Key Takeaways & Executive Findings
- •• Aerodynamic optimization of high-speed train cross-sections reduces drag by 2.4% in both windless and windy conditions. • In windy conditions, the aerodynamic lateral force on the leading car is reduced by 37.8%. • A flat and wide cross-sectional shape lowers aerodynamic drag and lateral loads. • The Kriging surrogate model combined with genetic algorithm effectively optimizes train body shapes.
Abstract
A train body's cross-sectional shape has a significant impact on aerodynamic drag and operational safety in high-speed trains (HSTs). This study extracts five design variables from a real-world HST body: height, width, side arc radius, arc radius at the connection between the side and the roof, and arc radius at the connection between the side and the train's bottom. The cross-validated Kriging surrogate model and the genetic algorithm are used to perform two types of aerodynamic optimization, with the cross-sectional area as a constraint. Cross-sectional shapes are optimized in both windless and windy conditions. Numerical results indicate that in a windless environment, the aerodynamic drag coefficient of the whole train is reduced by 2.4%; in a windy condition, the aerodynamic drag coefficient of the entire vehicle is reduced by 2.4%, and the aerodynamic lateral force of the leading car is reduced by 37.8%. These suggest that a flat and wide shape helps to reduce not only overall aerodynamic drag in a windless environment but also aerodynamic load in a windy environment, which can be accomplished by reducing the area of the side wall and top region, lowering the train body's height, increasing its width, and lowering the radius of the side and top arcs.
1. Introduction
With the increased speed of high-speed trains (HSTs), aerodynamic effects under high-speed operating conditions have become an important factor that limits further speed increases, energy conservation, and consumption reduction. There are two types of aerodynamic resistance: friction drag and pressure drag. In high-speed trains with low smoothness, pressure drag accounts for more than 70% of total aerodynamic resistance. In the open air, for high-speed trains with a nose length slightly greater than 5 m, aerodynamic resistance accounts for 85% of total resistance at a speed of 300 km/h; when running in a tunnel, the proportion of aerodynamic resistance to total resistance is even greater due to the compression effect of air. Overcoming aerodynamic resistance is the primary component of energy consumption for high-speed trains. Aerodynamic design, particularly aerodynamic drag reduction design, has emerged as the primary research direction for the exterior design of high-speed trains.
Aerodynamic drag for full-scale high-speed trains can generally be obtained through idling resistance tests. While for reduced-scale high-speed trains, it can be obtained through wind tunnel tests and moving model tests. Numerous research findings from experimentation and computational fluid dynamics (CFD) approaches indicate that operating speed, roadbed, head shape, train body cross-section, train length, bogies, pantographs, windshields, and other factors are the primary influences on aerodynamic drag of a high-speed train. For example, WANG et al used detached eddy simulation (DES) to investigate the flow around two different streamlined nose lengths, namely a short nose (4 m) and a long nose (9 m). They discovered that the nose length influences slipstream velocity along the entire train length in the lower and upper regions of the side of the train. However, no significant effect is observed at the train's middle height along its length, except in the nose area. JIANG et al employed a CFD approach based on Reynolds-average Navier-Stokes (RANS) equations to numerically study on the aerodynamic drag reduction based on bottom deflectors and streamlined bogies of a high-speed train. Three models were created and their aerodynamic properties were investigated: a single-bogie model, a simplified train model, and an eight-car high-speed train model. Their findings revealed that the single-bogie model with a streamlined design reduces drag significantly, with a 13.92% and 7.63% reduction in drag for the power bogie and trailer bogie, respectively. By adding the streamlined bogie and deflector to the simplified train model...
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PRASERT Prapamonthon, SUN Zhen-xu, YAO Shuan-bao, BAI Ye, GUO Di-long, YANG Guo-wei (2025). Investigation of aerodynamic shape optimization of cross-sectional body of high-speed train. Journal of Central South University. https://doi.org/10.1007/s11771-025-6151-8
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Frequently Asked Questions
What is the main objective of this study?
The study aims to optimize the cross-sectional shape of a high-speed train body to reduce aerodynamic drag and improve operational safety, using a Kriging surrogate model and genetic algorithm.
What design variables were considered in the optimization?
Five design variables were extracted from a real-world HST body: height, width, side arc radius, arc radius at the connection between the side and the roof, and arc radius at the connection between the side and the train's bottom.
What were the key results of the optimization?
In windless conditions, the aerodynamic drag coefficient was reduced by 2.4%. In windy conditions, the drag coefficient was also reduced by 2.4%, and the aerodynamic lateral force on the leading car was reduced by 37.8%.
What shape characteristics are recommended for reducing aerodynamic loads?
A flat and wide shape, achieved by reducing the side wall and top area, lowering the train body's height, increasing its width, and lowering the radius of the side and top arcs, helps reduce both drag and lateral loads.
What methods were used in this research?
The study employed a cross-validated Kriging surrogate model and a genetic algorithm for multi-objective optimization, with the cross-sectional area as a constraint.
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