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This thesis is concerned with the small amplitude response of coupled resonant systems which are subject to forcing. In particular, we consider systems consisting of a primary body with a fixed secondary, internal or external, component that each exhibit resonance. Motivated by the potential to exploit the coupled resonances we consider the effect of tuning the secondary component on the displacement or energy absorption characteristics of the system. Problems are studied in which the entire system is submerged in fluid of finite depth or in which the secondary system consists of a fluid-filled tank, fitted with some mechanism to provide damping, or both, all under the assumptions of linear water wave theory. In Chapter 1 a condition is derived which applies to submerged vertical slatted barriers and its adequacy tested in five model problems. This condition is then implemented in Chapter 2, in which sloshing in a horizontally-forced fluid-filled rectangular tank fitted with multiple screens is analysed. We proceed by fixing the tank to an externally-forced sprung mass and tuning the tank to minimise response amplitudes across all frequencies. The remainder of this thesis is concerned with the extraction of energy from ocean waves by coupled resonant absorbers. Chapter 3 gives a brief introduction and describes the existing power absorption theory for devices constrained to a single mode of motion. A submerged horizontal cylindrical wave energy converter (WEC) is used to illustrate the application of this theory. This analysis is extended to devices of the same geometry containing an internal power take-off system; in Chapter 4 the device contains a system of pendulums and in Chapters 5 and 6 a water tank. Chapter 7 continues this theme, now for a vertical cylindrical WEC containing an internal water tank. In each example, the focus is on determining the best device configuration to obtain a broad-banded response.

This work is concerned with the hydrodynamics and heat transfer characteristics of the liquid film formed when a liquid flows across a rotating, heated disc. Comprehensive reviews of both the hydrodynamic and heat transfer behaviour of planar gravitationally forced films, and rotating discs in homogeneous media of infinite extent, are presented in addition to the primary subject of this study. For the liquid film on the rotating disc, various hydrodynamic models are studied and the controlling parameters identified. Results obtained with water films are in good agreement with the theoretical models. A simple heat transfer model is developed as an extension to one of the hydrodynamic models. Experimental results for water films show fair agreement with the model and suggestions are made accounting for the discrepancies. Suggestions for future work in both the hydrodynamic and heat transfer fields are made.

A numerical and experimental study is presented of the flow in the gap between concentric rotating cylinders and of its interactions with a cylindrical probe. The radius ratio η of the cylinders is 0.53, 0.44, and 0.35 corresponding to an aspect ratio Γ of 11.36, 7.81 and 5.32. The test cases covered the Taylor number range 2.35 x 10[superscript]6 ≤ Ta ≤ 17.520 x 10[superscript]6, which is above the first critical Taylor number. The cylinders are laid horizontal with the inner cylinder rotating clockwise. The cylindrical probe, which is used to test the intrusiveness of an endoscopic probe on the ensued Taylor vortex flow, is 0.01m in diameter and 0.6m long into the annular region. To the author's best knowledge, no published study has analysed the intrusivity of a cylindrical probe on the flow in concentric rotating cylinders. The flow is herein analysed in the meridional and azimuthal planes. The results from this study further confirm that η, Γ, Ta, and the end-wall conditions are all important parameters that determine the flow regime in the annular gap between concentric cylinders. The results also show wavy vortex flow with aspect ratio Γ < 25 at high Taylor numbers, well beyond the published Taylor number for transition to turbulent flow. In this flow, the vortex centres shift toward the outer cylinder as the centrifugal force due to the rotation of the inner cylinder is greater than the pressure gradient due to the stationary outer cylinder wall. As the η increases, the vortex centres displace more towards the outer cylinder wall. Introducing the cylindrical probe changes the Taylor flow structure. It shifts and distorts the vortices from their original axial position, reduces and elongates the size of the vortices, and reduces the strength of the vortices located between the rotating inner cylinder and the stationary outer cylinder.

By means of finite Fourier transtorms the Green's function and hence the general solution is found for the Chaplygin equation of motion for an important class of flows i.e. 2-dimensional non-viscous compressible 'simple wedge flows' with circular sector hodographs (these flows have been defined and classified according to their hodograph diagrams by Birkhoff and Zarantonello). From the particular case of Réthy flows the solution is used to find the drag coefficient, firstly in an exact analytical form and then, for sonic jet flows past thin wedges, as a series inascending powers of the wedge angle; comparisons are made with the results obtained from the approximate equations of Tricomi and of Tomotika and Tamada. The study of sonic Réthy flows of small wedge angle is taken further and series which are uniformly valid for all possible source velocities are found for the wedge length and stand-off (i.e. distance of the wedge from the channel) in terms of the (small) wedge angle. From these series certain limitations on the lengths and pressure differences can be determined. Some examples of the general solution (including the solution for Réthy flows) are discussed in relation to earlier published papers and a discrepancy in some Russian papers is explained. The thesis ends with a theorem on sonic jets. This states that for simple wedge flows involving sonic jets, the physical changes due to the presence of solid boundaries in the flow are compared withina finite distance in those directions in which sonic jet flow prevails.

The work presented in this thesis consists of two parts. The first part deals mainly with the problems associated with flow patterns, pressure drops, settling lengths, void fractions, and their prediction. The second part describes methods evolved to define flow patterns from the characteristics of the pressure and void fraction fluctuations. A test rig was designed and constructed from transparent tubing with the main test section horizontal. The working fluids were air and water, at pressures and temperatures close to atmospheric, and the test conditions covered a range of air and water superficial velocities respectively of 0--> 28 m/s and 0 --> 5.1 m/s in a 127 mm nominal bore tube. 0 --> P-8.6 m/s and 0 --> 1.7 mf s in a 216 mm nominal bore tube. The experimental observations indicated asymmetric flows in general with a stratification effect superimposed on the normal flow patterns. Comparison with existing flow pattern maps showed an effect of tube diameter. The inadequacies of flow pattern maps are discussed. The experimental data relating to pressure drops and void fractions showed a strong flow pattern dependency, and correlations are presented for three main groups of flow patterns. These groups are (i) Annular Flows - incorporating annular, annular mist, rough wavy, etc. (ii) Intermittent Flows - incorporating bubble, plug and slug, (iii) Separated Flows - incorporating stratified and smooth wavy. Transition equations, defining the changes from one flow pattern group to another, were developed to enable predictions of flow. patterns for particular sets of conditions to be made. These were essentially based on a wave stability criterion. Comparisons were made between the experimental friction pressure drop and void fraction data and several well known correlations available in the literature. These showed poor agreement, in general. Pressure and void fraction probes were developed and tested with the object of obtaining more objective flow pattern measurements. These were used in conjunction with a high speed data acquisition system with a view to relating the statistical behaviour of the pressure and void fraction fluctuations to flow patterns. The results confirm the usefulness of these probes for this purpose.

No description available.

No description available.

No description available.