Turbulent mixed convection flow over a backward-facing step

Measurements of turbulent mixed convection flow over a two-dimensional, ver tical backward-facing step are reported. Laser-Doppler velocimeter (LDV) an d cold wire anemometer were used, respectively, to measure simultaneously t he time-mean velocity and temperature distributions and their turbulent flu ctuations. The experiment was carried out for a range of free stream air ve locities 0 m/s less than or equal to u(infinity) less than or equal to 0.41 m/s for a step height of 22 mm, and a temperature difference, DeltaT, of 3 0 degreesC between the heated walls and the free stream air. The step geome try consists of an adiabatic backward-facing step, an upstream wall and a d ownstream wall. Both the upstream and downstream walls are heated to a unif orm and constant temperature. The present results reveal that the introduct ion of a small free stream velocity causes a decrease in the turbulence int ensity of both the streamwise and transverse velocity and temperature fluct uations. Also, it was found that the reattachment length increases while th e heat transfer rate from the downstream heated wall decreases as the free stream velocity increases. (C) 2001 Elsevier Science Ltd. All rights reserv ed.