Wind/wave interactions in the surf zone are studied using a wave tank and environmental wind tunnel. The wind simulation is achieved over a relatively short fetch using accelerated growth techniques at a scale of roughly 1:100. Waves are scaled at approximately 1:50, and consequently there is some scaling mis-match between the wind and wave simulations. Results show that wind has a significant effect on the breaking of the waves. Both breaker location and breaker type are shown to be affected by the wind. Results are in agreement with those of Douglass (1989 & 1990), who used a wind/wave flume to simulate the prototype conditions, but made no attempt to correctly simulate the turbulence in the air flow. The main findings, are that onshore winds promote spilling waves and increase the surf zone width, whereas offshore winds promote plunging waves, decreasing surf zone width. Hot-film measurements of the air flow over the waves show that there exists significant differences between the air flow structure of offshore and onshore winds over the surf zone. Under offshore winds, the surf zone exerts a large drag on the air flow, dramatically increasing turbulence intensities aerodynamic roughness z0, and friction velocity, u*, near the point of wave breaking. Under onshore winds the air flow is less affected and at the point of wave breaking, z0 for onshore winds is an order of magnitude lower than the value under offshore winds. Phase-averaging techniques indicate large wave-induced perturbations to the mean velocity over the waves, and these are present to heights of up to 5 or 6 times the breaker height over the point of wave breaking. Spectra indicate that for onshore winds large wave-frequency fluctuations are present at the shore. Additionally, studies of particle motion offshore of the surf zone indicate wind effects on the drift velocities of suspended particles, although the precise nature of the wind effect was not clear.

The research into hydrodynamic loading on ocean structures is concentrated mostly on circular cross section members and relatively limited work has been carried out on wave loading on rectangular sections, particularly in waves and currents. This research work is therefore carried out focussing on the evaluation of hydrodynamic force coefficients for sharp edged rectangular cylinders of various cross-sections (aspect ratios), subjected to waves and currents. Three cylinders with three different cross-sections are constructed and tested vertically, as surface piercing and horizontally, as fully submerged with the cylinder axis parallel to the wave crests. The aspect ratios considered for this investigation are 1.0, 112, 2/1, 3/4 and 4/3. The length of each cylinder is 2000mm. The sectional loadings are measured on a 100mm section, which is located at the mid-length of the cylinder. The forces are measured using a force measuring system, which consists of load cells, capable of measuring wave and current forces. The in-line & transverse forces (for vertical cylinders) and horizontal & vertical forces (for horizontal cylinders) have been measured. For horizontal cylinder, to study the effect of depth of variation on submergence of the cylinder, the tests are carried out for two depths of submergence. The experiments are carried out at the Hydrodynamic Laboratory, Department of Naval Architecture and Ocean Engineering, University of Glasgow. The tests are carried out in a water depth of 2.2m with regular and random waves for low Keulegan-Carpenter (KC) number up to 4.5 and the Reynolds number varied from 6.397xl03 to 1.18xl05 • The combined wave and current effect has been produced by towing the cylinders in regular waves, along and opposite to the wave direction at speeds of ± 0.1 mis, ± 0.2 mls and ± 0.3 mls. Based on Morison's equation, the relationship between inertia and drag coefficients are evaluated and are presented as a function of KC number for various values of frequency parameter, {3. For the vertical cylinders, the drag coefficients decrease and inertia coefficients increase with increase in KC number up to the range of KC tested for all the cylinders. For the horizontally submerged cylinders, the drag coefficients showed a similar trend to vertical cylinders, whereas the inertia coefficients decrease with increase in KC number for all the cylinders. This reduction in inertia force is attributed to the presence of a circulating flow [Chaplin (1984)] around the cylinders. The random wave results are consistent with regular wave results and the measured and computed force spectrum compares quite well. While computing the force coefficients in the case of combined waves and currents, only the wave particle velocity is used, as the inclusion of current velocity tends to produce unreliable drag force coefficients. For vertical cylinders, the drag and the inertia coefficients in combined waves and currents are lower than the drag and the inertia coefficients obtained in waves alone. For horizontal cylinders the drag coefficients are larger than those obtained for waves alone and the inertia coefficients are smaller than those measured in waves alone. The Morison's equation with computed drag and inertia coefficients has been found to predict the measured forces well for smaller KC numbers. However, the comparison between measured and computed positive peak forces indicate that the computed forces are underestimated. It is suggested that if the wave particle kinematics are directly measured, this discrepancy between measured and computed forces might well be reduced. Wave excitation forces are also reported in non-dimensional forms in the diffraction regime, using 3D-Green function method. Wave induced pressure distribution around the cylinder in regular waves have been measured and are reported as normalised pressures. Wave run-up on the cylinder surfaces has been measured and simple empirical formulae are presented for run-up calculations on the cylinder surfaces. The results of this investigation show that the cylinder aspect ratio plays major role on hydrodynamic force coefficients, dynamic pressure distribution and on wave run-up on cylinder surfaces.

No description available.

The majority of the world's river basins remain ungauged and, therefore, the triedand- tested empirical techniques for predicting floods and droughts cannot be applied. An alternative approach, which is currently receiving a great deal of attention from research hydrologists, is to develop continuous simulation models whose parameters pertain to physical or hydrological properties of the river basins. However, difficulties related to scale, heterogeneity and complexity of real river basins have made a priori estimation of such parameters impossible: their estimation has always required calibration using river flow data. Therefore, estimating hydrological model parameters in ungauged river basins is one of the greatest challenges currently facing research hydrologists. In this thesis research advances towards this goal have been made at three different levels. First, at a conceptual level, a novel method for classifying river basins according to their physical properties is proposed. It is specifically designed for transferring hydrological model parameters from gauged river basins, where calibration is possible, to ungauged river basins. This approach relies on recognising that river basins can be similar in parts of their hydrological cycle but not in others. Thus, basins go through three independent classifications, one relative to each of the major components of the land phase hydrological cycle: interaction of soil water/vegetation and atmosphere; surface flow; and groundwater flow. This requires the ability to characterise the response of the components of the hydrological cycle independently, which leads to a second conceptual advance; rather than relying entirely on measured river flow data, from which it is difficult to separate out the effects of the three components, classification rules are devised on the basis of synthetic data produced by comprehensive, distributed, physically-based models. This thesis focuses on the surface flow component, applying the methodology to the identification of the best classifiers for surface flow through river networks. This required simulating river flow through a large number of Scottish river basins, which led to more practical research advances; all available commercial flow routing models were too cumbersome and required an impractical level of detail to be applied in such a large study. Therefore, a new flow routing modelling system was developed that extracts river network detail from digital databases and numerically solves a distributed flow routing model. Finally, on a detailed scientific level, significant insights have been made into the relationship between river network geomorphologic structure and stream flow response. In particular, it is shown that: a downstream hydraulic geometry relationship exists for Scottish rivers; although channel conveyance is a key factor in dictating network response, the features of the response hydro graph - namely the percentage attenuation of the flood peak and the lag in time to peak - scale linearly with both roughness and hydraulic geometry coefficients; much publicised invariant power law scaling rules for flood peaks in fact vary as a function of storm duration; statistical multivariate analysis of the simulated network flow responses demonstrated the low capacity of the network descriptors commonly used in regionalisation studies for characterising flow response. Four variables are shown to have significantly higher classifying power than the majority of the commonly used classifiers. Of these, two are entirely new to this thesis.

The accurate prediction of stress concentration factors (SCF) at weld toes is recognised as one of the most important factors in the design, against fatigue failure, of welded tubular joints in offshore structures. The objectives of this work are i) to study the influence of some important tubular joint and weld profile geometric parameters on the elastic SCFs at weld toes, ii) compare these values with strains which could be measured by strain gauges, and iii) to determine plastic-elastic strain distributions after local yielding has occurred in the weld. Using 3-d frozen-stress, photoelastic techniques elastic SCFs were determined in non-overlapped corner K joints in balanced axial loading and in X joints in axial loading. For typical tube parameters, results have been obtained for different brace angles, brace spacings, weld size, weld angle and weld toe radii in the crown and saddle planes at the brace and chord wall ends of the weld. They have been presented as the product of a shell SCF Ks and a notch SCF Kn . Ks, which was measured at the weld toe, depends on position in the brace intersection, brace angle, brace spacing and weld size. Kn depends on weld toe radius, weld angle and weld size. Large scale 2-d photoelastic and finite element models were used to study the influence of weld profile "qualities" on Ks and Kn. Weld shapes conforming with minimum profiling requirements are called "uncontrolled". Improved weld shapes wi th concave profiles are called "controlled". The reductions in SCFs, due to the different profiles, depend on position (crown or saddle) when the results are presented for identical weld geometry. Plastic-elastic and residual plastic strains were obtained in 2-d steel weldments using reflection photoelasticity and moire interferometry experimental techniques. A moire interferometer, using Helium-Neon laser light and high sensitivity diffraction gratings was designed and built for this purpose. Strains were measured in the range 20µε to 2%. Strain concentration factors of between 13 and 17 were determined in models in which the corresponding elastic values were 3.6 and 4.6 respectively.

Wave overtopping is one of the most important processes for the design of seawalls. During the past 50 years methods for predicting wave overtopping of coastal structures have continuously been developed. However, it is evident from the existing literature that additional investigations into overtopping of small positive, zero and negative freeboard are needed. The present thesis describes numerical investigations based in this background. Wave overtopping is dependent on the processes associated with wave breaking. Therefore, a two dimensional breaking wave numerical model has been developed and used to study the phenomena of wave overtopping. The model is based on the Reynolds averaged Navier-Stokes equations for the mean flow and k-epsilon equations for turbulent kinetic energy, k, and the turbulence dissipation rate, epsilon. The model accuracy in simulating propagation of linear and irregular waves has been evaluated. The overall performance of the model is considered satisfactory. The development of guidelines for calculating overtopping discharge for different seawall slopes is presented. All slopes have been subjected to a wide range of irregular waves. The influence of how the slopes of seawalls, wave type (breaking and non-breaking) and crest freeboard affect the overtopping discharges has been investigated. Based on the numerical data, a new expression for breaking and non-breaking waves on smooth impermeable slopes is proposed. With the new expression it is possible to predict overtopping discharges of smooth seawalls in small positive, zero and negative freeboard.

After many years of slow but progressive development, the wave energy industry is on the cusp of breaking through the economic and technical barriers to full scale deployment of wave energy electrical generating devices. As the major obstacles in device design are solved, and with several devices in the water, the scope for increasing their efficiency through advanced control techniques is now becoming clearer. In some cases, it would be advantageous to integrate an advanced prediction of wave behaviour (of some tens of seconds into the future) into these control methods. Past research on wave prediction has focused on utilising the Fourier theorem to deconstruct wave records and then make predictions ahead in space, with published results indicating promise. However, predicting ahead in time has so far not been achieved. This thesis takes the Fourier theorem method of prediction to its logical conclusion by exploring its limitations in predicting over both time and space. A discussion as to why these limits should exist, and possible work into the solution of the wave prediction problem, are also presented. A review of current devices under development, and the history and emergence of the wave generating industry (which is a comparatively recent technology and still in its infancy), are also included as appendices to the main thesis in order to put the work into context.

Thesis (M.E.)--University of Adelaide, Dept. of Civil Engineering, 1974.

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 168-176). Also available in electronic version.