Numerical Simulation Of Aerodynamic Loads On A High-Speed Train Running At 400km/h And Loads Spectrum Statistics

At present,our country is fully promoting the CR450 scientific and technological innovation project,and has started the development of high-speed trains with a speed of 400 kilometers per hour and the construction of related lines.As the speed of the train continues to increase,the aerodynamic effect of the train becomes more and more obvious,and the aerodynamic load encountered when two trains passing by each other in the open air and passing through a tunnel is more severe.At present,domestic studies have focused on tunnels and trains to describe the aerodynamic load and load spectrum of the car body and its influencing factors,but they have ignored the scene where two trains passing by each other in the open air,and the statistical method of load spectrum has not yet been perfected.Therefore,it is urgent to further develop and improve domestic trains.The relevant research on the aerodynamic load spectrum of the body and the statistical method of the load spectrum provide theoretical support for the design of the fatigue life of the high-speed train body in our country.In this dissertation,a certain type of high-speed train with a speed of 400 km/h is taken as the research object,and the three-dimensional compressible unsteady turbulent flow model is used to analyze the aerodynamic load characteristics of the train in three typical scenarios,such as two trains passing by each other in the open air,single train passing through a tunnel,and two trains passing by each other in a tunnel,and select domestic typical lines,and obtain the aerodynamic load spectrum suitable for the specific lines in my country according to the actual train operation diagram and the load statistical method that meets the standards.First of all,it comprehensively summarizes the basic composition of aerodynamic load and the research status of aerodynamic load spectrum at home and abroad,comprehensively analyzes the relevant standards of different countries on aerodynamic load and load spectrum formulation methods,and clarifies that the train aerodynamic load spectrum is mainly affected by traffic density,train speed,line Influenced by factors such as distance,tunnel cross-section area,and tunnel length,the composition of the main working conditions of the load spectrum is expounded.Secondly,the CFD numerical simulation method is outlined,and the overlapping grid method is used to calculate different working condition models,and the accuracy of the calculation results of the overlapping grid method is verified by the numerical simulation method results.In addition,the counting process of the rainflow cycle counting method is introduced,and the feasibility of the rainflow counting method is verified.Through the calculation,the critical tunnel length is obtained under single train passing through a tunnel,and two trains passing by each other in a tunnel.According to the distribution of typical tunnels in our country,the rationality of the selection of the critical tunnel length is illustrated.Based on the fluid analysis software,the scenarios of the intersection of two trains on open lines,the intersection of a single train passing through a tunnel and the intersection of two trains in a tunnel are simulated,the flow field characteristics and aerodynamic load characteristics of the three scenarios are analyzed,and the pressure load values are calculated,combined with the equivalent pressure load The formula compares and analyzes the difference between the UIC standard and the calculation results in this paper.The results show that the maximum positive and negative pressure values calculated in this paper are lower than the UIC standard by 32.0%and 10.1%,respectively.Finally,draw a train operation diagram by selecting the train operation conditions of the line,and count the corresponding times of two trains passing by each other in the open air,single train passing through a tunnel,and two trains passing by each other in a tunnel under the operating conditions of the whole line.Through the rainflow counting method,the relationship between the average load amplitude and frequency of the locomotive and tail car and the intermediate car under each working condition is obtained,and the load sets of the three working conditions are determined,and then the distribution of the average amplitude and frequency of the load spectrum on the entire line is counted.The proportions of load amplitude frequencies of two trains passing by each other in the open air,single train passing through a tunnel and two trains passing by each other in a tunnel are 19.4%,75.2% and 5.4% respectively.The statistics of aerodynamic load spectrum provide theoretical and technical support for the aerodynamic load design of high-speed train bodies in my country.