Green water problem and its loading effects on high speed containerships was investigated with the purpose of developing a modelling framework that can practically guide naval architects to a better understanding of this problem and improvements in design. The research began by reviewing extensive publications relevant to the understanding of green water, limitations in the ways the problem had been addressed and establishing a methodology that could effectively unlock the physics and efficiently solve the problem. As a first step, a summarised background to how green water started, developed and finally took place was presented. An experimental programme was then implemented in order to observe the occurrence and to explore the physics behind these events. From the outcome of the experiments, it was obvious that green water modelling could be developed and solved by Computational Fluid Dynamics (CFD) technique through Volume of Fluid (VoF) method. To provide a starting point for this research, theoretical background of CFD was briefly introduced. Furthermore, in order to validate this approach, two benchmark tests were implemented and compared with published experimental data. It showed that in both cases, the simulation could accurately reproduce the results obtained from experiments. Following this analysis, research continued to expand the CFD simulation to modelling of green water. Due to the complex and random nature of green water, development of the simulation framework was semi-empirical and based partly on experimental data. A pure theoretical approach could have been adopted. However, taking into consideration current limitations in ship motion prediction theories and sensitivity of green water to elemental factors, it was justified that semi-empirical approach was appropriate. The simulation was conducted and the output results were compared with experimental results for a variety of test conditions that involved ship velocity, wave height and period. Good agreement between simulation and experiment was obtained. For all loading cases, experimental results were reproduced fairly well. This suggested that the modelling framework was adequate for all practical purposes. Investigation was also conducted on a series of rectangular breakwaters that were fitted on the forecastle deck. Changes in water behaviour and loading following changes in the breakwater were well reflected. This implied that instead of a rectangular breakwater, the simulation model could also be applied to other types of breakwaters. The results suggested that the simulation methodology has many practical applications. Within naval architecture, it can be used to perform parametric studies in order to select an optimal design of breakwater for a ship. In other sectors such as coastal engineering, the methodology can be adopted to investigate the interaction between water surge and a seawall or offshore breakwater. In conclusion, it was found that the developed modelling framework shows potential for simple modelling of green water in which the behaviour of the water and its loading effects could be well reflected. It was further concluded that, provided appropriate principles are applied, the methodology has potential for other engineering applications. While it is acknowledged that current model may be limited by its semi-empirical basis and issues associated with computational requirements, it is noted that considerable possibilities for future research and development remains to be explored.

On December 17th 2002 the World Meteorological Organization issued a statement according to which the global mean surface temperature has risen and consequently 2002 was the warmest year in the 1961-2002 period.  Positive sea surface temperature anomalies across much of the land and sea surface of the globe in general contributed to the near record temperature ranking for the year along with climate anomalies in many regions across the globe.  Climate change as a result of global warming is a worldwide occurring phenomenon which the experts have only recently started to understand and which affects and significantly will affect us in the near future.  The effects of climate change have been somehow neglected by the ship and offshore related academic and research communities. In the case of thermal effects on ships structures, unless the problem solved is temperature dependent, this type of stress has often been neglected and not been taken into account in most types of analysis.  The most likely reason behind this would seem to be that the stresses produced from temperature changes would be too small to be taken into account compared with still water loads or wave bending stresses.  This is not the case though.  Records exist of ships having broken in half while moored in still water and major hull factures occurred in still water while the temperature was changing as it can be seen from the relevant published literature.  Very little work on thermal stress on ship structures has been published since the 1950s and 1960s and no work has been done that considers temperature effects on ultimate strength. Research undertaken aims to incorporate temperature effects on existing ultimate strength formulation by using a thermal stress approach, compare and use recently proposed corrosion models to model corrosion effects on ultimate strength and provide a foundation on which reliability analysis could then be performed for Tanker/FPSO structures operating in the North Sea.  After comparing a number of possible approaches that would enable to loading components to be combined in a stochastic fashion, the loading part of the reliability analysis is handled using extreme wave statistics and the Ferry Borges-Castanheta load combination method. Annual reliability indices and probabilities of failure are calculated for hogging and sagging conditions using both time-variant and time-invariant approaches and a variety of reliability analysis approaches showing the effects of temperature along with partial Safety Factors for all variables taken into account.

The range of an AUV is dictated by its finite energy source and minimising the energy consumption is required to maximise its endurance. For an individual AUV, this may be achieved by obtaining the optimum hydrodynamic hull shape design. For a fleet of multiple AUVs, this may be targeted for both individuals and the entire fleet. The purpose of this work is, firstly, to develop a rational approach to find an optimal hull shape, secondly, to provide guidance for operators on suitable configuration for multiple AUVs' missions, finally, to investigate the influence of the propeller on the drag of twin self-propelled AUVs. An AUV hull form has been optimised to obtain low resistance hull. Hydrodynamic optimisation of hull form has been carried out by employing five parametric geometry models with a streamlined constraint. Three Genetic Algorithm optimisation procedures are applied by three simple drag predictions which are based on the potential flow method. The results highlight the effectiveness of considering the proposed hull shape optimisation procedure for the early stage of AUV hull design. The influence on the drag of the fleet of multiple towed prolate spheroids is investigated with various configurations and spacings. A series of three-dimensional simulations are performed using a commercial RANS-CFD code ANSYS CFX 12.1 with the SST turbulence closure model at the length Reynolds Number of 3:2 x 106. The results show that the spacing between two hulls determines the drags. Seven zones based on the drag characteristic of twin towed models are classified. Both the multi vehicle vee and echelon configurations show limited influence against that of the entire fleet's energy budget. Then the investigation extended to determine the combined drag of a pair of propelled prolate spheroids at various longitudinal offsets and transverse separations. The RANS-HO propeller models are selected to estimate the time averaged thrust and torque of the propeller. The results show that the self-propelled vehicles experience an additional drag which is dominated by the thrust distribution of the propeller rather than torque. The drag of the following AUV is increased due to the upstream propeller, defined as a propeller race deduction. The two sources of self-propelled drag increment are the viscous interaction and a direct result of proximity to the propeller race upstream. The result highlights the importance of both thrust deduction and propeller race deductions when calculating the propulsive power consumption. Based on this optimisation procedure and this numerical data, operators can design the optimal hull shape of an individual AUV including the determination of the optimal configurations in transverse separation and longitudinal offset based on energy considerations of fleets of multiple AUVs, it can be very effective at the early design stage.

Modern Autonomous Underwater Vehicle (AUV) technology has a number of limitations and one of these is vehicle manoeuvrability. Conventional flight style AUVs generally have turning circle diameters of five or more vehicle lengths, but most marine animals can turn in under one body length. This shows there is merit in looking at marine animals for inspiration to improve the manoeuvrability of AUVs. Aquatic flight propulsion is one marine animal propulsion strategy that was identified early in the research as having the potential to full fill this role. Aquatic flight propulsion has been studied experimentally in the past, but most of the past research focused in one or two axis aquatic flight (foil pitch and dorsoventral roll). However, marine animal literatures show animal aquatic flight is a three axis problem and there is an additional motion component in anteroposterior yaw. The effect of this yaw motion is not well understood and this will be the focus of this thesis’s research. The effect of aquatic flight yaw motion is investigated using a combination of computation modelling and experimental studies. It found two-axis aquatic flight is better for producing propulsive thrust for most scenarios, but three-axis aquatic flight is useful for producing additional off axis force. In particular, the three axis slanted foil actuation path can produce a sizeable vertical force with very little change to the horizontal thrust coefficient, which would be very useful for a positively buoyant AUV to control its depth. The experiment verified the model’s results and many of the experiment data points were within 30% of the model prediction. The experiment has a relatively large uncertainty due to turbulences in the recirculating water channel, so 30% is a reasonably good fit. Whilst there is room for improvement for both the model and the experiment, the current model is sufficient to produce provisional estimates for actuator and control system design as well as identification of various cases of interest for further in depth analysis.

The use of adhesive bonding as a structural joining method has been gaining recognition in marine industry in recent years, though it has been widely adopted in other fields such as aerospace, automobiles, trains and in civil constructions. The type of materials used and design practices followed in marine structures are different from what is applied in other disciplines. Therefore new research approaches are required and recent novel ideas are ex- plored in the context of application of bonded joint configurations in marine environment. The research is directed at developing analysis tools for predicting the displacement, stress and strain fields in adhesively bonded joints between dissimilar adherends. In the finite element formulation, the adherends may be isotropic or orthotropic layered materi- als, which are assumed to behave linear elastically. The adhesive material is assumed to behave as elasto-plastic continuum, where the nonlinear behaviour is modelled as either a rigid or a semi-rigid adhesive solid that can be represented by the Ramberg-Osgood ma- terial model. The yield behaviour of the polymeric adhesive is modelled using a modified von Mises criterion, which accounts for the fact that plastic yielding of polymer materials may occur under the action of hydrostatic as well as deviatoric stresses. The geometric nonlinearity is based on the assumption of large displacement, large rotation but small strain, and it is implemented in the code using the total Lagrangian approach. The scheme is applied on three case studies viz.: a study of adherend imbalances in a single lap joint, stress analysis of a butt-strap joint system and a hybrid joint are un- dertaken. The influence of geometric and material nonlinearity on joint deformations and adhesive stresses, are studied for a single lap joint with dissimilar adherends, aluminium and a Fibre Reinforced plastic composite material, with varying adhrend thickness ratios. The adhesive stress-strain data obtained from the model are compared with the exper- imental stress-strain curve and the numerical results are validated with the analytical solution. Three dimensional effects like ’anticlastic’ and bending-twisting’ are shown in the joint with a dissimilar adherends. Key results are obtained that explains the state of nonlinear adhesive stress state in the joint. Analysis of butt-strap joint focussed on nonlinear modelling of a semi-rigid adhesive ma- terial that is used to bond two dissimilar adherends, steel and aluminium. The analysis demonstrate that the influence of geometric and material nonlinearity on the joint de- formations as well as the adhesive stresses is significant. Nonlinear adhesive stresses are compared with the actual strength of the highly flexible adhesive, highlighting the need for the consideration of material nonlinearity in the bonded joints. Failure modes for the joint are inferred from the observations made on the adhesive stress state in the butt-strap joint. Last study, deals with three dimensional analysis of a GRP-Steel hybrid joint carried out to model the initiation and propagation of crack under a set of static loading cases. Earlier studies were restricted only to two dimensional analysis. This three dimensional analysis showed that the adhesive normal stress is not constant across the width of the joint. Critical locations of stress concentrations are identified and the failure mechanisms are compared with the experimental specimens. The observations made from this research study using a three dimensional finite element program, compliments the present knowledge in the field of adhesively bonded joints.

Conventional marine fuels have always limited the endurance of high-speed ships leading to fast but inefficient cargo ships. This research considers the fuel weight barrier in high-speed ship design and the use of hydrogen as a marine fuel to overcome this barrier. Simultaneously, it is now accepted that environmental pollution from ships, particularly large containerships, contributes to climate change. Hydrogen marine utilization provides a solution for both. As common to other hydrogen research the fuel system spans production to utilization. This hydrogen marine system utilizes an established production method to obtain hydrogen from natural gas through steam methane reformation. To achieve an acceptable storage volume meeting the typical highspeed ship dimensions the hydrogen also requires liquefaction. The hydrogen is then converted onboard into shaft power via combustion in aero-derivative gas turbines. This research establishes the necessary system components spanning both onshore and ship components. The novelty of the research has resulted in new design tools. Research into large hydrogen transport applications is not new and a substantial body of research is available from passenger aviation studies performed during the 1980s and 1990s. Additionally, a more current body of research is available describing hydrogen utilization in large gas turbines for energy and oil/gas industries. This combined research provides the characteristics of the onboard hydrogen system of a high-speed foil-assisted containership. This ship is capable of transporting 600 industry standard 20’ containers on long-haul ocean routes, i.e. 5000 nautical miles, at a speed of 64 knots (118.5 km/hr). Such ship performance is not feasible with conventional marine fuels. The design is complex involving a combination of buoyancy and dynamic lift and two distinct operational modes at floating and dynamic draughts. Research involving this ship configuration is included here in conjuction with suitable design methodologies. Besides technical feasibility, economic feasibility of this containership has also been investigated based around the unit transport price required to recoup costs and achieve zero net present value. Such analysis identified that the containership has higher minimum freight rates than conventional containerships but substantially lower rates than aviation cargo. Due to its high-speed and improved endurance it can compete with aviation on transport time and price. Economic review also identified that shorter container door-to-door times are now demanded by the consumer production industry and this hydrogen marine container transport system meets this demand.

The Royal National Lifeboat Institution (RNLI) is the charity that aims to save lives at sea. The RNLI D-class is a five metre inflatable lifeboat that is used near the shore in waves and surf. Anecdotal evidence indicates that the D-class has improved performance due to its unique, flexible, fabric structure, and this flexibility is highly likely to affect the vibrations generated by the D-class. The boat motion is experienced by the on-board crew, and the air and water borne noise are heard by the on-board crew and the wildlife. This thesis aims to measure these two types of vibration, predict the perception of these vibrations and measure the effects of hydroelasticity on both the vibration and perception. Three aspects of hydroelasticity were identified within the D-class: hydroelastic slamming, hydroelastic planing surfaces and global hydroelasticity. This gives a new perspective with which to view the effects of hydroelasticity. A four stage full-scale holistic hydroelastic experiment was performed with each stage aiming to trigger one aspect at a time. The four stages were: static tests, flat water trials, drop tests and wave trials. The D-class was fitted with 52 sensors to measure the boat motion, engine thrust, sponson and keel pressures, deck hinge angles, deck panel deflections and the fabric hull deformation. The static trials measured the shape of the D-class under only buoyancy and weight forces. The flat water trials measured the effect of a hydroelastic planing surface on the forward speed and investigated a phenomenon termed the pulsing motion. The drop tests were performed at full-scale and quasi-2D, and they measured the effect of hydroelastic slamming on the peak acceleration and predicted the Whole Body Vibration (WBV). The open-water wave trials investigated the global hydroelasticity. The static tests showed that the shape of the D-class was more dependent on the keel pressure than the sponson pressure. The flat water trials proved that a flexible planing surface decreases the forward speed by 0.44 knots. The pulsing motion surprisingly exhibited the highest forward speed and it is hypothesised that the structure achieved an unstable equilibrium position of minimal potential energy. The full-scale and quasi-2D drop tests demonstrated that hydroelasticity can affect the peak accelerations and WBV, but the trend was inverted when the drop height was varied from 0.5 m to 1 m. It is believed that the keel is the dominant component during the flat water trials and drop tests, and this is coupled with the fabric hull. No statistical difference was found in the wave trials results but this was explained through the drop test results. The predicted WBV from the wave trials does emphasises the need for a new WBV reduction strategy and incorporating an element of hydroelasticity along with other reduction methods could make a significant impact on the WBV. The airborne noise of the D-class was measured using ISO 14509. The airborne noise was above the limits set out by the European directive 2003/44/EC. A method was developed to measure the water borne noise of small High Speed Craft (HSC) in shallow waters. The water borne noise propagation was modelled using an Image source Transmission Loss (ImTL) model. The perception of the air and water borne noise by a harbour seal was predicted and it showed that the D-class is unlikely to cause damage to the auditory system at one metre but will definitely be audible to the seal at 20 m. The horizontal and vertical transmission loss through a shallow water channel was investigated.

In recent years, faster, lighter and bigger are the key issues in a modern racing yacht for extreme performance. As a result, many yachts have experienced various structural failures caused by the hydrodynamic impact or ’hydro-impact’ phenomenon by slamming. The structural failure by hydro-impact originates from the facts that the external hydro-impact load and fluid structure interaction effect is somewhat misled and when applying the load into current structural design, the ’dynamic’ load is typically, manipulated in a ’static’ way with fluid structure interaction effect, generally, ignored. In this thesis, the hydro-impact load by slamming, its fluid structure interaction effect and dynamic response of the local structure of the yacht are studied. Firstly, to acquire insight into the hydro-impact phenomenon, a series of drop tests and seakeeping-slamming tests are carried out with various sensing instruments of pressure transducers, accelerometer and ’slam patch system’ - a specific application form of generally known pressure panel - are installed. The slam patch system is designed and implemented to investigate the hydro-impact loads and fluid structure interaction effect of slamming. Afterward, the measured hydro-impact loads are summarised via statistical manipulations with regard to pressure and duration time. Secondly, impact pressure by the rules and regulations of various organisations are provided to compare it with the experimental results and structural response calculations. The applicability of the rules and regulations on the high performance racing yacht is also pointed out. Finally, the manipulated loads are used as input data to simulate the transient response of local structure of the yacht structure. Throughout this study, the dynamic and fluid structure interaction effect by hydroimpact phenomenon on local composite structure can be easily visualised and calculated in a conservative way through conventional finite element analysis work.

Composite materials (herein means Fibre Reinforced Plastic, FRP) are increasingly usedin the construction of marine vehicles because of their outstanding strength, stiffness and light weight properties. However, the use of FRP comes with difficulties in the design process as a result of the large number of design variables involved: composite material design, topologies and laminate schemes. All variables are related to each other leading to a high dimensional and flexible design space. It is hard to use traditional design methods in order to gain solutions for an initial design stage in a short time. Hence, this thesis deals with the presentation of a structural synthesis (optimisation framework) for plate components of composite ship structures. The framework broadly consists of an optimisation technique and structural analytical methods. To make the framework compatible with the nature of composite ship structural design problems, the Genetic Algorithm (GA) is selected as the optimisation tool because of its robustness, its ability in dealing with both continuous and discrete variables and its excellent searching for a global optimum. The typical plate types in a ship structure are the stiffened and unstiffened plates. For a stiffened plate, the combination of the grillage analysis of energy method based on Navier solution and an equivalent elastic properties approach are introduced. Using this, it is possible to produce layer by layer optimisation results for the base plate, web and crown of the stiffened plate. Unfortunately, solutions of the adopted grillage analysis do not cover the mechanical behaviour of the plate between stiffeners so the Higher-Order Shear Deformation Theory (HSDT) must be employed. This method provides accurate solutions for thin to moderately thick plates with a compromised computational time. Then stiffness, strength and stability can be considered in the design problem. In addition, to achieve the program of the structural synthesis, various computational modules are implemented according to the evaluation of composite micromechanics properties, maximum stress failure criteria and structural weight function. Then the main modules are validated with available resources. The usefulness of the program has been proved by comparing it with the optimal solutions from finite element software. Finally, many application examples of secondary and tertiary composite ship structures are presented. The optimal results prove the success of the optimisation framework. This could be evidence for further improvement to obtain a valuable structural optimisation tool.

Yacht sail systems are subjected to low speed and transitional flow. Because of the supporting structure (mast and boom) of the sail system and the curvature of sail membrane, sail systems also have a partially separated flow. In this work, it is introduced the sectional method as a sail system flow analysis tool. The sectional method uses the surface discretization and it is based in the simultaneous approach for viscous-inviscid interaction but, it works independently to the initial panel mesh and inviscid panel method calculation, permitting the adjustment of sectional points to have a better local convergence. The sectional method is applied to the detection of separated flow regions by means of integral boundary layer parameters investigation. The investigation is used in cases of weak separation and strong separation, when analysing mast and sail configurations. The weak separation detection is applied to a three-dimensional sail shape in a sail design problem: the study of parameters such as twist and section curvature in order to control separation on the sail.