Study of wall roughness and surface tension effects in rain simulation for vehicles with SPH

Rainwater simulation plays a vital role in assessing pollutant deposition and water management in modern electric vehicles, especially under complex fluid dynamic conditions involving surface roughness and surface tension. This study investigates and compares two commercial implementations of the Smoothed Particle Hydrodynamics (SPH) method—weakly compressible SPH (WCSPH) in PartoX and incompressible SPH (ISPH) in PreonLab—focusing on their applicability to automotive scenarios. To improve the accuracy of wetting behavior predictions on complex surfaces, a parameter calibration approach is developed to establish a quantitative link between fluid–structure interaction parameters and static contact angles. Numerical experiments involving droplet impact on rough surfaces and inclined planes indicate that WCSPH (PartoX) exhibits comparable capability to ISPH (PreonLab) in capturing transient flow features such as jet formation and thin film dynamics. Validation against industry-relevant test cases, including A-pillar overflow and windshield exposure, demonstrates that WCSPH aligns more closely with experimental observations, especially regarding overflow timing, and surface film distribution, supporting its effectiveness for simulation-driven design. These findings suggest that WCSPH-based approaches hold practical advantages in the context of automotive water management, contributing to reduced reliance on physical prototypes and promoting the development of more efficient virtual testing workflows. Future research will aim to extend the methodology to multiphase flow scenarios and long-term pollutant transport analysis.