Heat and mass transfer at an upstream-facing blunt face situated in a uniform oncoming flow

A numerical investigation was performed to determine the heat /mass transfer from upstream-facing blunt faces of axisymmetric and plane two-dimensional bodies, which are situated such that a uniform flow approaches normal to the respective blunt faces. Face-average and stagnation-point Nusselt and Sherwood numbers, velocity and temperature profiles, and streamline maps are presented over the Reynolds number range from 5×10³ to5×10⁴. Average Nusselt number predictions for Pr=0.7 (heat transfer in air) and average Sherwood numbers for Sc=2.5 (naphthalene sublimation in air) agreed well with experiment. These results are well represented by a 0.5-power Reynolds number and 0.4-power Prandtl number fit. Stagnation-point Nusselt and Sherwood number predictions showed excellent agreement with boundary layer results using experimentally measured pressure distributions as input. Boundary layer results based on potential flow velocities as input overpredicted both the present numerical results and experimental results from the literature. The streamline maps and velocity profiles indicated that the boundary layer region on the blunt face was sensitive to the Reynolds number, while the outer region was not. A thinning of the boundary layer occurred with increasing distance from the stagnation point, which contrasts with the thickening that is characteristic of conventional stagnation flows. The thermal boundary layer thickness decreased with increases of both the Reynolds and Prandtl numbers.