Three-dimensional convection flow adjacent to inclined backward-facing step

Abstract

Simulations of three-dimensional laminar forced convection adjacent to inclined backward-facing step in rectangular duct are presented to examine effects of step inclination on flow and heat transfer distributions. The step height is maintained as constant while its inclination angle is changed from 15° to 90°. The inlet flow is hydrodynamically steady and fully developed with uniform temperature. The bottom wall is heated with constant heat flux, while other walls are maintained as being thermally adiabatic. Velocity, temperature, Nusselt number, and friction coefficient distributions are presented. The “jet-like” flow and its impingement do not appear as the inclination angle of backward-facing step is small ( α = 15°). At the center width of the duct and close to the stepped wall, the location where the streamwise velocity component is zero changes from a saddle point to a nodal point as the step inclination angle decreases. The downwash adjacent to the sidewall becomes stronger as the step inclination angle increases. The maximum Nusselt number on the stepped wall is located near the sidewall for α ⩾ 30° and it appears near the center width of duct for small step inclination angle ( α = 15°). The friction coefficient inside the primary recirculation region increases with the increase of the step inclination angle. Downstream of the primary recirculation region, increase of the friction coefficient becomes slower as the step inclination angle increases.