- Title
- Reynolds number effect on the velocity derivative flatness factor
- Creator
- Meldi, M.; Djenidi, L.; Antonia, R.
- Relation
- Journal of Fluid Mechanics Vol. 856, Issue 10 December 2018, p. 426-443
- Publisher Link
- http://dx.doi.org/10.1017/jfm.2018.717
- Publisher
- Cambridge University Press
- Resource Type
- journal article
- Date
- 2018
- Description
- This paper investigates the effect of a finite Reynolds number (FRN) on the flatness factor (F) of the velocity derivative in decaying homogeneous isotropic turbulence by applying the eddy damped quasi-normal Markovian (EDQNM) method to calculate all terms in an analytic expression for F (Djenidi et al., Phys. Fluids, vol. 29 (5), 2017b, 051702). These terms and hence F become constant when the Taylor microscale Reynolds number, Reλ exceeds approximately 104. For smaller values of Reλ, F, like the skewness −S, increases with Reλ; this behaviour is in quantitative agreement with experimental and direct numerical simulation data. These results indicate that one must first ensure that Reλ is large enough for the FRN effect to be negligibly small before the hypotheses of Kolmogorov (Dokl. Akad. Nauk SSSR, vol. 30, 1941a, pp. 301–305; Dokl. Akad. Nauk SSSR, vol. 32, 1941b, pp. 16–18; J. Fluid Mech., vol. 13, 1962, pp. 82–85) can be assessed unambiguously. An obvious implication is that results from experiments and direct numerical simulations for which Reλ is well below 104 may not be immune from the FRN effect. Another implication is that a power-law increase of F with respect to Reλ, as suggested by the Kolmogorov 1962 theory, is not tenable when Reλ is large enough.
- Subject
- isotropic turbulence; turbulence modelling; turbulent flows
- Identifier
- http://hdl.handle.net/1959.13/1441030
- Identifier
- uon:41296
- Identifier
- ISSN:0022-1120
- Language
- eng
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