Invetigation of skin-friction measurements using oil-film interferometry on airfoil wall in low speed wind tunnel

Oil-film interferometry is a possible technique for skin friction measurement quantitatively in a wind tunnel. Test principles, test methods, error correction, data analysis and some other related key issues of oil-film interferometry technique are investigated. A primary test system is established to measure skin-frictions of two laminar flow airfoils in a low speed wind tunnel. Error correction for high quality skin-friction measurements is also developed. Both laminar and turbulent skin friction are successfully obtained. Furthermore, skin-frictions are also calculated numerically. The results between tests and numerical calculation of chordwise skin friction distribution for two laminar airfoils shown good agreement.