Skin friction measurements on structured surfaces using Clauser-chart method and Oil film interferometry
U. Butt1 and C. Egbers2
1The University of Lahore, Lahore, Pakistan
2Brandenburg University of Technology, Cottbus, Germany
E-mail: mech.usmanbutt@gmail.com
Keywords: skin friction, Clauser-chart, Oil film interferometry
Pages: 367–377
Abstract
Measurements of skin friction have been performed on flat and hexagonal concave surfaces using the conventional Clauser-chart method and the Oil film interferometry. The values of shear stress coefficients measured by the conventional Clauser-chart method on a flat plate were found to be up to 13 % higher from the ones deduced by the Oil film interferometry. The velocity profiles required for the Clauser-chart were obtained by using hot wire anemometry. The analysis of the results suggested that the conventional Clauser-chart method cannot be used to predict shear stresses acting on the hexagonal concave surfaces due to the existence of strong pressure gradients. Oil film interferometry not only provides accurate and direct values of shear stress coefficients but also helps to visualize the flow above the surface.
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