Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Dr. Seussian Mystery Fluid Could Have Saved Top Kill
Dr. Seussian Mystery Fluid Could Have Saved Top Kill Wired article about using non-Newtonian fluids to plug leaking oil wells as we featured previously.
Reader Question: National Committee for Fluid Mechanics Films
lazenby asks: Have you seen these guys? http://web.mit.edu/hml/ncfmf.html Yes, absolutely! Those videos, which date from the 1960s, are so useful that they’re still shown to undergraduates today. (Or at least they showed several of them to us when I was junior!) They can seem a bit slow by current standards, but the films are full…
Flow Visualization
[original media no longer available] This video gives a neat introduction to some common and uncommon techniques used to visualize fluid flows.
Smokestack Plumes
On a cold and windy day, the plume from a smokestack sometimes sinks downstream of the stack instead of immediately rising (Figure 1). This isn’t an effect of temperature–after all, the exhaust should be warm compared to the ambient, which would make it rise. It’s actually caused by vorticity. In Figure 2, we see a…
Airfoil-shaped Ice
I discovered this interesting bit of icing a couple years ago near the foot of a waterfall in Ithaca, NY. The predominant wind was always heading toward the falls (left to right in these pictures), while the falls were always throwing spray up into the wind. The result was that ice airfoils (center) formed in…
Thixotropic and Rheopectic Fluids
There’s more to non-Newtonian fluids than shear-thickening and shear-thinning. The viscosity of some fluids can also change with time under constant shear. A fluid that becomes progressively less viscous when shaken or agitated is called thixotropic. The opposite (and less common) behavior is a fluid that becomes more viscous under constant agitation; this is known…
Liquid Settling
Despite the strange shapes of the arms on this container, the fluid inside will always settle to a common height. This is because each interconnected section is open to the outside air. The fluid’s surface has to reach a static equilibrium with the atmosphere–i.e. the surface of the fluid must be at atmospheric pressure–and the…
Ants as a Fluid
The collective behavior of ants can mirror the flow of a viscous fluid. It would be interesting to see if any such parallels carry over to the flocking of birds or schooling of fish. The latter two behaviors are thought to increase aero- and hydrodynamic efficiency for the group. #
Plugging an Oil Leak
Recent research indicates that adding cornstarch to drilling mud increases the likelihood that a “top-kill” procedure will plug a leaking oil well. Adding cornstarch to water (or mud) turns it into a non-Newtonian fluid with viscoelastic properties that prevent the instabilities that lead to turbulent breakup. On the left, an underwater photo of the Deepwater…
Wake of a Rising Sphere
This flow visualization shows the wake left by a freely rising sphere. Observations of rising and falling spheres date at least back to Newton, who observed that the inflated hog bladders he used “did not always fall straight down, but sometimes flew about and oscillated to and fro while falling”. That vibration is caused by…