Study On Aerodynamic Load Of Fully-Enclosed Sound Barrier Of High-Speed Railway

In recent years,as people’s demands for living environment continue to increase,the control of noise pollution caused by high-speed train driving has become stricter.The semi-enclosed form of sound barrier has gradually evolved into a fully-enclosed form with better noise reduction effect.The change in the structure will significantly alter the distribution characteristics of aerodynamic loads on the surface of the sound barrier caused by high-speed train passing through.Therefore,accurately grasping the aerodynamic load characteristics on the surface of sound barrier when trains pass through the structure becomes the key to conducting reasonable research on fullyenclosed sound barriers.This thesis takes a 410 m rectangular fully enclosed sound barrier on the Beijing-Xiong’an high-speed railway as the engineering background.Using CFD numerical simulation technology to obtain the structural surface aerodynamic loads of the sound barrier when trains pass through it under different working conditions,and the distribution characteristics of aerodynamic loads on the surface of the sound barrier caused by train passing through were studied.The main work completed includes:(1)Summarized the current development status and related research achievements of railway sound barriers.This thesis introduces the basic theory,related software and numerical simulation methods needed to calculate the aerodynamic load on the surface of the fully-enclosed sound barrier when the train passes through.(2)A three-dimensional numerical model was established for high-speed trains,fully-enclosed sound barrier,air system.Key steps in the model establishment were analyzed emphatically,including: the flow field area,grid division method,grid movement method,initial conditions and boundary conditions of the object studied in this thesis.In addition,wind pressure measurement points were arranged along the fully-enclosed sound barriers to conduct transient calculations of the entire train passing process.The study found that the closer measurement points were to the 1/2span position of the fully-enclosed sound barrier,the longer the duration of positive and negative wind pressure,and the more stable the wind pressure changes.(3)The aerodynamic loads on the surface of the fully-enclosed sound barrier were calculated and extracted for analysis under the condition of single train passing through with different parameters(train speed and cross-section blocking ratio of the fully enclosed sound barrier).The study revealed that as the train speed and crosssection blocking ratio increase,the aerodynamic wind pressure on the surface of the fully-enclosed sound barrier also increases.Additionally,there is an uneven distribution of wind pressure in the circumferential direction of the fully-enclosed sound barrier,especially at the entrance and exit of the sound barrier.(4)According to the worst parameters obtained from the single train passing through condition,the variation law of aerodynamic load on the surface of the sound barrier was studied under the condition that the train crosses the 1/2 span and 1/4 span of the fully-enclosed sound barrier,and compared with the single train passing through condition,it is found that the wind pressure fluctuation on the section of the fully-enclosed sound barrier is more frequent and complicated,and there are more sudden ups and downs of wind pressure,which makes the extreme value of wind pressure increase and the value is larger.(5)Under the condition of trains passing each other at 1/4 span,the extreme values of positive and negative wind pressure on the section measuring point are 1.23 times and 1.93 times of the single train passing through condition,respectively.Under the condition of trains passing each other at 1/2 span,the maximum positive and negative wind pressures appear at the measuring point of the section,which are 1.37 times and 2.23 times of the single train passing through condition,respectively.The trains passing each other at 1/2 span condition is the worst condition for the aerodynamic wind pressure on the surface of the fully-enclosed sound barrier.Under the worst conditions,the wind pressure at the measuring point of the fully-enclosed sound barrier section presents a "positive-negative-positive" variation law,and there is a large circumferential pressure difference at the entrance and exit of the fullyenclosed sound barrier,and the maximum circumferential pressure difference between the positive and negative sections reaches 40.4% and 29.1%,respectively.Therefore,it is suggested that the combination of the extreme value of positive and negative wind pressure and the corresponding circumferential pressure difference should be considered for the aerodynamic wind load design of the fully-enclosed sound barrier structure.