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  • Aerodynamic Design of a Subsonic Evacuated Tube Train System
  • Abstract The so-called Evacuated Tube Train (ETT) is currently being proposed as a high-speed transportation system potentially competitive with airplane transportation. Aerodynamic resistance is one of the most crucial factors for the successful design of an ETT. In the present work, a three-dimensional concept ETT model has been elaborated. The aerodynamic characteristics of the subsonic ETT have been numerically simulated under different conditions. The train’s running speed varies from 600 km/h up to 1200 km/h, and the blockage ratio is in the range between 0.1 and 0.3. As the blocking ratio and running speed increase, the resistance of the head car…
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  • Numerical Simulation of the Aeroacoustic Performance of the DSA380 High-Speed Pantograph Under the Influence of a Crosswind
  • Abstract The object of research of this paper is the DSA380 high-speed pantograph. The near-field unsteady flow around the pantograph was investigated using large eddy simulation (LES) while the far-field aerodynamic noise was analysed in the frame of the Ffowcs Williams-Hawkings (FW-H) acoustic analogy. According to the results, the contact strip, base frame and knuckle are the main aerodynamic noise sources, with vortex shedding, flow separation and recombination around the pantograph being related key physical factors. The aerodynamic noise radiates outwards in the form of spherical waves when the distance of the noise receiving point is farther than 8 m. The…
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  • Computational Simulation of Turbulent Flow Around Tractor-Trailers
  • Abstract A method to evaluate the properties of turbulent flow in proximity to the vehicle and close to the ground surface has been elaborated. Numerical simulations have been performed on the basis of the Unsteady Reynolds-averaged Navier-Stokes equations (URANS) written with respect to an arbitrary curvilinear coordinate system. These equations have been solved using the Spalart-Allmaras differential one-parametric turbulence model. The method of artificial compressibility has been used to improve the coupling of pressure and velocity in the framework of a finite volume approach. Time-averaged distributions of pressure fields, velocity components, streamlines in the entire area and near the tractor-trailer, as…
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  •   Views:100       Downloads:113        Download PDF
  • A Numerical Study of the Aerodynamic Characteristics of a High- Speed Train under the Effect of Crosswind and Rain
  • Abstract The performances of high-speed trains in the presence of coupling effects with crosswind and rain have attracted great attention in recent years. The objective of the present paper was to investigate the aerodynamic characteristics of a high-speed train under such conditions in the framework of an Eulerian-Lagrangian approach. An aerodynamic model of a high-speed train was first set up, and the side force coefficient obtained from numerical simulation was compared with that provided by wind tunnel experiments to verify the accuracy of the approach. Then, the effects of the yaw angle, the resultant wind speed, and the rainfall rate on…
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  • Effect of Streamlined Nose Length on the Aerodynamic Performance of a 800 km/h Evacuated Tube Train
  • Abstract The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train. For this reason, evacuated tube trains (ETT) are being considered as valid alternatives to be implemented in the future. The atmosphere in the tube, the so-called blocking ratio and the length of the streamlined nose are the key factors affecting the aerodynamic performances of these trains. In the present work, we investigate evacuated tube trains with different lengths of the streamline nose on the basis of computational fluid dynamics (CFD). The three-dimensional steady compressible Navier-Stokes equations are solved.…
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  • Operational Safety Assessment of a High-Speed Train Exposed to the Strong Gust Wind
  • Abstract The operational safety characteristics of trains exposed to a strong wind have caused great concern in recent years. In the present paper, the effect of the strong gust wind on a high-speed train is investigated. A typical gust wind model for any wind angle, named “Chinese hat gust wind model”, was first constructed, and an algorithm for computing the aerodynamic loads was elaborated accordingly. A vehicle system dynamic model was then set up in order to investigate the vehicle system dynamic characteristics. The assessment of the operational safety has been conducted by means of characteristic wind curves (CWC). As some…
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  • Numerical Investigation of the Deposition Characteristics of Snow on the Bogie of a High-Speed Train
  • Abstract To investigate the deposition distribution of snow particles in the bogie surfaces of a high-speed train, a snow particle deposition model, based on the critical capture velocity and the critical shear velocity, was elaborated. Simulations based on the unsteady Reynolds-Averaged Navier-Stokes (RANS) approach coupled with Discrete Phase Model (DPM) were used to analyze the motion of snow particles. The results show that the cross beam of the bogie frame, the anti-snake damper, the intermediate brake clamps in the rear wheels, the traction rod and the anti-rolling torsion bar are prone to accumulate snow. The accumulation mass relating to the vertical…
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  • Numerical Study on Aerodynamic Performance of High-Speed Pantograph with Double Strips
  • Abstract Pantograph is a critical component of the high-speed train. It collects power through contact with catenary, which significantly affects the running safety of the train. Pantograph with double collector strips is one common type. The aerodynamic performance of the collector strips may affect the current collection of the pantograph. In this study, the aerodynamic performance of the pantograph with double strips is investigated. The numerical results are consistent with the experimental ones. The error in the aerodynamic drag force of the pantograph between numerical and experimental results is less than 5%. Three different conditions of the strips are studied, including…
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  • A Study on the Reduction of the Aerodynamic Drag and Noise Generated By the Roof Air Conditioner of High-Speed Trains
  • Abstract In order to investigate how the aerodynamic drag and noise produced by the roof air conditioner of a high-speed train can be reduced, the related unsteady flow in the near-field was computed using the method of large eddy simulation. In this way, the aerodynamic source for noise generation has initially been determined. Then, the far-field aerodynamic noise has been computed in the framework of the Lighthill’s acoustics analogy theory. The propulsion height and flow-guide angle of the roof air conditioner were set as the design variables. According to the computational results, a lower propulsion height or flow-guide angle is beneficial…
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  • An Investigation into the Effects of the Reynolds Number on High-Speed Trains Using a Low Temperature Wind Tunnel Test Facility
  • Abstract A series of tests have been conducted using a Cryogenic Wind Tunnel to study the effect of Reynolds number (Re) on the aerodynamic force and surface pressure experienced by a high speed train. The test Reynolds number has been varied from 1 million to 10 million, which is the highest Reynolds number a wind tunnel has ever achieved for a train test. According to our results, the drag coefficient of the leading car decreases with higher Reynolds number for yaw angles up to 30º. The drag force coefficient drops about 0.06 when Re is raised from 1 million to 10…
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