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-   -   Calculated torque to low (http://www.cfd-online.com/Forums/cfx/79814-calculated-torque-low.html)

Adam S September 5, 2010 05:34

Calculated torque to low
 
Hi,
Im calculating forward curved centrifugal fans in steady state with SST. Grid is ICEM structured, y+ 2...30.
The throttle curves are in (very) good accordance with experimental data (deviation < 5%). But calculated torque (needed for calculating efficiency) ist ~ 25% to low.

Has someone an idea why? What does the torque function (torque_X@...) exactly do? How ist the mathematical or numerical equation? Is there a "changeable" coefficient??

Greetz
Adam

ghorrocks September 5, 2010 20:17

http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

Adam S September 6, 2010 03:00

Thanks, but this isnt very helpful.

I checked different models, grids...and Im advanced in CFD.

So:
Measured throttle curves (with a chamber test rig) as well as measured velocity fields (with PIV) are in (very) good accordance with the simulations...BUT NOT the torque?!

Anyone an idea?

ghorrocks September 6, 2010 07:34

Quote:

Im advanced in CFD.
Then you would know that unless the basics are covered there is no point proceeding - you made no mention of that in your initial question.

I do not have any answers for you, but this exact question has been asked a few times. Makes me suspicious that there is something wrong in the software in evaluating torques. But I have no idea what.


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