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on the run flow-rate evaluation on a cluster

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Old   August 25, 2014, 04:10
Default on the run flow-rate evaluation on a cluster
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Dear Foamers,


I've got a problem with coding a parallel calculation of the flow-rate which is to be evaluated on the run (not by integratePatchField).

My overall purpose is the following: I want the flow-rate to influence the inlet boundary conditions of an internal flow.

So far I've actually managed to evaluate the flow-rate, but it only works if I'm performing parallel calculations on my local machine or on one single node of a cluster. However if I try to run the very same calculation on a cluster distributed over several nodes, it always yields a zero flow-rate.
So obviously the problem must have something to do with parallelisation or with mpi ...

Finally here is the code, I added to the original icoFoam solver:
// Declaration and Initialisation of Variables
word outletPatchName = "OUTLET";
// search for label of the outlet patch by the name within the boundary dictionary

label inletPatchi = mesh.boundaryMesh().findPatchID(outletPatchName);

// Calculate volumetric flow-rate

scalar volFluxOutlet = sum(phi.boundaryField()[outletPatchi]);

// Write flow-rate

Info<< "Volumetric Flowrate: " << volFluxOutlet << " m^3/s" << endl;

/**********************************************/
I'd be glad for any helpful comments.

Waldemar
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Old   August 25, 2014, 22:41
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Kyle Mooney
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Hi Waldemar,

Try using

Code:
gSum(...)
instead of

Code:
sum(...)
I believe that gSum has built-in mpi reduction operators while 'sum' does not.

I hope that helps!
Cheers,
Kyle
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Old   August 26, 2014, 03:04
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Hi Kyle,

it works fine. Thank you very much!
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Old   August 26, 2014, 14:55
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Excellent! Good to hear.
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