BUOYANCY EFFECTS ON THE WAKE BEHIND A HEATED OBSTACLE IMMERSED IN A TURBULENT BOUNDARY-LAYER

The effects of buoyancy on the wake behind a two-dimensional (2-D) hea ted obstacle immersed in a turbulent boundary layer have been examined both experimentally and numerically in an effort to understand the th ermal release over complex terrain in an idealized environmental flow. Emphasis was placed on clarifying the modification of the production agencies of the turbulence kinetic energy, resulting both from the dir ect and indirect buoyant contributions. Buoyancy altered the mean velo city field along the extent of the recirculating region and resulted i n a reduction of the turbulent kinetic energy in the vicinity of the o bstacle and, through an enhanced shear production, a growth downstream . Buoyant production of turbulent kinetic energy dominated the shear p roduction outside the recirculating region, where the temperature vari ance was significant. Numerical predictions obtained by a recent buoya ncy-extended k-epsilon model were found to give the analogous properti es of buoyant motion appearing in the experimental results.