Roll reduction of ships at slow or zero speeds still remains a challenge in marine engineering. This thesis revisits tank stabilization systems, and starts with a critical review of their development since 1883 to the present. It goes on to investigate the application of modem control techniques, power consumption, and different tank configuration to monohulls and trimarans. It is shown that during the development of tank stabilizing systems the weak link in most cases was the control system, the technology to implement them was not available. Only now with advanced control theory and high speed computing power can the potential of some of these systems be exploited. This thesis applies the current advanced technological and computational techniques to some older ideas that could not be practically realized before. It is shown that the lack of an effective control system of anti-roll tanks is due to the philosophy of trying to control the system with feedback control while a much more suitable approach for this particular application is feedforward control. The thesis develops two strategies (both feedforward) to control the pumps used in active tanks: 1) Auto regression is used to predict the incident wave motion. The predicted wave motion is used as the input to the tank/pump system. 2) Control of the actuating pumps of an active U-tank with an adaptive inverse controller using a filtered-x least mean square algorithm. Both the methods are shown to provide excellent roll stabilization in different sea conditions for monohull and trimaran vessels. Historically tank stabilization systems have only been fitted to monohulls. The application of tank stabilization systems is extended to multihulls, the performance of U-tanks and free flooding (or n-tanks) is compared. The n-tanks can be located in the low value volume of the side hulls with minimum impact on the box structure, thus providing good ship stabilization at low speed with low ship impact.

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The rim driven thruster is a novel electromagnetic marine propulsion device that uses a motor in its casing to drive a propeller by its rim. There are many interacting flow features posing a number of challenges when it comes to simulating the device with computational fluid dynamics. The primary concern is finding a suitable simulation method to capture the flow behaviour accurately, though a secondary challenge is created by the complex interactions creating a rugged design landscape that is difficult to optimise. A steady-state simulation method has been developed and a verification and validation process was conducted on a B4-70 standard series propeller as a baseline case. Results show a great sensitivity to computational domain size below a radial distance of five propeller diameters. The Re-Normalisation Group (RNG) k-e and k-w Shear Stress Transport (SST) turbulence models were compared and the k-w SST model was found to be the most robust due to its better handling of separation that occurs at low propeller advance ratios. To investigate the capture of rotor-stator interaction by the frozen rotor formulation an unsteady simulation method was developed. The unsteady method was also verified and validated, showing good agreement for a standard series propeller, and subsequently applied to rim driven thruster simulations. The results show the frozen rotor formulation does capture some variation and has reasonable agreement with thrust variation over one rotation, but does not predict the variation in torque accurately and thus is considered insufficient for rotor-stator interaction modelling. While the capture of rotor-stator interaction is flawed in frozen rotors, if the stators are omitted, the steady state simulation method is suitable for performance prediction. Given the computational cost of full unsteady simulation, steady state was chosen for the objective function calculation method for the design optimisation. A library of functions was written to robustly automate the geometry creation, mesh generation, solution and post-processing. An initial design study of the sensitivity of 13 parameters showed that the most significant variables were pitch distribution, thickness distribution and hub diameter. These were factored into a second design optimisation study of six parameters, using Kriging for surrogate modelling, to produce an improved rim driven thruster design. The improved design features a greater pitch at the tip exploiting the lack of tip-leakage experienced with rim drive. A high sensitivity of the hydrofoil to Reynolds number was discovered and exploited by increasing the blade thickness and pitch to make the blade section produce more force over a greater area of the blade. The open water efficiency of the improved design is 0.06 higher than the baseline design, showing the optimisation was a success.

The primary objective of this PhD research is to develop an advanced understanding of the necessary and realistic performance expectations from a full form medium size ship system by means of numerical computer modelling. This includes the minimisation of the harmful environmental signature by increasing its efficiency in compliance with the EEDI requirements while in search of how the EEDI methodology might be enhanced. The investigation has focused on a medium sized products tanker acting as a midpoint of the spectrum of ship sizes within the range of 20,000 – 60,000 DWT of this type. In order to solve such an extensive problem, in the first place, it was important to analyse the energy efficient technology market in a structured manner and then, to identify the most favourable fuel consumption reduction methods that can be associated with the examined ship type. Next, an integrated computer simulation model, involving linked engine, propeller and hull analysis programs, has been developed and calibrated with the model tests and sea trial data. The ship system has been analysed under diverse conditions including various propulsion systems, innovative machinery arrangements, efficiency enhancing hydrodynamic appendages as well as changing weather and load conditions. The evaluation of potential benefits associated with the deployment of innovative technology(s), operation profile(s) or their combination has been made by comparing the designated Energy Efficiency Indicators (EDI), namely, the propulsive efficiency, fuel oil consumption, exhaust emissions footprint and EEDI, respectively associated with the technical, fuel savings, environmental and legal perspectives. In addition, such a comprehensive analysis has also helped to detect a number of uncertainties in the current EEDI formulation while pointing out ways in which it can be improved.

Yacht races are won by good sailors racing fast boats. A good skipper takes decisions at key moments of the race based on the anticipated wind behaviour and on his position on the racing area and with respect to the competitors. His aim is generally to complete the race before all his opponents, or, when this is not possible, to perform better than some of them. In the past two decades some methods have been proposed to compute optimal strategies for a yacht race. Those strategies are aimed at minimizing the expected time needed to complete the race and are based on the assumption that the faster a yacht, the higher the number of races that it will win (and opponents that it will defeat). In a match race, however, only two yachts are competing. A skipper’s aim is therefore to complete the race before his opponent rather than completing the race in the shortest possible time. This means that being on average faster may not necessarily mean winning the majority of races. This thesis sets out to investigate the possibility of computing a sailing strategy for a match race that can defeat an opponent who is following a fixed strategy that minimises the expected time of completion of the race. The proposed method includes two novel aspects in the strategy computation: A short-term wind forecast, based on an Artificial Neural Network (ANN) model, is performed in real time during the race using the wind measurements collected on board. Depending on the relative position with respect to the opponent, decisions with different levels of risk aversion are computed. The risk attitude is modeled using Coherent Risk Measures. The proposed algorithm is implemented in a computer program and is tested by simulating match races between identical boats following progressively refined strategies. Results presented in this thesis show how the intuitive idea of taking more risk when losing and having a conservative attitude when winning is confirmed in the risk model used. The performance of ANN for short-term wind forecasting is tested both on wind speed and wind direction. It is shown that for time steps of the order of seconds and adequate computational power ANN perform better than linear models (persistence models, ARMA) and other nonlinear models (Support Vector Machines). The outcome of the simulated races confirms that maximising the probability of winning a match race does not necessarily correspond to minimising the expected time needed to complete the race.

This study is dedicated to investigation of soot formed during combustion in diesel engine. Measurements were performed in a high speed direct injection optical diesel engine. Initially soot particle size, size distribution and soot volume fraction were investigated using time resolved laser induced incandescence (TR-LII) technique. For this study standard diesel fuel was used and measurements were performed for various injection timing and two different engine loads. Investigation showed that TR-LII is a powerful tool that can be used for characterization of in-cylinder soot in the engines. Subsequently TR-LII technique was developed to measure in-cylinder soot in two dimensional plane (planar laser induced incandescence PLII) and technique was combined with high speed imaging to investigate soot processes for ultra-low sulfur diesel (ULSD) and bio-fuel (RME). Two injection strategies of single and double injection were applied during these measurements. A high speed imaging technique was used to study the soot formation and oxidation during the combustion process within the cylinder and PLII was applied later in the stroke to study qualitatively the relative amount of un-oxidised soot that was left in the combustion chamber. In addition to PLII, TR-LII technique was used simultaneously to explore crank angle resolved variation of primary soot particle size and their size distribution during the expansion stroke. The same measurements were repeated for fuels with different composition investigating the relationship between the fuel properties and soot emission. Finally mathematical model for soot particle size and distribution width was modified by introducing assumption of multi-lognormal in-cylinder soot particle size distribution.

Maritime transport has profound importance for the world economy. Vessels of all sizes constantly transport large numbers of passengers and goods across the sea, often under adverse operational conditions. Vessels need to exhibit high levels of reliability, availability, maintainability and safety (RAMS). However, at the same time their performance needs to be optimised ensuring the lowest possible fuel consumption with the maximum operational capacity and range without compromising RAMS. Sweating of naval assets and profitability should be maximised for the operator ensuring investment in future projects and supporting the growth of maritime transport and world economy as a whole. Vessels have been traditionally manufactured using naval steel grades such AH, DH and EH. Smaller leisure and specialised purpose vessels such as patrol boats, etc. have been built using fibre-reinforced composite (FRC) materials. This trend is gradually penetrating the market of larger commercial vessels including freight and cruise ships. However, these are still the early days and further investigation of the optimum FRC manufacturing techniques and mechanical properties together with an in-depth understanding of the damage mechanics are required before such materials can become more commonplace. This project has investigated different glass FRCs using different manufacturing techniques. Glass fibres are preferred due to their lower cost in comparison with carbon fibres. The use of carbon FRCs in maritime applications is limited to the fabrication of racing and high performance speedboat vessels. Samples manufactured under laboratory conditions have been compared with those manufactured by a shipyard. It has been seen that the in-house samples had generally superior performance. Steel-to-composite joints have also been assessed including different designs. The effect of different features in the design such as drilled holes and bolts on the mechanical performance of the manufactured samples has also been evaluated. The damage mechanisms involved during damage propagation and features causing damage initiation have been considered. Damage initiation and subsequent evolution have been monitored using acoustic emission (AE). Various signal processing approaches have been employed (manual and automatic) for optimum evaluation of the AE data obtained in a semiquantitative manner. It has been shown that AE could be applied effectively for structural health monitoring of naval structures in the field. Several factors and parameters that need to be considered during acquisition and analysis have been successfully determined. The key results of the study together with mechanical testing and characterisation of samples employed are presented in summarised form within the present thesis.

There is significant worldwide environmental concern related to the transportation of Invasive Aquatic Species (IAS) by ships ballast water into non-native environments. This has given rise to the development of a vast array of technological ballast water treatment systems. The complex environmental challenges and tight operational characteristics of marine vessels limits the scope of the technologies used for Ballast Water Treatment (BWT). As a result few technologies have progressed beyond the research and development stage; however one of the most promising technologies for ship board use is the cyclonic separator, or hydrocyclone. Despite the use of hydrocyclones in a wide variety of engineering applications they have yet to be successfully adapted towards the removal of suspended sediment and marine organisms from large volumes of ballast water. The following primary objectives of this study have been met: • Via critical review identify the technological solutions for treating ballast water best suited to onboard use. • Define the critical flow regimes evident within hydrocyclonic separators. • Establish a series of Computational Fluid Dynamics (CFD) simulations, evaluating standard turbulence models in order to determine the capacity for commercial CFD to model hydrocyclonic flow. This study has detailed the operational characteristics of ballast water hydrocyclones with the aim of enabling hydrocyclones to be optimised for individual ship configurations. Flow simulations have been conducted using CFD, and in particular the Detached Eddy Simulation (DES) turbulence model. Finally the DES model is shown to be a legitimate turbulence model for hydrocyclonic flow regimes, validated against empirical and experimental data.