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#32 Possible bug cyclicGgi
Hi,
I'm using foam extend version 4.1. I'm simulating the incompressible flow through an impeller of a pump with a 7 blades with MRFSimpleFoam. I'm computing a single blade and using a periodic condition cyclicGgi, the simulation seems to converge but the mass flow rate is not conserved.
Thank you!
Based on your bug report, I have nothing I can look at, nor can I reproduce the error to check. You did not upload the geometry, log files, mass flow check (what is your continuity error?).
I run this every day and "it works for me". Can you provide further info?
Hi Hrvoje,
Attached you can find a case where I found this problem. I'm simulating impeller (7 blades) and diffuser (12 blades) of a pump with periodic condition and a mixingPlane interface. The log.MRFSimpleFoam is the log of the simulation. From the first timestep till the end the flow rate is not conserved, but the simulation seems to converge.
faceSource onTheFly_Q_inlet output:
sum(impeller_inlet) of phi = -0.00104441
faceSource onTheFly_Q_outlet output:
sum(vaneddiffuser_outlet) of phi = 0.000544802
faceSource onTheFly_Q_InterfaceInlet output:
sum(impeller_outlet) of phi = 0.000950297
faceSource onTheFly_Q_InterfaceOutlet output:
sum(vaneddiffuser_inlet) of phi = -0.000543617
sum(impeller_inlet) of phi should be equal to -sum(impeller_outlet) of phi and to 12/7*sum(vaneddiffuserinlet) of phi
Thank you!
Not a bug.
Your problem is the mixing plane, not cyclic GGI. If you replace the mixing plane with overlapGgi, the case runs fine without any conservation issues.
With a mixing plane, the non-orthogonality correction across the mixing plane interface is not treated, for stability reasons. In your case, you have a full tet mesh for both channels and the non-orthogonality is extreme.
The case was decently set up - you got both the cyclic GGIs and mixing plane right. I assume this is a strip-down of a real 3-D pump.
If you wish to use a mixing plane, you need a better mesh in the mixing interface region.