Leray-α LES of magnetohydrodynamic turbulence at low magnetic Reynolds number

Abstract

A series of large eddy simulations is performed for decaying homogeneous magnetohydrodynamic (MHD) turbulence at low magnetic Reynolds number (Re_m <<1) with different strengths of magnetic field. The initial isotropic turbulence problem has the Taylor scale Reynolds number (Re _λ) of 120. The regularization-based Leray-α model is used for sub-grid scale (SGS) closure for the first time and comparisons are made with our own direct numerical simulation (DNS) calculations conducted as part of this study. Analyses of turbulent kinetic energy decay rates, energy spectra, and vorticity fields are made between the varying magnetic field cases. The SGS model assessments are also made between the Leray-α model and the classic non-dynamic Smagorinsky with several model coefficients. Overall, the Leray-α model was unable to capture the anisotropy associated with MHD flows as well as the non-dynamic Smagorinsky model in this study or even the dynamic Smagorinsky model in previous studies.

Keywords:

• magnetohydrodynamic turbulence
• direct numerical simulation
• large eddy simulation, regularization models