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A semi-empirical method for determining aerodynamic load distribution along the helicopter blade span
Mirko Koziæ
A semi-empirical method for determining aerodynamic load distribution along the helicopter blade span in translational flight is presented. The method is based on the classical approach stating that the flow around the blade section is two-dimensional and quasisteady. The vortex wake effects and compressibility are approximated with a constant induced velocity in the plane perpendicular to the no-feathering axis and the Prandtl-Glauert rule, respectively. The modification involves the effect of blade flapping by an additional term in the local resultant velocity and the blade twist along the span. The presented method was applied in determining the Mi-8 helicopter blade load, and the obtained results were compared with those from the FLUENT 6.1. code that solves the averaged Navier-Stokes equations. The noticed differences at the tip of the blade occur due to the vortex wake and transonic flow nonlinear effects.
Key words: aerodynamics, helicopter, semi-empirical methods, computational fluid dynamics. |