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Old   November 9, 2013, 09:35
Default Torque or moment?
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abrahamgx
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I am now calculating a HAWT in CFX. I monitor the torque_y()@blade and normal moment on blade(y) in solver manager, where y is the axis. I find that there is difference between them as in the figure.
How does it happen?Which one is the real shaft torque of HAWT?

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Last edited by abrahamgx; November 10, 2013 at 04:14. Reason: add figure
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Old   November 10, 2013, 05:41
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Glenn Horrocks
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I am not certain but I suspect normal moment is the pressure force integrated over the surface. It does not include viscous forces. torque_y includes both pressure and viscous forces.
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Old   November 14, 2013, 10:21
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Quote:
Originally Posted by ghorrocks View Post
I am not certain but I suspect normal moment is the pressure force integrated over the surface. It does not include viscous forces. torque_y includes both pressure and viscous forces.
I wonder which one should I use? It seems that the normal moment which does not include the viscous forces is more consistent with the experimental results.

Last edited by abrahamgx; November 20, 2013 at 04:59.
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Old   November 14, 2013, 10:33
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Quote:
Originally Posted by abrahamgx View Post
I wander which one should I use? It seems that the normal moment which does not include the viscous forces is more consistent with the experimental results.
Your experimental results probably include the viscous forces, so you should use torque_y for comparison if Glenn is right.
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Old   November 18, 2013, 12:19
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Originally Posted by murx View Post
Your experimental results probably include the viscous forces, so you should use torque_y for comparison if Glenn is right.
OK. Thank you !
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Old   November 20, 2013, 17:39
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From my experience, CFD Post adds up the normal and tangential moments to get the total moment. The normal component represents the pressure contribution and the tangential component the viscous contribution to the total moment. Specifying an output monitor in CFD Pre as "torqure_y()@location" will output the total moment comprised of both the pressure and viscous contributions.
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