The primary function of seawalls and embankments is to protect against damage and injury caused by flooding. Coastal flooding is caused by combinations of high tides, waves, wind set-up and storm surges driven by low-pressure systems. However with global warming causing sea levels to rise and with increased storminess causing more extreme waves and storm surges, the likelihood of overtopping of seawalls with zero or negative freeboard may well be expected to increase. Researchers using physical and numerical models to develop design formulae have widely investigated wave overtopping of seawalls with positive freeboard. However the design of seawalls with zero or negative freeboard has attracted much less attention, and some variation exists between overtopping discharge calculated with current design formulae. The focus of this thesis is the extreme situation when overtopping caused by storm waves is combined with surge levels above the embankment crest. The local highly accelerative flow over the embankment crest caused by the high surge level will significantly alter the flow at the crest. This is likely to have a highly non-linear effect upon the overtopping waves. In this thesis, the flow is investigated with a 2DV numerical model based on the Reynolds averaged Navier-Stokes (RANS) equations developed by Lin and Liu (1998a). The model describes the flow characteristics of a breaking wave such as the velocities within the wave as well as the turbulence at the seabed boundary layer. As an example of the model’s ability to describe complex hydrodynamic flows, this study investigates its ability to represent the second order mass transport under progressive and standing waves. The model results are compared with available theory and experimental results. This shows that mass transport is successfully predicted, although there is some variation in the magnitude compared to the experimental and theoretical results. To consider the model’s ability to simulate storm surge wave overtopping of embankments, the RANS model has been used to simulate an experimental study conducted by Hughes and Nadal (2009). To examine the success of the model at reproducing the wave generation, transformation and overtopping processes the model results have been compared with the experimental laboratory data. This makes possible a wave-by-wave comparison of overtopping parameters such as discharge, depth and velocity for a storm surge event. Additionally the overtopping discharge predicted by the model is compared with design formulae and the differences in the overtopping discharge calculated with current design formulae are investigated and explained. Finally, the RANS model is used to determine the effect of embankment crest width on the magnitude of the overtopping discharge. Results from RANS model tests are used to provide design guidance in the form of an equation that allows the effect of crest width to be included when evaluating combined discharge at embankments.

The practical method of applying the variation principle to the calculation of the energy of an atom demands a trial function which contains variable parameters. The previous work done using this approach was based on the use of some combination of hydrogenic wave functions containing parameters inserted in appropriate places. The present calculation of the energy of the eleven-electron atom has been brought about using this method.

In this paper we consider an existence of a solution for a nonlinear nonmonotone wave equation in [0,π]xR and an existence of a positive solution for a non-positone Dirichlet problem in a bounded subset of R^n.

Efficient function of the left ventricle (LV) is achieved by coherent behaviour of its circumferential and longitudinal myocardial components. Little was known about the direct association between the long and minor axis velocities and the overall haemodynamics generated by ventricular systolic function such as aortic waves. The forward running expansion wave (FEW) during late systole contains important information about the condition of the LV and its interaction with the arterial system. The aim of this thesis was to underpin the mechanics and timing of the LV wall velocities, which are associated with the deceleration of flow. Both invasive and noninvasive data have been analysed in canines and humans and the following conclusions can be drawn. LV long axis peak shortening velocity lags consistently behind the minor axis, representing a degree of normal asynchrony. The FEW is seen to have a slow onset before a rapid increase in energy. The slow onset corresponds with the time that the long axis reaches its peak velocity of shortening. After both axes reach their respective maximum shortening velocity they continue to contract, although at a slow steady velocity until late ejection when there is a sudden simultaneous change of shortening velocity of both axes. This time corresponds with peak aortic pressure and the rapid increase in energy of the FEW. The time that the minor axis reaches its maximum velocity of shortening interestingly coincides with the arrival of the reflected wave at the LV during mid-systole. During canine aortic manipulation through the introduction of total occlusions along the aorta, the sequence of events observed in control conditions remains unchanged. In humans both LV wall movement and carotid wave intensity can be measured successfully using non-invasive methods. The FEW is generated when the last long axis segment begins to slow. The minor axis begins to slow before this time and corresponds to the time of peak aortic flow.

The scientific literature on airflow in the respiratory system is usually associated with rigid ducts. Many studies have been conducted in the frequency domain to assess respiratory system mechanics. Time-domain analyses appear more independent from the hypotheses of periodicity, required by frequency analysis, providing data that are simpler to interpret since features can be easily associated to time. However, the complexity of the bronchial tree makes 3-D simulations too expensive computationally, limiting the analysis to few generations. 1-D modelling in space-time variables has been extensively applied to simulate blood pressure and flow waveforms in arteries, providing a good compromise between accuracy and computational cost. This work represents the first attempt to apply this formulation to study pulse waveforms in the human bronchial tree. Experiments have been carried out, in this work, to validate the model capabilities in modelling pressure and velocity waveforms when air pulses propagate in flexible tubes with different mechanical and geometrical properties. The experiments have shown that the arrival of reflected air waves occurs in correspondence of the theoretical timing once the wave speed is known. Reflected backward compression waves have generated an increase of pressure (P) and decrease of velocity (U) while expansion backward waves have produced a decrease of P and increase of U according to the linear analysis of wave reflections. The experiments have demonstrated also the capabilities of Wave intensity analysis (WIA), an analytical technique used to study wave propagation in cardiovascular system, in separating forward and backward components of pressure and velocity also for the air case. After validating the 1-D modelling in space and time variables, several models for human airways have been considered starting from simplified versions (bifurcation trachea- main bronchi, series of tubes) to more complex systems up to seven generations of bifurcations according to both symmetrical and asymmetrical models. Calculated pressures waveforms in trachea are shown to change accordingly to both peripheral resistance and compliance variations, suggesting a possible non-invasive assessment of peripheral conditions. A favourable comparison with typical pressure and flow waveforms from impulse oscillometry system, which has recently been introduced as a clinical diagnostic technique, is also shown. The results suggested that a deeper investigation of the mechanisms underlying air wave propagation in lungs could be a useful tool to better understand the differences between normal and pathologic conditions and how pathologies may affect the pattern of pressure and velocity waveforms.

No description available.

To accommodate future power demands, wave energy converters will be deployed in arrays, but largely unanswered questions of the annual energy production and environmental impact of such installations present regulatory dilemmas. In recent years, Sandia National Laboratories (SNL) has developed a modified version of the Simulating Waves Nearshore (SWAN) wave model to simulate WEC energy extraction in a propagating wave field. This thesis presents a novel WEC meta-model that calculates the power intercepted by a WEC from the incident wave field. Two representations were developed with which a user could model a WEC’s impact on the incident waves in a spectral wave model. These alterations are based on power a WEC captures from the sea and power dissipated by hydrodynamic losses calculated in an external six degree of freedom (DOF) time domain WEC simulation. The two WEC meta-models were compared in terms of significant wave height reduction in the WEC’s lee and annual power production. The first WEC representation removes a constant percentage of power from each frequency bin while the second representation employs frequency dependent energy extraction. The representations were then applied in modelling a 54 MW WEC array off of Amphitrite Bank on the West Coast of Vancouver Island. Over the course of a year, the power captured by a farm when represented with a constant percentage extraction is reduced by 2.9% while a frequency dependent percentage extraction reduced the farm’s total captured power by 2.3% when compared to the reference case. Similarly small changes were observed in significant wave height reductions. The significant wave height in the lee of a farm was reduced by less than 2% for both representations at the shoreline, approximately six kilometres behind the farm. / Graduate / 0775, 0547, 0548 / eluczko91@gmail.com

Local and global loadings, which may cause the local damage and/or global failure and collapse of offshore structures and ships, are experimentally investigated in this study. The big research question is how the aeration of water and the elasticity of the structural section affect loading during severe environmental conditions. A further question is how the scattered waves from ships and offshore structures, the mooring line force and the structural response, which are known to affect local load and contribute to global load, will be affected by wave-structure interaction of a ship or offshore structure under non-breaking wave conditions. Three different experiments were undertaken in this study to try to answer these questions: (i) slamming impacts of a square flat rigid/elastic plate, which represents a plate section of the bottom or bow of ship structure, onto pure and aerated water surface with zero degree deadrise angle; (ii) wave impacts on a truncated vertical rigid/elastic wall in pure and aerated water, where the wall represents a plate section of a hull; and (iii) wave-structure interactions of different FPSO-shaped models, where the models were fixed or taut moored. The experiments were carried out at Plymouth University’s COAST Laboratory. Spatial impact pressure distributions on the square plate have been characterised under different impact velocities. It was found that the impact pressures and force in pure water were proportional to the square of impact velocity. There was a significant reduction in both the maximum impact pressure and force for slamming in aerated water compared to that in pure water. An exponential relationship of the maximum force and the void fraction is proposed and its coefficients are found from drop test in this study. There was also a significant reduction in the first phase of the pressure and force impulse for slamming into aerated water compared with pure water. On the truncated wall, aeration also significantly reduced peak wave loads (both pressure and force) but impulses were not reduced by very much. For the case considered here, elasticity of the impact plate has a significant effect on the impact loads, though only at high impact velocities; here the impact loads were considerably reduced with increasing elasticity. Wave loading on the truncated wall was found to reduce with increasing elasticity of the wall for all investigated breaking wave types: high aeration, flip-through and slightly breaking wave impacts. In particular, impact pressure decreases with increasing elasticity of the wall under flip-through wave impact. As elasticity increases, the impulse of the first positive phase of pressure and force decreases significantly. This significant effect of hydroelasticity is also found for the total force impulse on the vertical wall under wave impacts. Scattered waves were generated from the interaction of focused wave groups with an FPSO model. The results show that close to the bow of the FPSO model, the highest amplitude scattered waves are observed with the most compact model, and the third- and fourth-harmonics are significantly larger than the incident bound harmonic components. At the locations close to the stern, the linear harmonic was found to increase as the model length was decreased, although the nonlinear harmonics were similar for all three tested lengths, and the second- and third-harmonics were strongest with the medium length model. The nonlinear scattered waves increased with increasing wave steepness and a second pulse was evident in the higher-order scattered wave fields for the fixed and free floating models. In addition, the higher harmonics of the mooring line force, and the heave and pitch motions all increased with increasing wave steepness. Incident wave angles of 0 (head-on), 10 and 20 degrees were experimentally investigated in this study. As the incident wave angle between the waves and the long axis of the vessel was increased from 0 to 20 degrees, the third- and fourth-harmonic scattered waves reduced on the upstream side. These third- and fourth-harmonic diffracted waves are important in assessing wave run-up and loading for offshore structure design and ringing-type structural response in fixed and taut moored structures. The second-, third- and fourth-harmonics of the mooring line force, and the heave and pitch motions decreased as the incident wave angle increased from 0 to 20 degrees.

Dusty plasmas, defined as plasmas of ions, electrons, neutrals, and charged micron to sub-micron dust particles, support a rich diversity of physical states. These states (ranging from solids to liquids to gas) are determined by the ratio of the Coulomb potential energy between dust particles to the particles kinetic energy and allow for a broad range of phenomena, from crystallization to dust acoustic waves. Due to various dusty plasma interactions, dust acoustic waves can be nonlinear and exhibit various wave phenomena, from topological wave defects to shock waves to structure formations. In this thesis, I investigate a spectrum of plasma and wave interactions in liquid-like dusty plasmas and focus on a range of dust acoustic wave phenomena observed experimentally in a dc discharge dusty plasma. By developing various experimental techniques, dust acoustic wave diffraction and topological wave defects, dust acoustic shock waves, temporal dust acoustic wave growth, and structure forming dust acoustic waves were observed. I begin in Chapter 2 with the diffraction of dust acoustic waves, which I investigated by introducing a glass rod into the dusty plasma. The resulting diffraction pattern was compared to acoustic wave diffraction in a neutral gas. In addition to the diffraction pattern, topological wave defects were observed to form. I continue Chapter 2 with a preliminary investigation into topological wave defects in dust acoustic waves. Chapter 3 follows with three nonlinear dust acoustic wave experiments. I created a shock tube like profile for dust acoustic waves using a single slit. The shock-tube like potential resulted in two sets of nonlinear dust acoustic waves, coalescing high and low amplitude waves and dust acoustic waves that developed into dust acoustic shock waves. The self-excited dust acoustic shock waves were compared to theoretical models. The third nonlinear dust acoustic wave phenomenon that I investigated was a reverse drift mode that appears in high amplitude dust acoustic waves. I propose a wave process based on dust particle dynamics in high amplitude dust acoustic waves to explain the observations. In Chapter 4, I describe an experimental technique that I developed to create a quiescent drifting dusty plasma. The drifting dusty plasma was used to observe dust acoustic wave growth from thermal density fluctuations. The observed growth rate and frequency were compared kinetic and fluid models. In Chapter 5, I describe experimental observations of a structure forming instability in dusty plasmas. By increasing the discharge current, transient and aperiodic dust density striations formed. I characterized the transient and stationary modes and compared the stationary mode to an ionization/ion-drag instability and a polarization instability.

In this thesis, the author proposes and presents a novel simulation technique for the analysis of multilayered Flexural Plate Wave (FPW) devices based on the convergence of the Finite Element method (FEM) with classical Surface Acoustic Wave (SAW) analysis techniques and related procedures. Excellent agreement has been obtained between the author's approach and other more conventional modelling techniques. Utilisation of the FEM allows the performance characteristics of a FPW structure to be critically investigated and refined before undertaking the costly task of fabrication. Based on a series of guidelines developed by the author, it is believed the proposed technique can also be applied to other acoustic wave devices. The modelling process developed is quite unique as it is independent of the problem geometry as verified by both two and three dimensional simulations. A critical review of FEM simulation parameters is presented and their effect on the frequency domain response of a FPW transducer given. The technique is also capable of simultaneously modelling various second-order effects, such as triple transit, diffraction and electromagnetic feedthrough, which often requires the application of several different analysis methodologies. To verify the results obtained by the author's novel approach, several commonly used numerical techniques are discussed and their limitations investigated. The author initially considers the Transmission Matrix method, where it is shown that an inherent numerical instability prevents solution convergence when applied to large frequency-thickness products and complex material properties which are characteristic of liquids. In addition the Stiffness Matrix method is investigated, which is shown to be unconditionally stable. Based on this technique, particle displacement profiles and mass sensitivity are presented for multilayered FPW structures and compared against simpler single layer devices commonly quoted in literature. Significant differences are found in mass sensitivity between single layer and multilayered structures. Frequency response characteristics of a FPW device are then explored via a spectral domain Green's function, which serves as a further verification technique of the author's novel analysi s procedure. Modifications to the spectral domain Green's function are discussed and implemented due to the change in solution geometry from SAW to FPW structures. Using the developed techniques, an analysis is undertaken on the applicability of FPW devices for sensing applications in liquid media. Additions are made to both the Stiffness Matrix method and FEM to allow these techniques to accurately incorporate the influence of a liquid layer. The FEM based approach is then applied to obtain the frequency domain characteristics of a liquid loaded FPW structure, where promising results have been obtained. Displacement profiles are considered in liquid media, where it is shown that a tightly coupled Scholte wave exists that is deemed responsible for most reported liquid sensing results. The author concludes the theoretical analysis with an in-depth analysis of a FPW device when applied to density, viscosity and mass sensing applications in liquid media. It is shown that a single FPW device is potentially capable of discriminating between density and viscosity effects, which is typically a task that requires a complex and costly sensor array.