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-   -   Setting an external B0_x field in MHD module (http://www.cfd-online.com/Forums/fluent/94906-setting-external-b0_x-field-mhd-module.html)

fferroni November 29, 2011 14:18

Setting an external B0_x field in MHD module
 
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

fferroni November 30, 2011 14:36

solution
 
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

Ramnik July 30, 2012 03:00

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

Heera Lal October 5, 2012 13:31

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

nasser February 25, 2013 15:15

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.

meisammm July 2, 2014 03:21

Mhd module
 
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

gbrajtm July 13, 2015 05:29

MHD simulation for Magnetorheological Fluids in annular gap
 
1 Attachment(s)
Hi all,

I was trying to simulate MHD for finding the velocity profile of flow in the gap under different magnetic field.

Pressure inlet- 500pa
outlet - 0 pa

material - MR fluid

visco = 0.09 pas
permeability= 0.0008 H/m
Density= 3180 Kg/mm3.

i did simulation for 3T magnetic flux. But the velocity profile looks abnormal, velocity not reducing in the magnetic region, reduces only are the terminals of the field. Could any body please help me to find the profile.


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