Laminar boundary-layer wedge flows with evaporation and combustion

Abstract

Abstract A steady, laminar, boundary-layer flow of an oxidizer over a two-dimensional wedge (covered with fuel) involving evaporation (or sublimation) and combustion is studied for the case where chemical reaction is assumed to occur in an infinitesimally thin flame. Results presented include the effects of the Prandtl number, wedge parameter, and heat ratio on the profiles of the velocity, temperature, and composition in the boundary layer, the boundary-layer and displacement thickness, the flame position, the skin friction, and the rates of evaporation and combustion. Also included is a comparison of the boundary-layer characteristics with and without combustion. Because of the large density variation inside the boundary-layer as a result of combustion, the effect of pressure gradient is rather big. For a favorable pressure gradient, the velocity near the flame region is found to exceed the local freestream velocity. This velocity overshoot accounts for an increase in the skin friction for large favorable pressure gradients, in spite of the blowing effect due to evaporation. For an adverse pressure gradient, the effects of both mass addition and low density near the flame are to reduce the skin friction, thus causing separation to occur at an extremely small adverse pressure gradient.