EFFECT OF MASS, THERMAL AND MOMENTUM COUPLING ON CONDENSED BUBBLE LADEN SHEAR FLOWS
Injecting superheated water vapour bubbles into a sub-cooled shear flow will induce heat and mass transfer in the form of condensation. Of particular interest is finding the effect of mass, thermal and momentum coupling due to inclusion of condensed bubbles on large-scale vortices embedded in shear flows, which are characterised by vortex growth and pairing. Convection plays a significant role insofar as bubble collapse occurs earlier due to trapping within large-scale vortices. The aim of this paper is to investigate two-way mass, thermal and momentum interactions between condensed bubbles and large-scale coherent structures in plane turbulent shear layers, focusing on dependence of bubble dispersion and condensation on eddy structure patterns. Bubble numbers are large enough for cumulative buoyancy to influence the flow whilst small enough to neglect direct bubble-bubble interactions. Parameters such as initial bubble temperature, bubble injection location, and carrier fluid temperature were assessed for their effects on condensation and dispersion of bubbles. Because superheated vapour bubbles immersed within a sub-cooled shear flow field experience heat transfer, the bubbles eventually collapse if they were surrounded long enough by the sub-cooled liquid. Accordingly, the effect of condensed bubbles on evolution large-scale vortex structures is evident. It was revealed that the difference in temperature between the vapour bubble and the carrier fluid dominates bubble condensation.
The simulations show that two-way mass, thermal and momentum coupling causes reduction in the vorticity and associated pressure gradients in earlier shear layer growth, also delaying onset of vortex pairing. It is also revealed that the condensed bubbles acquire a larger dispersion in shear flows than bubbles that are not subject to mass and thermal coupling.