Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Leaping Ferrofluid
This video shows some of the dynamic behaviors of a ferrofluid near moving magnetic fields. Ferrofluids are formed from a suspension of ferrous particles in a liquid, usually oil.
Archimedes
Archimedes may be the world’s most famous fluid mechanician. The story of his discovery of the principles of buoyancy (and his subsequent running naked through the streets proclaiming “Eureka!”) is classic. His other famous fluid-related invention is the Archimedes screw, a type of pump still used today in applications from moving granular flows to maintaining…
Reader Question
aeronode-deactivated20130828 asks: What’s your academic/professional background? (Just curious.) Fair question! I am a fourth-year PhD student in aerospace engineering, focusing (naturally) on fluid dynamics. I have a bachelor’s and master’s degree, both also in aerospace engineering. My master’s thesis focused on turbulence and my current work is in high-speed aerodynamics.
Tubercles and Turbines
The flippers of humpback whales include bumps–called tubercles–on their leading edges. The tubercles create vortices that prevent the boundary layer from separating, which causes stall and a loss of lift. New research shows that adding similar bumps to the leading edge of tidal turbine blades results in greater energy production at low flow speeds compared…
Microgravity Water Films
In this video astronaut Don Pettit demonstrates some interesting laminar flow effects using a water film in microgravity. By using a film, fluid motion is essentially confined to two dimensions. This is important because it prohibits the development of turbulence, which is a purely three-dimensional phenomenon. Doing the experiment in microgravity allows Pettit to leave…
Seeing the Invisible
Schlieren photography is a common experimental flow visualization technique, especially in supersonic flows (where it enables one to see shock waves). Here the Science Channel’s “Cool Stuff: How It Works” show explains the technique and shows some examples from everyday life.
The ABCs of Physics
b=buoyancy is part of Ashley JM’s photo set The ABCs of Physics. In her words: Buoyancy is what causes less dense objects to float in a more dense fluid, such as a helium balloon in air. There is a buoyant force that pushes up on the object, equal to the weight of the displaced fluid.…
Vibrating Oobleck
[original media no longer available] This video explores some of the non-Newtonian behaviors of oobleck when shaken. The pattern across the surface once the vibrations start is called Faraday waves, a type of nonlinear standing wave that forms once a critical vibrational frequency is passed and the flat surface of the fluid becomes unstable. Toward…
Wavy Vortices
Shown above is the flow between two concentric cylinders (Taylor-Couette flow). In the laminar regime, the velocity profile between the two cylinders is linear. As the rate of rotation of the inner cylinder increases, the flow develops toroidal vortices known as Taylor vortices, seen in the video above after 9 seconds or so. This is…
Bristling Scales Give Sharks Speed
The shortfin mako shark is one of the ocean’s fastest and most agile hunters, thanks in part to flexible scales along its body. As water flows around the shark’s body, the scales bristle to angles in excess of 60 degrees. This causes turbulence in the boundary layer along the shark’s body and prevents boundary layer…