Based on the aerodynamics and vehicle dynamics, the aerodynamic performances and vehicle dynamic characteristics of two high-speed trains passing each other on the ground, embankment and bridge are studied. Firstly, a...Based on the aerodynamics and vehicle dynamics, the aerodynamic performances and vehicle dynamic characteristics of two high-speed trains passing each other on the ground, embankment and bridge are studied. Firstly, a train aerodynamic model and a vehicle dynamic model are established. Through the simulation of the two models, the pressure waves, aerodynamic forces, and vehicle dynamic responses are obtained. Then, the pressure waves and aero- dynamic forces on different foundations are compared. The results show that the variation trends of pressure wave and aerodynamic forces of trains passing each other on different foundations are almost similar. The peak-to-peak differ- ences in pressure wave and aerodynamic force are below 4% and 3% in three cases in open air. Besides, the differences of security indexes, including coefficient of derailment, wheel unloading rate, the wheelset lateral force, and the wheel- rail vertical force, are below 2% among the three cases; the differences of comfort indexes, including the lateral acceleration and the vertical acceleration, are also below 2%. It is concluded that the dynamic performances of trains pass- ing each other are influenced little by different foundations in open air.展开更多
A new method is proposed to numerically simulate problems of trains passing by each other at the same speed, and is implemented in UDF language of commercial software Fluent. Because only a half of the computational d...A new method is proposed to numerically simulate problems of trains passing by each other at the same speed, and is implemented in UDF language of commercial software Fluent. Because only a half of the computational domain is required and the dynamic mesh technique is avoided, the computational efficiency is greatly improved. A two-dimensional test case is used for validation, which shows that the flow field and the pressure wave during the train-passing events can be correctly calculated by this new method. This method can be easily extended to three-dimensional simulations, to deal with practical problems.展开更多
It is found with the method of multiple scales that there exists a new periodical processwith long period T_1= 2π(Δω~2-f^2ω)^(1/2) when f= ω_e^2A_r/g and Δω/ω=ω-ω_e/ω are O(ε), whereg is the gravitational ...It is found with the method of multiple scales that there exists a new periodical processwith long period T_1= 2π(Δω~2-f^2ω)^(1/2) when f= ω_e^2A_r/g and Δω/ω=ω-ω_e/ω are O(ε), whereg is the gravitational acceleration, ω_e half of the driving frequency, A. the driving ampli-tude, ω the frequency of (0, 1) mode of the water trough. Suggest that φ which is corre-lativc with the complex amplitude of velocity potential is a function of θ and ?φ/?θ is O(ω~3),where θ satisfies θ(t + T_1) =θ(t), e.g. θ=?/Ω sinΩ_t (Ω=2π/T_1). The NLS equation of theφ(x,θ) is obtained. The phenomena of passing--through and oscil- lating about each other ofa pair of solitary waves in a rectangular water trough can be explained.展开更多
基金supported by the National Natural Science Foundations of China (Nos. 50823004 and 50821063)the "Eleventh Five-year Plan" National Science and Technology Support Plan(No. 2009BAG12A01-C09)
文摘Based on the aerodynamics and vehicle dynamics, the aerodynamic performances and vehicle dynamic characteristics of two high-speed trains passing each other on the ground, embankment and bridge are studied. Firstly, a train aerodynamic model and a vehicle dynamic model are established. Through the simulation of the two models, the pressure waves, aerodynamic forces, and vehicle dynamic responses are obtained. Then, the pressure waves and aero- dynamic forces on different foundations are compared. The results show that the variation trends of pressure wave and aerodynamic forces of trains passing each other on different foundations are almost similar. The peak-to-peak differ- ences in pressure wave and aerodynamic force are below 4% and 3% in three cases in open air. Besides, the differences of security indexes, including coefficient of derailment, wheel unloading rate, the wheelset lateral force, and the wheel- rail vertical force, are below 2% among the three cases; the differences of comfort indexes, including the lateral acceleration and the vertical acceleration, are also below 2%. It is concluded that the dynamic performances of trains pass- ing each other are influenced little by different foundations in open air.
文摘A new method is proposed to numerically simulate problems of trains passing by each other at the same speed, and is implemented in UDF language of commercial software Fluent. Because only a half of the computational domain is required and the dynamic mesh technique is avoided, the computational efficiency is greatly improved. A two-dimensional test case is used for validation, which shows that the flow field and the pressure wave during the train-passing events can be correctly calculated by this new method. This method can be easily extended to three-dimensional simulations, to deal with practical problems.
基金Project supported by the National Natural Science Foundation of China
文摘It is found with the method of multiple scales that there exists a new periodical processwith long period T_1= 2π(Δω~2-f^2ω)^(1/2) when f= ω_e^2A_r/g and Δω/ω=ω-ω_e/ω are O(ε), whereg is the gravitational acceleration, ω_e half of the driving frequency, A. the driving ampli-tude, ω the frequency of (0, 1) mode of the water trough. Suggest that φ which is corre-lativc with the complex amplitude of velocity potential is a function of θ and ?φ/?θ is O(ω~3),where θ satisfies θ(t + T_1) =θ(t), e.g. θ=?/Ω sinΩ_t (Ω=2π/T_1). The NLS equation of theφ(x,θ) is obtained. The phenomena of passing--through and oscil- lating about each other ofa pair of solitary waves in a rectangular water trough can be explained.
