Mixed convection in a suddenly-expanded channel with effects of cold fluid injection

Abstract

This paper deals with a numerical study on mixed convection in a horizontal suddenly-expanded channel with a cold fluid injected along the backward-facing wall. Navier-Stokes/Boussinesq equations are solved by using the SIMPLER algorithm on a non-uniform staggered grid system. Effects of the foreign fluid injection and free convection on the flow and heat transfer characteristics are examined. For small amounts of cold fluid injection, the results reveal noticeable enhancement in local heat transfer rate on the backward-facing wall but slight degradation on the bottom wall beneath the separation bubble. The recirculation zone can be enlarged by either the foreign fluid injection and buoyancy force, and the physical interpretation about these mechanisms are addressed. Bi-linear correlations are proposed for the predictions of reattachment length at various injection and buoyancy conditions.