Study of Turbulent Flow and Heat Transfer Over a Backward-Facing Step Under Impingement Cooling

Abstract

Computations are presented to study the turbulent flow and heat transfer over a channel backward-facing step under impingement cooling. The problem was simulated for different parameters, such as the number of impinging jets, contraction ratio, size of jets, and jet and channel Reynolds numbers. The contraction ratio had the values 0.25, 0.35 and 0.5. The impinging jets were normal to the cross-channel flow. A control volume approach using staggered grid techniques was considered to integrate the continuity, fully elliptic Navier-Stockes and energy equations. A computer program was developed, and the SIMPLE algorithm was employed to determine the existence of coupling between the continuity and Navier-Stockes equations. The effect of turbulence was modelled using a k-ε model while the wall functions laws were used to treat the regions near the solid walls. The presented results show that the strength and size of re circulation regions near the reattachment region just after the backward-facing step increase as the contraction ratio increases. Also, the results show that the size of jets, number of jets, and jet and channel Reynolds numbers have a significant effect on the flow field, turbulent kinetic energy and variation of the Nusselt number.