Oil-Film interferometry measurement of skin friction - analysis summary and description of Matlab program

The measurement of wall shear stress is increasingly recognized as a critical element of aerodynamic testing. Wall shear stress is necessary to characterize fully a wall-bounded flow, to provide critical information necessary for computational simulations, and to serve as a sensitive quantity for use in flow-control applications. Oil-film interferometry is a method that can be used to measure wall shear stress quickly and accurately, but the analysis of the interferograms is complex and has limited the methods use. OILFILMTOOL is a Matlab program that has been developed to simplify the analysis process. The analysis steps required to determine wall shear stress from an interferogram obtained using oil-film interferometry are discussed, and those methods currently implemented in OILFILMTOOL are highlighted. The application of OILFILMTOOL to interferograms acquired on the surface of a wedge body is discussed. It is hoped that, by implementing the complex analysis process in a simple-to-use program, the use of oil-film interferometry in aerodynamic test facilities will become more widespread.