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Laser Doppler velocimetry studies of early turbulence

 

作者: J. L. Zakin,   C. C. Ni,   R. J. Hansen,   M. M. Reischman,  

 

期刊: Physics of Fluids(00319171)  (AIP Available online 1977)
卷期: Volume 20, issue 10  

页码: 85-88

 

ISSN:0031-9171

 

年代: 1977

 

DOI:10.1063/1.861763

 

出版商: AIP

 

数据来源: AIP

 

摘要:

Laser Doppler anemometry is employed to measure the mean velocity and turbulence intensity in the early turbulence regime of the flow of a dilute polymer solution through a small‐diameter tube. (This regime is initiated at an onset Reynolds number in the subcritical range, above which the polymer additive increases drag, and continues through the transitional Reynolds number range, where a continuous transition to turbulent flow with reduced drag is observed.) When the onset flow rate for early tubulence is exceeded, the mean velocity profile becomes progressively flatter with increasing flow rate. That is, a gradual transition from a laminar profile at onset to a more ’’turbulent‐like’’ profile takes place. Turbulence intensities at the tube centerline are about one half those of a fully developed turbulent flow. The inference is drawn from these results that the onset of eary turbulence corresponds to the flow becoming hydrodynamically unstable due to viscoelastic effects introduced by the polymer additive and that the character of the flow is intermediate between laminar and fully developed turbulent flow.

 

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