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An investigation has been undertaken to examine the stability of a gas-liquid interface in a vertical cylindrical vessel subjected to a sinusoidal vertical motion. Experimental results indicate that there is a certain limiting critical frequency at which the gas-liquid interface becomes unstable, significant amounts of liquid are thrown vertically from the interface and the interface thus loses its coherent structure. Experimental data are compared with analytical solution based on the reduction of governing non-viscous equations to Mathieu equation, and good agreement between theory and experiment is found.

An investigation has been made of air-water flow in Y-junctions, which are frequently used in industrial applications. The air-water flow is stratified in the sloping limbs approaching the junction and this paper examines the phenomena occurring at the junction and in the following freely discharging vertical pipe. It is shown that three flow regimes can exist in the vertical limb following the junction: freely-falling water, homogeneous flow of water and air, and flow of water with a small amount of residual air accompanied by the flooding of the junction. The flow regimes are described and predictions for transitions between them are developed.

Measurements were made of the size distribution and maximum size of drops in liquid-liquid systems. The data on the maximum drop size, together with other data available in the literature, are assessed in the light of Hinze's [1] theory. It is shown that the dispersion of drops in a gravitational field transverse to the flow can be predicted using correlations for the terminal velocity and for the drop diffusivity.

Two parameters of particle or droplet dynamics which are of importance in describing their behaviour in turbulent pipe flows are their settling velocity and eddy diffusivity. It is usually assumed that the settling velocity in turbulent flow is equal to that in still fluid and on the basis of this assumption the eddy diffusivity is usually determined experimentally from the distribution of droplets or particles in horizontal turbulent flow. Since the settling velocity has a strong influence on the resultant value of the eddy diffusivity, the influence of turbulence on settling velocity is investigated in this work. A simple stochastic model of settling in turbulent flow is developed and it is shown that a considerable retardation of still fluid settling velocity is possible for a wide range of conditions.

The distribution of voidage in the wall regions of randomly packed beds of uniform spheres is investigated. A general equation relating the local voidage to the distribution of the spheres is derived and is combined with some simple observations about the bed to develop a model of particle packing near containing walls. The results of the analysis are in good agreement with available experimental data.