A NEW APPROACH TOWARDS SUBGRID MODELING IN MAGNETOHYDRO-DYNAMIC TURBULENCE

摘要

The performance of different dynamic gradient-diffusion type subgrid-models is evaluated in large-eddy simulations (LES) of magnetohydro-dynamic (MHD) turbulence with a maximum of 64~3 collocation points. The reference data stems from high-resolution direct numerical simulations of decaying and forced MHD turbulence with up to 512~3 spectral modes. In addition direct divergence modeling and the effects of additional explicit Gaussian filtering in combination with a tensor-diffusivity term are considered. A new genuine MHD subgrid model, based on the cross-helicity invariant, is presented and observed to perform extraordinarily well.