Experiments have been performed in wave flumes to investigate the kinematics of flows over a rippled sea bed. Results from Particle Image Velocimetry (PIV) measurements of a variety of flows over sharp crested vortex ripples are presented. Tests were carried out for oscillatory flows, a pure wave, steady currents and a wave plus co-directional currents. PIV generates instantaneous, full-field velocity data and as such is ideal for studying the step-by-step evolution of complex flows. The fine grid of data points in each velocity field is used to derive vorticity data. Both velocity vector maps and vorticity plots are presented. Velocity profiles are obtained and used to calculate physical and apparent roughnesses and friction velocities. The trajectories, circulations and radii of the periodically shed vortices are determined and compared to the predictions of a discrete-vortex model with good agreement within the limitations of the model.

This research aimed to investigate experimentally the effect of particle shape on air-particle flow fields. The dynamics of streams of free falling irregular particles was observed by means of Particle Image Velocimetry and Laser Doppler Anemometry. Glass crushed beads and glass spherical particles with mean diameters varying from 60 to 300 μm were employed in the measurements, yielding particle Reynolds numbers between 1 and 70. Results on the particle-particle interaction and air-particle interaction mechanisms have been attained for both dilute and dense particle streams. Significant differences between the behaviour of irregular particles and spherical particles have been found in terms of spatial velocity distribution, terminal velocity, fluctuation velocity and turbulent energy content of the gas phase. The velocity of the gas phase. The velocity of the particles in the stream was higher than the predicted single particle velocity at the flow centreline and converged towards it at the stream edges in all experimental conditions. Irregular particles exhibited a velocity consistently lower than that of spherical particles and the stream of irregular particles was characterised by a larger radius. The velocity profile of the particle stream was load-dependent with the maximum velocity moving outwards from the stream centreline with increasing mass flow rate. The particle concentration was revealed to have an important effect on the velocity of the particle stream and the generation of turbulence. In the case of a dense particle stream, the turbulent energy content of the gas phase in the presence of irregular particles was significantly reduced than in the presence of spherical particles at both low and high frequencies.

The coarsening of emulsions and foams due to a diffusive flux of dissolved disperse phase between droplets and bubbles is considered, and the effects of trapping an extra species within droplets /bubbles are studied. It is demonstrated that the extra species may provide an osmotic pressure to counteract the effects of surface tension and "osmotically stabilise" an emulsion/foam. For dilute emulsions a rigorous condition to prevent coarsening by a diffusive flux of disperse phase is derived, which remains valid with polydispersity in droplet size and number of trapped species. The coarsening of dilute, insufficiently stabilised emulsions was found to proceed as when no trapped species were present, but with a reduction in the volume fraction of the growing droplets due to the volume fraction now residing in stable, shrunken droplets. Foams are studied by considering the osmotic compression of previously dilute foam bubbles by an osmotic pressure II. Careful arguments are given for the dependence of bubble pressure on II, which are confirmed for a monodisperse 2D model. The arguments are believed to be valid for sufficiently dry and monodisperse foams, for which the stability requirement is shown to be of the same order of magnitude as for dilute foam bubbles, regardless of the magnitude of II. In the absence of bubble rearrangements, the elastic energy from the necessary deformation of surrounding bubbles is also found to stabilise a foam. Sources of dissipation in coarsening nondi-lute foams are considered, and for given parameters enable prediction of the rate limiting mechanism and the associated coarsening rate. Since an osmotically stabilised emulsion may be destabilised by a rapid transport of the trapped species between droplets, the extent to which micelles may affect the rate of coarsening by transporting oil between droplets is considered. Different mechanisms of micelle-mediated exchange are considered, and the applicability of the different mechanisms indicated.

Automatic sequencing of all stages of the filter press operating cycle is well known and has long been widely incorporated in industrial filtration operations. The objective in this work was to achieve full, automatic, discharge without the operator intervention currently required to guarantee complete detachment of filter cake from the filter cloths of a filter press. This is a particularly desirable objective when the filtered materials are hazardous or subject to contamination, and where labour costs are of critical importance. Means have been devised for identifying residual filter cake deposits on the filter cloths of a small production-scale filter press after normal gravity discharge has occurred. A scanning laser-generated image of each cloth face is analysed to identify cake deposits and establish their size and location. This information is used by the control code of a four-axis gantry robot to direct and actuate a scraper blade in such a way as to dislodge each deposit from the filter cloth. The imaging and robot systems are designed to serve a group of presses, thus reducing the capital cost per press installed.

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A number of accurate measurements of the kinematics under the crests of regular waves and two-component uni-directional wave groups have been made in a laboratory wave flume using Particle Image Velocimetry. The waves were in intermediate to deep water, with relative depths in the range of <I>d/gT<SUP>2</SUP></I> = 0.05 to 0.085 and were of moderate to high relative steepnesses, in the range <I>H/gT<SUP>2</SUP></I> = 0.005 to 0.018. (Here <I>d</I> is water depth, <I>T </I>wave period, <I>H</I> wave height and <I>g </I>gravitational acceleration.) The main conclusions are: (1) Regular waves were accurately modelled using an implementation of high order Fourier theory by Rienecker and Fenton, providing Stokes second (zero mass transport) definition of wave celerity was used. (2) Steep, near-breaking two-component waves were modelled accurately using superposition stretching, a derivative linear theory. The input for this is the measured was spectrum, including first and second harmonics. The second harmonic contribution was found to be significant. (3) The kinematics in the crests of different waves of a given height and period can vary considerably. Here, differences of over 20% were noticed at the crest. (4) Wave group lenght affects the internal wave kinematics. (5) Measurements must be made above the level of the wave troughs and should be made above the mean water level also, if experimental results are to have much credence. (6) Particle image velocimetry proved to be an excellent measurement technique to use for measuring velocities as it was capable of measuring close to the free surface of high waves, with a high degree of accuracy.

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First, a programme to model concentration polarisation was written using the finite difference approach developed by Ilias and Govind. It was validated with experiments using Centrisystem C-300 and C-400 cartridges and BSA solutions (1-5 g/L), and experimental data from Yeh and Cheng with an H1P30-20 Amicon cartridge and Dextran T-500. The next step was to incorporate fouling into this model. To calculate the configurational Derjaguin-Landau-Vervey-Overbeek (DLVO) forces and the resulting osmotic pressures, large use was made of the work of Bowen <I>et al</I>. Concentration dependent diffusivities were calculated from the generalised Stokes-Einstein equation, and used in the transport equation to describe the concentration polarisation profile. It was shown that, when the transport equation did not have a solution at the membrane (or membrane + cake) surface, and that concentration was greater than the highest-concentration local maximum for the diffusivity, coagulation would occur. In this case, a monolayer of globular protein was assumed to deposit, and concentration polarisation was recalculated with this additional resistance. Experiments with 1g/L BSA solutions and Amicon H1P30-20, for a range of transmembrane pressure, ionic strengths and pH, were compared with the model predictions. Both showed that fouling increased with ionic strength away from the Iso-Electric Point of BSA (IEP), and decreased with zeta potential. Simulation also showed that fouling could decrease with increased ionic strength around the IEP, in accordance with classical results. Total resistance to flux from experiments and simulation were in a similar range, although the lack of data relating zeta potentials and pH prevented further comparison. The model would also determine the critical pressure above which fouling occurred. However, observed values were significantly lower than predicted. Direct adsorption of the BSA onto the polysulfone membrane or the effect of high local pore velocities may both explain these discrepancies.