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Setting an external B0_x field in MHD module

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Old   November 29, 2011, 14:18
Default Setting an external B0_x field in MHD module
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Hello.

I'm trying to do a simple simulation of pipe flow flowing through a transverse applied external magnetic field.

I've followed religiously the Manual provided by Ansys but I think it's not doing the job I'm wanting it to do.

In the Problem Set-Up/MHD Model/ I have a DC Field with B0_x Mean (Tesla) as 10 Tesla. I have applied the external field. In the boundary conditions I have a conducting wall.

In the Boundary Conditions section, I have a "Velocity-Inlet", "Pressure-Outlet", "Symmetry", and "Wall". There are UDS tabs for the inlet, outlet and wall zones. I have these all set to udf mhd_bc_conduct::mhd.
I'm not too sure what these UDS BV actually do... so if someone would want to elucidate?

I then initialize the problem etc. and the solution turns up exactly like there was no external applied magnetic field! During solving iterations, it also prints out residuals for uds-0, uds-1, uds-2.. and these are all zero, so I'm guessing it's not considering the huge magnetic field that I'm applying?!

For the record, in the Results section, when I display the Contour for Symmetry of "User Define Memory" / B0_x I get a pretty homogeneous 10 Tesla!
I know for a fact that the liquid (fast flowing molten metal) changes it's behaviour but it appears like it's not considering the applied external magnetic field?!
Please help!

Thank you,

Kind Regards,

Francesco
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Old   November 30, 2011, 14:36
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Hello everyone.

Fortunately I figured this out myself.

The reason is that you have to click "Apply" for the external magnetic field in the problem set-up AFTER initializing the solution... i believe that by initializing the solution in general it cancels the application of the external magnetic field done by the MHD module. The MHD manual is a bit counter-intuitive in this regard!

Thanks

Francesco
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Old   July 30, 2012, 03:00
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Ramnik Singh
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Hello Mr Fferroni,

I was wondering if you could help me out with this problem related to MHD using Fluent.

I have been trying to implement conducting wall boundary condition for the MHD module using the Electric Potential Method. It requires to specify a fixed current or voltage.

I am trying to simulate turbulent flow in a square pipe and have not been able to figure out a way to calculate the required potential/voltage at the boundary.

Please comment if you have any ideas.

Thanks in advance.

Regards
Ramnik
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Old   October 5, 2012, 13:31
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Heera Lal
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hi mr. fferroni,
i was facing the same the same the problem .But your suggestion worked. thanks a lot.
but i am not able to get the lorentz force contour and also i am not sure bout boundary condition for uds-0 and uds-1. If you have any idea then please tell me .

Thanks .
Heera lal
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Old   February 25, 2013, 15:15
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Nasser
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hi friends
the total magnetic flux through a closed surface is equal to zero. if your surface is close you havnt any induce magnetic field b.
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Old   July 2, 2014, 03:21
Question Mhd module
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i want to model mhd ( by fluent mhd module) in a channel with sea water flowing in it.
B=15 tesla
i solve the problem with no problem (solution converges also uds-0 , ... all converge) but the existence of mhd and magnetic field has no effect of mass flow rate or velocity in outlet boundary!

Can anybody help me out?
Thank you
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