An enhanced one-dimensional mathematical model for simulating flood levels and calculating stage-discharge relationships is presented. Enhanced conveyance subroutines have been developed and incorporated into the commercially available river modelling software ISIS. The newly developed software has been verified using experimental and field data. When a river overtops its banks there is a vigorous interaction between slow moving flood plain flow and faster moving main channel flow. This interaction mechanism has been the focus of intense research over the past forty years. A selective review of this research is detailed with particular attention to the case of meandering channels. The Ackers Method and the James and Wark Method are two discharge capacity methods that have emanated from this recent research and are considered to be the most practically suitable methods and are indeed recommended by the Environment Agency of England and Wales. The methods account for interaction effects when flow is overbank in a straight and meandering channel respectively. It is these methods that have been incorporated into the commercially available and industry leading one-dimensional river model ISIS to enable an enhanced conveyance calculation. The newly developed software has been tested against the Flood Channel Facility Series A and B experiments to a satisfactory level of accuracy. The testing included predicted of stage discharge relationships and water level prediction. In addition it has been applied to the River Dane in Cheshire which is highly meandering and suited to the James and Wark methodology. This was intended to give practical advice concerning the use of the James and Wark Method and the degree of accuracy in estimating the 'channel parameters' which are required by this method. The results of this work showed that a significant rise in water level prediction is obtained when using the enhanced code. Also, it was clear that a high degree of accuracy was not required in estimating the 'channel parameters' with the possible exception of the sinuosity term.

The present work presents a study of unsteady aerodynamic modelling of horizontal axis wind turbine performance. The unsteady aspects addressed in this work include effects of variations in turbine inflow velocity due to operation in yawed flow, in the atmospheric boundary layer, in a wind tunnel, and due to the tower wake. In each case, the basis for the analysis is a prescribed wake vortex model, the development and enhancement of which has been the main focus of the work. A high resolution model has been developed to meet the requirement for adequate representation of the tower shadow effects. A near wake dynamic model has been enhanced with appropriate modifications and integrated into the prescribed wake scheme to produce a hybrid method capable of predicting the detailed high resolution unsteady response in the tower shadow region. The azimuthal interval used within the shadow region can be reduced to 0.5° whilst the computational cost introduced by the high resolution near wake model is almost negligible. A low order source panel method and the prescribed wake model have been combined into a coupled scheme capable of assessing the basic effect of wind tunnel walls on wind turbine flow and performance. The wind tunnel walls are discretised into a series of panels on which source singularities are placed. The source strengths are related to the turbine bound and wake vorticities via their induced velocities. The geometry of the turbine wake is obtained by superposition of the contribution of the disturbance velocities due to the source panels upon the prescribed wake. This new wake structure modifies the wind turbine aerodynamic performance in turn.

This thesis contains the formulation, development and initial tests of a computer model for the prediction of fully three dimensional turbulent free surface flows typically found at localised areas of river systems. It is the intention that the model will be used to predict flow situations which are fully three dimensional. The model is, therefore, tested against a fully three dimensional test case of flow in a two-stage meandering channel. However, the model is not intended simply to be for computing flows in meandering river channels. Rather the model is intended to be used in a variety of problems which are outlined in the thesis. The Reynolds Averaged Navier-Stokes equations form the basis of the physical system. The Reynolds stresses are represented by two different stress-strain relationships: (1) a linear relationship and (2) a non-linear relationship. These relationships rely on an eddy viscosity and a turbulence time-scale which are calculated from two characterising turbulence quantities, a velocity squared scale, k, and an inverse length scale, . These quantities are computed from differential transport equations. Non-linear stress-strain relationships are relatively new and, it has been argued by their originators, require application to several different problems to fully ascertain their potential for future use. The author addresses this demand by applying them to two new problems. These are flow in a plenum chamber and open channel flow over a backward facing step. The equations are solved by an operator splitting method which, it is argued, allows for an accurate and realistic treatment of the troublesome advection terms at low spatial resolutions. This is thought to be essential since for three dimensional problems owing to computer time limitations achieving grid independent solutions with low order schemes is at present very difficult. The advantage of the present approach is demonstrated with reference to a simple one dimensional analogue.

Results of an experimental study of the incipient motion of streambeds are reported. The experiments were conducted in an 8 m long, and 0.30 m wide by 0.30 m deep glass-walled tilting flume and an 18 m long, 0.80-1.10 m wide by 0.15 m deep trapezoidal concrete channel. The purpose of the experiments was to determine flow conditions associated with the initiation of bed sediment motion and to investigate near-to-threshold bedload transport. Uniform and graded natural sands and gravels were used as bed material. A new approach to the description of critical state of the bed based on the intensity of sediment motion, or transport intensity, is proposed. This approach describes the state of the streambed mobility in terms of the fraction of bed particles mobilized in unit time, which eliminates the subjectivity in defining threshold conditions and provides a probabilistic description of the process of sediment entrainment. On the basis of the flume data obtained for uniform sediment, a relationship between the intensity of particle motion and sediment transport rate is established. This relationship allows any measured transport rate to be expressed in terms of the probability description of the process of sediment entrainment. The experiments reveal that critical bed shear stress for incipient motion of uniform sediment depends not only on the grain size, but also on the bed slope. This is explained by the effect of relative depth (depth to grain size ratio) on overall flow resistance. It is also shown that the value of critical dimensionless bed shear stress is not coarser gravel. The same conclusion follows from the measurements of turbulence characteristics near the bed. A revised Shields diagram relating critical stress, grain (or alternatively, different probabilities of sediment entrainment). The experimental results are formalized to provide a generalized method for calculating the bedload transport rate and critical Shields stress of coarse uniform sediments.

The pseudodynamic test method is a tool for obtaining the non-linear response of structures to transient ground acceleration. The modelling technique relies on representing the inertial and viscous damping components of the equation of motion computationally, while obtaining a measure of the non-linear elastic restoring forces experimentally. A pseudodynamic implementation system is presented, displaying innovations within both the computational and experimental domains. A SDOF pseudodynamic test facility has been designed and manufactured employing a computer controlled servo-hydraulic actuator system. The experimental facility enables displacements of up to 50mm under forces of up to 50kN with all required instrumentation. The experimental apparatus is controlled by algorithms running in the LabView environment, fully integrated within the execution system, rendering the requirement for a hardware controller obsolete. The execution system allows interactive control of the experiments, and offers a large range options with respect to both control and time integration. The execution routine incorporates both the time integration and control algorithms, and combines these such that they effectively execute as an integrated system. This enables semi-continuous implementation of the pseudodynamic tests with very limited resources. A novel, integral form time stepping scheme is proposed, based on an explicit integral form algorithm (Chang et al. 1998) and the Newmark Implicit scheme. The proposed formulation offers an implicit, and thus unconditionally stable alternative to Chang's algorithm without introducing further approximations. This yields improved dissipation and accuracy properties in addition to enabling combination of the integral form schemes' advantages of representing non-linear force variations during a time step with an unlimited time step size. The improvements have been shown both through analytical analyses and numerical examples in linear and non-linear systems. Implementation of the implicit integral form algorithm has been enabled by coding parts of the algorithm directly into the digital controller.

The work of this thesis is an experimental study of flow in a compound or two-stage channel, where the flow in the main channel is skewed slightly to the flood plain flow direction. The purpose of the study is to investigate flow mechanisms and flow behaviour in a situation which is more complex than a straight/parallel compound channel and less complex than meandering compound channel. In other words, an element of `lq cross over flow is introduced, where the flood plain flow crosses over a skewed main channel beneath. This element is absent in study of a straight and parallel channel/flood plain system. The thesis begins by introducing the subject of two-stage channels and river flooding in Chapter 1, followed by a literature survey in Chapter 2. The literature survey attempts to draw together various strands of two-stage channel research including stage-discharge assessment, lateral turbulent shear, bend behaviour for inbank and overbank situations, and flow behaviour in the cross-over region. Chapter 3 describes the experimental rigs used during the experiments including the main flume for the skewed compound channel flow tests, and also a smaller straight flume with a slot of variable length in the main bed, designed to simulate certain aspects of cross-over flow. This chapter emphasises the instrumentation used to measure accurate point velocities and accurate streamline angles throughout the flow field. Both these measurements were crucial in determining transverse velocity components. Chapter 4 describes flow resistance and stage-discharge data for the skewed compound flume with both smooth and rough flood plains, and also the skewed main channel operating in isolation from adjacent flood plains. An analysis of drag coefficients for the vertical roughening rods for the flood plain is also presented. Chapter 5 presents the experimental data of longitudinal velocities throughout the flow field and transverse velocities within the skewed main channel, for the case of both smooth and rough flood plains. Observations are made on the asymmetry of the longitudinal velocity profile, the magnitude of transverse velocity components, as well as variations in the downstream direction. Chapter 6 concentrates on flow measurements in a smaller flume with a slot in the channel bed, representing an idealised version of flow crossing-over the skewed main channel. Measurements are presented of variations in water surface level, energy losses at the expansion and contraction region as well as velocity measurements at various sections throughout the slot region in an attempt to produce a universal velocity profile. Finally Chapter 7, attempts to draw together experimental evidence in Chapter 4, 5, and 6, to draw some conclusions about the behaviour of two-stage channels. This is done by putting forward ten ideas on the behaviour of two-stage channels involving stage-discharge assessment for the smooth boundary case, stage-discharge assessment for the rough boundary case, flow resistance concepts for two-stage channels, deviation of the flood plain streamlines in the cross-over region, entrainment of flood plain flow down into the main channel flow, the magnitude and distribution of secondary circulation within the skewed main channel (and how this is influenced by boundary roughness, aspect ratio and relative flow depth), the magnitude and distribution of the depth-averaged longitudinal velocity (including comparison of left and right flood plain velocities, position of maximum velocity filament, width of lateral shear layers on either flood plain), variations of flow behaviour in the downstream direction, application of the result to two-stage channel design and finally some speculations on the longer term behaviour of two-stage channels from the viewpoint of scouring and deposition of bed load and suspended sediment. The thesis shows very clearly that flow is a skewed compound channel, even at a small skew angle of 5.84o, is in many ways dissimilar to flow in the straight/parallel case. This is highlighted in the magnitude of secondary cells in the skewed main channel, deviation of flood plain streamlines, greater horizontal shear and less lateral shear between main channel and flood plain and asymmetry of the depth-averaged velocity. This thesis also reveals a very limited application of energy losses at a slot in the channel bed to a skewed cross-over flow situation.

Several approaches to the dynamic analyses of pile driving are explored in this Thesis. These include pile driving formulae, single degree of freedom (SDOF) models, the wave equation approach and a finite element model. In the elementary models, the pile is modelled as a rigid mass while the soil is represented by various simple rheological mechanisms (spring-slider-dashpot models). Analytical and numerical formulations are developed and the parametric results of the analyses are presented in non-dimensional form. A study of the wave equation method of the analysis culminates in the development of some simple analytical expressions (analogous to the pile driving formulae) which may prove useful in practice. Some comparisons between the elementary SDOF models, the pile driving formulae and the wave equation have been undertaken in order to assess their strengths and highlight their various shortcomings. The development of a finite element model for pile driving is discussed in detail with particular emphasis on spatial discretisation (especially the viscous boundaries) and the time integration schemes. A limited parametric study has been conducted in order to gain some insight into the behaviour of piles during driving and to follow the evolution of failure in soils around and beneath the piles. Further work in this area is indicated although computational costs seem to be too high to justify use of the finite element method.

Chapter 4 describes the synthesis and development of a Conceptual Design Evaluation Method (CDEM) that is an amalgam of a number of methods and approaches taken principally from the probability, reliability, and quality domains. Decomposition of design is employed to enable evaluation at design characteristic level with the total design evaluation being achieved via recomposition by means of Conceptual Design Factor Ratings (CDFR) and Conceptual Design Solution Ratings (CDSR). This methodology is next tested, within a controlled design environment, in order that its validity can be assessed. The experimental approach used is described in Chapter 5. The results of this experiment, which uses students along with technical and academic staff from the Department of Mechanical Engineering at the University of Glasgow as subjects, indicate that the developed Conceptual Design Evaluation Methodology does exhibit validity within the limits of the experimental environment. It is shown that the CDEM can match expert selection of preferred concept options thus offering the potential of enhancing novice capability and of providing advisory support to experienced designers. The experiment also exposes the problem of objectivity in design evaluation however it is also shown that the CDEM approach acts to mitigate against this tendency by effectively reminding the designer of the benefits of a range of conceptual options. In parallel, the experiment also exposes the limits of human objective evaluation in terms of the complexity of criteria addressed as well as the number of conceptual options considered. Once again CDEM is shown to enable evaluative objectivity to be maintained with increasing complexity. It is also suggested that the CDEM approach is appropriate for a concurrent engineering environment since it displays a capacity to enhance traceability of design decision making. Finally, conclusions are provided regarding the specific outcomes of the described research along with implications for the wider issues of coherent design research strategy and professional engineering design practice.

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This thesis presents and extends the J-value framework for assessing expenditure on risk mitigation, and then applies the method in a comparative risk assessment of UK electricity generating systems. The thesis is split into two volumes. The first volume contains part one, in which the J-value framework is introduced and developed. The loss of life expectancy is a key parameter in the framework, and general risk models for calculating this parameter are developed in terms of exposures and responses. Specific examples of radiation and pollution models are also presented. The “Hazard Elimination Premium” is also introduced as a useful common metric for risk comparisons. Part one also contains an assessment of the uncertainty of the J-value and its input parameters and it is found that the J-value has an internal accuracy of around 3%, but that other, context dependant parameters can degrade this accuracy. A sensitivity analysis of the J-value framework also found that the J-value was reasonably robust against random variation of the input parameters as well as against the use of simplifying assumptions used in the development of the J-value. The second volume contains parts two and three. Part two describes the comparative risk analysis of the electricity generating systems. The analysis is carried out on nuclear, coal, natural gas, onshore wind and offshore wind. The analysis assesses human mortality impacts arising from the current and future plants over the sixty year period from 2010 to 2070 for the entire fuel chain. The results indicate that nuclear generally has the lowest impacts, while gas, onshore and offshore wind have indicative impacts that are about an order of magnitude greater, although the estimates for both wind technologies carry considerable uncertainty. Coal power was found to present high impacts compared with the other technologies, mainly as a result of pollution emissions. Total nuclear impacts were found to be sensitive to assumptions regarding the use of collective dose and the assumptions which are then used to calculate impacts. For the most pessimistic case, when world exposures are taken, total nuclear impacts increase by about an order of magnitude, which would render the risks from nuclear generation comparable with those from gas and wind generation. Part three presents the conclusions, further work, bibliography and appendices.