https://www.youtube.com/watch?v=aQFm3PB9iNw?rel=0

Although the purpose of the video is scientific, I find the movement of the dye incredibly beautiful and hypnotic. The high contrast makes the flow easily visible.  I appreciate how the creator has included two different frequencies of this experiment because comparing the two  creates a better visual understanding of the physics behind the vortexes created by the flapping foil.

Video by Ramiro Godoy-Diana, CNRS researcher at PMMH, ESPCI.

more of his work can be found at: https://blog.espci.fr/ramiro/home/