How to average the torque coefficient for vertical axis wind turbine?
 

Hello,

I 've carried out a simulation in Ansys Fluent of the flow around a vertical axis wind turbine. I got the Cm (torque coefficient) as a function of time, hence azimuthal angle. I have used the rotor radius as the reference length, the swept area = diameter * height. In my case height = 1 because it's a 2D simulation.

Since the Cm coefficient is not constant over one rotor revolution, how to average it? because when I simply average:



And The average power:


(where λ is the tip speed ratio).

The result is a very low Cp value. I have tried to run the simulation for several Tip speed ratios, but still, the Cp value is very low, less than 5%. (Unfortunately, I don't have experimental data to compare with).

I wonder if there is something wrong with the averaging of Cm. In VAWT nomenclature, how is the Cm value averaged?

I hope someone can give me insight.

Thank you in advance

i have made some simulation like this, and find the same problem, in fluent , i can not get the real torque , maybe we should change the reference value

Hi,


I would simply write out to a file the total torque instead of the coefficient (given that it is not clear what it is doing). Then you can average as many timestep values as you want.


Regards