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innvah June 1, 2019 09:22

MRF simpleFoam
 
Hi,

I am currently running a steadyState MRF case with a turbine in OpenFOAM 6. I am trying to evaluate the behavior of torque/moment output for different RPM values (defined in MRFProperties) to create a RPM-torque table.

Why do I get the same output torque for different turbine geometries with constant RPM and inlet flow? The case set-up is identical, the only thing that have changed is the number of blades on the turbine.


Is there something I've missed? Thanks for responses in advance!

Lookid June 5, 2019 05:02

Hello,

Did you properly define the patches where you calculate the forces/moment in controlDict?

Code:

libs
(
"libforces.so" // this is for forces
);

functions
{
    forces{
        type forces;
        functionObjectLibs ("libforces.so");
        patches (BLADE HUB SHROUD); // sum the forces and moments on those patches
        writeControl timeStep;
        writeInterval 1;
        p        p;
        U        U;
        log true;
        rhoInf 1000;
        rho rhoInf;
        CofR (0 0 0); //centreOfRotation
        }
}

Is the MRF zone well defined?
Do you control other parameters to see if the simulation is proper? (does the head, efficiency changes with the flowrate for example)


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