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Decay of passive-scalar fluctuations in slightly stretched grid turbulence

Decay of passive-scalar fluctuations in slightly stretched grid turbulence Isotropic turbulence is closely approximated by stretching a grid flow through a short (1.36:1) secondary contraction. The flow is operated at small values of the Taylor microscale Reynolds number (about 25–55) and is slightly heated just downstream of the grid, so that the temperature serves as a passive scalar and the initial velocity/thermal length-scale ratio is about 1. For the same grid, the contraction reduces the skewness and kurtosis of the thermal fluctuations and their derivative. The thermal fluctuations and their mean dissipation rates follow a power-law rate of decay that depends on the geometry of the grid. Comparison with velocity measurements shows that, for three different grids, the ratio between the temperature and velocity power-law exponents closely matches the velocity/thermal timescale ratio. For the present measurements, the timescale ratio is slightly larger than 1 but does not exceed 1.2, in accordance with the proposal by Corrsin (J Aeronaut Sci 18(6):417–423, 1951b). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Decay of passive-scalar fluctuations in slightly stretched grid turbulence

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References (41)

Publisher
Springer Journals
Copyright
Copyright © 2012 by Springer-Verlag
Subject
Engineering; Engineering Thermodynamics, Heat and Mass Transfer; Engineering Fluid Dynamics; Fluid- and Aerodynamics
ISSN
0723-4864
eISSN
1432-1114
DOI
10.1007/s00348-012-1331-3
Publisher site
See Article on Publisher Site

Abstract

Isotropic turbulence is closely approximated by stretching a grid flow through a short (1.36:1) secondary contraction. The flow is operated at small values of the Taylor microscale Reynolds number (about 25–55) and is slightly heated just downstream of the grid, so that the temperature serves as a passive scalar and the initial velocity/thermal length-scale ratio is about 1. For the same grid, the contraction reduces the skewness and kurtosis of the thermal fluctuations and their derivative. The thermal fluctuations and their mean dissipation rates follow a power-law rate of decay that depends on the geometry of the grid. Comparison with velocity measurements shows that, for three different grids, the ratio between the temperature and velocity power-law exponents closely matches the velocity/thermal timescale ratio. For the present measurements, the timescale ratio is slightly larger than 1 but does not exceed 1.2, in accordance with the proposal by Corrsin (J Aeronaut Sci 18(6):417–423, 1951b).

Journal

Experiments in FluidsSpringer Journals

Published: Jun 14, 2012

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