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Coupling.gif | 4.3 MB |

EM and HD trans...nt coupling.mph | 291 KB |

MHD_strong_coup...ing_3D_view.gif | 4.4 MB |

Download all files (Zip-archive) | ~ 7.2 MB |

## Electromagnetic and hydrodynamic transient coupling

Linards Goldsteins, CEA

In this model transient electromagnetics and hydrodynamics are coupled

in a so-called strong MHD coupling in a 2D axisymmetric geometry, with

k-epsilon RANS turbulence equations for the fluid flow.

This model focuses on the strong coupling process involved and no

specific checking regarding solver or mesh convergence analysis has been

performed here. Moreover, there is no special treatment of the Hartmann

boundary layer (interaction between the fluid boundary layer and the

transverse magnetic field). Default wall functions available with

k-epsilon model have been used, together with a continuity in the

magnetic vector potential Aphi at the wall. Aphi is in this model not

modified by the turbulent boundary layer.

To be successful, one should take into account that good initial

conditions for the fluid flow must be provided to the time-dependent

solver. This process makes use of 5 stationary steps.

It is possible to use fewer stationary steps, however it may cause more

convergence errors (Tfails and NLfails) or even not converge at all.

Also, one should adjust the time-dependent solver by segregating the

magnetic vector potential Aphi in a separated segregated step. Sometimes

it might be useful also to exclude algebraic degrees of freedom from the

evauation of error in the time-dependent algorithm. This is done in the

advanced options of the solver.

One should note that the conductivity of mercury if significantly

increased in order to better illustrate the physical phenomena that

appears at this moderate magnetic Reynolds number. Highly conducting

flow "takes" magnetic field in the direction of the flow and therefore

it is not symetric as it would be in case of zero velocity (magnetic

Reynods number 0). The full time-dependent solution reveals the

behaviour in time of this kind of strong coupling, which is not

frequently described in the literature.

Many thanks to Eric Favre, from COMSOL France, for his technical support

associated with this case.

## User Comments

Feb 15, 2013 at 10:06am UTC |

We recently built a similar model for a customer demo and possible future consultancy project with COMSOL Multiphysics. This model is great as verification of our model and a good tutorial for future developments. |

Feb 15, 2013 at 9:30pm UTC |

The closest we have to this is: |

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