| 1. |
- Chen, Guang, et al.
(författare)
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Dynamic analysis of the effect of nose length on train aerodynamic performance
- 2019
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 184, s. 198-208
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Tidskriftsartikel (refereegranskat)abstract
- The improved delayed detached eddy simulation (IDDES) was used to study the influence of the train’s nose length on its aerodynamic performance. Both the time-averaged and instantaneous near-wake structures and the associated distribution of slipstream velocity are compared for three nose lengths. As the nose length increases, the mean and Std values of the drag and lift force are decreased. The shorter nose-length case results in a higher slipstream velocity. In particular, at the TSI track-side position, the TSI value U_2δ for the 5-m nose length case is 30% and 32% higher than the corresponding values for the 7.5-m and 10-m nose length cases, respectively. The dynamical flow topology in the wake reveals that the flow structures of the 5-m nose length are different from those of the other two cases in the tail streamline surface. As nose length increases, the longitudinal vortices are weaker, and the angle and distance between the longitudinal vortices are smaller. The shear production from the P_xy caused by the separation of the boundary layer at the lateral wall of the tail train is greater than that of the P_xz caused by the separation of the boundary layer at the top and bottom of the tail train.
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| 2. |
- Dong, Tianyun, et al.
(författare)
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Effects of simplifying train bogies on surrounding flow and aerodynamic forces
- 2019
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 191, s. 170-182
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Liu, Tanghong, 1976, et al.
(författare)
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Wave effects in a realistic tunnel induced by the passage of high-speed trains
- 2019
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 86, s. 224-235
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Tidskriftsartikel (refereegranskat)abstract
- As a high-speed train passes through a tunnel, aerodynamic pressure waves propagate backwards and forward in the tunnel, and they persist for a long time after the train is gone. Understanding the aerodynamic characteristics influenced by various factors on a tunnel is essential for ensuring the safety of tunnel structures. Field measurements were conducted in a 2812 m-long tunnel to systematically investigate the pressure characteristics during the passage of CRH2-150C and CRH380AL high-speed trains through the tunnel, both in single-train and intersecting cases. The results reveal that as the train speed increases, the location of the maximum peak-to-peak pressure variation shifts toward the tunnel entrance, mainly driven by the change in the negative pressure peak. The train length induces significant differences in peak pressures on the tunnel wall in the middle of the tunnel, and a long train brings more massive subsequent pressure waves than a short train in the post-train stage, but they decay faster. The intersection of two trains in the tunnel not only causes a significant change in the peak pressure and its location, but also has a significant effect on damage factor (the damage level on a structure subjected to a specific load) after train leaving the tunnel, with a 65.3% of this factor during trains operating in the tunnel.
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| 4. |
- Wang, Jiabin, et al.
(författare)
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Impact of rotation of wheels and bogie cavity shapes on snow accumulating on the bogies of high-speed trains
- 2019
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Ingår i: Cold Regions Science and Technology. - : Elsevier BV. - 0165-232X. ; 159, s. 58-70
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Tidskriftsartikel (refereegranskat)abstract
- The snow accumulation on the bogies of a high-speed train was studied using the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The effects of the rotation of wheels, shape of bogie fairings and length of bogie cavities on the flow characteristics and snow accumulation around bogie regions are discussed. The results show that the rotation of wheels significantly affects the flow characteristic and snow distribution around rear plates and the snow accumulation on the top surface of bogies. The shape of bogie fairings has been found to have large influence on the velocity profiles at the inlet and the outlet of bogie cavity, and thereby on the snow accumulation. The bogies without fairing have been found to be less influenced by the snow in the flows without crosswinds. The length of the bogie's cavity was found to have dominant role on the distribution of particle concentration and snow accumulation on the bogie surface. The total mass of snow accumulation on the bogie surface was shown to decrease with the shorter bogie cavity. Finally, the shorter bogie cavity is recommended for the design of the high-speed trains running under the circumstances permitted by the vehicle gauge.
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