Washing fabrics is a ubiquitous process that has been found to have been common even in early civilisations. The process can be performed by hand or with the aid of a washing machine, giving rise to a wide range of wash conditions. Although this process is very common the mechanisms involved are poorly understood, but are thought to involve chemical, mechanical and hydrodynamic inputs. The main aim of this project is to test whether these inputs can be used to improve the efficiency of cleaning fabrics at lower temperatures, and to better understand the mechanisms involved in these individual actions. The cleaning of polyester and cotton fabrics soiled with artificial sebum has been investigated with 20 °C, 40 °C and 60 °C wash solutions. Fabrics have been cleaned with a model surfactant system consisting of Linear Alkylbenzene Sulfonate (LAS) at 0.1 times and twice the Critical Micelle Concentration (CMC), and results compared to water. Bespoke rigs to simulate rubbing, stretching and flow have been optimised and methods developed for cleaning and analysis of fabrics. Cleaning has been characterised by mass change, colour change and resistance change. Mass change gives an indication of the overall removal, whereas colour gives an analytical measure of the difference in the appearance of the fabrics, and change in resistance to flow of water through the fabric shows how much sebum has been removed from the pores. Additional analysis has been completed on the fabrics including FTIR, mass per unit area, SEM and zeta potential measurements. Removal was highest when the fabric was washed at 60 °C with a high concentration of surfactant. Soaking alone removed some of the mass, but this increased when mechanical action was also used. Of the mechanical actions, rubbing was found to be the most effective under most conditions. On the whole, cleaning was more effective at 40 °C than 20 °C, and a higher concentration of surfactant aided removal of soil to a greater extent that at a lower concentration or with water alone. However, some exceptions to these trends have been identified.

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An arbitrary Lagrangian-Eulerian (ALE) three-dimensional hydrodynamic free-surface numerical model has been developed based on the time-dependent Reynolds-averaged Navier-Stokes (RANS) equations and the finite volume method (FVM). The model with non-hydrostatic pressure distribution and a structured nonorthogonal curvilinear staggered mesh is capable of simulating non-homogeneous stratified flows and problems involving complex bathymetry. A projection method is deployed for solving the set of the equations, and a buoyant k-ε turbulence model is included in the numerical model. Six new advection schemes are introduced, and a fifth-order-accurate upstream scheme was utilised in the numerical model. Extensive numerical tests showed the capability of the model in simulating free surface flows and non-linear terms in Navier-Stokes equations. To achieve a better understanding of hydrodynamics, mixing, and salt transport and stratification and their interactive mechanisms in estuarine harbours and barrages, a laboratory tidal basin was designed, set up and employed for velocity, water surface elevation and salinity measurements of an idealised vertically distorted model harbour. For despiking and denoising the velocity data a linear algorithm was established, which successfully lowered the noise level and removed the spikes. The measurements showed a horizontal circulation in the harbour and weak vertical circulations. The salinity suppressed the circulation across the water depth, resulting in less mixing in vertical direction and stronger flushing on the surface. Comparisons of the numerical model simulations against the experimental data showed that the velocities and flow patterns were in generally good agreement with the measured values. For the fresh water the model under-predicted the dominant velocity components for the areas with strong circulation and for the saline water the simulated results showed an overprediction in lower layers and good agreements with the measured values for the top layer. The water elevations exhibited very close predictions compared with the measured data. The salinity simulated profiles showed good agreements with the measured values for lower layers and an over-prediction for the top layer. The investigations showed that the dominant velocities inside the harbour were increased for taller barriers, but with the increase of mean water depth the circulations weakened. The saline water flushing into the harbour flows underneath the fresh ambient water resulting in higher salinity concentration in the harbour over time.

A technique has been developed for investigating the detailed mechanism of gas-side mass-transfer from packings. An element of packing is coated with a thin film of naphthalene of known uniform thickness. The disappearance of this film is followed as it evaporates in an air stream. This allows local mass-transfer coefficients to be determined. The method has been applied to grid packings. It was found that the details of the transfer process were controlled by the flow patterns existing around the slats. The behaviour and effectiveness of different shapes and arrangements of slats were compared. It proved possible to correlate the mass-transfer coefficients for arrays of rectangular cross-sectioned slats, and to extend the correlations over the ranges of grid dimensions and air velocity normally used in industrial practice. Experiments in a water cooling tower showed that the correlations of average mass-transfer coefficient were applicable to this system of irrigated packings. At the water rates used, no modification of the correlations was found necessary, although reported results indicate that a correction would be necessary at other water rates. The relevance of the correlations to water cooling towers was confirmed by the limited quantity of reported data thought to be reliable. Pressure-drop results obtained on the cooling tower were found to be correlated by a single equation, the form of which had been predicted by separate considerations of skin friction and form drag. The equation was found to fit reported pressure drop results with reasonable accuracy and should be applicable to all grid packed columns. The correlations of gas-film mass-transfer coefficients and the expression for pressure-drop enable the optimum grid dimensions to be chosen for any operation which is gas-film controlled and yield reliable design data for water cooling towers.

Both biological micro-organisms and synthetic micro-robots propel through viscous liquids to achieve their goal, be it to invade new territories or to deliver drugs to infected regions. Considerable attention is devoted to learning how to prevent or encourage these processes, and understanding the interactions between micro-swimmers and their complex environments is an essential part of this. In vivo conditions provide a challenge to model, although novel experimental, computational and theoretical techniques have provided clear insights into the continuous interplay between the effects of strong confinement, hydrodynamic interactions, and local activity that drives living systems out of equilibrium. To analyse the underlying mechanisms of micro-swimmer processes, we develop a hydrodynamic framework based on the fundamental solutions of the Stokes equations to compute swimmer-generated flow fields. These flows affect the motion of swimmers via reflections in surfaces, mix and enhance the uptake of nutrients, and enable cells to sense one another's presence. Hence, we study the accumulation of microbes on surfaces, which could be relevant for the initial stages of biofilm formation, and compute the strength required for externally imposed flows to detach them. Moreover, we evaluate the ability to swim upstream and uncover that viscoelasticity can provide a natural sorting mechanism for sperm cells. Other ecological effects are considered, including the transport of nutrients by micro-flows, the interaction with water-air interfaces, and the impact of thermal noise and biological fluctuations. To verify our results, we compare our theory to extensive simulations using a `Raspberry' swimmer model in combination with the Lattice-Boltzmann fluid solver algorithm. This allows us to determine previously unknown model parameters and hence make suggestions to improve micro-organism treatment and micro-robot design.

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hy2Foam is a newly-coded open-source two-temperature computational fluid dynamics(CFD) solver that aims at (1) giving open-source access to a state-of-the-art hypersonic CFD solver to students and researchers; and (2) providing a foundation for a future hybrid CFD-DSMC (direct simulation Monte Carlo) code within the OpenFOAM framework. Benchmarking has firstly been performed for zero-dimensional test cases and hy2Foam has then been shown to produce results in good agreement with previously published data for a 2D-axisymmetric Mach 11 nitrogen flow over a blunted cone and with the dsmcFoam code for a series of Fourier cases and a 2D Mach 20 cylinder flow for a binary reacting mixture. This latter case scenario provides a useful basis for other codes to compare against. hy2Foam and dsmcFoam capabilities have eventually been utilised to derive and to test a new set of chemical rates based on quantum-kinetic theory and that could be employed for Earth atmospheric re-entry computations.

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Iron oxide particle deposition is a common form of fouling of heat exchange surfaces and is important in radioactive corrosion product transport. The present work relates to deposition in fully turbulent isothermal conditions from non-boiling aqueous suspensions onto metal tubes using particles of Haematite (Fe303) for which transport through the boundary layer was expected to be predominantly diffusional. A radioactive technique has been used to measure deposition rate onto clean stainless steel and aluminium surfaces, the growth of deposit with time and the rate of removal of particles as clean water is passed over the deposit. In view of the known effect of particle size on mass transfer, attempts were made to use particles of uniform size. The performance of a small diameter hydrocyclone was investigated as a means of obtaining a monodisperse suspension from commercially available powders but these were eventually discarded in favour of particles manufactured using a controlled precipitation process. Water chemistry has been demonstrated to have a profound effect on particle deposition from turbulent flow which is similar to that found by workers experimenting in systems with laminar flow. The mass transfer coefficients measured under favourable conditions of water chemistry agreed extremely well with predicted values. The asymptotic level of deposit was found to decrease as fluid velocity increased approximately to the power 1.3 which cannot easily be explained using currently available mechanistic descriptions. The rate of decrease in deposit thickness as clean 'water is passed over it was finite. However this was around an order of magnitude lower than that required to indicate that continuous removal of particles by turbulent bursting in the laminar sublayer or other fluctuations in the forces of the particles is the major factor responsible for asymptote formation.

The characteristics of fully developed turbulent flow in smooth open channels of simple trapezoidal cross-section have been examined experimentally in the range 0.5 < Fr < 3.5,1.9 x 104 < Re < 6.2 x 105 and 0.3 < 2b/H < 15.0. Subcritical flow in a compound trapezoidal channel has also been studied for relative depths between 0.05 < Dr 0.5. The effect of secondary flows and the interaction between the main channel and the flood plain flows have been shown to influence the boundary shear stress and velocity distributions significantly. For simple channels, the boundary shear stress distributions have been correlated with the geometry parameters 2b/H or Pb/Pw, and empirically derived equations are presented giving the percentage of the total shear force carried by the wall. Ancillary equations are also presented giving the correlation between the geometry parameters and the mean and maximum shear stresses. Attention is also focussed on the effect of the hydraulic parameters on flow resistance. A comparison is made between the data and traditional formulations for smooth pipes and rectangular channels. The Froude number effect is also examined and found to be important. For compound channels, the transfer of momentum between the main channel and the flood plain has been studied in detail. Boundary shear force results have been used to calculate the apparent shear forces on vertical, horizontal and inclined interfaces. An empirically derived equation relating the geometry parameters and the boundary shear force on the flood plain bed and walls is presented. In order to quantify the momentum transfer within the whole section, the Navier-Stokes equation for steady uniform flow is used, and an analytical solution to the depth averaged form of the equation compared with the experimental results. A comparison of the depth-averaged values of flow resistance with those values obtained from a one-dimensional formulation is also made, and distinct differences noted. Improvement may be made by using the resistance radius in place of the traditional hydraulic radius. Use is made of the apparent shear force results in assessing channel discharge calculation methods which are based on sub-dividing the flow area. Equations are presented giving the main channel discharge for both vertical and horizontal division planes. The methods for evaluating the critical depth in a compound channel are also reviewed and assessed against experimental data. The free overfall for simple trapezoidal channels has been studied and an analytical relationship obtained between the ratio of brink depth to critical depth and the channel bed slope. Experimental data confirm this relationship.