Mixed convection flows in a vertical plane duct preceded by a sudden expansion

Abstract

PurposeThe purpose of this paper is to numerically investigate the effects of different heating and cooling scenarios on the flow structure in a vertically oriented plane sudden expansion. Four different heating and cooling scenarios are considered. The scenarios include symmetric or asymmetric heating or cooling of the downstream channel walls.Design/methodology/approachThe governing equations are formulated using a stream function‐vorticity approach. Second‐order accurate central differencing is used to discretize all terms, including the nonlinear convection terms in the vorticity transport and energy equations. Numerical test cases are simulated for Reynolds number values up to 200 and Grashof number values up to 400.FindingsNumerical simulations show that symmetric heating results in the reduction and ultimately the elimination of flow separation zones near the channel walls while creating a region of reversed flow in the core. On the other hand, symmetric cooling causes the flow to adopt a wavy structure which significantly enhances heat transfer due to jet impingement effects. Finally, it is shown that asymmetric heating causes the flow to preferentially attach to the high‐temperature wall while asymmetric cooling causes the flow to separate completely from the low‐temperature wall.Originality/valueThe behaviour of fluid flow in a plane sudden expansion under symmetric heating is available in the literature. In the present study, the flow structure under alternative heating and cooling scenarios is investigated for the first time.