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- Dong, Tianyun, et al.
(author)
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Effects of simplifying train bogies on surrounding flow and aerodynamic forces
- 2019
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In: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 191, s. 170-182
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Journal article (peer-reviewed)abstract
- © 2019 Elsevier Ltd In this study, the numerical solution of a high-speed train with several simplified bogies is investigated. The time-averaged flow field around the train, the surface pressure, and the aerodynamic forces on the train are discussed. The results reveal that a simpler bogie structure can achieve a higher underbody flow velocity and change fluctuations beneath the train owing to the resulting turbulence level. The simplification of bogies has a smaller effect on the side slipstream velocity and pressure compare to which in underbody, and at 3 m away from the centre of the track, the simplified bogie with wheels and a simple side frame used in this study obtains similar results to cases wherein more complex bogies are used. The surface pressure under the train is affected by bogie simplification, especially in the bogie cabin end area, resulting in aerodynamic drag and lift variations. If underbody flow or aerodynamic drag and lift forces are the focus of study, then the geometry of the centre region of the bogie, i.e. its main structures features, should be maintained in simplified models.
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| 2. |
- Zhang, Jie, 1987, et al.
(author)
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Detached eddy simulation of flow characteristics around railway embankments and the layout of anemometers
- 2019
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In: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 193
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Journal article (peer-reviewed)abstract
- Anemometers are usually set up along railway embankments to monitor wind speeds, and the layout for them has to be investigated. This work used an improved delayed detached eddy simulation (IDDES) approach to explore the flow properties around railway embankments, and then a proposal was put forward for the layout of anemometers. The numerical method was validated against previous wind tunnel tests on the speed-up ratios of the flow around a 1/300 scale two-dimensional embankment with the slope gradient of 1:2. The effects of inlet velocity profiles, i.e., uniform velocity and atmospheric boundary layer velocity profiles, on the speed-up ratios around a 5 m high railway embankment were compared. The study indicates that using a uniform velocity profile to assess the operational safety of trains running across strong wind regions could be favourable, especially when complex local terrains contribute to different wind characteristics. The anemometers should be set upstream, i.e., at a well defined distance in locations with sufficient extent of open ground and on the electrification masts along railway lines. This is not in line with the anemometer layout of the existing SWEWS (Strong Wind Early Warning Systems), the difference being due to the speed-up effect of the railway embankment, which is usually not considered explicitly. Formulas have been developed on the basis of regression of the simulation results to express the relationships between e.g. top wind speed over the embankment (located in an area where it is not possible to install anemometers) and measured wind speeds. In this way it is possible to take into account the speed-up effect encountered by the wind passing over the embankment, which needs to be considered in the operational rules in order to ensure safe operations.
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