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

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February 28, 2010, 08:33 
High torque coefficient Cm for Vertical Axis Wind Turbine (VAWT)

#1 
New Member
Join Date: Nov 2009
Posts: 22
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Hello,
I am modelling the 2D vertical axis wind turbine (VAWT). The turbulence model is kepsilon 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 URANS 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 

March 16, 2010, 17:34 

#2 
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benoit paillard
Join Date: Mar 2010
Posts: 62
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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.


March 19, 2010, 09:26 

#3 
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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 

March 22, 2010, 23:43 
Change fluent reference values

#4 
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Haris Hameed
Join Date: Oct 2009
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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 

April 1, 2010, 00:59 

#5  
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SHIVA
Join Date: Feb 2010
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Quote:
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 

June 11, 2010, 05:15 

#6 
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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 

February 21, 2014, 01:07 
Doubt

#7 
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dynamic
Join Date: Oct 2013
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In the Cm definition, what is A(area)?


March 25, 2014, 02:56 

#8 
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June 2, 2014, 02:25 
high value of Cm

#9  
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Aalisha
Join Date: Jan 2014
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Quote:
Aalisha 

January 9, 2015, 23:27 

#10 
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For a 2D case should I take the area = 1, and in this case what should be the depth.


March 27, 2017, 01:51 
CM coefficient

#11 
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nima seyfi
Join Date: Feb 2017
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hi
can anybody help me please what is A and L in equation of CM blow: cm=M/0.5*RHO*U^2*A*I my case is a vertical axis wind turbine archimedes spiral wind turbine blade 

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