Numerical simulations for a fluid flow driven dynamo in a precessing cylinder
ORAL
Abstract
A magnetohydrodynamic dynamo process is supposed to take place in the
interior of the Sun or stars as well as in planets and smaller
celestial bodies like the ancient Moon or the asteroid Vesta, which
has motivated related studies in the laboratory. Currently, a new
dynamo experiment is under construction at Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), in which liquid sodium will be forced by a
precessing cylindrical container. In the present study, we conduct
related numerical simulations of dynamo action in order to examine the
interaction of flow and field and the associated transfer of kinetic
energy into magnetic energy. We compare self-consistent simulations of
the complete set of magnetohydrodynamic equations with a simplified
kinematic approach solely based on the magnetic induction equation
with a prescribed velocity field. In both cases, we observe an
optimal parameter range for the onset of dynamo action in a
transitional regime, within which the flow undergoes a radical change
from a large-scale to a smaller-scale turbulent behavior. In contrast
to the kinematic solution, the character of the dynamo is small-scale
in the MHD models, which in addition exhibit irregular magnetic bursts
with an increase in the magnetic energy by a factor of 3 to 5.
Nevertheless, the magnetic energy remains significantly lower than the
kinetic energy, so that the dynamo process is not particularly
efficient and there is nearly no noticeable feedback of the magnetic
field on the flow.
interior of the Sun or stars as well as in planets and smaller
celestial bodies like the ancient Moon or the asteroid Vesta, which
has motivated related studies in the laboratory. Currently, a new
dynamo experiment is under construction at Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), in which liquid sodium will be forced by a
precessing cylindrical container. In the present study, we conduct
related numerical simulations of dynamo action in order to examine the
interaction of flow and field and the associated transfer of kinetic
energy into magnetic energy. We compare self-consistent simulations of
the complete set of magnetohydrodynamic equations with a simplified
kinematic approach solely based on the magnetic induction equation
with a prescribed velocity field. In both cases, we observe an
optimal parameter range for the onset of dynamo action in a
transitional regime, within which the flow undergoes a radical change
from a large-scale to a smaller-scale turbulent behavior. In contrast
to the kinematic solution, the character of the dynamo is small-scale
in the MHD models, which in addition exhibit irregular magnetic bursts
with an increase in the magnetic energy by a factor of 3 to 5.
Nevertheless, the magnetic energy remains significantly lower than the
kinetic energy, so that the dynamo process is not particularly
efficient and there is nearly no noticeable feedback of the magnetic
field on the flow.
*This work benefited from support through Project Nos. GR 967/7-1 and GI 1405/1-1 of the Deutsche Forschungsgesellschaft.The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for funding this projectby providing computing time through the John von Neumann Institute for Computing (NIC) on the GCS Supercomputer JUWELSat Julich Supercomputing Centre (JSC).
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Publication: Wilbert, Giesecke, Grauer 2022, Phys. Fluids 34, 096607, doi: 10.1063/5.0110153
Giesecke, Vogt, Pizzi, Kumar, Garcia-Gonzalez, Gundrum, Stefani 2024, submitted to J. Fluid. Mech.
Giesecke, Wilbert, Simkanin, Stefani 2024, in preparation
Presenters
-
Andre Giesecke
- Helmholtz-Zentrum Dresden-Rossendorf