Ahmed Kabir,

My point of view is that

1) Span-wise tapering will not affect the angle of attack.

2) Span-wise twisting will create different angle of attacks along the span of the blade. However, you should have known how much twisting angle (rotation angle function) along the span with respect to the blade base or blade tip since you created the geometry.

3) Then, you should set the blade base angle of attack=0 or blade tip angle of attack=0 to the flow in simulation. So, it will make you easy to know angle of attack at different locations along the span of blade.

Hope my answer is match with your question.

Hi, Because of the induction, you cann't decide the angle of attack directly for the field velocity. Try to reference "Determination of Angle of Attack for Rotating Blades", by Wen Zhong Shen, DTU. Good luck!

Hi thanks Aung, Daniel and Lee. 

I'm now tryint to use Prof Wen Zhong Shen work

Hi, all my colleagues,

I apologize for my ineffective idea. Now, I have seen 3D flow field effect on angle of attack and a technique to mention pratical angle of attack. Thank you all.

By using the boundary conditions, when fluid strikes on the blade of turbine. Angle of attack gives only direction.