- Title
- Power-law exponent in the transition period of decay in grid turbulence
- Creator
- Djenidi, L.; Kamruzzaman, Md.; Antonia, R. A.
- Relation
- ARC
- Relation
- Journal of Fluid Mechanics Vol. 779, p. 544-555
- Publisher Link
- http://dx.doi.org/10.1017/jfm.2015.428
- Publisher
- Cambridge University Press
- Resource Type
- journal article
- Date
- 2015
- Description
- Hot-wire measurements are carried out in grid-generated turbulence at moderate to low Taylor microscale Reynolds number Reλ to assess the appropriateness of the commonly used power-law decay for the mean turbulent kinetic energy (e.g. k ∼ xn, with n ⩽−1). It is found that in the region outside the initial and final periods of decay, which we designate a transition region, a power law with a constant exponent n cannot describe adequately the decay of turbulence from its initial to final stages. One is forced to use a family of power laws of the form xni, where ni is a different constant over a portion i of the decay time during the decay period. Accordingly, it is currently not possible to determine whether any grid-generated turbulence reported in the literature decays according to Saffman or Batchelor because the reported data fall in the transition period where n differs from its initial and final values. It is suggested that a power law of the form k ∼ xninit+m(x), where m(x) is a continuous function of x, could be used to describe the decay from the initial period to the final stage. The present results, which corroborate the numerical simulations of decaying homogeneous isotropic turbulence of Orlandi & Antonia (J. Turbul., vol. 5, 2004, doi:10.1088/1468-5248/5/1/009) and Meldi & Sagaut (J. Turbul.,vol. 14, 2013, pp. 24–53), show that the values of n reported in the literature, and which fall in the transition region, have been mistakenly assigned to the initial stage of decay.
- Subject
- homogeneous turbulance; isotropic turbulance; turbulent flows
- Identifier
- http://hdl.handle.net/1959.13/1314884
- Identifier
- uon:22847
- Identifier
- ISSN:0022-1120
- Language
- eng
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