Effect of Yaw on Heat Transfer in a Cuplike Cavity Facing a Freestream Flow

Wind tunnel experiments were performed to determine the response of the heat transfer coefficient at the base of an open-ended cylindrical cavity to yawed (i.e., nonperpendicular) impingement of the freestream flow on the cavity opening. The experiments encompassed yaw angles from 0 (perpendicular impingement) to 45 deg, cavity depth–diameter ratios from 0 to 0.65, and Reynolds numbers from 4500 to 45,000. In the absence of yaw, very large reductions of the base surface transfer coefficient were brought about by increases of cavity depth. When the freestream flow is yawed relative to the cavity opening the coefficient rebounds from its low no-yaw values, with the rebound being accentuated for large yaw, deep cavities, and high Reynolds numbers. Notwithstanding the rebound, the resulting base surface heat transfer coefficients are lower than those for the no-yaw, zero-depth cavity. Operating conditions are identified for which reductions of the transfer coefficient of 50 percent or more are encountered. On this basis, cavities and recesses appear to be an effective means for reducing heat loss.