ANALYSIS REFINEMENTS FOR PREDICTION OF ROTOR VIBRATORY LOADS IN HIGH-SPEED FORWARD FLIGHT

A 3-dimensional Navier-Stokes Computational Fluid Dynamic analysis is coupled with a Comprehensive Analysis to improve prediction of rotor vibratory loads. The focus is on high-speed level flight. Measured normal force, chord force, pitching moment and damper force from the UH-60A Air loads Program are used to predict and validate the structural model of the Comprehensive Analysis. Once validated, a 3-dimensional CFD model is loosely coupled with the comprehensive analysis to obtain an improved aeroelastic solution from first principles. Predicted pitching moments and torsion loads show significant improvement compared to an unsteady table look-up based lifting-line comprehensive analysis. Predicted vibratory normal force (3-10/rev) show significant to moderate improvements at all blade stations. Improvements in 1-3/rev normal force are not significant enough to improve predicted flap bending moments. The advancing blade vibratory normal force impulse occurring at 67.5% R and 77.5% R is important for accurate flap bending moment waveform.