One of the most important features of unresolved small scales in Large-Eddy-Simulation is the rate at which they extract kinetic energy from the resolved flow. We examine an experimental surrogate of the subgrid (SGS) dissipation rate, by means of high Reynolds number experimental data in the cylinder wake. Mean profiles are measured and compared a priori with several models (Smagorinsky, similarity model, dynamic Smagorinsky). More detailed comparisons are achieved by means of conditional averaging, both with outer intermittency and with the phase of coherent structures (Karman vortices) in the near wake. The results provide evidence that learning from resolved scales (such as in the dynamic and similarity models) leads to more realistic predictions than the constant-coefficient eddy-viscosity model, when turbulence is spatially complex and when coherent structures affect the SGS dynamics directly.

References

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C. Meneveau 1994, "Statistics of turbulence subgrid-scale stresses: Necessary conditions and experimental tests," Phys. Fluids A 6, p. 815.