Physical-space decimation and constrained large Eddy simulation
Seminar Room 1, Newton Institute
AbstractTraditional decimation theory of fluid turbulence was proposed by Kraichnan and the analysis was carried out in the Fourier space. It has been shown that the low-order decimation theory leads to the direct-interaction-approximation, while the high-order decimation theory can include the effect of intermittency. In this talk, we propose a physical-space decimation method which can be used for large-eddy-simulation. In particular, we propose to impose physical constraints in the dynamic procedure of the dynamic subgrid-scale (SGS) stress model in large eddy simulation, and to calculate the SGS model coefficients using a constrained variation. One simple constraint for fluid turbulence in both physical and Fourier space decimation models is the conservation of energy across the inertial range. Numerical simulations of forced and decaying isotropic turbulence demonstrate that the constrained dynamic mixed model predicts the energy evolution and the SGS energy dissipation well. The constrained SGS model also shows a strong correlation with the real stress and is able to capture the energy backscatter, manifesting a desirable feature of combining the advantages of dynamics Smagorinsky and mixed models. It should be mentioned that all previous LES models do not satisfy underlying physical constraints. We have also extended the constrained LES to helical, passive-scalar and intermittent systems.
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