A coupled numerical framework was established employing Large Eddy Simulation (LES), the Volume of Fluid (VOF) method, and a multiphase liquid film model to investigate the external flow field around a high-speed vehicle and the behavior of raindrop motion. Full-scale wind tunnel experiments validated the simulations under static and dynamic conditions. The maximum and minimum errors in static pressure coefficients along the vehicle centerline were 0.070 and 0.002, respectively, while the power spectral density of fluctuating pressure also showed good agreement. Compared to the traditional Lagrangian Multiphase (LMP) method, the VOF method for raindrop impingement simulations revealed that the VOF method more accurately captured raindrop deformation, breakup, and the nonlinear accumulation process of the liquid film. Numerical results under the condition of a 33.33 m/s vehicle speed and moderate rainfall intensity indicated that the liquid mass accumulation on the Field of View surface (FOVs) on the vehicle roof follows a quadratic function, while the wetted area increases approximately linearly before rapidly stabilizing. Driven by aerodynamic shear, the liquid film was observed to propagate upward against gravity, with local thickness positively correlating to tangential velocity. Moreover, the average correlation coefficient was found to decrease with increasing height.
Shao et al. (Sun,) studied this question.