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July 13, 2011, 04:40 
Solving a Laplace equation for a scalar quantity

#1 
New Member
Ali
Join Date: Mar 2011
Posts: 27
Rep Power: 7 
Hello,
I am trying to solve , i.e. homogeneous Laplace equation, in which is a scalar quantity and is described in a zone(2D or 3D). We know boundary values of in borders of the zone. This problem is very analogous to head conduction at steady state, yet is the electric potential here, not temperature. I am wondering how to implement this problem in FLUENT. I think I have to mesh the zone and use a udf or something like that. Thanks for your help. 

October 2, 2014, 11:05 

#3 
Member
MarkClarence
Join Date: Jul 2014
Posts: 32
Rep Power: 4 
Hi Amir,
Can you elaborate your statement? How can we justify that unsteady and convective terms can be ignored for solving the laplace equation? (i need to find the change in electric field in my geometry) I think you know how my geometry looks like :P , I have to find the electric field in the rotor domain. If possible can you share the UDF with me? Thank you. Mark 

October 2, 2014, 13:34 

#4  
Senior Member

Quote:
"UDS" is "UserDefined Scalar" equation and is available in FLUENT, something like energy equation and totally different from "UDF"! In the process of enabling a UDS, you can manage the unsteady and convective terms. For more info, please refer to the manual. Bests,
__________________
Amir 

February 11, 2015, 20:56 

#5 
New Member

Hi,
Can we solve defined scalar in x, y, z direction separately (for 3D geometry) or how can we see the scalar values in x y z directions using post processing? Regards Tharanga 

February 12, 2015, 05:02 

#6  
Senior Member

Quote:
For sure you cannot solve it separately, but if you want to see the scalar values in a specified direction, you can simply draw a line and plot the scalar values over it... Bests,
__________________
Amir 

February 12, 2015, 06:08 

#7 
New Member

Hey, Thank you for the reply. I have solved the laplace eq (3D) and I need to get surface integration over x y z direction (separately) . Is there any method for that? cheers


February 12, 2015, 06:12 

#8 
New Member

If I elaborate more, I cant choose from the drop down menu xscalar values etc. Therefore, I'm struggling to find x y z values over a surface. Thank you.


February 12, 2015, 06:24 

#9 
Senior Member
Join Date: Nov 2013
Posts: 1,005
Rep Power: 14 
With a user defined scalar, you calculate a scalar, not a vector.
A scalar does not have a xcomponent... So your question does not make any sense. If you solved an electrostatic problem, your scalar is probably the electric potential. Which component do you want? The xcomponent of the electric field? You should know the relation between those two. 

February 12, 2015, 06:36 

#10 
New Member

It is a homogenized flow problem. Ultimately, I need to solve laplace eqn (vector) with BC's . Yes, you are right but there is no other way (I think) than UDS method in fluent to solve Laplace. Please suggest me an alternative method. Thank you


February 12, 2015, 07:00 

#11 
Senior Member
Join Date: Nov 2013
Posts: 1,005
Rep Power: 14 
You don't make clear why you need another way. What is wrong with the UDS method?
And are you sure you want a vector laplace equation??? That is very unusual. I don't know why a "homogenized flow problem" would lead to a vector variant of the laplace equation. 

February 16, 2015, 21:42 

#12 
New Member

Hi, Thank you very much for your kind replies. I solved it as three different problems in fluent. I got the results.
Regards, Tharanga 

Tags 
electric potential, heat conduction, laplace equation 
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