scholarly journals Analysis of Trailing Vortex Structure and Turbulent Features of High-Speed Train in Vacuum Pipeline

2021 ◽  
Vol 39 (5) ◽  
pp. 1601-1608
Author(s):  
Hongjiang Cui ◽  
Shenghui Wu ◽  
Ying Guan
Keyword(s):  
Reynolds Stress ◽  
High Speed ◽  
Flow Direction ◽  
Three Dimensional ◽  
Transient State ◽  
Turbulent Energy ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Long Distance ◽  
Low Dissipation

Through the improved delay-detached eddy simulation (IDDES), this paper establishes a 1:1 model for a high-speed train, and simulates the transient state of the train running 600km/h in a vacuum pipeline with the pressure of 1,000Pa. The results show that, following the Ω criteria, a pair of counterrotating vortexes can be captured, which alternatively shed near the tip of the last carriage, and propagate over a long distance along the flow direction. The motion and expansion of the vortexes are clearly three-dimensional (3D). Judging by the physical meaning of vortexes, the high vorticity vortexes mainly concentrate near the tip of the last carriage, while the low vorticity vortexes scatter across the wake zone. The latter vortexes have a low dissipation rate and are dominated by rotation. The turbulent energy and Reynolds stress of the wake field are very obvious near the tip of the last carriage, and attenuate quickly along the flow direction. This means the vortexes near the tip of the last carriage face a strong shear effect, and undergo apparent dissipation. Low turbulent energy and Reynolds stress are distributed in the downstream far from the tip of the last carriage, i.e., the interaction zone between vortexes and the ground / inner pipe wall.

The Calculation of Train Slipstreams on Platform of Underground High-Speed Rail Station

2013 ◽  
Vol 842 ◽  
pp. 445-448
Author(s):  
Wei Chao Yang ◽  
Chuan He ◽  
Li Min Peng
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Horizontal Distribution ◽  
Wake Flow ◽  
Railway Tunnel ◽  
Long Distance ◽  
Near Wake ◽  
High Speed Rail ◽  
Numerical Work ◽  
Rail Station

This paper describes the results of numerical work to determine the flow structures of the slipstream and wake of a high speed train on platforms of underground rail station using three-dimensional compressible Euler equation. The simulations were carried out on a model of a simplified three-coach train and typical cross-section of Chinese high-speed railway tunnel. A number of issues were observed: change process of slipstreams, longitudinal and horizontal distribution characteristics of train wind. Localized velocity peaks were obtained near the nose of the train and in the near wake region. Maximum and minimum velocity values were also noticed near to the nose rear tip. These structures extended for a long distance behind the train in the far wake flow. The slipstream in platform shows the typical three-dimensional characteristics and the velocity is about 4 m/s at 6 m away from the edge of platform.

The Vehicle Dynamical Analysis of a High-Speed Train Passing through a Tunnel

2010 ◽  
Vol 29-32 ◽  
pp. 835-840 ◽  
Author(s):  
Zhi Peng Feng ◽  
Ji Ye Zhang ◽  
Wei Hua Zhang
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Geometric Model ◽  
Three Dimensional ◽  
Grid Method ◽  
Dynamical Analysis ◽  
High Speed Train ◽  
Flow Induced Vibration ◽  
Running Safety ◽  
Dynamics Calculation

As the speed of train increases, flow-induced vibration of trains passing through tunnels has become a subject of discussion, to investigate this phenomenon, a simplified geometric model and a vehicle dynamics model of a high-speed train traveling through a tunnel were built. To analyze the unsteady three-dimensional flow around the train, the 3-D, transient, viscous, compressible Reynolds-averaged Navier-Stokes equations combined with the k- two-equation turbulence model were solved with the finite volume method. The motion of the train was carried out using the technique of sliding grid method. The dynamics response of the train was obtained by means of the computational multi-body dynamics calculation. Meanwhile the running safety and riding comfort of the train were analyzed. With the numerical simulation, the variation of aerodynamic forces was obtained. The research founds that, vibration of the train increases drastically during it passing through a tunnel. The running safety and riding quality of the train are reduced greatly but they are in the safe range.

Aerodynamic Characteristics Analysis of High-Speed Train on Cutting under Crosswinds

2013 ◽  
Vol 300-301 ◽  
pp. 62-67
Author(s):  
Kun Ye ◽  
Ren Xian Li
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
High Speed Train ◽  
Aerodynamic Forces ◽  
Cutting Depth ◽  
Cutting Slope ◽  
Characteristics Analysis ◽  
Relationship Of ◽  
The Relationship

Cutting is an effective device to reduce crosswind loads acting on trains. The cutting depth, width and gradient of slope are important factors for design and construction of cutting. Based on numerical analysis methods of three-dimensional viscous incompressible aerodynamics equations, aerodynamic side forces and yawing moments acting on the high-speed train, with different depths and widths of cutting，are calculated and analyzed under crosswinds，meanwhile the relationship of the gradient of cutting slope and transverse aerodynamic forces acting on trains are also studied. Simulation results show that aerodynamic side forces and yawing moments acting on the train（the first, middle and rear train）decrease with the increase of cutting depth. The relationship between transverse forces (moments) coefficients acting on the three sections and the cutting depth basically is the three cubed relation. The bigger is cutting width，the worse is running stability of train. The relationship between yawing moments coefficients acting each body of the train and the cutting width approximately is the three cubed relation. The transverse Aerodynamic forces decreased gradually with the increase of the gradient of cutting slope, the relationship between yawing moments coefficients acting each body of the train and the gradient of cutting slope basically is the four cubed relation.

Detached-Eddy Simulation of Ground Effect on the Wake of a High-Speed Train

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Chao Xia ◽  
Xizhuang Shan ◽  
Zhigang Yang
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Vortex Pair ◽  
Ground Effect ◽  
Longitudinal Vortex ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

The influence of ground effect on the wake of a high-speed train (HST) is investigated by an improved delayed detached-eddy simulation. Aerodynamic forces, the time-averaged and instantaneous flow structure of the wake are explored for both the stationary ground and the moving ground. It shows that the lift force of the trailing car is overestimated, and the fluctuation of the lift and side force is much greater under the stationary ground, especially for the side force. The coexistence of multiscale vortex structures can be observed in the wake along with vortex stretching and pairing. Furthermore, the out-of-phase vortex shedding and oscillation of the longitudinal vortex pair in the wake are identified for both ground configurations. However, the dominant Strouhal number of the vortex shedding for the stationary and moving ground is 0.196 and 0.111, respectively, due to the different vorticity accumulation beneath the train. A conceptual model is proposed to interpret the mechanism of the interaction between the longitudinal vortex pair and the ground. Under the stationary ground, the vortex pair embedded in a turbulent boundary layer causes more rapid diffusion of the vorticity, leading to more intensive oscillation of the longitudinal vortex pair.

A Study on Travel Demand for High-Speed Train Based on Nested Logit Model

2013 ◽  
Vol 361-363 ◽  
pp. 2096-2099
Author(s):  
En Jian Yao ◽  
Qi Rong Yang ◽  
Yong Sheng Zhang ◽  
Hong Na Dai
Keyword(s):  
Logit Model ◽  
High Speed ◽  
Travel Demand ◽  
Stated Preference ◽  
Rapid Development ◽  
Nested Logit ◽  
High Speed Train ◽  
Long Distance ◽  
Stated Preference Data ◽  
Nested Structure

High speed train (HST) has received plenty of attention due to the characteristics of safety, quickness, convenience and better service in China over recent years. With consideration of rapid development of HST and intense competition between HST and other transport modes, it is essential to estimate the travel demand for HST. In this research, a disaggregate logit model is applied to estimate the travel demand for high-speed train based on stated preference data. Considering the independence of irrelevant alternatives attribute, a nested structure is chosen to these alternatives. Besides, both the service attributes of transport mode and passengers' attributes are taken into account when establishes model. The results obtained confirm that HST occupies a significant position in modes conpetition and have an important impact on air in middle and long distance market.

scholarly journals Research on Aerodynamic Noise Reduction for High-Speed Trains

2016 ◽  
Vol 2016 ◽  
pp. 1-21 ◽  
Author(s):  
Yadong Zhang ◽  
Jiye Zhang ◽  
Tian Li ◽  
Liang Zhang ◽  
Weihua Zhang
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Low Noise ◽  
Broadband Noise ◽  
Full Scale ◽  
Noise Model ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Noise Sources

A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H) acoustic analogy. An analysis of noise reduction methods based on the main noise sources was performed. An aerodynamic noise model for a full-scale high-speed train, including three coaches with six bogies, two inter-coach spacings, two windscreen wipers, and two pantographs, was established. Several low-noise design improvements for the high-speed train were identified, based primarily on the main noise sources; these improvements included the choice of the knuckle-downstream or knuckle-upstream pantograph orientation as well as different pantograph fairing structures, pantograph fairing installation positions, pantograph lifting configurations, inter-coach spacings, and bogie skirt boards. Based on the analysis, we designed a low-noise structure for a full-scale high-speed train with an average sound pressure level (SPL) 3.2 dB(A) lower than that of the original train. Thus, the noise reduction design goal was achieved. In addition, the accuracy of the aerodynamic noise calculation method was demonstrated via experimental wind tunnel tests.

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