Numerical simulations of three-dimensional, laminar, buoyancy-assisting mixed convection flow adjacent to a backward-facing step in a duct are presented to demonstrate the influence of the Grashof number on the flow behavior, distributions of the Nusselt number, distributions of the friction coefficient, and the reverse-flow regions that develop adjacent to the duct's walls. Increasing the Grashof number results in an increase in the Nusselt number and the size of the reverse-flow regions adjacent to the sidewall and the flat wall. On the other hand, the size of the primary recirculation flow region adjacent to the stepped wall decreases and detaches partially from the heated stepped wall as the Grashof number increases. The reverse-flow region that develops adjacent to the sidewall is not connected to the primary recirculation flow region for the cases of low Grashof number (Gr = 0 and 500) but becomes connected to that region at higher Grashof numbers. The locations where the Nusselt number is at a maximum and where the friction coefficient is at a minimum move upstream toward the step and closer to the sidewall as the Grashof number increases. The peak Nusselt number occurs downstream from the location where the friction coefficient is at a minimum (equal to zero) where the jetlike flow impinges onto the stepped wall.
展开▼
