Airflow
As a car move forward, air passes over its body. But, unlike a boat that pushes water aside, in the case of cars, the fluid (air) is invisible. So, while an implication of the air movement can be gained by looking at the patterns of water droplets and the deposition of dust, in most cases people don't really have any idea of the paths that the air takes over, under and around their car.But help is at hand: it is a near zero cost process to wool-tuft a car and then drive it down the road, inspecting the pattern of airflow from another moving car!
And why would you want to do that? Well, two main reasons, really.
