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The generation of vortical structures by a strong magnetic dipole field in a liquid metal duct flow is studied by means of three-dimensional direct numerical simulations. The dipole is considered as the paradigm for a magnetic obstacle which will deviate the streamlines due to Lorentz forces which act on the fluid elements. Our model uses the quasi-static approximation applicable in the limit of small magnetic Reynolds numbers. The analysis covers the stationary flow regime at smaller flow Reynolds numbers Re as well as the fully time-dependent regimes at higher values with a turbulent flow in the wake of the magnetic obstacle. We present a systematic study of these two basic flow regimes on Re and the Hartmann number Ha, a measure of the strength of the magnetic dipole field. Furthermore, three orientations of the dipole are compared, the streamwise, spanwise and wall-normal ones. The most efficient generation of turbulence at a fixed distance above the duct occurs for the spanwise orientation in which we can observe the formation of Hartmann layers at the top plate.
Author(s):
Saskia Tympel
Institute of Thermodynamics and Fluid Mechanics, Ilmenau University of Technology
Germany
Thomas Boeck
Institute of Thermodynamics and Fluid Mechanics, Ilmenau University of Technology
Germany
Dmitry Krasnov
Institute of Thermodynamics and Fluid Mechanics, Ilmenau University of Technology
Germany
Jörg Schumacher
Institute of Thermodynamics and Fluid Mechanics, Ilmenau University of Technology
Germany