Visualizing Airflow Around a Car

At higher speeds aerodynamic drag is the primary contribution to the resistance to motion suffered by your car. In the spirit of the old saying "know your enemy" here are a couple of videos showing experiments that visualize airflow. Both are based on the idea of putting a dye into the flow to make it visible.



In the first video, the fluid used is not air, but water. Models of a truck and a NASCAR race car are placed into a trough of water. A water current flows down the trough. By using a needle, dye is injected into the current. This lets you see the boundary layer around the vehicle and the wake pattern.



In the second video, a real vehicle (a 2009 Infiniti FX) is placed in a wind tunnel. So this time the fluid is really air. Green smoke is used to visualize the flow. The experiment clearly shows the boundary layer.

Knowing a little aerodynamics can be handy when you find yourself buying a car and want to get one that saves on gas!