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# The large-scale structure of homogeneous turbulence

Saffman, P. G. (1967) The large-scale structure of homogeneous turbulence. Journal of Fluid Mechanics, 27 (3). pp. 581-593. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:SAFjfm67a

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## Abstract

A field of homogeneous turbulence generated at an initial instant by a distribution of random impulsive forces is considered. The statistical properties of the forces are assumed to be such that the integral moments of the cumulants of the force system all exist. The motion generated has the property that at the initial instant E(kappa) = Ckappa^2 + o(kappa^2) where E(k) is the energy spectrum function, k is the wave-number magnitude, and C is a positive number which is not in general zero. The corresponding forms of the velocity covariance spectral tensor and correlation tensor are determined. It is found that the terms in the velocity covariance Rij(r) are O(r^−3) for large values of the separation magnitude r. An argument based on the conservation of momentum is used to show that C is a dynamical invariant and that the forms of the velocity covariance at large separation and the spectral tensor at small wave number are likewise invariant. For isotropic turbulence, the Loitsianski integral diverges but the integral $\int_0^{\infty} r^2R(r)dr = \frac{1}{2}\pi C$ exists and is invariant.

Item Type: Article © 1967 Cambridge University Press. Reprinted with permission. (Received 1 March 1966) This work was stimulated by the belief of Prof. H.W. Liepmann that the K^4 dependence of the energy spectrum function was not a general law. CaltechAUTHORS:SAFjfm67a http://resolver.caltech.edu/CaltechAUTHORS:SAFjfm67a http://dx.doi.org/10.1017/S0022112067000552 No commercial reproduction, distribution, display or performance rights in this work are provided. 10122 CaltechAUTHORS Archive Administrator 14 Apr 2008 19 Nov 2018 23:53

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