MEASUREMENT OF WALL SHEAR STRESS IN TURBULENT BOUNDARY LAYERS USING AN OPTICAL INTERFEROMETRY METHOD N NISHIZAWA I MARUSIC and A E PERRY Department of Mechanical and Manufacturing Engineering

th Australasian Fluid Mechanics Conference Monash University Melbourne Australia December A new laser interferometry skin friction meter was built and was used to measure skin friction in a series of turbulent boundary layer ows This method has the advantage of providing a direct measure of skin friction through thin lm lubrication theory It does not rely on the existence of a law of the wall or a logarithmic mean ow region in the ow such as that assumed by the more conventional techniques such as Preston tube and the Clauser chart The measurements made with the laser interferom eter were compared with Preston tube and Clauser chart measurements in zero favourable and adverse pressure gradient ows Although the interferometer results show some scatter the agreement is seen to be satisfactory and suggests that the law of the wall based techniques are valid in the range of parameters investigated here