Research On Numerical Simulation And Distribution Of High-speed Trains'Aerodynamic Noise

This paper focuses on the near-wall surfaces and roadside aerodynamic noise characteristics of high-speed trains,the flow field and aerodynamic noise of the high-speed trains are simulated numerically with Fluent software based on the relevant hydrodynamics and acoustics theories,and the aerodynamic noise database of high-speed trains is established to scientifically manage and query the aerodynamic noise data.The main research work is as follows:(1)The computational fluid dynamics model for aerodynamic noise calculation of CRH3 high-speed trains is established in this paper,the model includes the head vehicle,the middle vehicle and the tail vehicle,a pantograph and six bogies,the model also includes streamlined curved surfaces of the head and tail of the train,as well as key components such as windshield,air-conditioning domes.There are 15.7 million fluid elements in the model,the surface of train' s body,bogie,pantograph and other structures are divided into 930 thousand triangular elements.The minimum size of the element is 5 mm.(2)Based on Fluent software,the steady-state solutions of high-speed trains' external flow field at 200 km/h,250 km/h,300 km/h and 350 km/h speeds are calculated by using of k-s turbulence model.The results show that the static pressure is greater in places where the curvature of train surface varies greatly,such as bogie,nose cone,etc.Where the turbulent motion is strong and the air flow separation is obvious,the static pressure on the train surface is also large,such as the pantograph head skateboard,the transition field between the head and the carriage,etc.(3)The steady-state fluid field data is used as the initial condition,the transient solution of the high-speed trains external flow field is calculated by using of the large eddy simulation method(LES)at different speeds,then the aerodynamic noise of high-speed trains is calculated based on Lighthill's acoustic analogy theory and FW-H equation.By analyzing the aerodynamic noise which including 528 monitoring points of near-wall and roadside at four speeds,it is concluded that the aerodynamic noise of trains mainly comes from pantograph system,nose cone of head and tail vehicles,bogie system and air-conditioning domes.(4)Sound pressure level spectrum of high-speed trains is achieved by fast Fourier transform(FFT).The spectrum characteristics of near-wall and roadside aerodynamic noise of high-speed trains are analyzed.The results show that the aerodynamic noise of train belongs to broadband noise without obvious main frequency,and the energy mainly concentrates in the frequency range of 100-1000Hz.(5)Based on the k-? turbulence model,the aerodynamic noise sources on the structure surface of high-speed trains at different speeds are calculated by using of the broadband noise source model,and the sound power level distribution on the structure surface of the train body is achieved.The results show that the main aerodynamic noise sources appear in the head,windshields,bogies,pantograph and air-conditioning domes of the train,moreover,the sound power level on the train surface is basically proportional to the static pressure,that is to say,the sound power level on the surface of the train is also high in the parts with high static pressure.(6)The database system of high-speed train aerodynamic noise is established by using MySQL database.Based on the development environment of Visual Studio 2008,the query interface of database management system is developed by using of C#language,the management,maintenance and query of aerodynamic noise data of high-speed trains are realized.Based on this database,high-speed trains aerodynamic noise data in different positions and velocities can be quickly queried and updated conveniently.