Turbulent wall-shear-stress fluctuations in fully developed and accelerating flows
A heated shear stress sensor was mounted at the wall of an air flow duct, and turbulent shear stress fluctuations were measured using constant temperature anemometry and analyzed by means of conditioned sampling. The lateral side walls of the duct could be moved so that the duct span could be reduced, resulting in acceleration of the flow in the streamwise direction. For the 27 flows examined, the Reynolds number varied from 7600 to 47,200 and the dimensionless acceleration, (..nu../V/sup 2/) dV/dx, ranged from 0.0 to 3.4 x 10/sup -6/, thus encompassing the full spectrum from turbulent to relaminarized flow. For the fully developed flows, i.e., those for which the acceleration was zero, the frequencies of the turbulent bursts and the times during the sweeps of the eddies toward the duct wall were independent of Reynolds number, when scaled with inner variables. When the flows were accelerated, the bursting frequencies approached zero as the dimensionless acceleration increased to 3.4 x 10/sup -6/; however, the dimensionless value of the conditionally averaged shear stress was unaffected suggesting that acceleration did not affect the individual burst or sweep per se, but only the frequency of these events.
- Research Organization:
- Los Alamos Scientific Lab., NM (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6774512
- Report Number(s):
- LA-8781-MS
- Country of Publication:
- United States
- Language:
- English
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