Two-dimensional stagnation point flows of binary mixtures

Abstract

Comprehensive numerical solutions have been obtained for axisymmetric and planar stagnation point flows of air with foreign gas injection. The injected species are H, H 2, He, C, CH 4, O, H 2O, Ne, Air, Ar, CO 2, Xe, CCl 4 and I 2, at wall cooling ratios of T s T e = 0.1, 0.5 and 0.9 . Thermodynamic properties are calculated assuming an inert ideal gas mixture and constant species specific heats; for the transport properties the rigid sphere model is used in order to eliminate temperature level as a problem parameter. The effect of injectant thermodynamic and transport properties on the reduction, due to mass transfer, of wall shear stress, mass transfer conductance and heat transfer rate, are explained with the aid of results calculated for synthetic injectants with adjusted specific heats and collision cross-sections. The increased pressure gradient at planar points ( β = 1.0) is found to yield results little different to those for the axisymmetric situation ( β = 0.5), except for the shear stress reduction with light injectants at high wall temperatures. Thermal diffusion effects with moderate to severe wall cooling are found to be interesting, but of little practical importance. Engineering correlations for mass and heat transfer are presented. These are of the exponential form suggested by a Couette flow model, with the blowing parameter B weighted by the factors a m,i=1·65 M air M i 5 6 ; a h,i=1·3 M air M i 1 3 C pi 5 2 R M 1 1 2 for mass and heat transfer, respectively.