A computational fluid dynamics study of the influence of sleeper shape and ballast depth on ballast flight during passage of a simplified train
A computational fluid dynamics study of the influence of sleeper shape and ballast depth on ballast flight during passage of a simplified train
The paper assesses the effect on the air flow regime underneath a simplified high-speed train of changing the ballast depth and the sleeper shape, with regard to its potential for causing ballast flight or pickup. The study was carried out numerically using the commercial Computational Fluid Dynamics (CFD) software AnSys Fluent. The flow profile beneath the underbody of the train was generated by means of a moving wall above the track. The Delayed Detached Eddy Simulation (DDES) with the SST (Formula presented.) turbulence model was used to simulate turbulent flow, and the ballast bed roughness was applied parametrically using the wall roughness feature when resolving the boundary layer. CFD simulations were validated for flow over a cube, showing good agreement with experimental results. Up to three different depths to the ballast surface and three different sleeper profiles were investigated. Velocity profiles and aerodynamic forces on cubes placed between or on top of the sleeper blocks were used to assess the propensity of individual ballast grains for movement. For a standard G44 sleeper, increasing the ballast depth and/or the ballast bed roughness was found to reduce aerodynamic loads on an individual ballast grain. A ballast grain on top of the sleeper is more prone to uplift than a grain on the surface of the ballast bed in the crib. A curved upper surface to the sleeper is beneficial in that it prevents ballast from settling on top, the most vulnerable position. However, the reduced flow separation associated with the curved top may increase the likelihood of ballast pickup from the crib. Hence new sleeper shapes intended to reduce the potential for ballast flight should not only prevent ballast from settling on top, but also increase flow separation through the provision of a sharp surface. A prismatic sleeper shape that achieves both is suggested.
Aerodynamic flow, Quantitative assessment, aerodynamically-induced ballast flight, air flow regime, ballast grain, commercial Computational Fluid Dynamics, track geometries, numerical modelling, ballast flight, High-speed trains, aerodynamics, sleeper blocks
692-705
Pardoe, Lee
23bb7a71-dd42-4f15-962c-286d6736a079
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Hu, Zhiwei
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
July 2024
Pardoe, Lee
23bb7a71-dd42-4f15-962c-286d6736a079
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Hu, Zhiwei
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
Pardoe, Lee, Powrie, William and Hu, Zhiwei
(2024)
A computational fluid dynamics study of the influence of sleeper shape and ballast depth on ballast flight during passage of a simplified train.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 238 (6), .
(doi:10.1177/09544097231226148).
Abstract
The paper assesses the effect on the air flow regime underneath a simplified high-speed train of changing the ballast depth and the sleeper shape, with regard to its potential for causing ballast flight or pickup. The study was carried out numerically using the commercial Computational Fluid Dynamics (CFD) software AnSys Fluent. The flow profile beneath the underbody of the train was generated by means of a moving wall above the track. The Delayed Detached Eddy Simulation (DDES) with the SST (Formula presented.) turbulence model was used to simulate turbulent flow, and the ballast bed roughness was applied parametrically using the wall roughness feature when resolving the boundary layer. CFD simulations were validated for flow over a cube, showing good agreement with experimental results. Up to three different depths to the ballast surface and three different sleeper profiles were investigated. Velocity profiles and aerodynamic forces on cubes placed between or on top of the sleeper blocks were used to assess the propensity of individual ballast grains for movement. For a standard G44 sleeper, increasing the ballast depth and/or the ballast bed roughness was found to reduce aerodynamic loads on an individual ballast grain. A ballast grain on top of the sleeper is more prone to uplift than a grain on the surface of the ballast bed in the crib. A curved upper surface to the sleeper is beneficial in that it prevents ballast from settling on top, the most vulnerable position. However, the reduced flow separation associated with the curved top may increase the likelihood of ballast pickup from the crib. Hence new sleeper shapes intended to reduce the potential for ballast flight should not only prevent ballast from settling on top, but also increase flow separation through the provision of a sharp surface. A prismatic sleeper shape that achieves both is suggested.
Text
pardoe-et-al-2024-a-computational-fluid-dynamics-study-of-the-influence-of-sleeper-shape-and-ballast-depth-on-ballast (1)
- Version of Record
More information
Accepted/In Press date: 2024
e-pub ahead of print date: 27 March 2024
Published date: July 2024
Additional Information:
Publisher Copyright:
© IMechE 2024.
Keywords:
Aerodynamic flow, Quantitative assessment, aerodynamically-induced ballast flight, air flow regime, ballast grain, commercial Computational Fluid Dynamics, track geometries, numerical modelling, ballast flight, High-speed trains, aerodynamics, sleeper blocks
Identifiers
Local EPrints ID: 490505
URI: http://eprints.soton.ac.uk/id/eprint/490505
ISSN: 0954-4097
PURE UUID: 98b0a467-c754-4a49-9061-388f0f33fbc5
Catalogue record
Date deposited: 29 May 2024 16:35
Last modified: 12 Jul 2024 01:35
Export record
Altmetrics
Contributors
Author:
Lee Pardoe
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
