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Average torque in transient vawt simulation

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Old   March 29, 2018, 06:53
Default Average torque in transient vawt simulation
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Patryk
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Dear users,
I'm simulating flow around 3 blades, vertical axis wind turbine (2D) for my master thesis using sliding mesh method. I have done 200 timesteps with 0,005s time step size which give 5s of real time simulation. My results looks really fine, but I need to know average torque over rotation axis (Z) on all blades of the turbine in that 5 seconds and I don't know how to calculate it. Value of torque is different in every timestep. Is it possible to export torque from all timesteps to excel and then calculate average of it ?
I tried to plot Momentum during the simulation (Solution -> Report Definitions -> Force Report -> Moment), and than select blades and Z axis, but values on that plot is always less than 1, so it looks like Cm, not really torque. When i calculate torque using CFD-Post calculator the values at any timestep looks fine. Thanks for help. Sorry for my english..
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Old   March 30, 2018, 08:33
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Please help. I'm stuck here because I can't compare my cases
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Old   March 31, 2018, 12:04
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Ok, problem solved.. if anybody else facing it, there is a solution :
You need to print a Cm plot (like I wrote in 1st post) and write this values to a file. Then export this file to excel and count torque using this formula for every timestep :

Cm = \frac{M}{\frac{1}{2}\rho v^{2}AL}

where M - torque, V - stream velocity, A - Area, L - lenght (rho, A, L in 'reference Value tab')
Finally, just do the average of all torque values.
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