A Preliminary Report on the Zero-Crossing-Rate Technique for Average Shear Measurement in Flowing Fluid.
Project rept. Oct 68-Apr 70,
MINNESOTA UNIV MINNEAPOLIS ST ANTHONY FALLS HYDRAULIC LAB
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The characteristics of a flush-mounted hot film sensor were investigated in turbulent flows of both water and drag reducing polymer solutions in a 4-inch-diameter pipe. For water flows, a linear relationship was found between the average power supplied to the sensor and the cube root of the wall shear stress. With the addition of polymer additives, the heat transfer rates at a given shear stress were reduced from those found with water alone. Analysis of the heat transfer fluctuations occurring in various flow facilities has shown that the zero crossing rate is related to the wall shear stress and to fluid properties for water, polymer, and air flows. The zero crossing rate of the surface pressure fluctuations was found to be related to the local wall shear stress. Modified author abstract
- Fluid Mechanics