Research On Aerodynamic Characteristic Of High-speed Helicopter Rigid Rotor At High Advance Ratios

There are great challenges to investigate the rotor flow mechanism and to analyze the rotor aerodynamic characteristics because of the complex flow features of high-speed helicopter.In the flow field of the rotor,for example,there may be transonic compressible flow over the advancing blade tip,low speed incompressible flow over the retreating blade at the same time,accompanied by some special flow phenomena of the reverse flows,radial flows,shock waves and blade-vortex interactions,etc.The flow field and aerodynamic characteristics of high-speed helicopter rigid rotor under different conditions are numerically simulated with unsteady RANS/DES method.Special flow phenomena and mechanism of high-speed helicopter rotor are analyzed in detail.The research work of the thesis mainly includes the following sections:Based on k-? and SST k-? turbulence models,the aerodynamic characteristics of a twodimensional airfoil of the blade section are simulated upon structured grid.The proper turbulence model for two-dimensional airfoil is chosen.The airfoil aerodynamic characteristics of the high-speed rigid rotor blade are analyzed based on the numerical results.In order to validate the reliability of computation method for helicopter rotor,the aerodynamic performance of AIAA Caradonna-Tung(C-T)helicopter rotor is simulated using unsteady RANS method.From the calculated results from S-A and SST k-? turbulence model,the suitability of the turbulence models and the reliability of the numerical method are investigated.Using the numerical simulation methods on the application of sliding mesh technique,the highspeed helicopter rigid rotor aerodynamic characteristics are calculated in the conditions of low and high advanced ratios,respectively.From the results at the two advanced ratios,the features of inverse flow around the retreating blade at high advanced ratio are mainly studied with comparison of the threedimensional and two-dimensional results.Compared to the DES method,RANS method presented is more efficient.Furthermore,this paper employs the density-based RANS method to simulate the transonic flow.Under the high advance ratio,shock wave occurs in the region of the blade,together with the phenomenon of boundary layer separation induced by shock wave.