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 sasanghomi January 30, 2013 17:48

relaxation factor for PISO algorithm

Hi every body,

I have a question about relaxation factor :
sonicTurbDymEngineFoam is a transient solver for compressible flow with mesh motion.(OP-1.6-ext)
It uses PISO algoritm for solving equations.when I use relaxation factor in a case with this solver I get correct result.Do you think using of relaxation factor in PISO algorithm is wrong??? why???
In a header file of the source code of this solver I saw this code :
Code:

`UEqn.relax();`
thanks,
Sasan.

 wyldckat February 2, 2013 06:51

In order to give a bump to this thread, here's what I answered Sasan the other day, through private messaging:
Quote:

Originally Posted by wyldckat
Hi Sasan,

1. Both PISO and SIMPLE can be used for transient simulations.
2. PISO algorithm is described here: http://openfoamwiki.net/index.php/Th...hm_in_OpenFOAM
3. SIMPLE algorithm is described here:http://openfoamwiki.net/index.php/Th...hm_in_OpenFOAM
4. Then there is PIMPLE, which is a mix of PISO+SIMPLE... and I quote:
Quote:
 Originally Posted by alberto (Post 320875) PISO simply does not iterate over the equations: it solves alpha, Theta, U, p, k, epsilon and proceeds in time. PIMPLE is a combination of PISO and SIMPLE. In other words you can have outer correctors, if you set the appropriate keyword in the fvSolution PIMPLE sub-dictionary.
Therefore, the relaxation factors you're talking about may depend on whether you're using PISO or PIMPLE.