Influence of Passive Perturbation on the Local Flow Structure of a Bubbly Turbulent Flow behind a Backward-Facing Step

Abstract

A numerical study is performed to investigate the effect of a perturbation generated by a vortex-generator rib on the local flow structure and turbulence of a bubbly flow in a plane channel behind a backward-facing step. The Eulerian approach is used to describe the flow dynamics and the heat and mass transfer in both the gas and dispersed phases. The problem is solved using the Reynolds-averaged Navier–Stokes equations, which are written to account for the presence of bubbles. The effects of bubble concentration, initial bubble diameter, and vortex-generator rib height on the turbulent flow structure and the length of the separated zone are examined. The presence of the vortex-generator rib causes a significant (twofold) increase in the turbulence level in both single-phase and two-phase bubbly separated flows. The rib also has a marked effect on turbulence in the separated flow, with the turbulence level increasing by up to 60%. The addition of bubbles reduces the length of the recirculation zone (by 60% for \(\Delta {\text{/}}H = 1{\text{/}}3\)).