Hi, I'm trying to simulate the trajectories of magnetic particles in fluid channel with external magnetic field applied, using discrete phase modelling (DPM) with magnetohydrodynamic (MHD) addon module. I can get the magnetic field data (B0) from Magnetostatic module, and apply it into Fluent and after running calculation, it would show me that the magnetic field (B0) applied in Fluent is equivalent to what was obtained from the Magnetostatic. However, even if I crank up the DPM material property (magnetic permeability) to see how the applied magnetic field would effect the trajectory of the magnetic particle, I wouldn't see any change in the trajectory at all. (So I would apply -1 T in the y direction throughout the channel (which should pull down the particles) but I would only see straight line in the particle trajectory) From the CFD-Forum, I've learned that I'm supposed to apply the magnetic field after the initialization so I've been doing that, but it wouldn't affect the particle trajectory at all so I was wondering if there is other specific steps that I would have to take. I also set up the UDF in the DPM so that the body force is equivalent to mhd_dpm_force::mhd and source as mhd_dpm_source::mhd. Does anyone have experience with this to help me out or give me any hints?
Thank you,
James Kim
Dear James,
when I consider numerically the MHD process, it is in a plasma assumed to be a continuum ionized gas which is on average neutral (equal number of ions and electrons), but sensible to electric and magnetic fields. So what I calculate is the whole effect resulting from acceleration of charged particles due to the presence of the electric and magnetic field, and the deceleration due to collisions. If the plasma is dense (nearly collision dominated plasma) the Hall parameter (little angle of the electron orbit around the magnetic field lines) is low and the trajectory of the charged particles and the electric current density is mostly in the direction of the electric field. If the plasma is rarefied (near collision less plasma) the current density tend to be in the direction perpendicular to the plane containing both the electric and the magnetic field. If you do not take the collisions and the force due to them into account the velocity of the electron and of the ions is in the same direction and perpendicular to the abovementioned plane.
I hope this explanation was usefull.
Best regards
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