A prominent feature of many practical flows is the hydrodynamic wave system attached to moving bodies or concentrations of vorticity. Sound waves are usually present, and these act as a mechanism for energy and momentum transport. With their source rooted in the unsteadiness of the flow, they can sometimes play an important role in determining the general flow structure, particularly if the flow is unstable. In this thesis we investigate the basic connection between sound, and hydrodynamic waves. By analysing the waves attached to boundaries which are in prescribed unsteady motion, details emerge concerning the linear production of sound from hydrodynamic motions. We show that the abrupt arrest or commencement of a steady hydrodynamic wave causes the production of a quantity of sound energy exactly equalling that of the hydrodynamic wave. For more gentle modulations of the steady state, we identify those aspects of the evolving hydrodynamic field which determine how much sound is produced. These results are used to suggest ways to improve procedures for minimising the noise from vibrating surfaces. According to linear theory, when waves on an infinite fluid boundary travel at sonic speed the fluid response is infinite. We use the ideas developed to cope with the sound generation problem to investigate the effects of unsteady transonic motion. We give a detailed analysis of acoustic 'Cerenkov radiation', which would occur if a body travelled through an inviscid medium supersonically, and decelerated to a subsonic speed. We assess the degree to which non-linear transonic effects are important. Sound waves are known to be a critical factor leading to the destabilisation of line vortices, and we were intrigued to know whether compressibility has a corresponding effect on the stability of a rigid body moving steadily in an irrotational, inviscid flow. Our investigation reveals that the motion is always stable.

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This thesis describes modulated methods using both voltammetric and microfluidic perturbations to study mechanisms of electrolysis reactions. The initial chapters provide an overview of applications and research development in the fields of micro-engineering and electrochemistry, including microfabrication methodology, electrochemical detection techniques and analysis methods. Some typical electrochemical reactions have been studied for different kinds of industrial applications. Also hydrodynamic modulation methods have been investigated. The result chapters begin in Chapter 3 with detailed investigation of various electrochemical reactions by using cyclic voltammetry (CV) and large amplitude Fourier transformed alternating current voltammetry (FTACV) under microfluidic conditions. Single electron transfer reactions with different kinetics were studied first by using potassium ferrocyanide and ferrocenecarboxylic acid (FCA). Dual electron transfer reactions with different pathways were investigated by using 2,5-dihydroxybenzoic acid for one step oxidation and N,N,N',N'-tetramethyl-para-phenylene-diamine (TMPD) for two consecutive one-electron step oxidation. An irreversible reaction was explored by using borohydride solution. Examples of homogeneous reaction mechanisms were studied by using the combinations of Fe(CN)64-/L-cysteine or TMPD/ascorbic acid. The current response of all the electrolysis reactions except single electron transfer reactions was first reported under microfluidic conditions with FTACV, which has shown sensitive with the change of volume flow rates and the substrate concentrations when homogeneous reactions are involved. The linear relationships between peak current and volume flow rates or substrate concentrations can be obtained in every harmonic component. In chapter 4, the modulated technique was applied to microfluidic hydrodynamic systems. A range of electrolysis mechanisms including single electron transfer reactions, dual electron transfer reactions, irreversible reaction and homogeneous reactions were studied under hydrodynamic modulated conditions. The system showed rapid response with the change of volume flow rates during one measurement. The linear relationships between peak current and flow rates, as well as substrate concentrations, can be obtained simultaneously in one scan, which reveals a promising approach to get more information in a short-time measurement. Chapter 5 demonstrated a new protocol by forcing an oscillation of the electrochemical active solution flowing. Analysis of transition time and its effect on limiting current are presented to begin exploration of this new tool for supporting researchers on understanding redox mechanisms. A short simulated study was carried out to help better understand the mechanism under different hydrodynamic conditions.

This thesis describes the study of the hydrodynamic boundary condition at the solid-liquid interface using the colloidal probe Atomic Force Microscope. Quantitative comparison between measured lubrication forces and theoretical lubrication forces show that the measured forces agree with theory when the no slip boundary condition is employed. We measure an effective slip length of 0 ± 2 nm at shear rates up to 250,000 sec-1. Our results are consistent with the Taylor lubrication equation without the need to invoke a slip length fitting parameter. Our results are also consistent with molecular dynamic simulations that predict no slip at the shear rates that are currently experimentally accessible.

This thesis describes the study of the hydrodynamic boundary condition at the solid-liquid interface using the colloidal probe Atomic Force Microscope. Quantitative comparison between measured lubrication forces and theoretical lubrication forces show that the measured forces agree with theory when the no slip boundary condition is employed. We measure an effective slip length of 0 ± 2 nm at shear rates up to 250,000 sec-1. Our results are consistent with the Taylor lubrication equation without the need to invoke a slip length fitting parameter. Our results are also consistent with molecular dynamic simulations that predict no slip at the shear rates that are currently experimentally accessible.

A process planning strategy was proposed to suppress the wear effect of tool in a polishing of axially symmetrical work. This strategy can keep machining rate of tool to be constant. In study, we need to design the proper dwelling time distribution for tool to remove error of axially symmetrical surface and use computer to simulate. Observe the residual error on surface of work. Analyze the outcome of experiment and estimate feasibility of the strategy. According to the way of motion of tool, it could cause two difficulties: 1.To design the dwelling time distribution of tool will be more difficult. 2.The load of tool will be unstable. In order to solve this first difficulty, in a new strategy of working, the dwelling time distribution of tool must be a multiple of integral of the period of work rotation. And experiment to prove it, analyze and discuss the outcome of experiment. Second problem cause the load of tool to be unstable in experiment. To improve the load of tool, a new strategy was proposed to control load and to verify effectiveness for the strategy. Finally, analysis and discuss the outcome of experiment, and estimate the practicability of the strategy.

Due to the complexity of body-shape, the investigation of hydrodynamic forces on mooring lines, especially those comprised of chain segments, has not been conducted to a sufficient degree to properly characterize the hydrodynamic damping effect of mooring lines on the global motions of a moored offshore platform. In the present study, an experimental investigation of the hydrodynamic characteristics of various mooring elements is implemented through free and forced oscillation tests. Since no direct measurement capability for distributed hydrodynamic forces acting on mooring line segments such as chain and wire rope is available yet, an indirect measurement technique is introduced. The technique is based on the fact that hydrodynamic forces acting on a body oscillating in still water and on a stationary body in an oscillatory flow are equivalent except for the additional inertia force, the so-called Froude-Krylov force, present in the latter condition. The time-dependent displacement of a slender body moving in calm water is acquired through optical tracking with a high speed camera. The distributed hydrodynamic measurements are then used to obtain the force by solving the equation of motion with the boundary condition provided from tension measurements. Morison’s equation is employed along with Fourier analysis to separate the inertia and drag components out of the total fluid force. Given the experimentally-derived information on hydrodynamic behavior, the resistance provided by a mooring line to a floating structure is briefly studied in terms of damping and restoring force in a coupled dynamic system.