INFLUENCE OF A PASSIVE PERTURBATION ON THE LOCAL FLOW STRUCTURE OF A BUBBLY TURBULENT FLOW BEHIND A BACKWARD-FACING STEP
M. A. Pakhomov
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: bubbly flow, planar channel, backward-facing step, vortex-generator fin, unsteady Reynolds-averaged Navier-Stokes equation, numerical simulation, turbulence enhancement
Abstract
A numerical study of the effect of a perturbation generated by a vortex-generator fin on the local flow structure and turbulence of a bubbly flow in a planar channel behind a backward-facing step is performed. An Eulerian approach is employed to describe the flow dynamics and heat and mass transfer in both the carrier gas and dispersed phases. The problem is solved using the Reynolds-averaged Navier-Stokes equations, modified to account for the presence of bubbles. The influence of air bubble concentration, initial bubble diameter, and vortex generator height on the turbulent flow structure and the length of the separation region is investigated. The presence of the vortex-generator fin induces a significant (twofold) increase in the turbulence level in both single-phase and two-phase bubbly separated flows. The fin is found to exert a substantial effect on turbulence in the separated flow, with the turbulence level increasing by up to 60%. The addition of bubbles reduces the recirculation zone length (by 60% for ∆/H = 1/3).
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