Aiding and opposing mixed convection in a vertical porous layer with a finite wall heat source

Two-dimensional, steady mixed convection in a vertical porous layer has been numerically studied for the case when a finite isothermal heat source is located on one vertical wall which is otherwise adiabatic and the other vertical wall is isothermally cooled. In the case of aiding mixed convection flow, the main flow separates from the cold wall and a recirculatory secondary flow exists in a region away from the heat source. However, when the main flow opposes buoyancy, the separation takes place on the heated wall, and the secondary flow is produced on the heated segment. Although the heat transfer rate increases with the aiding velocity, the effect is small at lower Peclet numbers (Pe). For the aiding flow, the slope of the Nusselt number curve increases with Peclet number unless the flow has approached the forced convection regime. For opposing flow, the heat transfer rate first decreases with an increase in Pe beyond zero and reaches a minimum before it starts increasing again. Under certain circumstances, the Nusselt number for a lower Rayleigh number may exceed that for a higher Ra.