GENERAL TIME-DOMAIN UNSTEADY AERODYNAMICS OF ROTORS

A GENERAL THEORY FOR THE TIME-DOMAIN UNSTEADY AERODYNAMICS OF HELICOPTER ROTORS WILL BE DEVELOPED. THE WAKE THEORY GIVES A LINEARIZED RELATION BETWEEN THE DOWNWASH AND THE WING BOUND CIRCULATION, IN TERMS OF THE IMPULSE RESPONSE OBTAINED DIRECTLY IN THE TIME DOMAIN. THIS APPROACH MAKES IT POSSIBLE TO TREAT GENERAL WAKE CONFIGURATIONS. THE IMPULSE RESPONSE CAN BE RELATED TO THE INFLUENCE COEFFICIENTS OF A TRIM WAKE MODEL, ALLOWING DIRECT USE OF SOPHISTICATED WAKE MODELS DEVELOPED FOR THE TRIM LOADING PROBLEM. THE DEVELOPMENT WILL ENCOMPASS IMPLEMENTATION OF THE WAKE THEORY, INCLUDING MODEL ORDER REDUCTION AND IDENTIFICATION OF A DIFFERENTIAL EQUATION REPRESENTATION. THE RESULT OF THIS ACTIVITY WOULD BE AN APPROACH FOR ANALYZING AEROELASTIC BEHAVIOR WHILE RETAINING THE IMPORTANT INFLUENCE OF THE COMPLICATED WAKE CONFIGURATION.