On the effects of microbubbles on Taylor–Green vortex flow

Abstract

The paper describes a numerical study of the effects of microbubbles on the vorticity dynamics in a Taylor–Green vortex flow (TGV) using the two-fluid approach. The results show that bubbles with a volume fraction ∼10−2 enhance the decay rate of the vorticity at the centre of the vortex. Analysis of the vorticity equation of the bubble-laden flow shows that the local positive velocity divergence of the fluid velocity, ∇·U, created in the vortex core by bubble clustering, is responsible for the vorticity decay. At the centre of the vortex, the vorticity ωc(t) decreases nearly linearly with the bubble concentration Cm(t). Similarly, the enstrophy in the core of the vortex, ω2(t), decays nearly linearly with C2(t). The approximate mean-enstrophy equation shows that bubble accumulation in the high-enstrophy core regions produces a positive correlation between ω2 and ∇·U, which enhances the decay rate of the mean enstrophy.