From passive tracer to bubbles dispersion in Taylor-Couette flows

Abstract

We investigate dispersion of passive tracer and bubble preferential accumulation in the flow between two concentric cylinders. The dispersive characteristics are analysed for Taylor Vortex Flow, Wavy Vortex Flows and fully Turbulent Taylor-Couette flows. Experiments based on flow visualization, PIV and PLIF measurements are compared to direct numerical simulations of Navier-Stokes equations coupled to Lagrangian tracking of fluid elements and bubbles. In vortical flows, bubble accumulation is driven by a competition between added-mass effect, lift and buoyancy forces. At low to moderate Reynolds numbers, the flow is strongly coherent and bubble accumulation patterns can be predicted theoretically (stability analysis of fixed points). When turbulence sets in, small scale structures enhance dispersion. This complex situation where large-scale coherent structures interact with fine scale turbulence leads to bubble mixing which have been analyzed by numerical simulations. Several distributions of bubbles are observed depending on the respective magnitude of turbulence and buoyancy force.