Effect of rearview mirror shape on the flow structures and water film accumulation in the side windows region of heavy-duty vehicles

Water accumulation on the side window of heavy-duty vehicles under rainy conditions impairs driver visibility and threatens driving safety. The lattice Boltzmann method (LBM) coupled with the Lagrangian Particle Tracking Model (LPTM) and Thin Film Model (TFM) is applied to investigate the wind-raindrop two-phase flow characteristic in the side window region. Additionally, a boundary seeded methodology has been implemented to improve computational efficiency by 66.7% while maintaining accuracy. The results indicate that the counterclockwise vortex formed in the gap between the A-pillar and the rearview mirror induces the breakup of the liquid film adhering to the mirror surface into fine droplets, which are entrained by the airflow and consequently exacerbate the deposition of rainwater in the side window region. The reduction in the height of the rearview mirror frame directs more droplets to the housing exterior, weakens the V1 and V2 vortices, and reduces average film thickness and water-phase distribution ratio by 8.1% and 41.85%, respectively. Increasing the inboard angle from 85° to 130° redirects high-momentum airflow toward the A-pillar, shifts the V1 vortex forward, and lowers its intensity, reductions of 18.5% and 42.17% in average water film thickness and water distribution ratio.