Classical and variational multiscale LES of the flow around a circular cylinder on unstructured grids |
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Authors: | Hilde Ouvrard Alain Dervieux |
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Affiliation: | a Département de Mathématiques, Université de Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex, France b INRIA, 2004 Route des Lucioles, 06902 Sophia-Antipolis, France c Dipartimento di Ingegneria Aerospaziale, Università di Pisa, Via G. Caruso 8, 56122 Pisa, Italy |
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Abstract: | The effects of numerical viscosity, subgrid scale (SGS) viscosity and grid resolution are investigated in LES and VMS-LES simulations of the flow around a circular cylinder at Re=3900 on unstructured grids. The separation between the largest and the smallest resolved scales in the VMS formulation is obtained through a variational projection operator and finite-volume cell agglomeration. Three different non-dynamic eddy-viscosity SGS models are used both in classical and in VMS-LES. The so-called small-small formulation is used in VMS-LES, i.e. the SGS viscosity is computed as a function of the smallest resolved scales. Two different grid resolutions are considered. It is found that, for each considered SGS model, the amount of SGS viscosity introduced in the VMS-LES formulation is significantly lower than in classical LES. This, together with the fact that in the VMS formulation the SGS viscosity only acts on the smallest resolved scales, has a strong impact on the results. However, a significant sensitivity of the results to the considered SGS model remains also in the VMS-LES formulation. Moreover, passing from classical LES to VMS-LES does not systematically lead to an improvement of the quality of the numerical predictions. |
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Keywords: | Large-eddy simulation Variational multiscale approach Unstructured grids Circular cylinder flow |
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