Abstract This paper focuses on methods used to model vehicle surface contamination arising as a result of rear wake aerodynamics. Besides being unsightly, contamination, such as self-soiling from rear tyre spray, can degrade the performance of lighting, rear view cameras and obstruct visibility through windows. In order to accurately predict likely contamination patterns, it is necessary to consider the aerodynamics and multiphase spray processes together. This paper presents an experimental and numerical (CFD) investigation of the phenomenon. The experimental study investigates contamination with controlled conditions in a wind tunnel using a generic bluff body (the Windsor model.) Contamination is represented by a water spray located beneath the rear of the vehicle. The aim is to investigate the fundamentals of contamination in a case where both fow feld and contamination patterns can be measured, and also to provide validation of modelling techniques in a case where fow and spray conditions are known. CFD results were obtained using both steady RANS and unsteady URANS solvers, combined with particle tracking methods. Steady RANS does not capture the wake structures accurately and this affects the contamination prediction. URANS is able to recover the large-scale wake unsteadiness seen in the experimental data, but the difference between the experimental and computational contamination distributions is still notable. The CFD is also able to provide further insight by showing the behaviour of particles of different sizes. Large particles are found to take on a ballistic trajectory and penetrate the wake. In contrast, small particles are shown to be less likely to become entrained into the wake. Introduction Contamination of vehicle rear surfaces is a signifcant issue. It can degrade the performance of lighting, obstruct visibility through the rear window and lead to glass degradation due to abrasion and premature wear of wiper blades [1]. Contamination can also infuence the performance of rear camera systems by obstructing camera lenses [2]. Furthermore, it can be a source of dissatisfaction in instances when dirt gets transferred onto the user upon contact with the vehicle exterior. In general, there are three sources of vehicle surface contamination. The frst two sources are wind-driven rain (referred to as primary contamination) and a mixture of water and solids raised by vehicles from the road surface which are consequently deposited on the surface of preceding cars (also referred to as third-party contamination). Finally, the third source is called self-soiling and results from the spray generated by the rotation of the vehicle’s wheels without any infuence from other road users. The contaminant spray is advected into the vehicle’s wake which deposits it onto the rear surfaces. These processes involve a complex and broad range of multiphase physics. The issue of self-soiling is particularly relevant for vehicles with a large base area, such as off-road vehicles, Sports Utility Vehicles (SUVs) and Estates (Station wagons). This is because the blunt rear geometry of these vehicles causes the formation of strong large-scale recirculating vortices which draw spray towards the rear surfaces [3]. To date, the most successful counter measures against contamination have been systems that redirect water and air away from the critical areas on the vehicle surface. For example, spray suppression has been achieved for heavy goods vehicles by the use of textured faps, combined with either fenders or valances [4]. However, such design solutions have historically focused on reducing spray hazard to other road users, rather than reducing deposition on vehicle surfaces. Experimental and Computational Study of Vehicle Surface Contamination on a Generic Bluff Body 2016-01-1604 Published 04/05/2016 Anton Kabanovs, Max Varney, Andrew Garmory, and Martin Passmore Loughborough University Adrian Gaylard Jaguar Land Rover CITATION: Kabanovs, A., Varney, M., Garmory, A., Passmore, M. et al., "Experimental and Computational Study of Vehicle Surface Contamination on a Generic Bluff Body," SAE Technical Paper 2016-01-1604, 2016, doi:10.4271/2016-01-1604. Copyright © 2016 SAE International Downloaded from SAE International by Loughborough University, Monday, October 10, 2016