Large scale structures and energy transfer in hydrodynamic and magnetohydrodynamic turbulence

P.D. MININNI, A. ALEXAKIS, Y A. POUQUET

Boulder, Estados Unidos

Workshop; GTP workshop “Coherent structures in atmosphere and ocean"; 2005

NCAR

With the help of direct numerical simulations (DNS), we investigate the transfer of energy and triadic interactions in fully developed forced three-dimensional hydrodynamic and magnetohydrodynamic (MHD) turbulence. The assumption of locality of transfer among the different scales is one of the building blocks of Kolmogorov (1941) theory of turbulence, and also extended (with some caveats) to the case of coupling to a magnetic field in the MHD framework. We find that nonlinear triadic interactions are dominated by their non-local components, involving widely separated scales, even though the nonlinear transfer itself is local and the scaling for the energy spectrum is close to the classical Kolmogorov law. The link between these findings and the intermittency of the small scales, and their consequences for modeling of turbulent flows are also briefly discussed.