Skin-Friction Measurements Using Oil-Film Interferometry in NASA's 11-Foot Transonic Wind Tunnel

摘要

Skin-friction measurements were obtained on two laminar flow airfoils in the NASA Ames 11-ft transonic wind tunnel using oil-film interferometry. Improvements in the experimental technique allowed skin-friction measurements at two conditions per run in conjunction with performance testing, thus reducing the impact on the run schedule. Quantitative measurements of skin friction were used to determine transition location and the extent of separation (if any) on the airfoils providing much more insight into the flow than flow viz. The technique has been extended to obtain a quantitative measure of shear in the reversed flow region. The effects of various disturbances to the boundary layer were also investigated. Laminar flow was found as far back as 60% chord at a Reynolds number of 4.5×10~6.