Influence of the upper liquid layer on vortex breakdown in the bioreactor model

Abstract

The motion caused by rotation of the upper disk in a stationary vertical cylindrical container filled with two immiscible fluids is studied experimentally. The vortex breakdown the emergence of reversed motion on the cylinder axis in the lower liquid is investigated as a function of the thickness of the upper liquid layer. It is found that despite the fact that the motion of the upper fluid converges spirally to the cylinder axis near the interface, the vortex breakdown in the lower fluid occurs similarly to what is observed in the case of a single fluid, with the upper disk swirling. This curious result may be practically important for the operation of vortex bioreactors. Keywords: Confined swirling flow, vortex dynamics, bubbly vortex breakdown, immiscible fluids.