ExternalWater Management andWetting Phenomenon Using CFD: Investigating the wetting phenomenon and droplet transport on the external surfaces of interest on a car using CFD solvers

Abstract

Advanced Driver Assistance Systems (ADAS) rely heavily on exterior mounted sensors such as cameras, radar and LiDAR to ensure safe and reliable vehicle operation. However, the performance of these sensing systems can be significantly affected by environmental conditions, particularly rain and water droplet accumulation on sensor surfaces. This thesis focuses on developing a methodology to quantitatively evaluate water droplet behavior on a prototype Camera Monitoring System (CMS) using both experimental and numerical approaches. The study combines wind tunnel experiments with computational water droplet transfer simulations to investigate the interaction between airflow and water droplets around the CMS geometry. High speed experimental videos obtained from controlled wind tunnel testing were systematically analyzed to extract quantitative metrics. These metrics served as a validation framework for the numerical simulations and enable a direct comparison between experimental observations and computational predictions.

The numerical methodology employs a hybrid Eulerian Lagrangian approach using Computational Fluid Dynamics (CFD) approach. The external airflow around the CMS is modeled using the Finite Volume Method (FVM), which solves the governing Navier Stokes equations to accurately capture the aerodynamic flow field and pressure distribution surrounding the sensor housing. Based on the computed airflow solution, water droplet transport and surface interaction are simulated using Smoothed Particle Hydrodynamics (SPH), a mesh free Lagrangian particle method well suited for modeling free surface flows, droplet breakup, coalescence, adhesion and detachment phenomena. The outcomes of this work provide a foundation for the future development of predictive design tools aimed at enhancing the reliability, robustness and safety of ADAS sensor systems operating under adverse weather conditions.