# model particle movement under magnetic force

 Register Blogs Members List Search Today's Posts Mark Forums Read

 March 23, 2007, 06:33 model particle movement under magnetic force #1 phsieh2005 Guest   Posts: n/a Dear CFD experts: I am wondering whether anyone here had done anything like this and can offer some suggestion: Problem descriptions: iron particles suspended in water inside a cup. The dimension of the cup is on the order of 1cm x 2cm x 10cm, wheras the diameter of the iron particles are on the order of 2 micron-meter. There are thousands of iron particles in the domain, but, we will only track 1 iron particle to simplfy the problem. At time 0+, this cup is exposed to a permanent magnet, locaed on one side of the cup. Hence, magnetic force will track the iron particle toward the magnet. The difficulty lies in computing magnetic force exerts on the iron particle. Any suggestion? phsieh2005

 March 23, 2007, 08:30 Re: model particle movement under magnetic force #2 Harish Guest   Posts: n/a Did you try looking for papers in the field of magnetoydrodynamics. Also books on astrophysics will have some chapters on the topic.

 March 23, 2007, 09:57 Re: model particle movement under magnetic force #3 phsieh2005 Guest   Posts: n/a Hi, Harish, Thanks for the suggestion. I never thought about looking into Magnetohydrodynamics. I will look into it. phsieh2005

 March 23, 2007, 10:19 Re: model particle movement under magnetic force #4 opaque Guest   Posts: n/a Dear phsieh, If your problem does not include applied electric field, and the magnetic field is steady, you can model the problem as a magnetostatics problem. That is, using Ampere's law curl H = 0 div B = 0 B = mu * H You can simplify the problem by introducing a magnetic scalar potential, ie. H = grad Phi, then Ampere's law is automatically satisfied, and div (mu grad Phi) = 0 must be solved for Phi. The force on the particle due to electromagnetic effects includes several contributions: electrostatics (Coulomb), magnetohydrodynamic (Lorentz), magnetostatic/phoretic (Kelvin), etc.. In your case, I think that only the Kelvin force is needed: F_mag = mu_o * M dot grad H Just add this force to your particle force balance. You should search for information on Ferrohydrodynamics. Magnetohydrodynamics is for conducting fluids. Either way, you will learn a lot of by searching on both. Opaque Sasank K likes this.

 March 23, 2007, 11:25 Re: model particle movement under magnetic force #5 phsieh2005 Guest   Posts: n/a Dear Opaque: Thanks a LOT for the reply! The past month, I have learned a lot about magnetostatics. I have computed the magnetic flux density field using GetDP (I have tried both scalar potential and vector potential). It looks like F_mag = mu_o * M dot gradH is what I need. But, what is M? I just realized another problem I am facing: Although the magnetic field is static in general, when the iron particle moves to a new location, I need to re-mesh, re-calculate the magnetic flux density and magnetic force. Because the length scale of the particle is 3 order of magnitude smaller than the fluid domain, it will be a big job to remesh the magnetic field, especially for a 3D problem. Is it possible to calculate the magnetic flux density field "without" the iron particle. Then, somehow estimate the "pull" force on the particle based on this static magnetic flux? The iron particle is very small compared to the fluid domain. phsieh

 March 23, 2007, 17:33 Re: model particle movement under magnetic force #6 phsieh2005 Guest   Posts: n/a Dear Opaque: Could you please post the reference that showed the Kelvin force equation (that is: "F_mag = mu_o * M dot grad H")? I did searches for Kelvin force and was not able to find a good source for it. Thanks! phsieh

 March 27, 2007, 09:28 Re: model particle movement under magnetic force #7 opaque Guest   Posts: n/a Dear phsieh, M stands for Magnetization.. It is a material property, and there are different ways of how to model it as well. For a reference on the topic try the book, Ferrohydrodynamics R. E. Rosensweig Dover Publications Inc.,1985. Also, you could try the following link http://web.mit.edu/nse/nanofluids/events/pdfs/Zahn.pdf Hope this helps, Opaque

 March 27, 2007, 11:35 Re: model particle movement under magnetic force #8 opaque Guest   Posts: n/a Dear phsieh Here is another link that you may like. http://www2.mic.dtu.dk/research/MIFT...thesisCMIK.pdf Enjoy, Opaque

 March 28, 2007, 07:12 Re: model particle movement under magnetic force #9 phsieh2005 Guest   Posts: n/a Thanks a lot Mr. Opaque! I quickly read through the abstract. This thesis is very helpful to me. Best Regards, phsieh

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post jranita OpenFOAM Programming & Development 1 August 23, 2011 19:44 bzhang7 FLUENT 0 May 27, 2009 13:36 hsieh OpenFOAM Running, Solving & CFD 6 April 9, 2007 21:06 zhaoh FLUENT 0 February 5, 2007 05:10 Fabiana CFX 0 January 10, 2006 16:00

All times are GMT -4. The time now is 04:11.