Crown Splash

When a falling drop hits a thin layer of water, the impact sends up a thin, crown-shaped splash. This research poster shows a numerical simulation of such a splash in the throes of various instabilities. The crown’s thick edges are undergoing a Rayleigh-Plateau instability, breaking into droplets much the way a dripping faucet does. On the far side, the crown has rapidly expanding holes that pull back and collide. The still-intact liquid sheet at the base of the crown shows some waviness, as well, hinting at a growing instability there. (Image credit: L. Kahouadji et al.)

#2024gofm #CFD #computationFluidDynamics #crownSplash #fluidDynamics #instability #physics #PlateauRayleighInstability #science #splashing

“The Ballet of Colors”

Thomas Blanchard’s short film “The Ballet of Colors” plunges viewers into a warm spectrum of roiling oil and paint. Fluid dynamically speaking, it could be subtitled “the Plateau-Rayleigh instability” thanks to its focus on retracting paint ruptures and ligaments breaking into droplets. Unlike some other videos of this genre, Blanchard uses a high-speed camera here, filming the action at 1,000 frames per second, and the result is smooth, crisply focused, and absolutely delectable. (Video and image credit: T. Blanchard et al.)

#droplets #fluidDynamics #fluidsAsArt #instability #physics #PlateauRayleighInstability #science

Instabilities in Competition

When two liquid jets collide, they form a thin liquid sheet with a thicker rim. That rim breaks into threads and then droplets, forming a well-known fishbone pattern as the Plateau-Rayleigh instability breaks up the flow. This poster shows a twist on that set-up: here, the two colliding jets vary slightly in their velocities. That variability adds a second instability to the system, visible as the wavy pattern on the central liquid sheet. The sheet’s rim still breaks apart in the usual fishbone pattern, but the growing waves in the center of the sheet eventually that structure apart as well. (Image credit: S. Dighe et al.)

#2024gofm #fishbone #fluidDynamics #fluidsAsArt #instability #jetCollision #physics #PlateauRayleighInstability #science

When a drop settles gently against a pool of the same liquid, it will coalesce. The process is not always a complete one, though; sometimes a smaller droplet breaks away and remains behind (to eventually do its own settling and coalescence). When this happens, it’s known as partial coalescence.

Here, researchers investigate ways to tune partial coalescence, specifically to produce more than a single droplet. To do so, they add surfactants to the oil layer surrounding their water droplet. The surfactants make the rebounding column of water skinnier, which triggers the Rayleigh-Plateau instability that’s necessary to break the column into more than one droplet. (Image and video credit: T. Dong and P. Angeli)

https://fyfluiddynamics.com/2024/10/tweaking-coalescence/

#2022gofm #coalescence #coalescenceCascade #fluidDynamics #instability #physics #PlateauRayleighInstability #science #surfaceTension #surfactant