Helium bubbles used in wind tunnel for flow visualization

[MetroMPG]

This is cool:

Angus Lock, Mira’s head of aerodynamics, said: “Wind tunnels detect forces like downforce and drag but never explain how those forces are generated.
“To reveal the flow structures at play you need to use flow visualisation.

So the folks at MIRA set up an array of high-speed cameras to capture helium filled bubbles introduced into the airstream, then analyzed the footage to track the bubbles' paths around the vehicle in 3-D.

Real world CFD... um RWFD?

Mira’s system works by seeding the airflow in the tunnel with tiny helium bubbles which serve as targets to be tracked by a 12-camera array. Provided that at least two cameras see a bubble, a 3D fix is obtained using stereo-photogrammetry.

Each bubble is tracked, revealing where flows originate and how they interact with the bodywork and other structures in the flow field.

Hundreds of bubbles can be tracked at the same time.

Source: Professional Engineering Magazine : Wind tunnel bubble technology