Control of Turbulent Channel Flow over a Backward-Facing Step by Suction

Abstract

The Turbulent channel flow over a backward-facing step was investigated experimentally by using suction through a slit at the bottom corner of the step. Suction was continuously applied, and the direction of the suction was perpendicular and horizontal to the main flow. The suction flow ratio was varied from 0.00 to 0.15. The wall static pressure and local heat transfer coefficient were measured behind the backward-facing step. The velocity profiles and turbulent quantities were measured by PIV. It was found that the pressure drop at the step was reduced and the heat transfer coefficient in the recirculating region was improved by suction. The suction direction did not affect the heat transfer or fluid flow characteristics. Enhancement of the heat transfer coefficient was related to the increase in turbulent energy, Reynolds shear stress and turbulent diffusions. However, the region where these quantities increase was limited to the area immediately behind the step. When strong suction was applied, periodic fluctuating motion occurred.