Effects of a baffle on separated convection flow adjacent to backward-facing step

Abstract

Numerical simulations of three-dimensional laminar forced convection flow adjacent to backward-facing step in rectangular duct are presented to examine effects of the baffle on flow and heat transfer distributions. The step height is maintained as constant. A baffle is mounted onto the upper wall and its distance from the backward-facing step is varied. The inlet flow is hydrodynamically steady and fully developed with uniform temperature. The Reynolds number based on the double height of the duct upstream of the step is equal to 343. 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. A baffle mounted onto the upper wall increases the magnitude of maximum Nusselt number at the stepped wall. One segment of the x u -line developing close to the backward-facing step becomes shorter with decrease of the distance of the baffle from the backward-facing step. It becomes more relatively uniform in the spanwise direction as the distance of the baffle from the backward-facing step decreases. The other segment developing adjacent to the sidewall moves further downstream as the baffle moves in the streamwise direction away from the backward-facing step. The maximum Nusselt number on the stepped wall develops near the sidewall, and it moves further downstream as the location of the baffle moves in the streamwise direction. The friction coefficient at the stepped wall decreases as the distance of the baffle from the inlet increases.