We sweat the details. To illuminate the details, this video is shot at 5000 frames per second with laser sheet lighting. Check out the leading edge of the spray, double vortex all the way.
Beautiful phenomena can be hidden by size, cloaked with speed, and shrouded by chaos. But they can be perceived if you know how to look.
The spray from a bottle of fragrance is driven by pressure. When the button is depressed, the pressure inside the bottle increases, forcing fragrance out the nozzle. This liquid is ejected forcefully enough that it breaks into tiny droplets. As the droplets vaporize and encounter wind resistance, they take on certain patterns that can be illuminated with the proper imaging technique. For this video, I created a laser sheet using a cylindrical lens, and used the sheet to illuminate the spray. Sheet illumination allows you to track individual droplets more clearly. A high-speed camera is then synced with the laser at 5000 frames per second, and it’s lights, camera, action.
As the spray exits the nozzle, you can see the large droplets at the beginning, before the spray really hits its stride. Once into the heart of the spray, a double vortex forms at the leading edge. This shape occurs because as droplets at the front slow down due to wind resistance, they are pushed out of the way by the speedier droplets behind. As the speedy droplets come to the front, they too are slowed down, and the vortex pattern is created. Although it appears to be two distinct vortices, don’t forget that we are only viewing a 2D slice of the spray because of the laser sheet illumination. The pattern formed at the leading edge of the spray actually more closely resembles a smoke ring, being a fully circular vortex traveling in space. After the bulk of the spray has passed, a vortex street appears, showing alternately rotating vortices within the bulk spray.
All these phenomena are hiding in plain sight if you just know how to look.