An experimental study in leading edge separating-reattaching boundary layer flows

Laminar separation and turbulent reattachment was investigated. The study was conducted on a simple, two-dimensional geometry in a low speed wind tunnel facility. A recently developed constant heat flux surface, instrumented with thermocouples, was used to acquire local heat transfer coefficients. Velocity, temperature, and turbulence intensity profiles were measured using a hot wire sensor as a dual purpose anemometer and resistance thermometer. A precise examination of the reattaching flow lead to the conclusion that the flow was in a highly nonequilibrium state, resulting in heat transfer rates greater than predicted by equilibrium theories or computer codes. The conclusion to be reached is that the use of a simple turbulent heat transfer mechanism at reattachment is incorrect. The key to revising such near equilibrium models is to account for the higher turbulence and shear stress levels and their downstream decay.