Aerodynamic Shape Optimization of High-Speed Train Noses: A Comparative Study between China's Fuxing and Japan's Shinkansen

Aerodynamic comparison of high-speed-train noses requires consistent geometric definitions, operating conditions, and evaluation objectives. This study compares documented characteristics of the CR400AF Fuxing and E5 Shinkansen and proposes a Cross-Platform Multi-Output Surrogate Optimization framework for subsequent matched-condition evaluation. The framework integrates geometry harmonization, shared multi-output prediction, ensemble uncertainty estimation, adaptive Pareto-region sampling, and uncertainty-penalized NSGA-III optimization. Public specifications show that the CR400AF operating speed is 9.38% higher than the E5, whereas their reported body widths differ by approximately 0.30%. The speed difference corresponds to a calculated dynamic-pressure difference of 19.63% at equal air density and an aerodynamic-power difference of 30.84% when drag coefficient and reference area are additionally held equal. These conditional calculations isolate speed effects and do not represent measured performance differences. The design comparison further identifies tunnel-pressure response, explicitly associated with the E5's approximately 15 m nose, as an objective not captured by head drag, tail drag, and tail lift alone. Incomplete surface geometry and the absence of matched aerodynamic data prevent platform-specific performance rankings and verification of the proposed framework. The findings establish the conditions and objective coverage required for a defensible comparison, with subsequent optimization requiring independent aerodynamic validation. Ultimately, this research highlights the critical need for standardized aerodynamic evaluation protocols in international high-speed rail development, ensuring that future cross-platform optimizations are both scientifically rigorous and practically applicable.