The main focus of the work presented within this thesis was the testing and development of condition monitoring procedures for detection and diagnosis of HATT rotor imbalance faults. The condition monitoring processes were developed via Matlab with the goal of exploiting generator measurements for rotor fault monitoring. Suitable methods of turbine simulation and testing were developed in order to test the proposed CM processes. The algorithms were applied to both simulation based and experimental data sets which related to both steady-state and non-steady-state turbine operation. The work showed that development of condition monitoring practices based on analysis of data sets generated via CFD modelling was feasible. This could serve as a useful process for turbine developers. The work specifically showed that consideration of the torsional spectra observed in CFD datasets was useful in developing a, ‘rotor imbalance criteria’ which was sensitive to rotor imbalance conditions. Furthermore, based on the CFD datasets acquired it was possible to develop a parametric rotor model which was used to develop rotor torque time series under more general flow conditions. To further test condition monitoring processes and to develop the parametric rotor model developed based on CFD data a scale model turbine was developed. All aspects of data capture and test rig control was developed by the researcher. The test rig utilised data capture within the turbine nose cone which was synchronised with the global data capture clock source. Within the nose cone thrust and moment about one of the turbine blades was measured as well as acceleration at the turbine nose cone. The results of the flume testing showed that rotor imbalance criteria was suitable for rotor imbalance faults as applied to 4 generator quadrature axis current measurements as an analogue for drive train torque measurements. It was further found that feature fusion of the rotor imbalance criterion calculated with power coefficient monitoring was successful for imbalance fault diagnosis. The final part of the work presented was to develop drive train simulation processes which could be calculated in real-time and could be utilised to generate representative datasets under non-steady-state conditions. The parametric rotor model was developed, based on the data captured during flume testing, to allow for non-steady state operation. A number of simulations were then undertaken with various rotor faults simulated. The condition monitoring processes were then applied to the data sets generated. Condition monitoring based on operational surfaces was successful and normalised calculation of the surfaces was outlined. The rotor imbalance criterion was found to be less sensitive to the fault cases under non-steady state condition but could well be suitable for imbalance fault detection rather than diagnosis.

The water quality deteriorations in river and estuarine waters are a global issue. Particularly, the water quality impairment due to contamination of Faecal Bacteria Indicator, such as E. coli and Faecal Coliform in river channel, estuary bathing and shellfish waters are of special interests due to potential risks to human health. These indicators are important in water quality assessment outlined in both EU Water Framework Directive and US Clear Water Act. The hypothesis of the study is that the global climate change and intensive farming would cause severe deterioration to faecal coliform levels in these water bodies. Approaches to quantify these impacts are carried out with numerically modelling through catchment model Soil and Water Assessment Tool (SWAT) and hydrodynamic model DIVAST with the focus in the coastal catchment of river Frome and Piddle connected to a natural harbour in Dorset, southern England.

This thesis investigated the non-dimensional performance characteristics of a tidal stream turbine and how they varied in response to changes in flow direction. The problem was considered from an industrial perspective and used the commercial software package ANSYS CFX and a 1:20th scale experimental turbine. Initial considerations analysed the performance of the turbine in an ‘upstream’ or ‘downstream’ configuration relative to the turbines support structure. The conclusions resulting from this were that up to a point by increasing separation between an upstream turbine and its support structure the greater average nondimensional performance characteristics became. Also, more significantly, it was identified that this orientation and clearance reduced the blade stanchion interaction considerably relative to the downstream orientation. The study made justification for the inclusion of a yaw mechanism to rotate the turbine to face the flow for flood and ebb phases of the tide. In an operational environment this would be expected to enhance the life of the turbine’s blades, thrust bearings, and gearbox - which are known to be prone to fatigue failure, due to highly dynamic loads. The thesis continued to expand into the potential uses of a yaw mechanism to address flow misalignment experienced throughout the tidal cycle. In order to justify this, the non-dimensional performance characteristics of the same turbine were compared for a series of flow misalignment cases. The CFD analysis showed that increased flow misalignment in either the positive and negative direction had the effect of reducing turbine torque and power performance characteristics, and also significantly increases the out-ofplane bending moments. A distinction between the positive yaw angles and negative yaw angles was identified in the turbine’s performance. The negative flow misalignment showed more favourable performance changes than the positive flow misalignment, this was due to the turbines rotational direction. The subsequent recommendations to industry were included making use of the turbines rotational direction and yaw mechanism, to experience lower performance reductions in the case of flow misalignment. Experimental results from tow tank testing at CNR-INSEAN using the 0.5 m diameter turbine validated the nondimensional performance characteristics of the CFD results. It was identified that steady state CFD results did not capture the performance characteristics of flow misalignment cases as well as the transient CFD results. The experimental turbine captured temporal features identified in the CFD analysis. Recommendations to industry include the careful consideration of steady state CFD analysis in non-idealised flow conditions.

Coastal areas are heavily populated in countries around the world and are a source of economic activity, both recreational and industrial. Waves and tides interact with sediments in a dynamic equilibrium which leads to coastal morphological changes at different temporal and spatial scales. Natural or human-induced changes in this equilibrium may lead to an alteration of the coastline causing environmental or economic impacts. Coastal defences are often needed in order to protect specific areas and reduce such impacts. Therefore, understanding the impact that coastal defence structures have on coastal morphological changes is important for coastal managers. There are different methods to study morphological changes in coastal areas. Process-based numerical models are powerful and precise tools but they are more effective for small to medium spatial scales (km) and short to medium-term temporal scales. Data-driven methods have been proven useful to study morphological changes in the long-term. However, data is not always available in the quantity or quality needed for such methods to provide meaningful results. This study uses jointly process-based numerical models, COAST2D, and data-driven methods, Empirical Orthogonal Functions method (EOF), taking advantage of the strengths of both methods to overcome their own weaknesses. A novel methodology for EOF components extrapolation, named Dynamic EOF method, is developed. Results show that, COAST2D is an efficient tool to simulate morphological changes in the scale of months and kilometres. These scales exceed the ones reached previously by the model, increasing the confidence on its capabilities. The Dynamic EOF method, which extrapolates both temporal and spatial EOF components, was found to yield better results than previous attempts using the EOF method to extrapolate results beyond the training period based on EOF temporal component extrapolation only. Keywords: EOF method, Dynamic EOF method, forecasting, shore-parallel breakwaters, morphological changes, COAST2D.

Much of the world's available hydropower potential has been exploited, and within the western world attention is increasingly being focussed on hydropower sites with very low head dierences. These are sites where the vertical distance through which water falls is less than ve metres, and remain unexploited as there is a recognised lack of hydropower technology avaiable to exploit these low-power sites economically. The aim of this work was therefore to develop a novel hydropower machine which could be used to viably exploit very low head dierences in river environments. A review of the hydropower technologies determined that the established machinery is primarily driven by the operational principles of impulse, reaction, or potential. It was however noticed that some less well established designs appear to be driven directly by the hydrostatic pressure which could be generated by a depth of owing water. This observation had not been previously acknowledged. It was also recognised that investigation into this operational principle could potentially result in machines that were both relatively simple, and have high ow and power capacities when compared to the established technologies. It was identied that there could be two approaches to exploiting hydrostatic pressure, and ideal theories were developed to describe both approaches. The resulting physical concepts were called Hy- drostatic Pressure Converters. Scale models of these concepts were hydraulically tested, veriying the proposed theories, and providing data from which estimates of full scale performance were made. These predicted that the two proposed designs of Hydrostatic Pressure Converter were suitable for head dif- ferences below 2.5m, normally the domain of the traditional waterwheel. They would operate with high hydraulic eciency, at around 80%, but have a signicantly greater ow capacity and power output per unit width of machine, at 500% that possible using a traditional waterwheel. In conclusion this work has identied, analysed and prototyped a novel approach to exploiting very low head hydropower potential. The resulting Hydrostatic Pressure Converters are a signicant and promising development in the eld of very low head hydropower.

The construction of water management and navigation structures often requires temporary works to exclude water to facilitate construction in the dry or at least under a lower water level within the construction area. The use of cellular cofferdams for both temporary and permanent earth/water retaining works is very common. A number of theories are presented that describe the failure mechanisms involved. These failure mechanisms were identified from model studies on circular type cofferdams are applied independent of cofferdam geometry. It is common to use diaphragm type cofferdams. To asses the validity of common failure mechanisms associated with cellular cofferdams when applied to diaphragm type cofferdams, a series of numerical modelling analyses were conducted. These were validated using field monitoring results of a large scale diaphragm type cofferdam constructed at St. Germans, Norfolk, UK. A series of plane strain analyses of a diaphragm type cofferdam were conducted using the geometry from a critical section of cofferdam. These analyses identified the lowest factor of safety based on the drained strength of the clay on which the cofferdam was constructed. The water level within the river was increased to accommodate flooding and soil strength was reduced to identify the general failure mechanism. The structural forces were calculated using both 2D and 3D models for a larger width section (13m wide) to allow comparison with wall bending moments and displacements measured in field. The 3D analyses used actual tie spacing and membrane effects whilst reducing the lateral stiffness of the wall to accommodate the stiffness reduction due to variation in the interlock forces. To measure the bending moment in sheet piles, resistance type strain gauges were installed on a 13m wide section of cofferdam. The cell deflection, river and cell water levels were also monitored to identify tidal river effect and the influence of cell water level on performance. Comparison of field and numerical results highlighted a number of important design and construction detail related to diaphragm type cellular cofferdams.

In this thesis, a study is made of the effect of random wave forces on self-supporting steel and concrete oil drilling platforms. Various methods of estimating the forces on the structure, and various ways of idealising both the forces and the structure itself, are compared, the- objective being a realistic and safe design. The sea is here represented by a wave amplitude spectrum,from which spectra for the forces on the structure are derived using a linear wave theory, in two ways. Firstly, using the well-known Morison equation, which requires experimental drag and inertia coefficients; and secondly by considering wave diffraction from the structural members. A quantitative comparison is made of the two methods. Using the diffraction theory, it is possible to guage the effect of sheltering - i.e. the effect on the forces on one member due to the presence of another. The principal structures considered here are idealised as plane framed structures (though the theory is applicable for structures with, say, plate elements also ), and in this connection wave forces on inclined frame members are considered. This is particularly useful for steel structures. A comparison is made between the results obtained by evaluating the forces 'consistently' and by 'lumping' them at element nodal points. In addition, a comparison is made of solution methods which ignore certain cross-correlation terms in the equations of motion for the response with one that includes such terms, in an attempt to show that a fuller analysis is no more difficult, and is likely to be safer, than the more approximate methods.

No description available.

The combination of a prime mover and an energy storage device for reduction of fuel consumption has been successfully used in the automotive industry. The potential of a load levelling strategy and the energy management optimisation through the use of a Hybrid Diesel propulsion system for ocean going ships is investigated. The goal of Diesel Hybrid systems is to reduce exhaust gas emissions by reducing fuel oil consumption though an introduction of an energy storage medium. Part of the research is based on operational data for a shipping fleet containing all types of bulk carriers. The engine loading and energy requirements are estimated and the sizing of suitable propulsion and the battery storage system is proposed. The changes in overall emissions are estimated and the potential for fuel savings is identified. The emission estimation is made by applying a bottom up approach, and the use of fuel based factors. The thesis includes an assessment of the calculation error imposed by the usage of fuel-based factors, and a determination of the uncertainty in the approximation of global shipping emissions is made. Constructional and volume constraints are identified and a concept feasibility is performed. The thesis demonstrates the use of developed ship voyage simulator, which is a time domain quasi-steady simulation tool. The system components of the Hybrid and the conventional machinery system are modelled, the weather characteristics and the hull-fluid interaction are implemented in a modular, scalable and expandable manner. Using the simulation tool, an assessment of simulated bottom up approach with the results of the IMO formula is presented for a number of examined voyages. Moreover, simulator outputs of the propulsive demand are fed to the optimisation algorithm, which is based on the equivalent cost minimisation strategy. In addition, a pseudo multi-objective optimisation algorithm for CO2 and PM reduction is also presented. The results indicate that the ship simulator estimates shipping emissions with a significantly smaller error than the adopted formulae of the IMO. The hybrid solution for diesel powered ships is under specific scenarios financially viable, and the fuel savings based on the statistical analysis are notable when ageing of the engines and performance deterioration models are included. Nevertheless, when the optimised performance of the Hybrid power layouts is compared to optimally tuned engines at ISO conditions, instead of the actual prime mover performance, the the fuel saving potential for auxiliary loads is reduced and also leads to non-feasible results for propulsive loads. Nonetheless, the Hybrid power systems permit the use of sophisticated prime mover energy management for both propulsive and auxiliary loads. This proved to lead to notable fuel savings for the combined shipboard power trains.

The research presented in this dissertation investigates the development and the performances of a new type of Wave Energy Converter (WEC) aimed to provide water delivery and energy storage in the form of potential energy. The Oscillating Water Column Wave Pump (OWCP) concept was proposed and tested through a series of experimental investigations supported by scientific theory. The OWCP was developed after an extensive study of the existing wave energy technology available, from which it emerged that the Oscillating Water Column (OWC) device could be further implemented for water delivery purposes. The existing theory of the OWC was employed to develop a mathematical theory able to describe the system wave response and water removal of the OWCP. In order to understand and validate the mathematical models of the OWCP, experimental investigations were carried out under the influence of incident linear waves in a two-dimensional (2D) and three-dimensional (3D) wave flume. The experimental equipment and methodology are outlined, including the description of wave flumes, models and data acquisition equipment. Experimental tests were used to verify the concept of the OWCP and assess its performances, investigating both the response of the device to the waves with and without water removal. In order to increase the efficiencies of delivery, array configurations of multiple OWCPs were adopted. The research demonstrated that up to 14% of the energy carried by the incoming waves can be converted into useful potential energy for a single device. Moreover a further increase of the efficiencies can be obtained with the array configuration improving the overall capability of the OWCP, for optimal separation distance between the array components. Further model tests are required to extended this research to validate the developed mathematical models as an effective prediction tool of the performances of the OWCP and further increase the efficiency of water removal that can be achieved.