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Flows of electrically conducting fluids in an external magnetic field tend to become 2D. We show experimentally that in channels flows normal to the field and electrically forced through one of the channel walls, the intensity of turbulent fluctuations scales as Re when the flow is quasi-2D, Re^(2/3) when the flow is 3D but strong near both walls, and Re^(1/2) if it is mostly concentrated along one wall only. We also partly confirm the theoretical prediction of [5] that structures of transversal wavelength k_perp become quasi-2D when they exceed a critical size k_perp~Nt^(1/2), where the true interaction parameter Nt represents the ratio of momentum diffusion by the Lorentz force to inertia for the large scales.
Author(s):
Alban Potherat
Coventry University
United Kingdom
Klein Rico
TU-Ilmnau
Germany