Abstract:Sand and gravel blown up by strong wind will cause damage to windows. Following up, it will cause the change in the flow field around a train immediately, which has a significant impact on the aerodynamic performance of the train. Delayed detached-eddy simulation based on the shear stress transport κ-ω turbulence model was used to investigate the aerodynamic characteristics of passenger vehicles under crosswind, and the effect of damaged windows on the train aerodynamic performance and flow field around the tr… Show more
“…The introduction of Q-criterion, a method of describing instantaneous eddy structure, has been shown in detail in previous literature, 53 , 54 and it has been widely used in wind engineering. 24 , 55–58 Figure 10 Figure 10. 3 D view of isosurfaces corresponding to the Q-criterion (Q = 100,000), rendered for mean velocity ratio u/U ref around the plates. shows that the turbulence of the downstream flow field around the tail car is aggravated by the opening of the plate and the number and intensity of the vortices around the train with an open plate and the affected area increase, which increases the fluctuation of the aerodynamic drag of the head car. Figure 10 also shows that more vortices appear on the top of the tail car, which increases the fluctuation of the aerodynamic lift force of the tail car.…”
The continuous increase in train speed has brought serious challenges to train braking safety. Aerodynamic braking technology can effectively improve the braking effect of trains at high speeds. In this study, an aerodynamic braking device installed in the inter-car gap region (ICG) of a high-speed train is proposed and the aerodynamic performance of the high-speed train with an aerodynamic braking device is assessed by improved delayed detached eddy simulation (IDDES) based on the κ-ω turbulence model. The results show that the opening of the plate significantly changes the aerodynamic performance of the train, thereby greatly increasing the aerodynamic forces of the train and their fluctuation degree. The effect of the opening of the plate increases the turbulence of the downstream flow field around the tail car. The affected area is mainly concentrated in the flow field around the location of the plate for the pressure field and the whole flow field behind the plate for the velocity field. The effect of the plate mounted on the uniform-car body region (UCG) on increasing the aerodynamic drag is better than that at the ICG, though the aerodynamic fluctuation and the influence on the surrounding flow field will also be great.
“…The introduction of Q-criterion, a method of describing instantaneous eddy structure, has been shown in detail in previous literature, 53 , 54 and it has been widely used in wind engineering. 24 , 55–58 Figure 10 Figure 10. 3 D view of isosurfaces corresponding to the Q-criterion (Q = 100,000), rendered for mean velocity ratio u/U ref around the plates. shows that the turbulence of the downstream flow field around the tail car is aggravated by the opening of the plate and the number and intensity of the vortices around the train with an open plate and the affected area increase, which increases the fluctuation of the aerodynamic drag of the head car. Figure 10 also shows that more vortices appear on the top of the tail car, which increases the fluctuation of the aerodynamic lift force of the tail car.…”
The continuous increase in train speed has brought serious challenges to train braking safety. Aerodynamic braking technology can effectively improve the braking effect of trains at high speeds. In this study, an aerodynamic braking device installed in the inter-car gap region (ICG) of a high-speed train is proposed and the aerodynamic performance of the high-speed train with an aerodynamic braking device is assessed by improved delayed detached eddy simulation (IDDES) based on the κ-ω turbulence model. The results show that the opening of the plate significantly changes the aerodynamic performance of the train, thereby greatly increasing the aerodynamic forces of the train and their fluctuation degree. The effect of the opening of the plate increases the turbulence of the downstream flow field around the tail car. The affected area is mainly concentrated in the flow field around the location of the plate for the pressure field and the whole flow field behind the plate for the velocity field. The effect of the plate mounted on the uniform-car body region (UCG) on increasing the aerodynamic drag is better than that at the ICG, though the aerodynamic fluctuation and the influence on the surrounding flow field will also be great.
“…It's widely utilized in the simulation of high-speed trains. [20][21][22][23][24] A compressible flow solver is adopted in the STAR-CCM + software due to the velocity of the incoming flow being 400-600 km/h (Mach number 0.32-0.49). The convection and diffusion terms contained in the flow control equation are discretized by using the second-order upwind and the central difference scheme respectively.…”
The objective of this study is to investigate the safety of high temperature superconducting (HTS) high-speed maglev trains operating in an open environment subjected to strong crosswinds. Therefore, a full-size numerical model of the HTS high-speed maglev engineering prototype is developed based on the 3-D, steady RANS method and SST k-ω turbulence model. Then, the aerodynamic loads are added to the simplified aerodynamic loading center of the train, and a dynamic vehicle model on basis of the special nonlinear magnetic-track relationship is established to study the variation of safety indexes of the HTS maglev train under different crosswinds and operation speeds. It is found that the safety indexes of the maglev train meet the requirements under different crosswind scenarios, indicating that the HTS maglev engineering prototype has great stability against crosswinds. It is expected to adapt to high-speed operation and withstand at least 20.7 m/s crosswind speed under 600 km/h operation speed, to provide a reference for future engineering applications of the HTS maglev train.
“…Like other bodies with high length-to-width ratios (Ghalandari et al, 2019;Mou et al, 2017), high-speed trains have more complex aerodynamic characteristics than other vehicles (Chen et al, 2016;Deng et al, 2019Deng et al, , 2020Hemida & Krajnović, 2010;Niu et al, 2020). To reduce the aerodynamic drag on a train, numerous tests and simulations were carried out CONTACT Hongkang Liu lhk1232008@163.com to investigate aerodynamic performances of various types of trains.…”
Double unit trains running at high speeds may create additional aerodynamic challenges due to two streamlined structures with close proximity, exploring the aerodynamic performance of double unit trains is now critical. In this study, detached eddy simulation (DES) approach was employed to study the aerodynamic performance and the nearby flow patterns of a double unit train, whose results were compared and analyzed with that of a single-unit train with a same length. The results showed that the coupling method could change the aerodynamic drag on each car and tended to increase the overall drag of the double unit train. The lift force of the front car near the coupler was significantly increased. Similar slipstream distributions were found around the front half single and double-unit train except in a region close to the coupler. Due to the coupling structure, the slipstream of the rear half of double unit train was much stronger compared to single unit train. The vortex region behind the double-unit train was much wider than that of the single-unit train and was accompanied by greater vortex-shedding.
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