On Mixed Convection in a Horizontal Channel, Viscous Dissipation and Flow Duality

The conditions defining a stationary fluid flow may lead to a multiplicity of solutions. This circumstance is widely documented in the literature when mixed convection in a vertical channel or duct is accompanied by an important effect of viscous dissipation. Usually, there are double stationary solutions with a parallel velocity field which satisfy given temperature boundary conditions and with a prescribed mass flow rate. However, in a vertical internal flow, the dual solutions can be determined only numerically as they do not have a closed analytical form. This study shows that, in a horizontal channel, stationary mixed convection with viscous dissipation shows up dual flow branches whose mathematical expressions can be determined analytically. The features of these dual flows are discussed.