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High torque coefficient Cm for Vertical Axis Wind Turbine (VAWT)

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Old   February 28, 2010, 08:33
Default High torque coefficient Cm for Vertical Axis Wind Turbine (VAWT)
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Hello,
I am modelling the 2D vertical axis wind turbine (VAWT). The turbulence model is k-epsilon with std wall function. I simulate 4 angular velocities: 5, 10, 15 and 20 rad/s. Wind velocity is 11 m/s. Model is using U-RANS with sliding mesh.
Problem is that I obtain excessively high torque calculated from the Cm (4 to 5 times larger than it should be). Cm is obtained from Fluent, torque calculated with the Cm definition(Cm=T/(0.5 x rho x v^2 x A x R).
Time step: tried both time steps corresponding to 1 degree and 1/8th degree. Results perfectly match so the 1deg step is fine enough.
I would be very grateful to the one who can spot if and/or where I am making a mistake and can contribute to making this simulation happen the best way.

Thanks
All the best
TonyMac

Last edited by tony00; March 17, 2010 at 06:25. Reason: wrote seconds instead of degrees to define the angular step increment
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Old   March 16, 2010, 17:34
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that might sound - and actually be - silly but check that you actually divided the torque by the appropriate value, to get a reduced coefficient instead of a Nm torque. That happened here not too long ago.
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Old   March 19, 2010, 09:26
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Hello Benoit,
all solved and getting pretty good results now. As you suggested it was indeed a problem with the constants entered in report-> reference values.
Thanks
Tony
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Old   March 22, 2010, 23:43
Default Change fluent reference values
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Haris Hameed
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Change fluent reference values

compute velocity form inlet
and change reference area to swept area
your cm will change
hope this work
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Old   April 1, 2010, 00:59
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Quote:
Originally Posted by tony00 View Post
Hello,
I am modelling the 2D vertical axis wind turbine (VAWT). The turbulence model is k-epsilon with std wall function. I simulate 4 angular velocities: 5, 10, 15 and 20 rad/s. Wind velocity is 11 m/s. Model is using U-RANS with sliding mesh.
Problem is that I obtain excessively high torque calculated from the Cm (4 to 5 times larger than it should be). Cm is obtained from Fluent, torque calculated with the Cm definition(Cm=T/(0.5 x rho x v^2 x A x R).
Time step: tried both time steps corresponding to 1 degree and 1/8th degree. Results perfectly match so the 1deg step is fine enough.
I would be very grateful to the one who can spot if and/or where I am making a mistake and can contribute to making this simulation happen the best way.

Thanks
All the best
TonyMac
Dear Tony,

I m also facing the same problem. still i m not able to reasolve the fluent case. please give some idea to predict the Torgue and Co efficient of the performance (Cp) of the wind Turbine.

With Regards

S.SIVAKUMAR
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Old   June 11, 2010, 05:15
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Hi tony, maybe I'm affected by the same problem you solved.
I hope you will share with me your solution.

Thanks
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Old   February 21, 2014, 01:07
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dynamic
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In the Cm definition, what is A(area)?
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Old   March 25, 2014, 02:56
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behzad shahizare
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Quote:
Originally Posted by harishameed33 View Post
Change fluent reference values

compute velocity form inlet
and change reference area to swept area
your cm will change
hope this work
what is the swept area in 2D model for vawt ?
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Old   June 2, 2014, 02:25
Default high value of Cm
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Aalisha
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Quote:
Originally Posted by skshivas View Post
Dear Tony,

I m also facing the same problem. still i m not able to reasolve the fluent case. please give some idea to predict the Torgue and Co efficient of the performance (Cp) of the wind Turbine.

With Regards

S.SIVAKUMAR
Hey I am also facing the same problem. I am trying to change the values for the references. IF you can share how you have solved this problem? Thanks.

-Aalisha
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Old   January 9, 2015, 23:27
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For a 2D case should I take the area = 1, and in this case what should be the depth.
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