Measurement of Wall Shear Stress on an Airfoil Surface by Using the Oil Film Interferometry

In this study, measurement of wall shear stress on an airfoil surface under the lifting condition by using oil film interferometry (OFI) is performed. Reynolds number of the airfoil flow is 8 × 10⁴. Silicon oil and sodium lamp are used for Fizeau fringes formation. The 300–600 images with time interval snap shot in 1–2 s depends on velocity by digital camera are acquired for the calculation of thickness of oil film and moving velocity on surface of it. Also, airfoil surface is covered with PET film for more clearly Fizeau fringes. Time-averaged wall shear stress measured by OFI are compared to numerical simulation by the LES. Maximum difference in the distributions between by the OFI and by the LES has at x/C = 0.58, and it has C _f  = 0.00439 by the OFI and C _f  = 0.00455 by the LES.