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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 :


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:

Originally Posted by wyldckat
Hi Sasan,

I don't know much about this. All I know is:
  1. Both PISO and SIMPLE can be used for transient simulations.
  2. PISO algorithm is described here:
  3. SIMPLE algorithm is described here:
  4. Then there is PIMPLE, which is a mix of PISO+SIMPLE... and I 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.

You might have gotten a better answer if you had asked in the public forum...

Best regards,

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