An Interferometric Investigation of Separated Forced Convection in Laminar Flow Past Cavities

Abstract

This study concerns the separated, laminar forced convection in cavities located on a flat plate in a low-speed wind tunnel. Temperature profiles and local heat transfer coefficients are measured by means of a Mach-Zehnder interferometer. With all walls maintained at a uniform temperature, experiments are conducted for cavity aspect ratios (length divided by depth) w/s = 4 and w/s = 1 at different Reynolds numbers. Results show that the temperature distribution outside of the cavity is little influenced by flow in the cavity. The local heat transfer distribution on the cavity floor attains a maximum value that is located between the midpoint of the cavity floor and the downstream wall. Everywhere on the cavity floor, the local heat transfer is substantially less than the value upstream of the cavity. Compared with attached flow obtained by setting the cavity depth to zero, the average heat transfer on the cavity floor is more than a factor of two lower for w/s = 4 and more than an order of magnitude lower for w/s = 1. The average Nusselt number on the cavity floor is correlated by an equation of the form, Nus = C(Res)m, where m is nearly 1/2 and C varies with the aspect ratio. Downstream of the cavity, the local heat transfer is less than the value that would prevail if the cavity depth was set equal to zero.