Small things often sell cars and create brand loyalty: the positioning of the cup holder; how the seat molds to your body; the thunk of the door when it closes. Add to that list how particles – whether they are rain, snow or dirt – disperse across the surface of a car.

Particle behavior in relation to the surface of a car is known in the automotive industry as vehicle soiling, and up until recently, it was nearly impossible to simulate in a computer. But within the last few years, Audi has made major strides in using CFD simulation and visualization to better predict the complex interactions that constitute vehicle soiling.