Abstract
Natural convection of air over an upward-facing horizontal two-dimensional heated plate is investigated by means of direct numerical simulation (DNS). The Rayleigh number based on the length of the plate and the representative temperature difference is 108 in the present study. A plume uprising from the central region of the plate induces two-dimensional boundary layer flow over the plate from its edge to the center. This boundary layer flow develops from laminar state with the ambient quiescent fluid entrained. In the present study, special attention is focused on turbulence structure of separated boundary layer flow under a practically important high Rayleigh number condition. According to the preliminary study of threedimensional thermal instability, spanwise temperature disturbance within a narrow band region along the edge is employed to encourage spontaneous flow separation and transition to turbulence. Turbulence structure near the center of the plate is statistically discussed.
