Research On Helicopter Rotor Blade-vortex Interaction Noise Based On Coupling CFD/Viscous Vortex Particle Method

Helicopter Rotor Blade-Vortex Interaction Noise is a challenging subject in the field of Helicopter Technology.A high resolution hybrid method with combined Navier-Stokes equation,viscous wake model and FW-H(Ffowcs Williams-Hawkings)equation is developed for BVI airload and noise,and the corresponding code is established.The aerodynamic and acoustic analysis of blade-vortex interaction is investigated,and the mechanisms for the impacts of four flight parameters(i.e.tip-pathplane angle,thrust coefficient,tip Mach number,advance ratio)on BVI noise have been further discussed.Meanwhile,the effects of three blade tips on BVI noise are simulated.The major research work is as follows:The research background and the purpose of this thesis are expatiated in first chapter,and the domestic and international research status of hybrid CFD method and the rotor blade-vortex interaction is generalized.On these basis,through analyzing the interaction flowfield characteristics of the rotor blade-vortex,then,the numerical method used in this thesis is also presented.A high-resolution method coupling CFD and viscous vortex method is established for the study of rotor wake simulation and impulsive airload calculation.By this method,several hover and forward flight cases are performed.The validity of the method on the rotor blade-vortex flowfield aerodynamic characteristics is verified by comparing the calculated results with the available experimental values.In third chapter,the generalized Farassat formulation based on Ffowcs Williams-Hawkings(FWH)Equation is applied for noise prediction.A high-resolution computational model for analyzing helicopter aeroacoustics is established.The validity of the comprehensive computational model on the rotor blade-vortex noise prediction is verified by comparing the calculated sound pressure signals with the available experimental values.Then,the aerodynamic and acoustic characteristics of blade-vortex interaction for AH-1/OLS rotor are studied deeply.The mechanisms for the impacts of four flight parameters(i.e.tip-path-plane angle,thrust coefficient,tip Mach number,advance ratio)on blade-vortex interaction noise characteristics are further discussed.And some meaningful conclusions for rotor BVI noise reduction are drawn.The noise calculations of the rotor with such tips as anhedral,forward sweep and backward sweep shapes are performed based on that blade-vortex interaction noise can be reduced by the increase in miss-distance and interaction angle.And the influence of their changing interaction types on the blade-vortex interaction noise characteristics are investigated,which can provide reference for the design of helicopter rotor.At last,the work of the thesis is summarized,and the main features and innovations of this thesis are also pointed out.The future research work is further prospected.