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-   -   UDS question (http://www.cfd-online.com/Forums/fluent/36227-uds-question.html)

Z April 1, 2005 02:12

UDS question
 
How to access the previous iteration data of uds

is it C_UDSI_M1(c,t,0) and this is just of time step ?

ap April 1, 2005 07:45

Re: UDS question
 
Yes, the value of the scalar you're solving for at the previous time step can be obtained using

C_UDSI_M1 (cell, thread, scalar)

Best regards, ap

Z April 1, 2005 10:21

Re: UDS question
 
what about steady state solver Then what does C_UDSI_M1 mean is it previous iterations.

ap April 1, 2005 17:58

Re: UDS question
 
In a steady calculation you can't access to the previous time step data, because it doesn't exist.

Regards, ap

Z April 2, 2005 08:11

Reply to ap
 
Hi, I posted this questions long back and saw your reply.

1) I would like to know when UDS is solved at what positions scalar is solved is it after k and epsilon equation or before k and epsilon equation. 2) I wrote an UDS and it was not working fine it generally gives me values less than 0 and more than 1. When I browsed in this site I cam to know when scalar values are less than 0 then it should be set 0 and more than 1 value should be set to 1. Is this correct what I am doing?

3)When I used this setting discussed above Everything seems to be okay but the problem is URF in that case should not be more than 0.1 and if I use URF to be more than 0.1 then fluent gives me very big numbers e+20 something like that. So the problem is that simulation is very slow with URF is there any solution to this problem.

Your reply was 1) Go to Control -> Solution -> Multigrid and increase the verbosity parameter. (Can you explaine me more here)

2) What do you mean with less than 0 and more than 1? It depends on the problem you're solving. When you implement a UDS equation in FLUENT you should write it in its dimensional form. So the values of the variable are not bounded in the standard range [0; 1]. (I am solving for a scalar which is just values from 0 and 1)

Z


ap April 2, 2005 14:45

Re: Reply to ap
 
If you increase the verbosity parameter, you can see the order in which the equations are solved, and monitor the residuals at each single iteration.

However, UDS should be solved after other variables.

For your scalar equation, I should have more information, What kind of equation is it? What's its coefficients? What are the boundary conditions?

Best regards, ap


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