Simulation of external circulating water management for vehicle air conditioning based on the SPH method - A study on the coupling effect between the blower and driving conditions

• Innovative SPH Simulation: Leveraged SPH method for realistic vehicle AC water management simulation, capturing blower-driving condition coupling effects. • Nonlinear Water Intake: Revealed nonlinear water intake jump under heavy rainfall (>60mm/min), highlighting drainage system limits. • Speed Impact Variability: Uncovered non-monotonic water intake changes with vehicle speed, peaking at medium speeds, challenging conventional wisdom. • Design Flaws Exposed: Exposed significant intake cavity design flaws, guiding next-gen water-resistant AC system development. . This study transforms vehicle air conditioning water management by pioneering a coupled SPH-aerodynamic simulation framework, revealing multiphysics interactions between blower operation, rainfall intensity, and driving speed. Traditional analyses focused solely on intake grille water paths, but our SUV model simulation demonstrates that blower speed escalation (2600–3600rpm) boosts fresh air flow by 138% while causing airflow deflection that reduces separation efficiency, yielding 10.7× higher water ingress at peak speeds. Rainfall intensity exhibits threshold behavior: moderate rain (20–40mm/min) shows linear correlation, whereas heavy rain (>60mm/min) triggers non-linear jumps (7.08g max) due to drainage system saturation. Vehicle speed impacts reveal counterintuitive trends—medium speeds (40km/h) produce maximum water intake (1.31g) as surface rainwater movement and fresh air flow compete, while high speeds (60km/h) reduce ingress via enhanced airflow-driven drainage. Critical design flaws emerge: insufficient Z-directional cavity space promotes droplet re-entrainment, turbulent energy dissipation is 37% lower than optimal, and gas-liquid separation efficiency drops to 58% under combined loading. These findings redefine engineering priorities for water-resistant AC systems, offering actionable guidelines for cavity redesign, blower control optimization, and multi-factor rainfall testing protocols. This methodology offers a novel approach and perspective for water management research in automotive climate control systems.