Experimental and numerical investigation of coherent structure dynamics on mass transfer in a separated cavity flow

Abstract

This study presents the experimental and numerical investigation of coherent structure dynamics on mass transfer in a separated cavity flow. The flow field dynamics of a cavity type stagnation zone with a length to width ratio of 2 were studied. The cavity was driven by a channel flow with a Reynolds number of 1.8E5. The study utilised flow visualisation, laser Doppler velocimetry (LDV) and electrical conductivity probe measurements. Measurements of mean velocity and turbulence intensity profiles across the separated flow field showed the development of the shear layer and the recirculating flow pattern in the cavity. The numerical simulations were also performed for comparison with the experimental results considering the solution of the RANS, LES model and two-layer turbulence model. LES produced the formation and dynamics of coherent structures within the separated shear layer. Flow visualisation revealed a pulsatile motion in the separated flow region associated with the formation and passage of coherent structures and was supported by measurements of tracer concentration. The study showed how coherent structures in the separated shear layer enhanced the mass transport process from the stagnation zone and how the recirculating flow in the cavity influenced the development of those structures.