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HRT

Seminar

Non-universality of the turbulence dissipation constant in homogeneous isotropic turbulence and the universal relations which account for it

Vassilicos, JC (Imperial College London)
Wednesday 01 October 2008, 14:00-14:30

Seminar Room 1, Newton Institute

Abstract

The dimensionless dissipation constant of homogeneous isotropic turbulence is equal to the third power of a number which reflects the number of large-scale eddies multiplied by a function of Reynolds number. This function of Reynolds number may tend to a constant in the limit of very high Reynolds number as a result of an eventual balance between a slow growth of the range of viscous length-scales and the increasing non-Gaussianity of the small scales. However, when the turbulence is generated by fractal grids this function of Reynolds number is inversely proportional to the Reynolds number for a very wide range of Taylor length-based Reynolds number up to about 1000 even though the turbulence energy spectrum has a well-defined -5/3 range. See Mazellier, N. & Vassilicos, J.C. 2008 The turbulence dissipation constant is not universal because of its universal dependence on large-scale flow topology. Phys. Fluids 20, 015101 Seoud, R.E. & Vassilicos, J.C. 2007 Dissipation and decay of fractal-generated turbulence. Phys. Fluid 19, 105108

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