This cannot be the case in practice as it is well known that such a sharp leading edge and midchord corner both lead to premature stall and large turbulent losses because of separation. This is not the case, especially for angles of attack near stall, and one must use empirical data for the aerodynamic coefficients to determine the force. Thus it is clear that the optimum twist has not yet been theoretically determined. To proceed, the efficiency h and the windmill blade shape must be related. It should be noted that V is the wind speed at the plane of the windmill.
V is less than the wind speed far ahead of the windmill.
This is true if one ignores the rotational energy in the slipstream downstream of the windmill and any losses due to turbulence of friction. V, f is a known function of r from Eq. 5. It is the blade angle b that must be known in order to design and construct a windmill blade. The drag coefficient C D increases quadratically with a for small a . As a increases further, so does C D , although not as a 2 .