Hybrid RANS/LES modelling

Description

Hybrid RANS/LES computations, aka Very-Large-Eddy Simulations (VLES), are an alternative to RANS and LES simulations for unsteady turbulent flows in complex geometries, that try to combine the best aspects of both strategies.

Scope of research

A hybrid RANS/LES model has been developed, based on previous renormalization group (RG) calculations by Giles. The result of the RG approach is a one-equation LES subgrid model in well resolved regions of the flow, and a two-equation RANS model otherwise. The two modes of the model are linked by comparing the filter width with a length scale constructed from subgrid quantities. The one-equation subgrid model uses a transport-equation for the mean rate of dissipation, in which the inverse time scale is explicitly filter width dependent. The model has a clear physical interpretation and is easy to implement. Recently the model has been put in one-equation form. Only the transport equation of the mean subgrid dissipation rate is retained, and the lengthscale is determined geometrically. The low-Reynolds modelling is also simplified in the new model.

Publications

  • Renormalization Group Approach to Hybrid RANS/LES Modelling, De Langhe C., PhD thesis, Ghent University, 2003.
  • De Langhe C., Merci B. and Dick E., Hybrid RANS/LES modelling with an approximate renormalization group. I: Model development, Journal of Turbulence 6 (13), 2005
  • De Langhe C., Merci B., Lodefier K. and Dick E., Hybrid RANS/LES modelling with an approximate renormalization group. II: Applications, Journal of Turbulence 6 (14), 2005
  • De Langhe C., Merci B. and Dick E., Application of a RG hybrid RANS/LES model to swirling confined turbulent jets, Journal of Turbulence 7 (56), 2006
  • De Langhe C., Bigda J., Lodefier K. and Dick E., One-equation hybrid RANS/LES computation of a turbulent impinging jet, Journal of Turbulence 9 (16), 2008
  • Summary of the two-equation model (1p)
  • Slides of a lecture on hybrid RANS/LES methods (given at TU Darmstadt, 30/01/06)