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Moment around and axis or on a plane

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Old   June 24, 2010, 15:48
Default Moment around and axis or on a plane
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Hello everyone,
I'm trying to have the air tumble in a pipe calculated.
I placed a cylindrical coordinate system in the centre of the pipe and need the moment/torque around the Z axis. Through the X-Y planes of the coordinate system I also placed a plane (not shown on the pic). Then I tried to have the generate torque calculated on the plane which was unsuccessful. I then tried another approach. I have created a report --> moment with the parts chosen "out". Here the coordinate system laboratory is chosen which I cant change to cylindrical coordinate system which would probably give me the torque.

Can anyone help me to get use of on of the approaches I have taken please.

Thank you very much.
regards, CS



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Old   June 24, 2010, 16:35
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Vinicius Girardi
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Just copy the Z direction of your cylindrical coordinate system in the "Axis" field and set the origin in a Moment Report... Go to the Tools->Coordinate system and select your Coord. to get this information...
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Old   June 25, 2010, 15:24
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Thank you for your reply. I have tried that and I get an result. Is there any way to cross check the result? The thing is I only get a torque if I chose an axis which is not on the centreline of the pipe. Currently Im having Z lying on the centreline. When I set in the report --> moment --> 0.0, 0.0, 1.0, it shows me 0.000Nm. When I switch to 1.0, 0.0, 0.0 I get some torque.

Thanks again
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Old   June 25, 2010, 16:43
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Does your pipe geometry suggest you should be expecting any tumbling? It might help to plot in-plane (XY) velocities to see what's going on ...
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Old   June 25, 2010, 16:51
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Yes it does. See the pic http://www.casa-tec.com/Bild1.jpg.
I applied streamlines to see what is happening. As said earlier, around x and y it gives me a moment, not around Z which it should.
I have been struggling with this for quite some time. I could upload the file on a server if anyone would be free to check the setting.

regards, CS
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Old   June 25, 2010, 18:42
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Are you running an inviscid simulation?
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Old   June 26, 2010, 07:46
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Hi sure what is meant by that.
I'm running the "turbulent visocisty ratio" at 10, "turbulence intensity" at 0.05 a "No-Slip" wall conditions. I have the measured mass flow data and the CFD prediction is closer to the testing results when "No-Slip" is set. Pressure applied at the outlet is -2500Pa.
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Old   June 26, 2010, 08:41
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Upload the file and I can take a look...
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Old   June 26, 2010, 08:51
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Thats great. Please send me your email on c.sansanelli@hotmail.com and Ill give you the link.

Thanks again.
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