Research On Drag Reduction Methods Of Helicopter Fuselage Under Interaction Of Rotor Flowfield

It is known that the aerodynamic shape of helicopter has great influences on its drag during flight,and the drag of fuselage is the main component of total drag of the whole helicopter.Therefore,this thesis conducts investigations on drag reduction methods of helicopter fuselage by aerodynamic shape parametric analysis and design,active and passive flow control methods such as steady blowing jet and vortex generator.In Chapter 1,as research background,investigations on drag reduction methods of helicopter fuselage worldwide are introduced fistly,and the research approach and procedure of this thesis are illustrated.In Chapter 2,the unstructured gird generation methods are developed by using hybrid body-fitted grid around rotor/fuselage.Besides,the CFD methods are established based upon the body-fitted grid method of fuselage and momentum source model of rotor to analyse the flowfield and aerodynamic characteristics for helicopter rotor/fuselage interaction.Then,the pressure distribution of ROBIN fuselage and dynamic pressure of a model rotor are calculated respectively,and the numerical results are in good agreement with the test data,which indicates the effectiveness of established CFD method.It provide a methodological foundation for further research on drag reduction methods of helicopter fuselage in this paperIn Chapter 3,through the preliminary analyses of aerodynamic shape influences on aerodyne mic characteristics of the model fuselage,the nose and transition section of fuselage are taken as research objects.For the nose part,the curvature radius of the front end of symmetrical section of fuselage,the length of nose and height of fuselage head apex are selected as variable parameters.For the transition section,the upswept angle and shape of transition section are set as analytical parameters.On these basis,the investigation of aerodynamic shape influences on helicopter fuselage drag reduction are conducted.In Chapter 4,vortex generators are set on the transition section,and the effects of vortex generators on drag reduction of helicopter fuselage are analyzed,and the influence mechanisms of vortex generator on fuselage aerodynamic characteristics are obtained by analysis on cross section vorticity distribution,pressure distribution of fuselage with and without vortex generator.By changing the installation position and angle of the vortex generator,the parameter analysis of its influences on the aerodynamic drag of fuselage are carried out.In Chapter 5,active blowing method is applied on the transition section to investigate the effects of active flow control on fuselage drag reduction.Three-dimensional model is simplified to a fuselage symmetrical section,and jet orefice position and jet velocity are selected as variable parameters to explore the role of blowing control in changing fuselage aerodynamic characteristics,which reveals the law of influence of steady blowing method on drag characteristics on the fuselage.In Chapter 6,the research contents and innovations of this paper are summarized,and the prospects of further research are put forward.