Bonn 2010 – wissenschaftliches Programm
EP 7.4: Vortrag
Dienstag, 16. März 2010, 15:45–16:00, AKM
Nonlinear Triad Interactions in 3D-MHD Turbulence — •Yasser Rammah and Wolf-Christian Müller — Max-Planck-Institut für Plasmaphysik, 85748 Garching
Nonlinear triad interactions in incompressible three-dimensional magnetohydrodynamic (MHD) turbulence are studied by analyzing high-resolution direct numerical simulations of decaying isotropic (5123 grid points) and forced anisotropic (10242× 256 grid points) turbulence. An accurate approach of analyzing nonlinear turbulent interactions is presented. It involves the direct numerical examination of every wavenumber triad that is associated with the nonlinear terms in the differential equations of MHD in the inertial range of turbulence. The technique allows to compute spectral energy transfer and energy fluxes, as well as the spectral locality property of energy transfer. To this end, the statistical distribution of the energy transfer over all triads is examined with regard to the shape of the underlying wavenumber triads. Results show that the total, kinetic, and magnetic energy transfer is local in decaying macroscopically isotropic MHD turbulence. In anisotropic MHD turbulence subject to a strong mean magnetic field the nonlinear transfer is generally weaker and exhibits a moderate increase of nonlocality in both perpendicular and parallel directions compared to the isotropic case. These results are in contradiction with previous numerical results, but they support recent mathematical findings which also claim the locality of nonlinear energy transfer in MHD turbulence.