The Use of Hot-Film Technique for Boundary Layer Studies on a 21% Thick Airfoil.

A heat transfer method of studying boundary layer flows over airfoils at transsonic test conditions has been investigated. The method employs very thin DISA hot-film gauges housing Constant Temperature Anemometer probes. Provided that the thickness dimension of the films remains less than the critical disturbances height for inducing transition of the laminar boundary layer, the heat transfer response from the films, positioned carefully on the model surface, can be studied to determine the boundary layer characteristics. Results from an application study on a 21 % thick laminar flow airfoil model are presented and discussed.