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what are the best solvers for P, U, cellDisplacement for overPimpleDyMFoam

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Old   May 21, 2019, 20:40
Exclamation what are the best solvers for P, U, cellDisplacement for overPimpleDyMFoam
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H.Ham
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Hi Guys,

I am a new Openfoam user, and i am currently working on flow around an airfoil profile (externel flow). I work with overPimpleDyMFoam (transient regime), my mesh is 100k cells (using overSet Mesh) my problem is that my simulation takes a lot of time, to reach a duration of 0.2 second, my computer calculates during 2 days (it's huge time)

knowing that my current number maxCO = 8, and y + = 10.


Please help me !!!!!!!! please, !!!!!!
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Old   May 23, 2019, 04:50
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Thomas Sprich
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Hi Hamdani,

I think you are unlikely to get a best fit answer as often the choice of solver is subject to the type of geometry and determining the best choice is a case of trial and error.

I have used the following in a overInterDyMFoam simulation I ran:

Code:
"cellDisplacement.*"
    {
        solver          PCG;
        preconditioner  DIC;

        tolerance       1e-09;
        relTol          0;
        maxIter         100;
    }
and

Code:
    "(U|k|omega|epsilon).*"
    {
        solver          PBiCG;
        preconditioner DILU;
        tolerance       1e-015;
        relTol          0;
    }
I didn't have P, so I can't help you there. You might need to look at your tolerences to see if they are too rigid, particularly as you are starting the simulation. Also, I found it helps to have the background and overset meshes to be similarly sized.

You can always try reduce the size of the overset region. This should be minimised to reduce the number of cells that have to be calculated. I have read you need at least four cells around your geometry for overset. You could look at your mesh resolution, although this is probably a last resort.

Lastly, your courant number is quite high, test to see if lower values give you less iterations to your convergence for your Correctors. Maybe as your simulations stabilises you can increase the courant number.

If its any consolation, this simulation also took me a long time to solve.

I'm sorry I can't offer you a better answer than that.

Good luck,
Thomas
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Old   May 23, 2019, 05:39
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H.Ham
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HI Thomas,

thank you very much Thomas, I will take into consideration everything you said to me, you helped me very well

You will find attached "systeme folder "

-
yes I use the version v1812 which is compatible with oversetMesh
- My computer : Intel xeon 12 cores, RAM 32GB,

- Yes i'm running the simulation in parallel with :

----------------------------------

numberOfSubdomains 10;

method hierarchical;

coeffs
{
n (5 1 2);
delta 0.001; // default=0.001
//order xyz; // default=xzy
}
----------------------------------------

cfd_Online1.png

cfd_online2.jpg

checkMesh.jpg

solver.jpg

system.zip
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