Numerical Simulation of Two-dimensional Unsteady Separated Flow and Heat Transfer around an Inclined Downward Step

Abstract

Direct numerical simulation methodology is employed to analyze the unsteady characteristics of a two-dimensional separated and reattached flow and heat transfer around an inclined downward step in a plane channel. Numerical calculations of the Navier-Stokes, energy and continuity equations are carried out using the finite difference method. The Reynolds number Re based on the mean velocity at inlet and the step height ranges from 300 to 2 000, and the inclination angle of step α is systematically varied from 15° to 90°. The expansion ratio of channel is 2.0. For all the inclination angles examined, the flow is steady at Re≤500 but becomes unsteady at Re=700. In a range of α from 30° to 75°, effects of α upon the reattachment length and the maximum Nusselt number are relatively small in a wide range of the Reynolds number.