Nonlinear Aerodynamic Load Response and Disaster Mechanism of Sedans in Strong Crosswinds

To address the frequent disasters caused by strong crosswinds in Xinjiang’s “Hundred Miles Wind Zone,” this study utilizes a CFD numerical simulation method, validated by wind tunnel tests with an error of less than 5%, to systematically analyze the nonlinear response characteristics of a sedan’s aerodynamic loads under coupled conditions of vehicle speeds ranging from 60 to 100 km/h and crosswinds from 15.5 to 26.5 m/s. The results indicate that the sharp increase in leeward negative pressure, driven by flow separation, governs the escalation of aerodynamic loads. A distinct decoupling is observed between lateral force and drag: while lateral force scales linearly with vehicle speed, aerodynamic drag exhibits a nonlinear hysteresis. This is attributed to a “Flow Alignment Mechanism,” where the reduction in resultant yaw angle improves the leeward streamline topology, thereby mitigating drag growth. Furthermore, the rolling moment is identified as the dominant instability factor (peaking at 551.12 N·m). Conversely, the yawing moment saturates at high speeds due to an “Antagonistic Effect,” wherein dynamic pressure amplification is effectively counteracted by the shortening of the moment arm induced by the rearward migration of the Center of Pressure (CoP). These findings provide a robust theoretical basis for establishing speed limits and stability control strategies in extreme wind zones.