On the two-dimensionalization of quasi-static MHD turbulence

Benjamin Favier (1) , Fabien Godeferd (1) , Claude Cambon (1) , Alexandre Delache (2)

1 LMFA - Laboratoire de Mecanique des Fluides et d'Acoustique
2 LA MUSE - Laboratoire de Mathématiques Unifiées de Saint-Etienne

We analyze the anisotropy of turbulence in an electrically conducting fluid in the presence of a uniform magnetic field, for low magnetic Reynolds number, using the quasi-static approximation. In the linear limit, the kinetic energy of velo city components normal to the magnetic field decays faster than the kinetic energy of component along the magnetic field [Moffatt, JFM 28, 1967]. However, numerous numerical studies predict a different behavior, wherein the final state is characterized by dominant horizontal energy. We investigate the corresponding nonlinear phenomenon using Direct Numerical Simulations. The initial temporal evolution of the decaying flow indicates that the turbulence is very similar to the so-called “two-and-a-half- dimensional” flow [Montgomery & Turner, Phys. Fluids 25(2), 1982] and we offer an explanation for the dominance of horizontal kinetic energy.

Mots clés: Flow simulation; Magnetohydrodynamics; Turbulence

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Benjamin Favier, Fabien Godeferd, Claude Cambon, Alexandre Delache. On the two-dimensionalization of quasi-static MHD turbulence. Physics of Fluids, 2010, 22 (7), pp.075104. ⟨10.1063/1.3456725⟩. ⟨hal-00516503⟩