Skin friction measurements in three-dimensional flows by white-light oil-film interferometry

A low-cost setup for oil-film interferometry with white light was used to determine the flow topology and the wall shear stress on a delta wing at different angles of attack. Despite the simple setup, well reproducible and plausible comprehensive wall shear stress distributions on the upper side of the delta wing could be determined from experimental interference images. For the image evaluation, a new algorithm was proposed and developed, helping to determine automatically and quickly the local oil film thickness from a sequence of interference images