Surface contamination of cars: A review

Abstract

This review surveys the problem of surface contamination of cars, which poses a growing engineering challenge to vehicle manufacturers, operators and users. Both the vision of drivers and the visibility of vehicles need to be maintained under a wide range of environmental conditions. This requires managing the flow of surface water on windscreens and side glazing. The rate of deposition of solid contaminants on glazing, lights, licence plates and external mirrors also needs to be minimised. Maintaining vehicle aesthetics and limiting the transfer of contaminants to the hands and clothes of users from soiled surfaces are also significant issues. Recently, keeping camera lenses clean has emerged as a key concern, as these systems transition from occasional manoeuvring aids to sensors for safety systems. The deposition of water and solid contaminants on to car surfaces is strongly influenced by unsteady vehicle aerodynamic effects. Airborne water droplets falling as rain or lifted as spray by tyres interact with wakes, vortices and shear flows and accumulate on vehicle surfaces as a consequence. The same aerodynamic effects also control the movement of surface water droplets, rivulets and films; hence, particular attention is paid to the management of surface water over the front side glass and the deposition of contaminants on the rear surfaces. The test methods used in the automotive industry are reviewed, as are the numerical simulation techniques.

Robust Optimization of a Permanent-Magnet Synchronous Machine Considering Uncertain Driving Cycles

“…Instead of manipulating the velocity-time profile itself, one can also variate the rolling resistance coefficient C rr and the drag coefficient C d , which are used to compute M m (t) from v(t) (scenario C). In this way, uncertain weather and road conditions can be simulated, as C rr can increase by a factor up to δ rr = 1.3 on a wet road [12], and C d by a factor up to δ d = 1.2 due to rain drops contaminating the vehicle surface [13]. It is assumed that these mechanical coefficients are uniformly distributed, C rr (θ) ∈ U (C rr,dry , δ rr C rr,dry ) ,…”

Unsteady pressure analysis of the near wall flow downstream of the front wheel of a passenger car under yaw conditions

“…Gaylard & Duncan [21] as well as Gaylard et al [22] describe in their work the significant level of contamination onto the side of a SUV and notchback car due the wheel wake flow. In experimental and numerical investigations it is shown that the side soiling is mainly caused by flow being driven out the wheel house.…”

Modelling the Effect of Spray Breakup, Coalescence, and Evaporation on Vehicle Surface Contamination Dynamics

“…Management of surface contamination is becoming an increasingly important research area and design criterion for all major vehicle manufacturers. Apart from aesthetic considerations, vehicle soiling can also affect customer satisfaction in instances when dirt gets transported to their hands and clothes upon the contact with the vehicle exterior [1]. Contamination of rear surfaces represents a particular inconvenience, as dirt accumulating on these surfaces can degrade visibility through the rear screen, reduce rear wiper life, deteriorate the performance by lighting and rear view camera systems, as well as reduce visibility of rear lamps to other road users.…”

“…This is particularly problematic for square backed vehicle types, such as hatchbacks, estates and Sports Utility Vehicles (SUV) because the blunt rear geometry of these vehicles causes the formation of strong large-scale recirculating vortices that draw spray towards the rear surfaces [4]. Unlike rain droplets, spray generated by wheels can contain a diverse range of solid contaminants, such as soil, salt, sand, components of fuels and oils, carbon from combustion sources, brake and tyre wear and tarmac [1]. These materials, especially salt used for de-icing of roads, in combination with water can corrode the metalwork [5].…”