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We study the effect of a turbulent flow of liquid sodium generated in the von K\'arm\'an geometry, on the localized field of a magnet placed close to the frontier of the flow. We observe that the field can be transported by the flow on…

We numerically examine dynamo action generated by a flow of an electrically conducting fluid in a precessing cylindrical cavity. We compare a simplified kinematic approach based on the solution of the magnetic induction equation with a…

Fluid Dynamics · Physics 2025-04-07 André Giesecke , Mike Wilbert , Ján Šimkanin , Rainer Grauer , Frank Stefani

The experimental realization of dynamo excitation as well as theoretical and numerical examinations of the induction equation have shown the relevance of boundary conditions for a self-sustaining dynamo. Within the interior of a field…

Fluid Dynamics · Physics 2012-08-08 Andre Giesecke , Frank Stefani , Gunter Gerbeth

Magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows…

Plasma Physics · Physics 2016-10-19 F. Stefani , M. Gellert , Ch. Kasprzyk , A. Paredes , G. Ruediger , M. Seilmayer

We present results from numerical simulations of nonlinear MHD dynamo action produced by three-dimensional flows that become turbulent for high values of the fluid Reynolds number. The magnitude of the forcing function driving the flow is…

Astrophysics · Physics 2009-11-07 Vasilis Archontis , Bertil Dorch , Aake Nordlund

In the present paper, some elementary test cases in laminar flow with magnetic forcing terms are analyzed (Hartmann flow, Couette flow, Rayleigh flow); equations of the coupled problem are exposed and analytical solutions are derived in…

Classical Physics · Physics 2010-02-18 David Cebron , Jean-François Sigrist , Vincent Soyer , P. Ferrant

The Derviche Tourneur Sodium experiment, a spherical Couette magnetohydrodynamics experiment with liquid sodium as the medium and a dipole magnetic field imposed from the inner sphere, recently underwent upgrades to its diagnostics to…

Fluid Dynamics · Physics 2018-04-18 Elliot Kaplan , Henri-Claude Nataf , Nathanaël Schaeffer

It is widely known that cosmic magnetic fields, i.e. the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields…

Astrophysics · Physics 2009-05-13 Frank Stefani , Agris Gailitis , Gunter Gerbeth

Hydrodynamic and magnetohydrodynamic numerical studies of a mechanically forced two-vortex flow inside a sphere are reported. The simulations are performed in the intermediate regime between the laminar flow and developed turbulence where a…

Fluid Dynamics · Physics 2015-05-14 K. Reuter , F. Jenko , A. Tilgner , C. B. Forest

The kinematic dynamo problem is investigated for the flow of a conducting fluid in a cylindrical, periodic tube with conducting walls. The methods used are an eigenvalue analysis of the steady regime, and the three-dimensional solution of…

Astrophysics · Physics 2009-11-07 Wolfgang Dobler , Peter Frick , Rodion Stepanov

We consider the induction of magnetic field in flows of electrically conducting fluid at low magnetic Prandtl number and large kinetic Reynolds number. Using the separation between the magnetic and kinetic diffusive lengthscales, we propose…

Fluid Dynamics · Physics 2009-11-10 Yannick Ponty , Helene Politano , Jean-Francois Pinton

We investigate the dynamics of very large particles freely advected in a turbulent von Karman flow. Contrary to other experiments for which the particle dynamics is generally studied near the geometrical center of the flow, we track the…

We study flow around a cylinder from a dynamics perspective, using drag and lift as indicators. We observe that the mean drag coefficient bifurcates from the steady case when the Karman vortex street emerges. We also find a jump in the…

Numerical Analysis · Mathematics 2023-11-15 L. Ridgway Scott , Rebecca Durst

This Minireview summarizes the recent efforts to solve forward and inverse problems as they occur in different branches of fundamental and applied magnetohydrodynamics. As for the forward problem, the main focus is on the numerical…

Fluid Dynamics · Physics 2015-06-12 Andre Giesecke , Frank Stefani , Thomas Wondrak , Mingtian Xu

In a previous paper, we have reported numerical simulations of the MHD flow driven by a travelling magnetic field (TMF) in an annular channel, at low Reynolds number. It was shown that the stalling of such induction pump is strongly related…

Fluid Dynamics · Physics 2016-03-23 Paola Rodriguez Imazio , Christophe Gissinger

In a cylindrical container filled with an eutectic GaInSn alloy, an electro-vortex flow (EVF) is generated by the interaction of a non-uniform current with its own magnetic field. In this paper, we investigate the EVF phenomenon numerically…

Fluid Dynamics · Physics 2019-10-24 K. Liu , F. Stefani , N. Weber , T. Weier , B. W. Li

We analyze the nature of dynamo action that produces horizontally averaged magnetic fields in two particular flows that were studied by Roberts (1972, Phil. Trans. R. Soc. A 271, 411), namely his flows II and III. They have zero kinetic…

Solar and Stellar Astrophysics · Physics 2014-04-25 Matthias Rheinhardt , Ebru Devlen , Karl-Heinz Rädler , Axel Brandenburg

The stability problem of MHD Taylor-Couette flows with toroidal magnetic fields is considered in dependence on the magnetic Prandtl number. Only the most uniform (but not current-free) field with B\_in = B\_out has been considered. For high…

Astrophysics · Physics 2008-09-22 M. Gellert , G. Ruediger

We consider inverse problems related to the velocity reconstruction in electrically conducting fluids from externally measured magnetic fields. The underlying theory is presented in the framework of the integral equation approach to…

Fluid Dynamics · Physics 2007-05-23 Frank Stefani , Thomas Gundrum , Gunter Gerbeth , Uwe Guenther , Mingtian Xu

We perform kinematic simulations of dynamo action driven by a helical small scale flow of a conducting fluid in order to deduce mean-field properties of the combined induction action of small scale eddies. We examine two different flow…

Fluid Dynamics · Physics 2014-07-28 Andre Giesecke , Frank Stefani , Gunter Gerbeth