Numerical study on aerodynamic noise reduction of high-speed pantograph using base-frame fairing
A hybrid improved delayed detached eddy simulation (IDDES) and Ffowcs Williams–Hawkings (FW-H) acoustic analogy framework is applied to quantify the aerodynamic noise mitigation potential of base-frame fairings on a high-speed pantograph operating at 400 km/h. Two fairing configurations—solid and perforated—are evaluated without altering the pantograph's bottom structural architecture. The solid fairing effectively shields the base-frame and suppresses flow separation at the pantograph bottom, yet it introduces flow deflection and acceleration that elevate noise generation in the top and mid regions. A previously underreported self-noise mechanism is identified: wake impingement from unshielded insulator beams onto the fairing side surface generates high-amplitude pressure fluctuations, compromising net noise reduction. Smoothing the insulator beams mitigates this effect. The perforated fairing outperforms the solid variant by providing an additional airflow pathway through small holes, which reduces lateral and upward flow acceleration and promotes wake vortex suppression. Airflow ejected from leeward holes pushes vortex structures downstream, forming a stable, low-fluctuation region near the fairing tail and significantly reducing dipole source strength. Aerodynamic drag is reduced by 21.8% with fairing installation, though lift fluctuation of the strip is exacerbated by flow deflection. These findings establish perforated base-frame fairings as a superior noise-control strategy for high-speed pantograph systems.