Turbulent Mixed Convection Flow Over a Vertical Backward-Facing Step

Turbulent mixed convection adjacent to a two dimensional, vertical backward-facing step is predicted numerically to explore the effect of step height on turbulent mixed convection using a two-equation k-ε turbulence model. Computations are performed for air with a Prandtl number of 0.71 for different step heights ranging from 11 mm to 44 mm, and at a temperature difference of 30°C between the heated upstream and downstream plates and the free stream. The effects of different step heights on the reattachment length, the local Nusselt number, the mean velocity and temperature distributions, the turbulent kinetic energy and its dissipation rate are examined. The computational results reveal that for small expansion ratios, the step height effect is small on the upstream flow, but it has a strong impact on the turbulent flow characteristics and heat transfer rate downstream from the step