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The paper presents experimental and theoretical investigation of the outflow of liquids from single-outlet vessels incorporating a vertical downcomer. In such vessels the liquid leaving through the outlet of the downcomer is replaced by another fluid, which enters the vessel-downcomer system through the same opening. Experimental results of the variation of the void fraction and pressure in the vessel with elapsed time are presented. It is shown that the flow is generally oscillatory, and the conditions required for the establishment of the fully developed oscillatory flow are reported. A theoretical model of the fully developed oscillatory flow is developed. The model describes well the frequency of the oscillatory flow and the variation of the gas void fraction in the vessel with elapsed time. The model somewhat overpredicts the amplitude of the pressure oscillations. Thermodynamic aspects of this flow are also considered.

This paper considers the oscillatory behaviour of liquids in single-outlet vessels, i.e. vessels in which the outflowing liquid is replaced by another fluid which enters the vessel through the same opening. A theoretical model is developed and an equation for the natural frequency of oscillations obtained. The model is in good agreement with the available experimental data. It is shown that the natural oscillations of the liquid govern the hydrodynamic processes involved.

This paper considers the influence of viscosity and circulation on the effect of vortices on the liquid outflow from open vessels. One of the simplest possible arrangements is investigated: an axisymmetric vertical cylindrical vessel with an outlet in its base with the vortex flow generated by supplying the liquid through pipes located at the perimeter of the vessel. It is shown that for low liquid levels in the vessel the vortex provides a hindrance to the flow, but that for high liquid levels it is the vortex flow which discharges more freely. It is also shown that the liquid level in the vessel is proportional to the liquid flowrate, with the constant of proportionality being a function of viscosity and initial circulation.

This paper considers the outflow of a liquid from a single outlet vessel, i.e. a vessel in which the outflowing liquid is displaced by another fluid which enters the vessel through the same opening. The simplest possible arrangement is investigated: a sealed axisymmetric cylindrical vessel with an outlet in its base, in which water is displaced by air. It is shown experimentally that the average liquid discharge velocity is independent of the liquid level in the vessel and the shape of the outlet for the range of outlets employed; it increases weakly with both the diameter of the vessel and the diameter of the outlet.

One of the flow regimes occurring in horizontal two-phase flows is characterized by periodic large waves “surging” along the tube. This flow, called “slug” flow, has been frequently observed in low and high pressure gas liquid systems, but it has been noticed that slugging is absent in certain liquid-liquid two-phase systems. A method is developed giving the necessary conditions for the presence of slug flow. This method quantitatively explains the observed absence of slugging in certain liquid-liquid flows.

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 influence of gas bubbles on heat transfer in gas fluidized beds has been investigated. A platinum wire has been used as a heat-transfer probe and the aggregative gas fluidized bed has been simplified by generating a single continuous stream of gas bubbles into an incipiently fluidized bed. It has been found that in the case of aggregative gas fluidized beds of small particles operating below the radiative temperature level, transient conduction into the emulsion phase is responsible for at least 90% of heat transfer and that the remainder is contributed by the superimposed gas convection. A theoretical model of the bubble induced heat transfer has been developed. Finally, experimental justification for the concept of the property boundary layer introduced in [2] is presented.

An investigation has been made of flow phenomena associated with outflow from large horizontal cylindrical vessels with a vortex-free outlet on their bottom surface. This paper concentrates on the flow regimes and the variation of the level in the vessels with the flowrate. It is shown, both theoretically and experimentally, that there are two distinct regimes of outflow from the vessel, which are separated by a critical flowrate which is a strong function of the diameter of the outflow orifice. For the flowrates below the critical the level variation does not depend on the diameter of the outflow orifice, but the level variation depends strongly on it for the flowrates above the critical value. A model of transition between the flow regimes is also developed.

The influence of gas bubbles on heat transfer in two phase gas-liquid systems has been investigated. Platinum wires have been used as heat-transfer probes and the two phase flow has been simulated by generating a single continuous stream of discrete gas bubbles into a stationary liquid. The contribution of various modes of heat transfer has been determined. It has been found that transient conduction into the liquid is the predominant mode of the bubble induced heat transfer and is responsible for about 75 per cent of heat transfer. Convection contributes the remainder. A theoretical model of the bubble induced heat transfer based on the surface renewal and penetration theory has been developed.