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MRF solvers give diffenrent results when MRF zone's diameter is different

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Old   May 14, 2013, 03:25
Default MRF solvers give diffenrent results when MRF zone's diameter is different
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Dongyue Li
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Hi,

Nowdays I intend to make a test of my mrf case's result with the paper.But I find the result vary with the different diameter of my rotating size.I made a comparision in two situation in which only the MRF zones size is different.As you can see in the image.(its a slice of a 3D case)

The first one's MRF zone is smaller than the other.expect this everything is the same.But after 2000 iterations,the velocity is a little different.I dont know if it gets convergence but in 2500s iterations,the velocity looks dont change anymore.

in this thread linnemann happend to run into this situation. but I didnot try his case.http://www.openfoam.org/mantisbt/view.php?id=409

Code:
Time = 2093

smoothSolver:  Solving for Ux, Initial residual = 0.000157922, Final residual = 1.01677e-05, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.000172252, Final residual = 9.70874e-06, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.000168408, Final residual = 1.10209e-05, No Iterations 2
GAMG:  Solving for p, Initial residual = 0.00286416, Final residual = 6.07327e-05, No Iterations 3
time step continuity errors : sum local = 0.000134333, global = -1.86372e-05, cumulative = 0.176384
smoothSolver:  Solving for epsilon, Initial residual = 5.02636e-05, Final residual = 1.76898e-06, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 0.000214597, Final residual = 1.16413e-05, No Iterations 2
ExecutionTime = 3003.18 s  ClockTime = 3019 s
Code:
MRF1
{
    type            MRFSource;
    active          true;
    selectionMode   cellZone;
    cellZone        innerCylinder;

    MRFSourceCoeffs
    {
	nonRotatingPatches ();
        origin      (0 0 0);
        axis        (0 1 0);
        omega       31.4159;
    }
}
Attached Images
File Type: jpg paper's mesh.jpg (93.1 KB, 38 views)
File Type: jpg 11.jpg (94.0 KB, 44 views)
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Old   February 18, 2014, 05:30
Default Are there some news?
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Hi,
I found a similar result issue in a different geometry MRF problem.
Are there some news?

Dothan
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Old   March 10, 2014, 12:22
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Pengchuan Wang
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Hi everyone,

Same thing happens to me as well. Different size of MRFzones gives different results.
And for me, none of these gives me the same results as the analytical solution.
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Old   March 11, 2014, 03:44
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Hi pechwang,
Do you have a turbomachinery analytical solution to compare CFD solutiuons?
I know only Eckardt Impeller.

Dothan
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Old   March 11, 2014, 11:06
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Pengchuan Wang
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Hi Dothan,

No, the analytical solution is for lubrication model. Unfortunately, MRF cannot give me correct results.

Thanks,
Pengchuan
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Old   May 29, 2015, 07:00
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M. Montero
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Same problem here. When MRFZone limit is near walls ( sometimes it is required because stator zone is quite near) the pressure field around the walls is modified. The pressure lines are modified to accommodate its shape to the limit of the MRF Zone so suction lobe is affected and so all the aerodynamics of the wall (wake,....). The solution is wrong.

I do not have AMI interfaces so the solution proposed does not work.
Did you start a bug report?
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