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The axisymmetric laminar boundary-layer flow along a circular cylinder under an accelerated free-stream is investigated. Considering flow past a slender cylinder, the boundary-layer equations are developed with a linear velocity-slip and temperature-jump boundary condition imposed near the cylinder wall. For small and large axial distances, series solutions are obtained for the Bingham and Nusselt numbers; these take account of prescribed values of momentum and temperature-slip coefficients and the index of acceleration; at intermediate axial distances, exact and interpolated numerical solutions are obtained. In addition, the flow past a Rankine half-body is considered. Given a prescribed Reynolds number, asymptotic series solutions for the non-dimensional drag coefficient for flow close to the forward stagnation point and downstream are obtained; for intermediate flow) the solution is obtained by interpolation. The unsteady case is then investigated. in which the boundary-layer flow along a cylinder of infinite extent moves impulsively from rest with both uniform velocity and acceleration under velocity-slip. Consideration is then given to the case in which an infinite stationary cylinder is impulsively heated in still-air having a fixed temperature, while a temperature-jump boundary condition is imposed. In relation to non-dimensional time, the Bingham and Nusselt numbers are derived analytically by means of Laplace transform techniques. Finally, the amplitude of a disturbance caused by an air draught acting on a part of the fibre in the melt-spinning process is investigated.. The flow, modeled as a wave propagating on a moving string, takes account of the influence of air drag and variable tension. Using the method of characteristics, the disturbance amplitude is analytically obtained along the leading characteristics that emanate from the boundaries of the localised. initial disturbance while the general solution of the damped disturbance is numerically evaluated. The magnitude of the disturbance is determined for the region close to the orifice where the extruded polymer is molten and thus, susceptible to disturbances.

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A new technique known as the bubble function method is developed for the modelling of fluid flow problems. The main motivation for this work has been the desire to resolve difficulties that traditional methods show in dealing with multi-scale behaviour in flow regimes. All of the traditionally used methods require excessive mesh refinement in the simulations of systems that combine different scale of behaviour in one domain. The present bubble function method avoids such crude remedies and instead of using an elegant mathematical technique for the conjunctive approximation of fine and coarse scale phenomena. Using numerical experiments it is shown that the implementation of the bubble function method generates accurate and stable solutions for a wide range of problems. This range includes convection and reaction dominated transport phenomena, and various types of porous flow systems, it can also be extended to transient flow simulations. To demonstrate the applicability of the present technique it has been used to solve a realistic problem, namely solute dispersion in an estuary. The results of this simulation show good agreement with field survey data.

The nature of digital hydraulic systems may cause pressure pulsation problems. For example, switched inertance hydraulic systems (SIHS), which are applied to adjust or control flow and pressure by a means that does not rely on dissipation of power, have noise problems due to the pulsed nature of the flow. An effective method to reduce the pulsation is important to improve system performance and increase efficiency. Although passive systems to reduce the noise have been shown to be effective in many situations, their attenuation frequency range is limited and they may be bulky. Furthermore, attenuation devices based on expansion chambers, accumulators or hoses are likely to be unsuitable for SIHS as they add compliance to the system and would impair the dynamic response. This thesis is concerned with issues relating to the development of an active noise canceller for attenuating the pressure pulsation which is caused primarily by pulsed flow from high-speed valves in SIHS. Active control methods are widely and successfully applied in the area of structureborne noise (SBN) and air-borne noise (ABN) cancellation. The idea is using the intentional superposition of waves to create a destructive interference pattern such that a reduction of the unwanted noise occurs. However, applications for fluid-borne noise (FBN) attenuation based on the ‘Active noise control (ANC) principle’ are rare due to the restriction of the hardware and experimental apparatus in previous researches. In this thesis, an adaptive controller has been developed for active control of pressure pulsation in hydraulic system. The principle of the adaptive LMS filter and details of the controller design are described and the implementation was carried out through simulation. The designed controller was applied on a vibration test rig initially prior to the hydraulic testing in order to investigate its advantages and limitations in practice. Extensive testing on a switched inertance hydraulic rig proved that the controller, which used a piezoelectric valve with fast response and good bandwidth, is effective and that it has several advantages over previous methods, being effective for low frequency cancellation, with a quick response, and is robust and versatile. A novel method for the accurate measurement of unsteady flowrate in a pipe was proposed. This was applied and validated on a pipe, and was shown to give good results. This method solves the difficulty for measuring the unsteady flowrate currently by using easy-measured signals, such as pressures. It can be used widely for predicting the unsteady flowrate along the pipe.

In recent years, the study of synchronization phenomena in nonlinear systems has made a number of significant advances in various areas of physics, engineering and the life sciences. Ideas of chaos synchronization have been used recently in some atmospheric phenomena as an attempt to better understand certain kinds of cyclic behaviour and teleconnection patterns, and at least some have shown promising results.

Lifting technologies are used in sub-sea and underground mining for the transport of solids, as well as this oil well drilling operations require the management of vertically rising slurry flow. Monitoring and control of these processes are essential for minimizing energy wastage as well as avoiding pipeline blockages; however solid-liquid transport systems present considerable metering and visualization challenges. The coarse particle [ad en slurry is highly abrasive and opaque, and in addition the pipeline is required to be open bore and the measurement scheme non-intrusive. Currently there is no single device available commercially that can provide a complete metering solution of the transport process that is also not compromised in terms of measurement capability or by other process restraints. This thesis investigates a measurement technique capable of sensing essential transport variables for the determination of mass flow rate of slurry in-situ , by combining technologies electrical resistance tomography (ERT) with other auxiliary sensing technologies such as differential pressure measurement and an electromagnetic flow meter. The tandem function of these sensing technologies allows all unknown variables for determining the mass flow rate to be established, namely; solid phase concentration and velocity from cross correlation techniques, and liquid phase concentration and velocity. Experimentation has been conducted in a solids handling flow loop using silica sand in water as a medium to test the performance of the proposed measurement scheme. Slurry density and velocity measurements determined by electrical resistance tomography technique at various transport velocities and solids concentration are reported. A validation of the proposed measurement scheme is made against a newly designed measurement scheme comprising a load cell weigh system from which samples can be taken on line. The precision of the mass flow measurement, its potential application and future prospecting are discussed.

As part of the long-term effort for deepening our understanding of the physics of the damage powers of cavitation, a Markov stochastic model has been developed to describe the interaction of bubbles with nearby boundary walls. The objective of the PhD programme is to calibrate the newly designed and purposely constructed venturi-cavitation test rig at Warwick University, on which the Markov model will be studied; and to develop feasible and effective (experimental and numerical) approaches for implementating this stochastic study.

We study the dispersion of of multi-heavy-particle sets in an isotropic turbulent flow using the Lagrangian model, Kinematic Simulation. The simplified equation of motion of heavy particle in turbulent flow is introduced with a full description of the Kinematic Simulation model. The evolutions of the multi-heavy-particle sets in turbulent flow, shape and size, are plotted for different particle characteristic; different particle inertia and gravity, which leads to some information about the turbulent structures.

A principal aim of the present study is to analyse further the physical mechanisms at work in this formulation and also to undertake a more complete analysis of the lodel performance for jets pulsed over a range of frequency from 1 to 10 Hz after following the encouraging results obtained by Bremhorst et al. (2003) using the two-time-scale eddy viscosity model of Hanjalic et al. (1980).