# Need help on calculation of power coefficient for contra-rotating turbine

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 October 4, 2012, 22:01 Need help on calculation of power coefficient for contra-rotating turbine #1 New Member   Hoang Anh Dung Join Date: Jul 2010 Location: Korea Posts: 19 Rep Power: 9 Dear all, I am making a contra-rotating wind turbine using S822-S823 airfoil. The turbine is designed for 10kW scale (rotor radius is 3.58m, wind speed is 10m/s) This is my first work for 3D simulation of turbine, and I use BEM. My problem is regardless of whatever I set up, meshing... the power coefficient is always unreasonable (please refer to my document here): https://docs.google.com/file/d/0B3JU...JGNy1KTDA/edit So, please guide me how to validate the performance of the turbine, or introduce me any reference that have detailed thoery, study about contra-rotating turbine and its performance analysis. Thank you very much!

 October 5, 2012, 06:08 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,336 Rep Power: 110 This is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F In your case I see big separations off the blades. If this simulation is at the operating point of a well designed turbine you will not have separations. Something is generating massive separations in your simulation.

October 5, 2012, 10:33
#3
New Member

Hoang Anh Dung
Join Date: Jul 2010
Location: Korea
Posts: 19
Rep Power: 9
Quote:
 Originally Posted by ghorrocks This is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F In your case I see big separations off the blades. If this simulation is at the operating point of a well designed turbine you will not have separations. Something is generating massive separations in your simulation.
Thank you so much Mr, Ghorrocks. When you mention the "separation", you meant the flow pattern? This model I made from a software and has no relation to any actual turbine. It is kind of for study purpose.

By the way, I've checked my Cp calculation again. It's strangle that if I input the formula to CCL, calculated Cp is very low. But if I just extract the torque from blade and then calculate the Cp manually using the same formula, the result is reasonable (Cp = 0.2-0.4)

Anyway, because this is my very beginning of 3D model simulation and study (I used actuator disc method before), can you advice me for any reliable books, deep theory references about the contra-rotating turbine? So that I can create proper model?

 October 6, 2012, 07:48 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,336 Rep Power: 110 I do not know of any references for contra rotating turbines. Your application is quite specialised and outside my area of expertise.

October 6, 2012, 13:26
#5
New Member

Hoang Anh Dung
Join Date: Jul 2010
Location: Korea
Posts: 19
Rep Power: 9
Quote:
 Originally Posted by ghorrocks I do not know of any references for contra rotating turbines. Your application is quite specialised and outside my area of expertise.
Oh, it's OK. Thank you so much for your advice. You've been helping me a lot, Sir.

 October 7, 2012, 06:26 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,336 Rep Power: 110 But you should be able to find lots on normal single rotor turbines, and if you can model them accurately you are just about there. So I would concentrate on single rotor turbines initially.

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