CFD Online Discussion Forums - torque calculation of impulse turbine

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torque calculation of impulse turbine

Dear foamers

I created a case by combining the interDyMFoam (tutorials/multiphase/interDyMFoam/ras/damBreakWithObstacle) and pimpleDyMFoam (tutorials/incompressible/pimpleDyMFoam/propeller) to achieve the simulation of impulse turbine (multiphases flow and AMI). The screenshot of velocity field is shown in attachment containing three nozzles and a runner.
And now, I want to calculate the efficiency. A great issue comes out HOW can i obtain the torque (pressure and viscocity torque ) of runner. I have no idea about this issue. Any advice will be appreciated.

Haven't got much of experience on this but… couldn't you just use a force calculation to computer the moment aruond the axis of rotation?

Hi,

Now, I dont know how to report force in multiphase case. So i cant obtain torque without force. In singlephase case, the force/torque can be obtained by adding the following code in controlDict

Quote:

functions
{
forces
{
type forces;
functionObjectLibs ("libforces.so"); //Lib to load
patches (sphere_region0); // change to your patch name
rhoName rhoInf;
rhoInf 1000; //Reference density for fluid
CofR (2 0 0); //Origin for moment calculations
outputControl timeStep;
outputInterval 1;
}
forceCoeffs
{
// rhoInf - reference density
// CofR - Centre of rotation
// dragDir - Direction of drag coefficient
// liftDir - Direction of lift coefficient
// pitchAxis - Pitching moment axis
// magUinf - free stream velocity magnitude
// lRef - reference length
// Aref - reference area
type forceCoeffs;
functionObjectLibs ("libforces.so");
patches (sphere_region0);
rhoName rhoInf;
rhoInf 1000;
CofR (2 0 0);
liftDir (0 1 0);
dragDir (1 0 0);
pitchAxis (0 0 1);
magUInf 1e-7;
lRef 0.06; // sphere diameter
Aref 0.0014137; //1/2 * projected area = pi*r2/2

outputControl timeStep;
outputInterval 1;
}

}

more detail visit:
http://www.cfd-online.com/Forums/ope...es-of15-8.html

regards,
liping