Learning Forum

[bv169]

Good afternoon, 

I am running an MHD model with a set external field and a static velocity field. I am running it in transient. When doing so, there is no development in the magnetic field. I set monitors that showed the field is unchanged. What could be the cause of this?

 

Thanks,

Breanna

[bv169]

Following up as this has not been resolved.

[Ulrich Schmidt]

To be honest I am not sure whether I fully understand what you are doing or expecting.

You have an external magnetic field. I presume that this is static. Is that correct?

In addition, you have a static velocity field.

If I have a static magnetic field and a static velocity field, I am not sure why I should expect transient changes.

[bv169]

The interaction of the initial constant flow with the magnetic field induces another magnetic field which is the one we've been plotting and doesn't seem to evolve as our analytic solution predicts. The flow field itself should be affected (very slightly) by the Lorentz force. So in summary, the magnetic and velocity fields are indeed initially constant but evolve because of the coupling of the equations into something (in our case slightly) different, but they are not static. But we do not see this in the Fluent MHD model. 

[Ulrich Schmidt]

I would start with running MHD in stationary. Do you get reasonable results in stationary (e. g. induced magnetic field )?

Which settings have you chosen for the MHD Model (MHD Method, value of external  field …)? Perhaps you can add some screenshots here.

Which time step have you chosen? How long have you calculated?

[bv169]

Magnetic induction and the external field is in the attached screenshot. So far was ran 831 s of flow time with no evolution. Time step size of 0.001 s. Thanks!