Separated Flow Over a Pyramid

The photo below shows an example of flow separation. The flow is from left to right and the flow behind the pyramid is random and chaotic. Flow separation causes excess drag and pressure drop in many products and systems.

^ The dark triangle on the left is due to the refraction of the laser light as it goes through the top of the pyramid.

^ In this photo, the flow is slower, and the pyramid is shedding vortices.

A couple of videos are available, one at full speed ( 1.2 MB) and one in slow motion. ( 1.4 MB)