Enhancement of stagnation flow heat and mass transfer through interactions of free stream turbulence

Abstract: At the forward stagnation point of a bluff body the laminar flow is influenced by externally generated free-stream turbulence, such as from grids, in such a way that heat and mass transport are significantly enhanced above their normal values. The basis of this enhancement is an unsteady, threedimensional flow pattern formed at the forward stagnation point and triggered or altered by the free-stream turbulence. Such complex flows can be interpreted as roll cells oriented with their axes parallel to streamwise coordinates. Such roll cells have been observed by other investigators using special experimental visualization techniques. This complex flow was introduced into the momentum and transport equations, which were then solved numerically to produce the relationships between Nusselt, Reynolds, and Prandtl numbers and free-stream turbulence. Not only were these relationships nearly identical with earlier established empirical correlations, but they revealed in addition a strong augmentation for high Prandtl number flows. Predictions in slurry flows around bluff bodies were also found to be reasonable.