Heat transfer at the base of a cylindrical cavity oriented perpendicular to a freestream flow

The average and local heat transfer at the base surface of a cylindrical cavity whose opening is perpendicular to an oncoming freestream have been determined experimentally. During the course of the experiments, the cavity depth was varied from zero to 65% of the diameter, while the freestream Reynolds number ranged between about 5000 and 50,000. The average heat transfer coefficient decreased sharply with increasing cavity depth, the reduction being slightly greater than 50% at a depth-diameter ratio of 0.10 and greater than 90% when the depth-diameter ratio was 0.65. For the finite-depth cavities, the local heat transfer coefficient attained its maximum value at the center of the base surface and decreased with increasing radial distance from the center until a minimum was reached, after which there was a moderate increase adjacent to the outer edge of the base. The minimum occurred at the location where the radial outflow along the base separated from the surface, and a toroidal-shaped recirculation zone occupied the corner region at the intersection of the cavity base and side wall. In contrast, for the zero-depth cavity (i.e. a free disk oriented perpendicular to the oncoming flow), the local coefficient attained its minimum at the center of the surface and increased with increasing radial distance from the center.