A CONSISTENT APPROACH FOR MODELING THE AERODYNAMICS OF SELF-GENERATEDROTOR BLADE-VORTEX INTERACTIONS

A numerical procedure has been developed far the prediction of the thr ee-dimensional unsteady aerodynamic response of a helicopter rotor dur ing self-generated blade-vortex interactions (BVI), Pertinent vortex w ake parameters (e.g,, spatial and temporal trajectories, strengths) we re computed using the lifting-line rotor/helicopter trim code CAMRAD/J A, In this code, tracking of the near-field BVI vortex-wake segments w as accomplished using a new ''box'' technique which involves tracking all tip vortex elements tying inside a user specified box-like domain which encloses the rotor, Unsteady blade surface pressures were then p redicted using a modified version (designated FPRBVI) of the full pote ntial rotor code FPR (v2,1), Two approaches were used to model vortex- induced effects in the FPRBVI solver; the efficient surface or ''trans piration'' approach, and the more comprehensive split potential approa ch, The numerical procedure was used to predict the unsteady aerodynam ic response of the one-seventh scale two-bladed AH-IG OLS model rotor and a United Technologies Corporation 17.5% scale four-bladed model ro tor during self-generated BVI, Accuracy of the numerical procedure was assessed using wind tunnel data.