How to get the distance from an unknown point and an axis?

redline · July 21, 2015, 06:55

Hi there. Im pretty new here but just read much the last couples of months, now I have a prob.

I have a domain with a blade of a Windturbine. I want to calculate the torque which is the result of the force at the bladesurface and the distance to the pitch axis. For the distance (actually the moment arm), I need the point where the integral pressure stresses the blade, so how can I get this point to use it in an expression?

If I could find this anywhere in the Forum, you guys maybe give me a hint and apologize.

Thanks!

ghorrocks · July 21, 2015, 07:24

Have a look at the equations which define centre of pressure. CFX has a wide range of integration functions in the CEL, so you should be able to adapt the CEL to the equation you require.

redline · July 22, 2015, 11:18

Alright, thanks mate, I think I'll find a solution, maybe I tried it to complicated and just have to use the torque functions in the right way.

singer1812 · July 22, 2015, 13:04

Yes, why are you doing it that way? Put a coord system at the point of blade rotation and get the torques around it.

redline · July 23, 2015, 10:21

Got it, sorry :/ ... aaaaand: THX!

July 21, 2015, 06:55	How to get the distance from an unknown point and an axis?	#1
redline New Member Felix Join Date: Apr 2015 Location: GER Posts: 9 Rep Power: 11	Hi there. Im pretty new here but just read much the last couples of months, now I have a prob. I have a domain with a blade of a Windturbine. I want to calculate the torque which is the result of the force at the bladesurface and the distance to the pitch axis. For the distance (actually the moment arm), I need the point where the integral pressure stresses the blade, so how can I get this point to use it in an expression? If I could find this anywhere in the Forum, you guys maybe give me a hint and apologize. Thanks!

July 21, 2015, 07:24		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Have a look at the equations which define centre of pressure. CFX has a wide range of integration functions in the CEL, so you should be able to adapt the CEL to the equation you require.

July 22, 2015, 11:18		#3
redline New Member Felix Join Date: Apr 2015 Location: GER Posts: 9 Rep Power: 11	Alright, thanks mate, I think I'll find a solution, maybe I tried it to complicated and just have to use the torque functions in the right way.

July 22, 2015, 13:04		#4
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	Yes, why are you doing it that way? Put a coord system at the point of blade rotation and get the torques around it.

July 23, 2015, 10:21		#5
redline New Member Felix Join Date: Apr 2015 Location: GER Posts: 9 Rep Power: 11	Got it, sorry :/ ... aaaaand: THX!