Flow and heat transfer characteristics in the reattachment zone downstream a backward facing step 'Inlet flow structure effect'

摘要

A combined numerical and experimental study is performed in order to investigate the effects of the inlet flow structure on the flow and heat transfer characteristics in the reattachment zone downstream a backward facing step. The numerical approach is based on two-scale energy-flux model coupled with a full Reynolds stress closure valid at low turbulence Reynolds numbers. Two inlet flow configurations are considered; a turbulent wall jet (WJ) which presents a particular structure with two sources of turbulence production (one is due to the shear flow related to the inner layer with small scale eddies and another one corresponds to the free shear jet flow with entrainment of large turbulence scales) and a standard boundary layer (TBL) The turbulence kinetic energy budgets and the length scales that are of particular interest were presented in this paper. So the present study would contribute to emphasize the role of the large eddies in the outer flow interacting with the wall region and the recirculation zone. The results show a significant effect on the turbulent kinetic energy and Nusselt number.