This dissertation is concerned with studies of highly viscous Newtonian and non-Newtonian liquids in bubble columns with, and without, draft tubes. The importance of the parameters influencing bubble column reactors is discussed with reference to previous work. The shapes and rise velocities of single bubbles in these liquids were studied in an 8.8cm diameter column, and the gas holdup, resulting from continuous bubbling of gas into this column, was also measured. Agreement between holdup predicted by the equation of Nicklin et al (1962), and experimental data in die present work and that of other workers is good. The limiting result of Dumitrescu (1943) was found to apply for fully developed slug flow in viscous non-Newtonian liquids in large columns. Gas holdup, in a 15cm diameter bubble column with a draft tube, consisted of large bubbles (slugs), which rapidly rose through the liquid, and very small bubbles, which accumulated in the liquid. These small bubbles were generated near the gas distributor and also at the liquid surface; less than 1% of the total gas flowrate into the system was converted into small bubbles for a highly viscous Newtonian liquid. The gas holdup due to small bubbles in non-Newtonian liquids was much less than that in Newtonian liquids. Large bubble velocities deduced from the bubble column measurements were consistent with the single bubble measurements. Liquid velocities in the 15cm column were measured by a neutrally buoyant flow follower; the liquid circulation rate was found to decrease with an increase in liquid viscosity. A model to predict the liquid circulation rate is outlined. The effect of scale-up on the gas holdup and liquid circulation rate was also studied experimentally in a 60cm square bubble column with a 30cm square draft tube. The bubble size distribution in this column was similar to the 15cm column but liquid velocities were higher, and gas holdup was smaller in the 60cm column.

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An investigation is described of the instability of the horizontal free surface of a thin layer of liquid metal. The instability is due to the interaction of imposed electric and magnetic fields which are both initially horizontal. The interaction of fields produces a vertically upward magnetic force within the layer. Various two-dimensional theoretical models of the instability are described. A linear, viscous analysis of free surface instability is presented, and an analytical expression is obtained for the rate of growth of amplitude of a plane sinusoidal wave on the liquid free surface. A nonlinear model of a wave is also discussed on the assumption, later justified by experiment, that the waveform remains approximately sinusoidal providing the ratio of its amplitude and wavelength is small. An exact analysis is presented of a stationary wave in dynamical equilibrium. An experiment is described investigating the instability of a thin layer of liquid gallium. A new method for making instantaneous measurements of two-dimensional wave profiles is presented. Experimental observations are described of waves on an initially undisturbed free surface. It is confirmed that wave corrugations of the orientation predicted by linear theory to grow most quickly are observed to grow more quickly than other wave modes. Qualitative observations indicate the presence of secondary horizontal motions much larger than previous linear analyses have suggested. Quantative results indicate certain stability at non-zero amplitudes of linearly unstable waves if the Weber number is less than 0.12 and the Reynolds number is less than 75. Conversely, separation of gallium from the layer is observed invariably if the Weber number is greater than 0.31 and the Reynolds number is greater than 130.

The liquid impact properties of a range of infra-red and optical transmitting materials have been investigated using the liquid jet impact technique. In particular the effects of temperature and pre-existing stress fields on the liquid impact performance of certain materials have been examined. Consideration of these aspects of liquid impact has been supplemented by measurements of related fracture properties. The correlation between liquid jet impact and liquid drop impact has been re-examined for normal impact by comparing impacts on perspex. This correlation has been extended to consider angled impact. Components that are subjected to liquid impact may simultaneously be subjected to elevated temperatures. A system has been developed to allow experimental investigation of the liquid impact performance of materials at elevated temperatures. Preliminary results were obtained on a polymer (PEEK). The amount of damage resulting from liquid impact increased with temperature. Subsequently two brittle materials (glass and zinc sulphide) were investigated. Thermal shock has been shown to be the dominant failure mechanism for these materials at temperatures of 300<SUP>o</SUP>C and greater. Pre-existing stresses in a material can affect not only its static but also its dynamic loading response. The liquid impact performance and some associated fracture properties of toughened glass systems have been investigated. Chemically and thermally toughened systems were compared. There is a small increase in the threshold velocity for the toughened glasses considered compared to soda-lime glass. The toughening stresses distributions led to differences in the behaviour under single and multiple impact. A novel computer simulation of liquid impact onto pre-stressed substrates has been developed. It is based on the interaction of a model Rayleigh surface wave with a flaw distribution. Good agreement with experiment was obtained for a thermal toughening stress distribution.