Gaylard, A., Pitman, J., Jilesen, J., Gagliardi, A. et al., "Insights into Rear Surface Contamination Using Simulation of Road Spray and Aerodynamics," SAE Int. J. Passeng. Cars - Mech. Syst. 7(2):673-681, 2014, doi:10.4271/2014-01-0610.
Contamination of vehicle rear surfaces is a significant issue for customers. Along with being unsightly, it can degrade the performance of rear camera systems and lighting, prematurely wear rear screens and wipers, and transfer soil to customers moving goods through the rear tailgate. Countermeasures, such as rear camera wash or automated deployment add expense and complexity for OEMs.This paper presents a rear surface contamination model for a fully detailed SUV based on the use of a highly-resolved time-accurate aerodynamic simulation realised through the use of a commercial Lattice-Boltzmann solver, combined with Lagrangian Particle Tracking to simulate droplet advection and surface water dynamics via a thin film model. Droplet break-up due to aerodynamic shear is included, along with splash and stripping from the surface film. The effect of two-way momentum coupling is included in a sub-set of simulations.The simulations are qualitatively validated in terms of surface contamination distribution against full scale (climatic) wind tunnel experiments using a UV fluorescent dye in water introduced onto dynamometer rollers.Three different contamination source configurations are examined: front tyres only, rear tyres only and all four tyres. The simulation is seen to recover the experimental rear surface contamination distribution, along with the trend in differences between these cases.The rear tyres are seen to be the dominant source, with front wheel spray and front wheel rotation only making small relative contributions.Two-way momentum coupling is seen to influence the rear surface contamination distribution.