Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Kelvin-Helmholtz in the Lab
The Kelvin-Helmholtz instability looks like a series of overturning ocean waves and occurs between layers of fluids undergoing shear. This video has a great lab demo of the phenomenon, including the set-up prior to execution. When the tank is tilted, the denser dyed salt water flows left while the fresh water flows to the right.…
Forming a Jet
Many situations can generate high-speed liquid jets, including droplet impacts, vibrated fluids, and surface charges. In each of these cases, a concave liquid surface is impulsively accelerated, which causes the flow to focus into a jet. The image above shows snapshots of a microjet generated from a 50 micron capillary tube visible at the right.…
AEDC 16-ft Supersonic Tunnel
This 1960 photo shows three men standing inside Arnold Engineering Development Complex’s 16-ft supersonic wind tunnel facility. The wind tunnel was capable of Mach numbers between 1.60 and 4.75 through a test section 4.8 meters wide and 20.2 meters long. It served as a large-scale testing facility for aircraft and propulsion systems. Like many large-scale…
Colliding in Microgravity
On Earth, it’s easy for the effects of surface tension and capillary action to get masked by gravity’s effects. This makes microgravity experiments, like those performed with drop towers or onboard the ISS, excellent proving grounds for exploring fluid dynamics unhindered by gravity. The video above looks at how colliding jets of liquid water behave…
Droplets Surfing
The Leidenfrost effect can make water droplets skitter across a hot griddle or briefly protect a hand dunked in liquid nitrogen. When a liquid is exposed to a solid surface much, much hotter than its boiling point, the contact vaporizes part of the liquid, and, in the case of a droplet, forms a thin lubricating…
Advantages of Schooling
Many fish swim in close proximity to one another in large schools, causing scientists to wonder if this behavior is motivated primarily by defense against predators or whether fish derive some hydrodynamic advantages from schooling. Examining the fluid dynamics of an entire school of fish is rather impractical, so researchers approximate two neighboring swimmers using…
The March of Drops
I love science with a sense of humor. This video features a series of clips showing the behavior of droplets on what appears to be a superhydrophobic surface. In particular, there are some excellent examples of drops bouncing on an incline and droplets rebounding after impact. For droplets with enough momentum, impact flattens them like a…
Putting Out Wildfires Using Explosives
Wildfires damage millions of acres of land per year in the United States alone. Using explosives to put out an uncontrolled wildfire sounds a bit crazy, but it’s actually not that far-fetched. The animations above are taken from high-speed footage of a propane fire interacting with a blast wave. The first animation shows what the human…
Oily Foams
It is common in many industries to use oil as a defoamer to break up existing foams or prevent foams from forming. But with the right surfactants–additives that change the foam’s surface tension–it’s possible to make aqueous foams that are actually stabilized by the presence of oil. This video explores some of the ways that…
Supercell Timelapse
The storm chasing group Basehunters captured this stunning timelapse of a supercell thunderstorm forming in Wyoming. This class of storm is characterized by the presence of a mesocyclone, seen here as a large, rotating cloud. These rotating features form when horizontal wind shear is redirected upright by an updraft. This requires a strong updraft, which…