Dynamic Blade Response Calculations Using Improved Aerodynamic Modeling

Two independently developed finite difference aerodynamic codes and finite element comprehensive rotor dynamic codes are coupled loosely to predict structural bending and aerodynamic loads on an advanced geometry rotor blade of the SA349/2 Gazzle helicopter. Predicted results are correlated with flight test data for three level flight conditions at speeds of 200km/h, 260km/h and 290km/h. The dynamic code calculates nonlTnear coupled elastic flap-lag-torsion response of a t rimmed rotor using a finite element procedure in space and time coordinates. Then, using the calculated angle of attack distribution from the dynamic code, the finite difference code predicts the detailed flow field on the blade including transonic shock formation on the advancing blade tips. Correlation between two analytical codes show substantial differences because of threedimensional effects. Correlation between predicted and measured results are inconclusive; however three-dimensional effects in the analysis did not substantially improve the correlation with experimental results in the limited investigated cases.