๐”– Bobbio Scriptorium
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Measurement of turbulent wall velocity gradients using cylindrical waves of laser light

โœ Scribed by A. A. Naqwi; W. C. Reynolds

Publisher
Springer
Year
1991
Tongue
English
Weight
817 KB
Volume
10
Category
Article
ISSN
0723-4864

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โœฆ Synopsis

A new optical instrument has been developed for direct measurement of instantaneous velocity gradients at the bounding wall. Light emerging from two tiny optical slits in the surface is used to form a "fan of fringes" in the region very near the wall. Doppler frequency of the light scattered by the seed particles is directly proportional to the velocity gradient. The system has been used to measure the statistics of the streamwise and spanwise velocity gradients in a turbulent boundary layer. The streamwise and spanwise rms fluctuations were found to be 38% and 11% of the mean streamwise value respectively. The latter result is subject to a large uncertainty.

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