Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Hydraulic Jumps
Chances are that you’ve seen plenty of hydraulic jumps in your life, whether they were in your kitchen sink, the whitewater of a river, or at the bottom of a spillway. Practical Engineering has a great primer on this oddity of open channel flow. When water (or other liquids) flow with a surface open to…
Amber Waves
When I was a teenager, I liked riding my bike along the river boardwalk near my house. There were fields there, like those in the image above and video below, with tall grass that would bend and sway in the wind. The long stalks undulated almost like a fluid, and they were mesmerizing. This video…
Exploding a Drop
Leidenfrost drops levitate over a hot substrate on a thin layer of their own vapor, constantly replenished as the drop evaporates. For the most part, previous studies have focused on pure droplets, but a new one looks at what happens when you add surfactants – and the results are, well, explosive. Surfactants are a type…
Inside Fondue
Cheese fondue is a complex – and delicious – Swiss delicacy. The perfect fondue requires the right mix of ingredients and preparation to get the rheology – the flow character – just right. Fondue is a colloid, a fluid containing a mixture of suspended insoluble particles. The major components, rheologically speaking, are fat globules and…
Collective Motion: Nematodes
We often imagine that collective motion creates an advantage – that the schooling fish and flocks of birds gain something from this behavior – but that’s not always the case. Above, you see nematodes moving through a thin liquid layer. Random collisions occasionally bring the nematodes into contact, and once that happens, surface tension holds…
Collective Motion: Waving Bees
Giant honeybees live in huge open nests. To protect themselves, they’ve developed a mesmerizing wave-like defense known as shimmering. When shimmering, the bees in a hive, beginning from a distinct spot, will flip over to expose their abdomens. Taken together, this creates large-scale patterns like those seen above. Scientists have connected the behavior to the…
Collective Motion: Crowds
It’s sometimes taken for granted that, in groups, people can behave a lot like a fluid or a granular material. This allows scientists to adapt models developed for those materials to understand how crowds move. But in doing so, it’s always important to test just how far the comparison holds; in other words, just how…
Collective Motion: Worms
Although most animals are more solid than fluid, what happens when you put many of them together can be strikingly fluidic. Above you see the black aquatic worm, Lumbriculus variegatus, which must keep moist to stay alive. An individual worm will die within an hour of being removed from the water, but, in a group,…
Collective Motion: Intro
Herds, flocks, schools, and even crowds can behave in fluid-like ways. On Science Friday, Stanford professor Nicholas Ouellette explains some of the physics behind these similarities. Fluids are, after all, made up of a many, many individual particles – typically molecules – just the way a crowd of people or a school of fish contains…
Avoiding Ice
Keeping ice from forming on a surface is a major engineering challenge. Typically, there’s no controlling certain factors – like the size and impact speed of droplets – so engineers try to tame ice by changing the surface. This can be through chemicals – as with deicing fluids used on aircraft – or by tuning…