A novel passive flow control method employing vortex generators to suppress wake flow characteristics of a high-speed train: Mechanism and application

Abstract

This paper proposes a passive control method to reduce peak values of slipstream and turbulent kinetic energy in a high-speed train wake by attaching vortex generators (VGs) onto the upper surface of the tail car. The impact of the VGs is assessed through the improved delayed detached eddy simulations (IDDES) after validating predictions against previous experimental measurements and other numerical predictions for the base case. The simulations indicate that strategically installed VGs can reduce the average slipstream velocity (U_slipstream) and the upper limit of slipstream velocity (U_{slipstream, max}) by ∼17% and ∼15%, respectively, as well as moving the peaks downstream by approximately train height, thus reducing the danger posed by slipstream to waiting passengers and trackside workers. Analysis shows that the wake turbulent kinetic energy diminishes as the vortex generators decelerate the downwash flow and reduce shear production in the wake. It is also found that the presence of VGs significantly impacts the flow on the upper surface near the tail by modifying the unsteady trailing longitudinal vortices through the formation of additional counter-rotating longitudinal vortices from the VGs. These latter vortices prevent the merging of vortical airflow around the trailing nose tip, which is otherwise induced by the longitudinal vortex of the train. They also reduce vortex intensity through cross-annihilation and cross diffusion as the wake advects downstream, limiting outwards advection through interaction with the image pair, and contributing to a decrease in the peak slipstream value. The method proposed offers a simple approach to wake control leading to significant slipstream benefits.

Keywords

high-speed train / vortex generators / slipstream / wakes / passive control

References

[1] Gao H-r, Liu T-h, Chen X-det al. . Aerodynamic and dynamic behaviour of a train in cutting-viaduct-cutting sections with windbreaks in complex terrains under crosswinds: Key factors. Engineering Structures. 2025, 328: 119728. J]

[2] Zhang J, Zhang M-l, Han Set al. . A novel asymptotic linear method for micro-pressure wave mitigation at high-speed maglev tunnel exit: A case study with various open ratios on tunnel hoods. Journal of Central South University. 2025, 32(5): 1955-1972. J]

[3] Chen J-z, Xu A, Liu T-het al. . On enhancing anti-overturning performance of a high-speed train with side airfoils in crosswinds. Journal of Wind Engineering and Industrial Aerodynamics. 2025, 264: 106151. J]

[4] Baker C J, Dalley S J, Johnson Tet al. . The slipstream and wake of a high-speed train. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. 2001, 215283-99. J]

[5] Huang F-y, Xu A, Zhang Jet al. . A passive flow control method with winglets installed on leeward side of a high-speed train for improvement of anti-overturning performance under crosswinds. Physics of Fluids. 2025, 373035180. J]

[6] Zhang J, Xu A, Huang F-yet al. . A novel vortex control method for improving anti-overturning performance of a high-speed train with leeward airbag structures under crosswinds. Physics of Fluids. 2024, 366065146. J]

[7] Han S, Zhang J, Xiong X-het al. . Influence of high-speed maglev train speed on tunnel aerodynamic effects. Building and Environment. 2022, 223: 109460. J]

[8] GAO Guang-jun, XIANG Nan-shen, DING Yan-si, et al. A smooth-guiding method for aerodynamic drag reduction on key regions of a high-speed train [J]. Mechanics Based Design of Structures and Machines, 2025: 1–25. DOI: https://doi.org/10.1080/15397734.2025.2537310.

[9] Jiang C, Long J-l, Li Y-set al. . Numerical investigation on the aerodynamic drag reduction based on bottom deflectors and streamlined bogies of a high-speed train. Journal of Central South University. 2024, 3193312-3328. J]

[10] Morel T. Effect of base slant on flow in the near wake of an axisymmetric cylinder. Aeronautical Quarterly. 1980, 312132-147. J]

[11] Muld T W, Efraimsson G, Henningson D S. Flow structures around a high-speed train extracted using proper orthogonal decomposition and dynamic mode decomposition. Computers & Fluids. 2012, 57: 87-97. J]

[12] Bell J R, Burton D, Thompson Met al. . Wind tunnel analysis of the slipstream and wake of a high-speed train. Journal of Wind Engineering and Industrial Aerodynamics. 2014, 134: 122-138. J]

[13] Wang X-r, Liu T-h, Xia Y-tet al. . Effect of railway cutting depths on running safety and pantograph – catenary interaction of trains under crosswind. Journal of Wind Engineering and Industrial Aerodynamics. 2024, 245: 105659. J]

[14] Baker C. The flow around high speed trains. Journal of Wind Engineering and Industrial Aerodynamics. 2010, 98(6): 277-298. J]

[15] Lin J C. Review of research on low-profile vortex generators to control boundary-layer separation. Progress in Aerospace Sciences. 2002, 384389-420. J]

[16] Katz J. Aerodynamics of race cars. Annual Review of Fluid Mechanics. 2006, 38: 27-63. J]

[17] Gibertini G, Boniface J C, Zanotti Aet al. . Helicopter drag reduction by vortex generators. Aerospace Science and Technology. 2015, 47: 324-339. J]

[18] Mereu R, Passoni S, Inzoli F. Scale-resolving CFD modeling of a thick wind turbine airfoil with application of vortex generators: Validation and sensitivity analyses. Energy. 2019, 187: 115969. J]

[19] Manolesos M, Chng L, Kaufmann Net al. . Using vortex generators for flow separation control on tidal turbine profiles and blades. Renewable Energy. 2023, 2051025-1039. J]

[20] Kerho M, Hutcherson S, Blackwelder R Fet al. . Vortex generators used to control laminar separation bubbles. Journal of Aircraft. 1993, 30(3): 315-319. J]

[21] Katz J, Morey F. Aerodynamics of large-scale vortex generator in ground effect. Journal of Fluids Engineering. 2008, 130(7): 071101. J]

[22] Wang S-b, Burton D, Herbst A Het al. . The effect of the ground condition on high-speed train slipstream. Journal of Wind Engineering and Industrial Aerodynamics. 2018, 172: 230-243. J]

[23] Krajnovlć S. Shape optimization of high-speed trains for improved aerodynamic performance. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. 2009, 2235439-452. J]

[24] Li T, Liang H, Zhang Jet al. . Numerical study on aerodynamic resistance reduction of high-speed train using vortex generator. Engineering Applications of Computational Fluid Mechanics. 2023, 17: e2153925. J]

[25] Zhang J, Huang F-y, Yu Y-zet al. . A novel wake flow control method for drag reduction of a high-speed train with vortex generators installing on streamlined tail nose. Physics of Fluids. 2023, 35(10): 105139. J]

[26] DIN EN14067-4Standards Committee Railway. Normenausshuss Fahrweg and Schienenfahrzenge (FSF). 2014[S]

[27] Wang S-b, Burton D, Herbst Aet al. . The effect of bogies on high-speed train slipstream and wake. Journal of Fluids and Structures. 2018, 83471-489. J]

[28] He K, Su X-c, Gao G-jet al. . Evaluation of LES, IDDES and URANS for prediction of flow around a streamlined high-speed train. Journal of Wind Engineering and Industrial Aerodynamics. 2022, 223: 104952. J]

[29] Bell J R, Burton D, Thompson M Cet al. . A windtunnel methodology for assessing the slipstream of highspeed trains. Journal of Wind Engineering and Industrial Aerodynamics. 2017, 1661-19. J]

[30] Wang D-w, Chen C-j, Hu Jet al. . The effect of Reynolds number on the unsteady wake of a high-speed train. Journal of Wind Engineering and Industrial Aerodynamics. 2020, 204: 104223. J]

[31] Han S, Wang Y-h, Zhang M-let al. . An adaptive drag reduction method for high-speed trains across variable Reynolds numbers. Physics of Fluids. 2025, 378085208. J]

[32] HUANG Feng-yi, SHANG Wen-fei, ZHANG Jie, et al. Optimization of crosswind stability for high-speed trains: Aerodynamic analysis of leeward winglet deflection angles [J]. Journal of Central South University, 2025. DOI:https://doi.org/10.1007/s11771-025-6036-x.

[33] Zhang J, Ding Y-s, Wang Y-het al. . A novel bionic Coleoptera pantograph deflector for aerodynamic drag reduction of a high-speed train. Journal of Central South University. 2023, 3062064-2080. J]

[34] Adamu A, Zhang J, Tajudeen H. Aerodynamic drag reduction of a high-speed train with cavities on bogie regions. Physics of Fluids. 2025, 376065143. J]

[35] Spalart P R. Detached-eddy simulation. Annual Review of Fluid Mechanics. 2009, 41: 181-202. J]

[36] Zhang J, Wang F, Han Set al. . An investigation on the switching of asymmetric wake flow and the bi-stable flow states of a simplified heavy vehicle. Engineering Applications of Computational Fluid Mechanics. 2022, 1612035-2055. J]

[37] Zeng H-y, Liu T-h, Chen X-det al. . Study on the influence of asymmetric mountain structures at tunnel portals on the aerodynamics of intersecting trains. Transportation Safety and Environment. 2025, 7: tdaf016. J]

[38] Zhang J, Wang Y-h, Wang Y-get al. . Pressure wave characteristics in high-speed maglev tunnels with various arch lattice-shell lengths inside hoods. Physics of Fluids. 2025, 37(2): 026125. J]

[39] Wang S-b, Bell J R, Burton Det al. . The performance of different turbulence models (URANS, SAS and DES) for predicting high-speed train slipstream. Journal of Wind Engineering and Industrial Aerodynamics. 2017, 16546-57. J]

[40] Han S, Xiang N-s, Huang F-yet al. . On reducing high-speed train slipstream using vortex generators. Physics of Fluids. 2025, 375055115. J]

[41] Bell J R, Burton D, Thompson M Cet al. . Moving model analysis of the slipstream and wake of a high-speed train. Journal of Wind Engineering and Industrial Aerodynamics. 2015, 136: 127-137. J]

[42] Xia C, Wang H-f, Shan X-zet al. . Effects of ground configurations on the slipstream and near wake of a high-speed train. Journal of Wind Engineering and Industrial Aerodynamics. 2017, 168: 177-189. J]

[43] European Union Agency for Railways. Commission regulation (EU) No. 1302/2014: Concerning a technical specification for interoperability relating to the “rolling stock-locomotives and passenger rolling stock” subsystem of the rail system. 2014[R]

[44] Chen G, Li X-b, Liu Zet al. . Dynamic analysis of the effect of nose length on train aerodynamic performance. Journal of Wind Engineering and Industrial Aerodynamics. 2019, 184: 198-208. J]

[45] ZHANG Jie, HAN Shuai, JI Peng, et al. Windproof performance improvement of windbreak walls on the transition connecting a realistic embankment and a hill cut along the high-speed railway [J]. Mechanics Based Design of Structures and Machines, 2025: 1–22. DOI: https://doi.org/10.1080/15397734.2025.2510583.

[46] Graftieaux L, Michard M, Grosjean N. Combining PIV, POD and vortex identification algorithms for the study of unsteady turbulent swirling flows. Measurement Science and Technology. 2001, 1291422-1429. J]

[47] Wang Y, Yu Y, Han Set al. . A novel arch lattice-shell tunnel hood design for mitigating pressure wave characteristics during a high-speed maglev train passage through a tunnel at various train speeds. Tunnelling and Underground Space Technology. 2026, 168107015. J]

[48] Zhang J, Melaku T G, Adamu Aet al. . Impact of incoming flow on wake asymmetry of a simplified vehicle: The Reynolds number effect. Journal of Wind Engineering and Industrial Aerodynamics. 2026, 268106291. J]

RIGHTS & PERMISSIONS

Central South University