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## Main Question or Discussion Point

I need a reference for the exact solution for lift at high angles of attack, when an airfoil behaves like a flat plate. I am pretty sure the theoretical solution is CL = 2 sin(α)*cos(α) based on two papers I read on lift through 180 degrees angle of attack, but I cant find in any of my books where this is stated. This would also be consistent with the small angle approximation for flat plate lift, as the cosine term becomes 1 and the sin term equals α.

See the Sandia publication:

Aerodynamic Characteristics of Seven Symmetrical Airfoil Sections Through 180-Degree Angle of Attack for Use in Aerodynamic Analysis of Vertical Axis Wind Turbines"

See the Sandia publication:

Aerodynamic Characteristics of Seven Symmetrical Airfoil Sections Through 180-Degree Angle of Attack for Use in Aerodynamic Analysis of Vertical Axis Wind Turbines"