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June 26, 2019, 10:39 
Torque calculation on a cylinder

#1 
New Member
Join Date: Jun 2019
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Hello everyone,
I have problems understanding the forces function in OpenFoam 5.x. My simulation contains a TaylorCouette 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. 

June 28, 2019, 05:20 

#2 
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Zander Meiring
Join Date: Jul 2018
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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 

June 30, 2019, 04:37 

#3  
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Quote:
With this definition the results I receive do not make any sense. I would expect a torque on the zaxis which is the axis of the cylinders. But the calculated torque form OpenFOAM on the zaxis 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? 

July 1, 2019, 04:50 

#4  
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Zander Meiring
Join Date: Jul 2018
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Quote:
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 

July 1, 2019, 09:29 

#5  
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Quote:
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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