Shear Measurement Techniques for Rough Surfaces

by Li-San Hwang,
Emmett M. Laursen,

Serial Information: Journal of the Hydraulics Division, 1963, Vol. 89, Issue 2, Pg. 19-37

Document Type: Journal Paper


Preston's technique of using a pitot tube that touches the boundary in order to measure the local shear has been extended to rough surfaces. An analysis, assuming the logarithmic velocity distribution, provides an estimate of the relationship between the dynamic-pressure reading and the intensity of shear. Experiments with sandpaper-roughened surfaces confirm the general nature of the analytical relationship and provide correction factors that could be used for surfaces of a similar texture. For other surface types, the relationships can be used for qualitative studies, but calibration would be necessary to obtain absolute values of shear.

Subject Headings: Velocity distribution | Boundary shear | Hydraulic roughness | Domain boundary | Dynamic analysis | Dynamic pressure | Shear stress | Calibration

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