FLOW STRUCTURES AND HEAT TRANSFER DURING TRANSITION IN PERTURBED MIXED-CONVECTION CHANNEL FLOWS

Abstract

This research seeks to increase our understanding of fluid mechanics and heat transfer phenomena in transitional mixed-convection flows between two heated vertical plates. A direct numerical simulation by the spectral method with weak formulation is used to solve the transient three-dimensional (3-D) Navier-Stokes equations and energy equation. Initial disturbances consist of the finite amplitude two-dimensional Tollmien-Schlichting wave and two 3-D oblique waves. The Nusselt number (Nu) is mainly a function of the Rayleigh number (Ra) and also depends on the Reynolds number (Re) and the Richardson number (Ri). Nu dependence on Re increases with increase of Ra. Disturbance competitions among different modes during transition are shown for different sets of dimensionless parameters. Flow visualization by passive particles is also presented.