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Negative moment while simulating wind turbine

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Old   October 19, 2016, 06:59
Default Negative moment while simulating wind turbine
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Angelika
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Hi everyone,

I'm simulating rotating wind turbine and my aim is to find maximum power.

Specification:
-rated power 6,150 kW,
-rated wind speed (inlet) 14 m/s,
-rated rotor speed 12,1 rpm (rigid body motion).

I'm getting good thrust value (about 4300 kN), but torque value is negative (about -30 MNm) what is non acceptable, it should be about 5 MNm.

I have tried many things (refine mesh, size domain etc).

I think the problem may lie in wrong defining moment report.
What should be my coordinate system for moment report? Local coordinate system which I have placed in the center of rotating plane?

Please help me.

domain.jpg

Torque.jpg

turbina wiatrowa 1 - nowy kat 1_Q Monitor Plot.png

Thrust.jpg

turbina wiatrowa 1 - nowy kat 1_Residuals.jpg
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Old   October 19, 2016, 09:08
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Matt
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What does your residual plot look like?
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Old   October 19, 2016, 09:24
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Angelika
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The first one with k-epsilon turbulence model, second with k-omega SST.
On the second one, there is a change in values of residuals in 5s (one rotation). And the second one simulation has no tower, only rotor.

turbina wiatrowa 1 - nowy kat 1_Residuals.jpg

turbina wiatrowa 1 - unsteady - nowy kat 3 v=14 I=18_Residuals.jpg
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Old   October 19, 2016, 09:26
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Matt
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Why are you plotting residuals against physical time?

Can you share a screen shot of your physics continua?
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Old   October 19, 2016, 09:33
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Angelika
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This is how it looks like. I have 5 mln cells in rotating region and 1,8 mln in stationary region.


Time step 0,013(8) s, because 12 rpm, so takes 5 s to complete one full revolution. 5s/360 deg = 0,013(8) s.
Don't know where is the problem, I'm beginner with cfd..

resiudua.jpg
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