Rotor aerodynamic characteristics analysis and helicopter trimming

The UH-60A rotor aerodynamic model suited to accurately predict the detail of rotor aerodynamic characteristics and helicopter trimming was established. The momentum element theory and the proposed rotor aerodynamic model were respectively embedded into the trimming procedure and applied to trim UH-60A helicopter, the comparison among the computational results, test data and the referenced data indicated that the model was effective and more precise. On this basis, the distributions of induced velocity, angle of attack and lift-drag ratio on the rotor disk at various advance ratios were analyzed. The results show that with the increase of the advance ratios, the induced velocity distribution on rotor disk is more asymmetric and the rotor sideward incline is intensified. At high advance ratio, the flow separation region on the retreating blade side becomes large, the angle of attack distribution exhibits rapid change on the boundary of the reverse flow region. Due to effects of air compressibility and the reverse flow region, at high advance ratio, the lift to drag ratio is relatively low in the tip area of the advancing blade and the reverse flow region.