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Monitoring Torque on rotating body in MRFSimpleFoam

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Old   November 15, 2008, 07:53
Default Monitoring Torque on rotating body in MRFSimpleFoam
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Mahendra
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Dear Foamers Hi !

Hope you all are doing very well.

It has been a very good experience with OpenFOAM till date and I am enjoying it a lot.
Thanks for the support and courtesy that you guys are extending to beginners like me.
This only drive us to learn more and more about OpenFOAM.

Right now I am looking into the MRFSimpleFoam cases and I was wondering how to set a monitor point that monitors the torque on the rotating body.
So when I see that the torque has become flat I can stop my simulation and it will add to my confidence about the results.

Hope to hear from you

Thanks and Regards,
Mahendra
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Old   November 17, 2008, 12:45
Default Hi Mahendra, I found a tool
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Hi Mahendra,

I found a tool to calculate torque on the board and modified it a little bit to match my requirements. It now calculates the torque based on pressure and wall shear stress on patches wich are entered in a dict file. I can send you a copy of it to your email address.

PM
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Old   November 18, 2008, 00:33
Default Dear Pual, Thanks for the r
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Dear Pual,

Thanks for the reply and Are you talking of computeTorqueMRF?

Can I use it in the form of probes?

You can reach me at mahendra.wankhede@gmail.com

Regards,
Mahendra.
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Old   November 19, 2008, 00:13
Default Dear Paul, Thanks for the u
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Dear Paul,

Thanks for the utility now I can calculate the torque on the required patch.

Still I was wondering if I can use the torque as a monitor point on a patch and how to do it. I beg your pardon as my know-how of C++ is very limited.

functions
(
Probes
{
// Type of functionObject
type probes;

// Where to load it from (if not already in solver)
functionObjectLibs ("libsampling.so");

// Locations to be probed. runTime modifiable!
probeLocations
(
(0 0 0.25)
);

// Fields to be probed. runTime modifiable!
fields
(
p
U
Torque // Like this
);
}
);

Regards,
Mahendra
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Old   November 19, 2008, 00:56
Default Dear Paul, I am a little co
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Dear Paul,

I am a little confused with this two utilities.

1.computeTorqueMRF
2.calculateTorque

When I execute the two on my case, it gives me different results.

So now I am confused with which utility should I use to compute the torque.

Regards,
Mahendra.
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Old   November 19, 2008, 04:15
Default Hi Mahendra, have a look in
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paul_mathis
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Hi Mahendra,

have a look into the code - maybe computeTorqueMRF calculates torque just based on pressure forces and does not take into account the viscous forces (calculated by wallShearStress), whereas the utility I sent you does.

Regards,
Paul
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Old   November 19, 2008, 04:31
Default Hi Paul, As you have said,
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Hi Paul,

As you have said, I checked the computeTorqueMRF.C and found that it computes the pressure torque on a given surface.

So I think the utility you sent to me is the one I need.

Still my earlier question remains...about monitoring torque (Like Probes for Pressure or velocity)

Regards,
Mahendra
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Old   November 19, 2008, 15:11
Default Hi Paul, Any chance I could
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Jason Dale
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Hi Paul,

Any chance I could also get a copy of your utility? Would really appreciate it.

jason.dale (at) tesco.net

Many Thanks

Jason
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Old   November 19, 2008, 17:50
Default Hi Paul I request you to pl
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Hi Paul

I request you to please post the utility on the this thread for all of us to use

Kind Regards
Jaswi
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Old   November 20, 2008, 04:59
Default Dear foamers, here are my u
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Dear foamers,

here are my utilities to calculate torque for incomressible (calculateTroque) and comressible flows (calculateTroqueCompressible).

Torque is computed based on pressure and viscous forces on patches specified in the calculateTorqueDict file which has to be located in the system directory.

Enjoy,
Paul

\Client\C$\Documents and Settings\c563640\Desktop\calculateTorque.tar.gz
\Client\C$\Documents and Settings\c563640\Desktop\calculateTorqueCompressib le.tar.gz
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Old   November 20, 2008, 05:03
Default Something seems to go wrong wi
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paul_mathis
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Something seems to go wrong with the path...
What is my mistake while uploading?
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Old   November 21, 2008, 04:49
Default If they are general perhaps th
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If they are general perhaps they can go onto http://openfoamwiki.net?
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Old   November 21, 2008, 05:59
Default Dear Paul, I ran a simple M
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Dear Paul,

I ran a simple MRF case and compared the results with Fluent. The velocity vectors seems ok and matches fairly with Fluent.

But when I see the torque it does not match with Fluent. I checked each and every thing thoroughly, but could not dig into why the torque is not matching?

Paul, what could be the possible cause?

Regards,
Mahendra
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Old   November 21, 2008, 06:03
Default I did multiply the torque form
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I did multiply the torque form OpenFOAM with density. Even then it is not matching?
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Old   November 25, 2008, 10:02
Default Hello, a useful tool for mo
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Hello,

a useful tool for monitoring forces/torque during calculation process is found here:

http://www.cfd-online.com/cgi-bin/Op...4787#POST24787

Regards, Paul
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Old   July 22, 2011, 00:12
Question Monitor torque in each time step in MRFSimpleFOAM
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Hi,
This is Jeya, doing Vertical Axis Wind Turbine Simulations. I already simulated this in Ansys Fluent. In Fluent, we can monitor torque. From this I able to find Cp of Vertical Axis Wind Turbine.
Now I tried to do the same simulation in OpenFOAM. I manage to do other settings and I able to run my simulation in OpenFOAM. In the following thread (Monitoring Torque on rotating body in MRFSimpleFoam) I found a file "calculateToque". By using this I able to calculate torque at a particular times (i.e.: calculateTorque -time 10) But I am interested to plot torque versus time graph. Therefore I need to monitor torque in each timestep. Please help me. I am stuck on this for long time. My programming skills also very poor. Your helps are very much appreciated.
Thank you so much

Sincerely,
Jeya
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Old   July 25, 2011, 12:28
Default
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Hi Yeya!

I'm using OF 1.6 ext and I Coudn't compile it with wmake.
What did you do to compile it?

Regards Christian
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Old   July 25, 2011, 12:44
Default I figure it out my torque problems in openfoam. Thank you very much
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Hello Christian,
I am using Openfoam from my university cluster. It is already installed. I tried in my home computer(Linux fedora). I couldn't install it. Then I give up to install in my home computer. I deal with more than a million elements therefore I need the help of cluster.
You could find some other threads where you may find some answers
Thanks.
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Old   July 26, 2011, 01:43
Default calculate torque
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hi, i hope that all are well
i wanna calculate torque in the VAWT,i modeled it successfully but when i use computeTorque, the result is wrong!!!
some questions a bout the code are :
1-what's the meaning of "r0" in the code, what is the unit?
2-is it just needed to compile calculateTorque utility and run it ?
3-in my case, the radius is 0.75, density is 1.205kg/m^3 and the name of 3Blades is "rotor", how to understand these to the code??!
4-is it needed a file added in the system directory or add code to the controlDict??!

tanx
_______
Rasoul
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Old   July 26, 2011, 01:56
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Just a question.

Why dont you just use the forces library already present in OF?

put this in the end of the controlDict.

Code:
functions
(
    forces
    {
        type forces;
        functionObjectLibs ("libforces.so");
        outputControl timeStep;
        outputInterval 1;
        patches (wallBlade);
//        pname p;
//        Uname U;
        rhoName rhoInf;
        log true;
        rhoInf 1.205;
        CofR (0 0 0);
    }
);
This will output the forces/torque in x,y,z direction.

The output to the terminal will look like this.

Code:
    forces(pressure, viscous)((2162.2 -313.192 35.8823) (12.5865 3.1166 3.97532))
    moment(pressure, viscous)((1162.4 6862.37 100.944) (-12.5067 35.4299 -50.9462))
Then you can always make your own script to add the pressure torque with the viscous torque or just calculate them by hand.
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