Aerodynamic Interaction Characteristics For Side-by-Side Rotor Helicopters By Using Free Wake Method

In this thesis, the aerodynamic interaction characteristics for side-by-side rotorhelicopters has been investigated based on a relaxation free wake analysis. The majorresearch work can be summarized as follows:First, for the rotor free wake model, the effect factors of the vortex model wereanalyzed comprehensively and an expression of vortex core radius was given by theconsideration of vortex diffusion and filament stretching. The pseudo-implicitpredictor-corrector based relaxation free wake difference method has been established,including the boundary conditions, the initial prescribed wake geometry and theconvergence criterion.Second, based on the free wake model, a computational method has been developedfor the calculation and analysis of the rotor wake and aerodynamic characteristics forsingle rotor in steady flight, combining with blade aerodynamics model, universal-hingedrotor blade flap equations and single rotor trim model. Meanwhile, a computationalmethod has been developed for the calculation and analysis of the aerodynamicinteraction characteristics for side-by-side rotor, coupling with a whole helicopter trimmodel deduced from the dynamics equations and the induced velocity contribution fromthe other rotor.Third, the wake geometry and induced velocity in the flow field of single rotor andside-by-side rotors were calculated and the effect of different distance between rotors androtation direction was compared and analyzed.Fourth, based on the free wake model of the side-by-side rotor, a method for thecalculation on aerodynamic interaction characteristics of rotor/wing has been developed,coupling with wing panel model and a close vortex-surface interaction model. Then somepreliminary calculation and analysis of rotor/wing interaction on hovering state wereconducted and some reference conclusions were obtained.