Maple tree seeds flutter and spin as they descend. The above video, which shows flow visualization of a freely falling seed, demonstrates that the so-called helicopter seed’s autorotation creates a vortex Keep reading
One common experimental technique for measuring velocity in a flow is particle image velocimetry (PIV), shown above. Special particles are introduced–seeded–into the flow. Typically, these particles are small, neutrally buoyant, and Keep reading
[original media no longer available] This video gives a neat introduction to some common and uncommon techniques used to visualize fluid flows.