Oil film interferometry in high Reynolds number turbulent boundary layers

Abstract

There is continuing debate regarding the validity of skin friction measurements that are dependent on the functional form of the mean velocity profile, for example, the Clauser chart method. This has brought about the need for independent and direct measures of wall shear stress, τ w. Of the independent methods to measure τ w, oil film interferometry is the most promising, and it has been extensively used recently at low and moderately high Reynolds number. The technique uses interferometry to measure the thinning rate of an oil film, which is linearly related to the level of shear stress acting on the oil film. In this paper we report on the use of this technique in a high Reynolds number b..