensors have a percentage difference of more than 10%, while the maximum difference for an entire array is 2.5%. A cross-check between the upper and lower arrays showed a percentage difference above 15% for 28% of the sensors, with a maximum difference of 1.2% at the array level. The pressure distributions at 0∘ roll angle, from Set 1, match the general pressure distribution characteristics. Comparing the 3D lift coefficient computed from the pressure measurements to that of the force data or an empirical method yields ambiguous results. The 3D lift coefficient based on the pressure measurement is within a 4% difference to Xfoil. The result of the high roll angle runs, Set 2, show the effect free-surface proximity has on the chord-wise pressure distribution. For the shallowest pressure reconstructions, close to the free-surface, the pressure distribution shows a minor peak near the leading edge after which the curve drops to near zero quickly. The operational conditions do not affect the quality of measurements. During two runs ventilation occurred, this is Set 3. The time-traces of the three forwardmost sensors show a dip prior to ventilation, with one sensor displaying an oscillating response. It is hypothesised that this is the position where ventilation is induced, but based on the results this can not be proven. All sensor response follows the same pattern when the ventilation bursts over the surface. The set-up is able to capture quick pressure changes. Conclusion -The percentage difference is too high for too many sensors. On the array level, however, the difference is considered small enough. The results of set 1 are in good agreement with known data. The results obtained at 60∘ roll angle are concluded to be of the same quality as for 0∘ roll. The method is capable of providing results in a wide range of operational conditions. Based on the ventilation runs, no correlation to pressure reading has been found. The time-traces of the sensors near the leading edge of these runs do show fluctuations prior to ventilation. With more ventilation runs available, it is highly likely that a correlation can be established. Due to the slim data set, it is possible that the conclusions drawn will be refuted in the future when a larger data set is available. Currently, the goal has not been achieved, and it cannot be stated with certainty that the method used here to attain a full surface pressure reconstruction can be used to correlate pressure to ventilation.