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-   -   What are the definitions of nOuterCorrectors and nCorrectors (http://www.cfd-online.com/Forums/openfoam-solving/111790-what-definitions-noutercorrectors-ncorrectors.html)

 immortality January 15, 2013 12:38

What are the definitions of nOuterCorrectors and nCorrectors

in rhoPimpleFoam we have below coefficients.what do they refer to?
Code:

```nOuterCorrectors 1;     nCorrectors    2;```

 immortality January 15, 2013 19:18

could anyone give a hint?

 Linse January 16, 2013 05:40

Just a hint (I do not know more exact for the moment) : Depending on the number of the different correctors there will be different numbers of iteration cycles within one "timestep".
Putting up this numbers CAN lead to better convergence within the timestep, but it also WILL cause an increase of computational demand...

 immortality January 16, 2013 09:49

thank you bernhard.does anyone knows the difference between them?

 msuaeronautics January 21, 2013 15:55

nCorrectors is the number of times a solution for pressure is attempted within each timestep.

For instance, when nCorrectors = 2, you might see something like this in your output file:

Quote:
 DICPCG: Solving for p, Initial residual = 0.00394327, Final residual = 0.00016442, No Iterations 3 time step continuity errors : sum local = 2.90239e-11, global = 1.2422e-13, cumulative = 3.82086e-10 DICPCG: Solving for p, Initial residual = 0.000361647, Final residual = 3.99177e-06, No Iterations 101 time step continuity errors : sum local = 7.04328e-13, global = 1.35611e-13, cumulative = 3.82221e-10
Someone correct me if I'm wrong, but nOuterCorrectors essentially controls how many times you want all of it, including U and p, to be solved for in an iteration. I've never used anything yet other than nOuterCorrectors = 0.

 vonboett November 12, 2013 05:43

Quote:
 Originally Posted by msuaeronautics (Post 403194) nCorrectors is the number of times a solution for pressure is attempted within each timestep. For instance, when nCorrectors = 2, you might see something like this in your output file: Someone correct me if I'm wrong, but nOuterCorrectors essentially controls how many times you want all of it, including U and p, to be solved for in an iteration. I've never used anything yet other than nOuterCorrectors = 0.

As far as I see, nOuterCorrectors has an effect, when the viscosity of your fluid changes in dependency to the flow. For example, shear thinning fluids etc., but also when your turbulence model produces a turbulent viscosity that adds to the molecular viscosity.

 simt November 12, 2013 05:49

nOuterCorrectors determines no. of iterations over the non-linear coupling. So nOuterCorrections = 1 equals to PISO where the non-linear coupling is neglected.

 aujamal20 November 29, 2013 13:34

Hello Everybody,
It would be very nice if somebody explain nOuterCorrectors and its influence in pimple solver and what is the max limit of its value. For instance, can i use nOuterCorrectors=10 (or higher value) in a simulation using pimple solver.

Thanks
Jamal

 akidess November 30, 2013 08:55

Jamal, the max value for nOuterCorrectors should be 9223372036854775807 (assuming it's of datatype label, and you are on a 64bit system). It's just a counter for a loop, so you can use any number of iterations you require to reach convergence. Of course the more correctors you use the longer your simulation will take, so if you need a large amount of correctors you should ask yourself why convergence is so slow. For more explanation, see the answer by simt.

 powpawell June 13, 2016 06:31

hi Guys,

If you're coming back to this topic, there is an more recent (2015) explanation on this topic:
OpenFOAM guide/The PIMPLE algorithm in OpenFOAM

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