Reynolds for a rotary wing/blade

mohammad · December 13, 2011, 00:07

Hi dear All,

I want to know that when we are working with a wind turbine with a very long blade, for "Lift coefficient_ AOA" calculation which Reynolds number must be worked with.
I am thinking because in different radial positiions the velocity is changing according to the "Local R".

For example:
-Please consider the chorld length is constant;
-Velocity of wind is 10 m/s , and think R= 5 m , =7.5 Rad/s
So, the Relative Velocity at the tip = [ (10)^2+(5*7.5)^2 ]^ 0.5 ~ 39 m/s and then the Reynolds at the TIP will be 4 times the Reynold of free stream.
Now when we want to check the values of Cl-AOA , which Reynolds number we must consider? I think I must work with local Re and for different radial positions I must calculate Re number and work with that local Re.

Would you please tell me the answer for this question

ghorrocks · December 13, 2011, 17:12

Your comment about local Re number sounds about right.

December 13, 2011, 00:07	Reynolds for a rotary wing/blade	#1
mohammad Senior Member mohammad Join Date: Dec 2010 Location: UK Posts: 245 Rep Power: 16	Hi dear All, I want to know that when we are working with a wind turbine with a very long blade, for "Lift coefficient_ AOA" calculation which Reynolds number must be worked with. I am thinking because in different radial positiions the velocity is changing according to the "Local R". For example: -Please consider the chorld length is constant; -Velocity of wind is 10 m/s , and think R= 5 m , =7.5 Rad/s So, the Relative Velocity at the tip = [ (10)^2+(5*7.5)^2 ]^ 0.5 ~ 39 m/s and then the Reynolds at the TIP will be 4 times the Reynold of free stream. Now when we want to check the values of Cl-AOA , which Reynolds number we must consider? I think I must work with local Re and for different radial positions I must calculate Re number and work with that local Re. Would you please tell me the answer for this question

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December 13, 2011, 17:12		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Your comment about local Re number sounds about right.