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Wavelet analyses of velocities in laboratory isotropic turbulence

Published online by Cambridge University Press:  25 June 1999

H. MOURI ,
H. KUBOTANI ,
T. FUJITANI ,
H. NIINO  and
M. TAKAOKA
H. MOURI
Affiliation:
Meteorological Research Institute, Nagamine 1-1, Tsukuba 305, Japan
H. KUBOTANI
Affiliation:
Institute of Computer Science, Faculty of Engineering, Kanagawa University, Kanagawa, Yokohama 221, Japan
T. FUJITANI
Affiliation:
Meteorological Research Institute, Nagamine 1-1, Tsukuba 305, Japan
H. NIINO
Affiliation:
Ocean Research Institute, University of Tokyo, Nakano, Tokyo 164, Japan
M. TAKAOKA
Affiliation:
Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-01, Japan
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Abstract

Orthonormal wavelet transformations are used to decompose velocity signals of grid turbulence into both space and scale. The transforms exhibit small-scale enhancements of (i) the spatial fluctuation, (ii) the correlation in space between the adjacent scales, and (iii) the correlation in space between the longitudinal and transverse components. The spatial fluctuation and the scale–scale correlation at small scales are more significant in the transverse component than in the longitudinal component. These features are the same for different families of wavelets.

Turbulence contains tube-like structures of vorticity. We demonstrate that wavelet transforms of velocities are enhanced at the positions of the tubes, by using a direct numerical simulation. Thus our wavelet analyses have captured the effects of those coherent structures on velocities measured in the experiment, which would be difficult for traditional analysis techniques such as those with velocity increments.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 389 , 25 June 1999 , pp. 229 - 254
Copyright
© 1999 Cambridge University Press

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