Underwater animals such as salps, squid, and jellyfish move around by ejecting pulsed jets of water. For animals like salps, many individuals can combine together to form a chain that pulses in sync to get around. Such animals inspired us to study what fluid behaviors emerge when multiple jets are used instead of just one.
When an underwater jet is pulsed, it produces a vortex ring that propagates steadily, entraining external fluid into the vortex swirls. When a second jet is introduced parallel to the first, the two vortex rings can interact strongly and change how the vortices evolve. If the jets are comprised of dyed fluid, the vortex ring interactions produce complex structures that evolve gracefully as they propagate through the water.