Advancement of the SNUF Blade Design through Flap Configuration Parametric Study and Optimization Framework

This paper focused on improving a small-scaled prototype of a helicopter rotor blade with a flap-driving mechanism termed as the Seoul National University Flap (SNUF). The design of SNUF included realizing vibratory load reduction. First, a multibody structural dynamics analysis was performed to determine the influence of the flap dimension and location within the rotor blade with respect to hub vibratory load reduction. This process selected a specific blade configuration that maximized vibration reduction capability. Then, a numerical optimization technique was applied to improve the cross-sectional design of the SNUF blade. The design optimization procedure established improved blade sectional design with desired first torsional frequency and reduced blade weight while satisfying sufficient structural integrity. Three-dimensional nonlinear static structural analysis was also performed for the optimized SNUF design. Von Mises stress distribution on the blade and components were predicted by considering external aerodynamic loads, centrifugal loads due to rotation, and contact among the internal components. Future studies will include fabricating the prototype blade based on the optimized design and performing a whirl tower test.