# UDS diffusivity for Joule Heating problem

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 February 16, 2018, 12:25 UDS diffusivity for Joule Heating problem #1 New Member   RJC Join Date: Jun 2015 Posts: 18 Rep Power: 10 I am trying to simulate resistive heating in fluid. I am writing a UDF for joule heating and also introducing a UDS in the model. The UDS is to solve the current continuity equation. Grad J = Grad (Sigma Grad Phi ) sigma= electrical conductivity, Phi= Potential, Grad= Gradient and the UDF is for joule heating: q= j^2/phi I am not sure what would be the UDS diffusivity? Say my fluid has a electrical conductivity of 0.005 S/m, then what should be the UDS diffusivity here. Also, how do I define my boundary condition? My boundary condition would be an applied current density of 1e7 A/m2. How do I define that?

February 25, 2018, 21:21
#2
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Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34
Quote:
 Originally Posted by redwanamit034 I am trying to simulate resistive heating in fluid. I am writing a UDF for joule heating and also introducing a UDS in the model. The UDS is to solve the current continuity equation. Grad J = Grad (Sigma Grad Phi ) sigma= electrical conductivity, Phi= Potential, Grad= Gradient and the UDF is for joule heating: q= j^2/phi I am not sure what would be the UDS diffusivity? Say my fluid has a electrical conductivity of 0.005 S/m, then what should be the UDS diffusivity here. Also, how do I define my boundary condition? My boundary condition would be an applied current density of 1e7 A/m2. How do I define that?
From my point of view:
1. your UDS diffusivity is the same as electrical conductivity, you put it as material property.
2. you can apply current density as source. So you need to write UDF script for that
3. as boundary conditions I think you should define inlet Phi (potential) value

By the way, fluent has built-in electric potential model. You may try to find how to use in in manuals ANSYS Fluent User's Guide Chapter 28: Modeling Electric Potential Field
On the other hand, you may find information regarding fluent implementation of single potential battery model in ANSYS Fluent Advanced Add-On Modules file
Look into Part II Chapter 2: Single-Potential Empirical Battery Model

Best regards

December 23, 2022, 06:43
what if the current density has to be set to boundary consition
#3
New Member

zhubin
Join Date: Dec 2022
Posts: 8
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Quote:
 Originally Posted by AlexanderZ From my point of view: 1. your UDS diffusivity is the same as electrical conductivity, you put it as material property. 2. you can apply current density as source. So you need to write UDF script for that 3. as boundary conditions I think you should define inlet Phi (potential) value By the way, fluent has built-in electric potential model. You may try to find how to use in in manuals ANSYS Fluent User's Guide Chapter 28: Modeling Electric Potential Field On the other hand, you may find information regarding fluent implementation of single potential battery model in ANSYS Fluent Advanced Add-On Modules file Look into Part II Chapter 2: Single-Potential Empirical Battery Model Best regards
I have conducted a similar simulation with low voltage and high current density, to obtain the flow field under self induced Lorentz force. The total current is determined and varies at the boundary.

As you mentioned, in the UDS function electric potential, a potential value can be set as boundary condition. I have solved the electric potential problem, but still want to add the variation of current density on the boundary.

Do you have any advice? thanks a lot

just set the specified flux of zone uds boundary value using udf?

 December 26, 2022, 03:38 #4 Senior Member   Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34 as far as I understand at the same boundary you may specify scalar value (potential) or flux (current density). You should choose one of them __________________ best regards ****************************** press LIKE if this message was helpful

 Tags diffusivity, uds