To highlight the variety and artistic and scientific value of flow visualization techniques, I have chosen this fantastically entertaining music video by an artist called Nigel Stanford. It showcases a multitude of techniques for visualizing sound waves, which are collectively called cymatics. Many of these techniques involve fluids, and characterize how sound waves can drive different forms of fluid flow while serving as visual interpretation of the music.
In the video, a variety of fluids are used to visualize the standing waves created by the different tones that make up the musical composition. The most direct example of this is the plate atop a speaker, which allows the sound wave generated by the speaker to become visible. A variation of this is seen in the tube attached to a speaker; water flows out of the tube and the end of the tube moves as the speaker vibrates, creating a spiral as the flow of water is redirected. The tube does not appear to move because the frame rate of the camera was matched to the vibration rate of the tube. A similar visualization is created using the Ruben’s tube, in which a speaker generates a standing pressure wave inside a tube filled with propane. The propane then exits the tube via a series of small holes on top and is set alight. In this way, the height of the flames gives a measure of the pressure at each point along the tube and thus allows the sound wave to be visualized. Ferrofluid was also utilized in this video, though in this case pressure created by sound waves was not the direct driver of the fluid motion. Instead, a series of electromagnets were set up to pulse in correspondence with notes played on the keyboard. This means that electromagnetic forces being exerted on the iron nanoparticles in the fluid were the primary impetus for its motion. More details regarding how the experiments in the video were conducted can be found at https://nigelstanford.com/Cymatics/.
A notable aspect of the artistic value of this piece is that, while designing the experiments, the artist found frequencies of sound that produced aesthetically pleasing patterns in the fluids and then used these frequencies while writing the song used in the video. Thus, scientific principles actually informed the artistic composition of the music, which is particularly poignant in that, in my opinion, it demonstrates that science and art are not the antithesis of each other and can in fact be used to inform and complement one another.