Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
The Angle of Repose
[original media no longer available] Granular materials like sand tend to form heaps when poured. The steepness of the heap at rest is described by the angle of repose, which is determined by a balance between gravity, normal force, and friction on the grains. When a heap of grains is disturbed, it can trigger an…
How Dogs and Cats Drink
We humans do our hands-free drinking via suction, using the shape of our lips and mouths to create low pressure that draws liquids in. Dogs and cats, on the other hand, have no cheeks and, therefore, no suction. Instead, both cats (top) and dogs (bottom) drink using adhesion, or the tendency of a liquid to…
Boiling Water in Oil
Most people know that throwing water into hot oil is a bad idea. But, as dramatic as the results can be, the boiling of a water droplet submerged in oil is remarkably beautiful, as seen in the animations above. The initial water droplet expands as it shifts from liquid to vapor (top). At a critical…
The Challenges of Micro Air Vehicles
Interest in micro-aerial vehicles (MAVs) has proliferated in the last decade. But making these aircraft fly is more complicated than simply shrinking airplane designs. At smaller sizes and lower speeds, an airplane’s Reynolds number is smaller, too, and it behaves aerodynamically differently. The photo above shows the upper surface of a low Reynolds number airfoil…
Shock Waves in Flight
Schlieren optical systems have been used to visualize shock waves in labs for more than a century, but the technique did not translate well to photographing shock structures outside the lab. But now NASA’s Armstrong Research Center and Ames Research Center have developed a method that allows them to capture highly-detailed images of the shock…
“The Chase”
Sometimes it takes timelapse photography to truly appreciate the dynamic behavior of our atmosphere. In “The Chase” Mike Olbinski, whose work we’ve featured previously, has captured some of the most incredible and stunning weather timelapse footage I have ever seen. Despite watching it repeatedly, I continue to be awed to the point that I have…
Vapor Cones
Vapor cones typically appear around aircraft flying in the transonic regime–near, but still below, the speed of sound. Air moving over the vehicle accelerates and decelerates as it moves around different parts of the plane; if it didn’t, the plane couldn’t generate lift and wouldn’t fly. When the local flow accelerates past the speed of…
Fire Tornadoes
View this post on Instagram Saw a firewhirl for the first time last night. This sucker was shooting flames 100 ft in the air before it passed right in front of the line, all while dropping hot dirt on our helmets. A post shared by Craig (@lecraix) on Aug 14, 2015 at 6:53pm PDT Fire…
Bubbles and Hurricanes
You may think of soap bubbles as a childhood plaything, but there’s a lot to be learned from them. In her newest video, Dianna of Physics Girl explores some of the fascinating research scientists use soap bubbles for and how you can recreate some of their experiments at home. Scientists have used bubbles to explore…
Turbulent Ink
Turbulence is found throughout our lives, but rarely is it as startlingly beautiful as in this Slow Mo Guys video. Here they show high-speed videos of ink being injected into water. The resulting plumes are turbulent from the very start, with innumerable folds and eddies billowing outward as the plume expands. The large difference in…