#2019gofm

Fluids like air and water are called Newtonian because their viscosity does not vary with the force that's applied to them. But many common fluids -- almost everything in your fridge or bathroom drawer, for example -- are non-Newtonian, meaning that their viscosity changes depending on how they're deformed. (Image, video, and research credit: S. Arora and M. Driscoll) Read the full article

Vibrate a pool of water in air and the interface will form a distinctive pattern of waves called the Faraday instability. But what happens when you vibrate the interface between two fluids that can mix?  (Video, image, and research credit: G. Louis et al.) Read the full article

When a vortex ring forms, it's often from fluid forced through a round outlet, whether that's someone's mouth, a pipe, or a dolphin's blowhole. But vortex rings can come from other shapes, too. (Image, video, and research credit: B. Steinfurth et al.) Read the full article

In this award-winning video from the 2019 Gallery of Fluid Motion, we see how the geometry of a superhydrophobic surface can alter a splash. (Image and video credit: The Lutetium Project)

In nature, we often find turbulence mixed with convection, meaning that part of the flow is driven by temperature variation. Think thunderstorms, wildfires, or even the hot, desiccating winds of a desert. To better understand the physics of these phenomena, researchers simulated turbulence between two moving boundaries: one hot and one cold. (Image, research, and video credit: A. Blass et al.) Read the full article

In the ocean, breaking waves trap air into bubbles that then cluster into foam, but conventional simulations don't capture this foaminess. For bubbles to cluster into foam, there has to be a force preventing -- or at least delaying -- their coalescence. (Image and video credit: P. Karnakov et al.) Read the full article

In industry, drying droplets often have many components: a liquid solvent, solid nanoparticles, and dissolved polymers. The concentration of that last component -- the polymers -- can have a big effect on the way the droplet dries, as seen here. (Video, image, and research credit: J. Zhao et al.) Read the full article

In 5th grade, I grew crystals by evaporating solutions of salt water from miniature pie tins. But it turns out I could have gotten much cooler results if I'd evaporated my salt water a drop at a time on a hot superhydrophobic surface. (Video, image, and research credit: S. McBride et al.) Read the full article