Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Mach Diamonds
Joe asks: Why does this rocket have that repeating pattern in its exhaust? I’m amazed that it’s so stable for so far as distance from the nozzle. Excellent question! The diamond-shaped pattern seen in the rocket’s exhaust is actually a series of reflected shock waves and expansion fans. The rocket’s nozzle is designed to be…
Microgravity Marangoni
Astronauts are preparing an experiment on the Marangoni effect, in which a variation in surface tension can cause mass flow, for flight aboard the International Space Station. The effect, also responsible for causing tears of wine, will benefit from study in microgravity because competing effects like gravity-induced sedimentation and buoyant convection will be negligible. Astronaut…
Reader Question: Oswald de Waele
fyeahhexagons-deactivated201103 asks: Could you do a quick post explaining the Oswald de Waele relationship please? Thanks! Sure! The Oswald-de Waele relationship (a.k.a. a power-law fluid) is an attempt to generalize the relationship between shear stress and shear rate in fluids. For a Newtonian fluid, that relationship is linear: This relationship describes many fluids–like air or water–very…
Crown Breakup
When a droplet falls into a pool of similar fluid, one often observes a crown-like impact effect. This student video shows high-speed footage of different fluids crowning and explores the effects of surface tension on crown breakup.
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.