Combined Forced and Free Convection in a Boundary Layer Flow

Abstract

Consideration is given to the combined forced and free convection flow and heat transfer about a nonisothermal body subjected to a nonuniform free stream velocity. Similar solutions for the laminar boundary layer equations are found to exist when the free stream velocity and surface temperature vary respectively as x^m and x^2m−1. The parameter controlling the relative importance of the free and forced convection is Gr/Re². A flow separation phenomenon may occur when the forced and free convection act in opposite directions. Extensive numerical solutions of the transformed boundary layer equations have been carried out for the cases of uniform wall temperature and uniform wall heat flux for a Prandtl number of 0.7 (gases) over a wide range of values of Gr/Re². Results are reported for the heat transfer, shear stress, and velocity and temperature fields. Criteria are given for cataloging flows as purely forced, purely free, and mixed.