RELATIONSHIP BETWEEN COHERENT STRUCTURE AND TURBULENCE CHARACTERISTICS IN BACKWARD FACING STEP FLOW

Abstract

 The characteristics of the coherent structure formed backward facing step flow were investigated by using the flow visualization method and DPTV (Dye streak pattern Particle Trackin Velocimetry), and the correlation with the flow velocity distribution characteristics was examined. As a result, it was clarified that the logitudinal vortex structure formed downstream of the backward facing step has remarkable rotation due to the high shear layer, and its size increases and its inclination angle increases in the downstreram direction. In addition, it was revealed that longitudinal vortex structures are hardly generated near the bottom wall of the flow field. Furthermore, it is inferred that the longitudinal vortex structure directly contributes to the instantaneous Reynolds stress (-uv), and their form and scale strongly influence the characteristics of the long-time average distribution of Reynolds stress.