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-   -   pseudo transient (http://www.cfd-online.com/Forums/fluent/117963-pseudo-transient.html)

chinna May 18, 2013 04:39

pseudo transient
 
Hai, as i choosing coupled solver in solution method.. why there is no pseudo transient option for me..??:confused:

Far May 18, 2013 15:03

pseudo transient option is available for coupled solver. Which version you are using?

behest September 9, 2013 08:51

Hello Far,
I've used Ansys Fluent 14.5 and I want to apply Pseudo transient. Where is this option?
What is the diference between pseudo transient and transient?

Quote:

Originally Posted by Far (Post 428468)
pseudo transient option is available for coupled solver. Which version you are using?


Far September 9, 2013 10:32

pseudo transient is an option in solution methods.

or go to solve > Methods...

jamalf64 September 9, 2013 10:35

Quote:

Originally Posted by chinna (Post 428412)
Hai, as i choosing coupled solver in solution method.. why there is no pseudo transient option for me..??:confused:

you should set your problem STEADY

Marabelle September 9, 2013 11:57

what exactly is meant by pseudo transient?
 
Hello tehre!
I have a general question. I have to simulate a transient model. So far I just copied the settings of the precedent student working on that model. He enabled the "pseudo transient" option in the solution methods settings. What does the option "pseudo transient" mean resp. what does it cause/effect in the calculation?
Thanks so far, I would appreciate your answers!

jamalf64 September 9, 2013 12:21

Quote:

Originally Posted by Marabelle (Post 450699)
Hello tehre!
I have a general question. I have to simulate a transient model. So far I just copied the settings of the precedent student working on that model. He enabled the "pseudo transient" option in the solution methods settings. What does the option "pseudo transient" mean resp. what does it cause/effect in the calculation?
Thanks so far, I would appreciate your answers!

pseudo transient adds a term to equations(i.e d/dt=constant and not zero). This leads to a better convergence

Far September 9, 2013 12:26

It is like solving the problem with high gradient and initially unstable solution (and ultimately steady state and stable solution) with unsteady solver and choosing bigger time step. In this way the initial transients (non-physical) will wash away and you will get a very nice convergence.

duri September 10, 2013 04:56

Pseudo transient solves the unsteady equation with time stepping calculated from large scale domain information rather local cell information. And same time step is applied to all cells exactly like global time stepping. The main advantage is that convergence acceleration occurs in regions of mesh induced stiffness. (like boundary layer)

Tanjina March 20, 2014 16:41

Pseudo transient time step in unsteady problem
 
Hello everyone.

For my 3D unsaturated porous media model, I am using VOF. Water level will change with time and after some time it will become steady. So initially it is unsteady. For saving time, I used steady time step with pseudo transient option. Water level was falling perfectly, after some time it became steady also.

I just want to make myself sure that for unsteady model like this, I can use steady time with pseudo transient option. I was going through the literature available for pseudo-transient time step, but I kinda lost. Then I found this thread.

Could anyone please help me in this regard?

Thanks in advance.

Regards,
Tanjina


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