Simplification of the Razor Blade Technique and its Application to the Measurement of Wall-Shear Stress in Wall-Jet Flows

Summary Experiments in a in (6-35 mm) channel have yielded further information on the precision and convenience of the razor blade technique. It is shown that adhesive tape or carefully located cement can be used to secure a segment of razor blade over a static pressure hole: the resulting calibration for shear stress remains valid if the blade is removed and relocated over the same or a different, similar sized hole. Razor blade segments, calibrated in this manner, have been used to measure wall-shear stress in a turbulent boundary layer with tangential, secondary injection: the results indicate that V. C. Patel’s law of the wall is valid for such flows.