Oskar Hamidi presents his master’s thesis

Student: Oskar Hamidi
Main Supervisor: Tobias Eidevåg (Volvo Cars Corporation)
Examiner: Henrik Ström
Opponent: Chang Xu

Abstract

Increasingly advanced vehicle safety systems rely on optical sensors such as the side view camera monitoring system (CMS) for visual information and are expected to function under all road conditions. Together with Volvo Cars Corporation this project aimed to increase the knowledge of vehicle camera contamination by roadsprays and how airborne droplets behave within the turbulent wake of various CMS designs under different driving conditions.
Computational Fluid Mechanics (CFD) was used through STAR-CCM+ to simulate the multiphase flow of air and water droplets using an unsteady Eulerian-Lagrangian approach on a simplified geometry. Turbulence was simulated using Delayed-Detached Eddy Simulations (DDES) and the droplet motion through inclusion of gravity, drag, shear lift and pressure gradient droplet forces.
Several experiments in Volvo Cars’ aerodynamic wind tunnel were also conducted on the CMS designs and simplified geometry, providing comparable results to the simulations.

The results indicated that the CMS contamination was mainly caused by secondary sprays near the circumference of the camera face, originating from airborne droplets that deposited on the exterior surfaces of the CMS and propagated into films that rupture due to the aerodynamic forces and inject droplets into the CMS wake.

While a slanted face would provide a wider range of vision, results indicated that it would also be more susceptible to contamination. It was also suggested that the camera lens would be less contaminated when using CMS design with either a deeper or wider glareshield. Furthermore, by leading away water the water film from the camera face through a groove, contamination could also be reduced. Finally, it was found that higher driving velocities significantly increased contamination of the CMS.