Role of coherent structures in bubble transport by turbulent shear flows

Abstract

A brief account is given of major implications for transport modelling of bubbles travelling in turbulent shear flows with special attention to their capture and retention in coherent large eddies. In particular, Auton's Lagrangian force law is first applied to identify salient features of bubble motion in Rankine vortices as an idealised demonstration of the key scalings. We then outline the main findings from computer simulations of bubble trajectories in plane mixing layers exhibiting coherent eddies and eddy pairing events. Conditions favouring bubble entrapment are shown to agree probabilistically with the deterministic scalings deduced from the simplified Rankine vortex model. We close with mention of simulations of a vertical downflow for which the bubble number fluxes agree broadly with experimental studies reported elsewhere. We also briefly discuss the implications of these results for eddy diffusive modelling of turbulent shear flows.KeywordsShear LayerCoherent StructureTurbulent Shear FlowRankine VortexBubble TrajectoryThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.