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Intermittency and relative scaling of subgrid-scale energy dissipation in isotropic turbulence
ABSTRACT: The rate at which large-scale kinetic energy in turbulent flows is transferred to, or from, unresolved scales (smaller than a filter scale is given by P(x,t)= -tijSij, where tij is the subgrid stress, and Sij is the resolved strain-rate tensor. The spatial distribution of P(x,t) is computed from DNS of isotropic turbulence, and is found to be highly intermittent with increasing levels of intermittency as the filter size decreases. Relative scaling exponents of high-order moments of are measured using extended self-similarity, and are compared to those of longitudinal velocity structure function. Reasonably good agreement is found, both sets of exponents clearly departing from the Kolmogorov (1941) theory. Relative scaling exponents of the SGS dissipation as predicted by several models are measured a priori from the DNS, and are compared to those of the true dissipation. We find the constant and spectral eddy viscosity models to be significantly less intermittent, and the local dynamic model to be much more intermittent than the true SGS dissipation field. The traditional and volume-averaged dynamic Smagorinsky models, together with the similarity model, yield more realistic levels of intermittency. Phys. Fluids 10, (1998), p. 928 (©AIP, see http://ojps.aip.org/phf) Reused with permission from Stefano Cerutti, Physics of Fluids, 10, 928 (1998). Copyright 1998, American Institute of Physics.
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Charles Meneveau, Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles Street, Baltimore MD 21218, USA, Phone: 1-410-516-7802, Fax: 1-(410) 516-7254, email: meneveau@jhu.edu |
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05/25/2007
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