[Ruonin]

Hi folks,

I've run a MRF single fluid simulation where I've used the libforces.so library in the controlDict dictionary to get the Torque in two different impellers level on the same shaft. I'm using MRF with simpleFoam.

This would allow me to get the individual Power Number for each impeller.

After convergence, and looking at the forces.dat files the data is essentially the same.

My question to the forum is: is there a way to get individual torques for each level of impeller? or do I need to run the different simulations with each impeller independently?
Maybe I'm looking at the torque calculation the wrong way...

Hope I was clear in my explanation.

Best Regards,
RS

[tomf]

Hi,

This line is a bit vague:

After convergence, and looking at the forces.dat files the data is essentially the same.

Can you plot the data?

Also in order to help you I think it would be best if you show you controlDict, or at least the entry for the forces.

Regards,
Tom

[Ruonin]

Tomf,

I've uploaded the files.

My guess is that I need to separate the two levels of impellers into two different patches.

I'm guessing the shaft also has to be an independent patch.


FoamFile
{
version 2.0;
format ascii;
class dictionary;
location system;
object controlDict;
}

startFrom startTime;
startTime 0;
stopAt endTime;
endTime 100000.0;
deltaT 1.0;
writeControl timeStep;
writeInterval 100.0;
purgeWrite 0;
writeFormat ascii;
writePrecision 10;
writeCompression uncompressed;
timeFormat general;
timePrecision 6;
graphFormat raw;
runTimeModifiable yes;
functions
{

forces1
{
type forces;
functionObjectLibs ( "libforces.so");
patches ( impeller_Final );
rho rhoInf;
rhoInf 1000;
CofR ( -0.3418 -0.541 2.08 );
outputControl timeStep;
outputInterval 1;
}

forces2
{
type forces;
functionObjectLibs ( "libforces.so");
patches ( impeller_Final );
rho rhoInf;
rhoInf 1000;
CofR ( -0.3418 -0.541 2.9874 );
outputControl timeStep;
outputInterval 1;
}

}

forces1 ;
forces2 ;

Originally Posted by tomf

Hi,

This line is a bit vague:



Can you plot the data?

Also in order to help you I think it would be best if you show you controlDict, or at least the entry for the forces.

Regards,
Tom

[tomf]

Hi,

Yes, if you want them to be separated, you need different patches for each part. You now just have twice the forces on impeller_Final. So if you split this into separate parts and make an entry for each part than you will get individual forces.

Good luck,
Tom

[Ruonin]

Thanks, tomf.

I had already a ongoing simulation which confirmed your statement.

BR.

RS

Originally Posted by tomf

Hi,

Yes, if you want them to be separated, you need different patches for each part. You now just have twice the forces on impeller_Final. So if you split this into separate parts and make an entry for each part than you will get individual forces.

Good luck,
Tom