Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-21T17:20:16.540Z Has data issue: false hasContentIssue false
  • English
  • Français

Freely decaying, homogeneous turbulence generated by multi-scale grids

Published online by Cambridge University Press:  19 May 2011

P.-Å. KROGSTAD  and
P. A. DAVIDSON
P.-Å. KROGSTAD*
Affiliation:
Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
P. A. DAVIDSON
Affiliation:
Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
*
†Email address for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

We investigate wind-tunnel turbulence generated by both conventional and multi-scale grids. Measurements were made in a tunnel which has a large test section, so that possible side wall effects are very small and the length ensures that the turbulence has time to settle down to a homogeneous shear-free state. The conventional and multi-scale grids were all designed to produce turbulence with the same integral scale, so that a direct comparison could be made between the different flows. Our primary finding is that the behaviour of the turbulence behind our multi-scale grids is virtually identical to that behind the equivalent conventional grid. In particular, all flows exhibit a power-law decay of energy, u2 ~ t−n, where n is very close to the classical Saffman exponent of n = 6/5. Moreover, all spectra exhibit classical Kolmogorov scaling, with the spectra collapsing on the integral scales at small k, and on the Kolmogorov microscales at large k. Our results are at odds with some other experiments performed on similar multi-scale grids, where significantly higher energy decay exponents and turbulence levels have been reported.

JFM classification

Turbulent Flows: Homogeneous turbulence Turbulent Flows: Turbulence theory Mixing: Turbulent mixing
Type
Papers
Information
Journal of Fluid Mechanics , Volume 680 , 10 August 2011 , pp. 417 - 434
Copyright
Copyright © Cambridge University Press 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Comte-Bellot, G. & Corrsin, S. 1966 The use of a contraction to improve the isotropy of grid-generated turbulence. J. Fluid Mech. 25, 657–682.Google Scholar
Davidson, P. A. 2004 Turbulence: An Introduction for Scientists and Engineers. Oxford University Press.Google Scholar
Davidson, P. A. 2009 The role of angular momentum conservation in homogenous turbulence. J. Fluid Mech. 632, 329–358.CrossRefGoogle Scholar
Gad-el-Hak, M. & Corrsin, S. 1974 Measurements of the nearly isotropy turbulence behind a uniform jet grid. J. Fluid Mech. 62, 115–143.CrossRefGoogle Scholar
George, W. K. & Wang, H. 2009 The exponential decay of homogeneous turbulence. Phys. Fluids 21 (2), 025108.CrossRefGoogle Scholar
Hosokawa, I. 2008 One-point velocity statistics in decaying homogeneous isotropic turbulence. Phys. Rev. E 78, 066312.Google ScholarPubMed
Hurst, D. & Vassilicos, J. C. 2007 Scalings and decay of fractal-generated turbulence. Phys. Fluids 19 (3), 035103.Google Scholar
Ishida, T., Davidson, P. A. & Kaneda, Y. 2006 On the decay of isotropic turbulence. J. Fluid Mech. 564, 455–475.CrossRefGoogle Scholar
Kolmogorov, A. N. 1941 On the degeneration of isotropic turbulence in an incompressible viscous fluid. Dokl. Akad. Nauk. SSSR 31 (6), 538–541.Google Scholar
Krogstad, P.-Å. & Davidson, P. A. 2010 Is grid turbulence Saffman turbulence? J. Fluid Mech. 642, 373–394.CrossRefGoogle Scholar
Nagata, K., Suzuki, H., Sakai, Y., Hayase, T. & Kubo, T. 2008 Direct numerical simulation of turbulence characteristics generated by fractal grids. Intl Rev. Phys. 2 (6), 400–409.Google Scholar
Ossai, S. & Lesieur, M. M. 2000 Energy backscatter in large-scale simulations of three dimensional incompressible isotropic turbulence. J. Turbulence 1, 010.Google Scholar
Saffman, P. J. 1967 The large-scale structure of homogeneous turbulence. J. Fluid Mech. 27, 581–593.Google Scholar