# Problem with MHD module and writing the UDF

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

 July 1, 2017, 12:36 #2 New Member   Aureliano Sancho Join Date: May 2013 Location: Salvador-Ba-Brasil Posts: 26 Rep Power: 12 Dear Amin, I hope that have gotten to resolve your problem. I'm trying to do something similar and need help. I'm trying to do a model with flux of the fluid electrically charger in channel with surface density of charge too. Could you tel me how can I do this? How do I put charge in fluid and in channel? Thanks

 March 2, 2020, 04:57 #3 New Member   Krishnaprasad Join Date: Jun 2017 Posts: 3 Rep Power: 8 Dear Amin, I am working on a problem similar to yours. I hope you have resolved your problem. If you have, can you tell me how you accomplished it? TIA

 March 2, 2020, 05:23 Problem #4 Senior Member     Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35 Could you describe the problem you are facing? __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

 March 2, 2020, 07:21 #5 New Member   Krishnaprasad Join Date: Jun 2017 Posts: 3 Rep Power: 8 I am currently using Fluent to study the droplet deformation under the influence of Electric field using the leaky dielectric model. I am using a User Defined Scalar (phi) to obtain the electric potential. I am facing problems in using this solution to calculate the source term for the momentum equation. The equation for the Electric force, as mentioned above is F = q*E - 0.5*epsilon*E^2. where q = div(epsilon*E) where E = -grad(phi). q = epsilon*div(E) + E.grad(epsilon) I am unsure how to calculate the divergence of the electric field i.e. the Laplacian of the electric potential using a UDF. Can you direct me on how to calculate the Laplacian of a User defined scalar in Fluent? Am I proceeding in the right direction or do I need to adopt a different approach?

 March 2, 2020, 07:33 Gradient and Divergence #6 Senior Member     Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35 You may calculate gradient and divergence using UDSI_G or UDSI_RG (if you want to use bounded gradients), however, Fluent has an in-built Electric Potential model; separate from MHD module. You may use that, provided you are using rather newer version, such as 18.x or later. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

 Tags fluent 14.5, mhd, two-phase flow, udf