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Coupling transient EM and HD calculations

Posted Nov 27, 2012, 8:30 a.m. EST Low-Frequency Electromagnetics, Computational Fluid Dynamics (CFD), Studies & Solvers Version 4.3a 2 Replies

Linards Goldsteins
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Hello,

I am trying to perform 2D-axi transient calculation of time harmonic magnetic field impact on liquid metal. Generally I need to solve Induction eq., derive induced EM (Lorenz) force distribution, insert it into Navier-Stokes and solve velocity field, then but it back as velocity distribution in EM solver and loop like that for each time step.

Right now I can solve transient EM, but I am no sure how to couple both physics and loop for each time step.

If someone has experiance doing that or there is some good example of similar problem, such help and advises will be highly apreciated.

Thanks, and have a good day!

Linards
2 Replies Last Post Dec 7, 2012, 9:19 a.m. EST
Eric Favre COMSOL Employee

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Posted: 1 decade ago Dec 4, 2012, 9:12 a.m. EST
Hi Linards,

You have a number of examples that you can find typing "MHD pump" in the research field of the web page. It's usually a good idea to have a look there.
For EM in transient coupled to CFD in transient, it is of course possible, and should be the default if you create a new study with time-dependent solver. Just pay attention to the equation form in the equations section of the physics node (should be study controlled but not forced to frequency domain for emag especially). Usually you use averaging in time for the Lorentz force since the typical timescale for the fluid is often much larger than the one for the electromagnetics, so solving EM in the frequency domain coupled to time-dependent fluid is preferred when your hypothesis allow for it.In principle, you should use time-domain when, for instance, input currents are not sinusoidal (you cannot take the real part of A*exp(j*omega*t+phi) and the harmonic assumption is not valid anymore).

Best regards,
Eric Favre
COMSOL France
Hi Linards, You have a number of examples that you can find typing "MHD pump" in the research field of the web page. It's usually a good idea to have a look there. For EM in transient coupled to CFD in transient, it is of course possible, and should be the default if you create a new study with time-dependent solver. Just pay attention to the equation form in the equations section of the physics node (should be study controlled but not forced to frequency domain for emag especially). Usually you use averaging in time for the Lorentz force since the typical timescale for the fluid is often much larger than the one for the electromagnetics, so solving EM in the frequency domain coupled to time-dependent fluid is preferred when your hypothesis allow for it.In principle, you should use time-domain when, for instance, input currents are not sinusoidal (you cannot take the real part of A*exp(j*omega*t+phi) and the harmonic assumption is not valid anymore). Best regards, Eric Favre COMSOL France
Linards Goldsteins
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Posted: 1 decade ago Dec 7, 2012, 9:19 a.m. EST
Thank you very much for your help on coupling EM with HD transiently.

In my case I was really interested not to solve flow quasi-stationary but in time domain. At the moment looks like COMSOL handels it quite well - calculation is rather quick for the test model and physics are OK! I attached test model .gif.

Thanks again, Eric!
Thank you very much for your help on coupling EM with HD transiently. In my case I was really interested not to solve flow quasi-stationary but in time domain. At the moment looks like COMSOL handels it quite well - calculation is rather quick for the test model and physics are OK! I attached test model .gif. Thanks again, Eric!

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