RECEPTIVITY ANALYSIS OF MIXED CONVECTION FLOW PAST A HORIZONTAL PLATE: DIRECT SIMULATION

Mixed convection flow past a horizontal plate is investigated by direct numerical simulation (DNS) with the Boussinesq approximation to model buoyancy effects. Validity of a proposed similarity profile for mixed convection flow over a horizontal plate is established first. For this similarity boundary layer, an adiabatic condition has to be satisfied over the plate, while all heat transfer occurs singularly from the leading edge. Thus, its direct simulation is not straightforward. Here, a very high accuracy DNS methodology is used to simulate this equilibrium flow. Having obtained the equilibrium flow, nonlinear and nonparallel receptivity of the boundary layer is investigated using DNS with respect to vortical and entropic excitations applied at the wall. Linear stability analysis of the above similarity profile in Sengupta & Venkatasubbaiah (Stud. Appl. Math., 117, 265, (2006)) reported a critical buoyancy parameter, Kcr above which neutral curve displayed two lobes, indicating the presence of hydrodynamic and thermal modes of instability in post-critical range of parameters. Present investigation validates this observation with DNS methodology, including nonlinear and non-parallel effects on receptivity and stability. More over, this receptivity analysis also helps one to understand the role of these two modes at different parts of the growing shear layer