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Torque calculation on a cylinder

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Old   June 26, 2019, 10:39
Default Torque calculation on a cylinder
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Hello everyone,

I have problems understanding the forces function in OpenFoam 5.x.
My simulation contains a Taylor-Couette flow with a rotating outer cylinder and I want to know the torque on the inner cylinder. Therefor I am simulating a quater of the cylinder and use the forces function on the inner wall patch.
Now to my questions:
1. is the moment calculated by the function the torque I want?
2. how do I have to understand the three coordinates of the moment? Do I have to calculate the magnitude?
3. Is it possible to calculate the torque on a whole axis instead of a single point? (the function calculates forces in the z axis which are several magnitudes smaller, but also irrelevant)

I would be grateful for every help and idea.
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Old   June 28, 2019, 05:20
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The three directions are the torque in each Cartesian axis.
So the first value given is torque around the x axis. The second value is torque around the y axis, etc
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Old   June 30, 2019, 04:37
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Quote:
Originally Posted by yambanshee View Post
So the first value given is torque around the x axis. The second value is torque around the y axis, etc
Thank you for your answer.
With this definition the results I receive do not make any sense. I would expect a torque on the z-axis which is the axis of the cylinders. But the calculated torque form OpenFOAM on the z-axis is negligible small whereas the values for the x and y axis are pretty similar and correlate with the values obtained by the rheometry calculations.
Do you have any explanation for this?
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Old   July 1, 2019, 04:50
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Quote:
Originally Posted by berne View Post
Thank you for your answer.
With this definition the results I receive do not make any sense. I would expect a torque on the z-axis which is the axis of the cylinders. But the calculated torque form OpenFOAM on the z-axis is negligible small whereas the values for the x and y axis are pretty similar and correlate with the values obtained by the rheometry calculations.
Do you have any explanation for this?
Without knowing anything about your simulation, it's hard to say.

What is your physical problem you are trying to solve?
what solver/boundary conditions are you using?
Maybe share your function object file along with a cad model from paraview showing the axis system you're using
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Old   July 1, 2019, 09:29
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Quote:
Originally Posted by yambanshee View Post
What is your physical problem you are trying to solve?
what solver/boundary conditions are you using?
Maybe share your function object file along with a cad model from paraview showing the axis system you're using
The problem I am trying to simulate is a Coaxial Cylinder Rheometer. Two concentric cylinders, the outer one rotates and on the inner one the applied torque is measured.
I am using the simpleFoam solver with laminar flow. The Boundary conditions are: - symmetryPlane for top and bottom
- cyclic on the sides of the quater
- rotatingWallVelocity on the outer wall (origin ( 0 0 0 );axis ( 0 0 1 );omega 1
- noSlip wall on the inner wall

I hope the information is the one you wanted and the pictures are sufficient.

forces.png

eigenes_Mesh.jpg
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