Numerical investigation of droplet dispersion and atomization in the wake turbulence of an isolated rotating wheel splash

The rapid development of vehicle intelligence has heightened concerns regarding driving safety, as splash and atomized droplets from vehicles on wet roads. To decipher the underlying physics governing droplet dispersion, this study employs the shear stress transport k–ω (SST k–ω) improved delayed detached eddy simulation (IDDES) turbulence model combined with Lagrangian particle tracking to systematically investigate droplet transport across various speeds and droplet sizes. Two-way coupling and proper orthogonal decomposition (POD) are applied to uncover the inherent links between vortex dynamics and droplet behavior. Results show that increased vehicle speed significantly widens lateral dispersion, enhances droplet breakup probability, and extends the spray's downstream penetration. The droplet diameter nonlinearly influences the surrounding turbulent kinetic energy field via modulated two-phase coupling. Larger droplet diameters intensify droplet–vortex interactions and shear forces, leading to higher breakup rates and modifying the turbulent kinetic energy field. POD analysis further reveals that the combined energy of the first ten modes drops from 59.95% (40 km/h) to 50.26% (120 km/h). Higher speeds amplify localized small-scale structures, which critically modulate droplet trajectories. A critical droplet diameter of approximately 0.3 mm is identified, beyond which the dominant flow structure remains stable in form and energy. The study provides a theoretical basis both for aerodynamic optimization to control splash and for recommending operational measures such as speed reduction in rain, thereby enhancing visibility and safety.