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turbine force_y vs dP * area

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Old   May 3, 2019, 00:02
Default turbine force_y vs dP * area
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Svetlana Tkachenko
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In ansys 19.2 the built in function

force_y()@turbine Default

and a similar manual calculation (here 'top' and 'bottom' are circular surfaces below and above the turbine)

(areaAve(Pressure)@bottom - areaAve(Pressure)@top ) * area()@top

give different results 2-3 times, inconsistently in different cases as it is not a linear relationship. Is this a known issue? How do I troubleshoot this? Can attach a small test case if anyone is interested.
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Old   May 3, 2019, 02:26
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Glenn Horrocks
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your areaAve functions just average the pressure over the surface, they do not take into account direction. The force_y function only gets the force in the y direction. So your function is not working out the force in the y direction.
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Old   May 3, 2019, 02:31
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Svetlana Tkachenko
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In this case my calculations should give larger values than CFX's force_y,
because they do not multiply by cos (direction angle) in each point.
However in my case the "dP * area" calculation gives results which are 0.3 to 0.7 of the force_y value predicted by CFX.
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Old   May 3, 2019, 02:34
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If you want us to help you, you are going to have to post an image of what you are analysing, a description of what the top and bottom surfaces are and a plot of the pressure distribution.
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lift and drag, post procesing, propeller, turbine

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