Frost formation and ice adhesion on superhydrophobic surfaces
For anyone with further interest in the ice formation on superhydrophobic surfaces story we posted recently, the published paper is currently offered by AIP for free. #
Search results for: “lift”
Frosting on Superhydrophobic Surfaces
Icing on airplane wings can be disastrous for lift and control, and thus how ice initially forms on a wing is an active area of research. New work shows that superhydrophobic (water-fearing) surfaces may actually promote ice buildup. Superhydrophobic surfaces are prone to frosting–collecting ice that forms directly from a vaporous state–and that fine layer of frost is conducive to further ice buildup from a liquid state. The photo above shows a water droplet striking a dry superhydrophobic surface (top) and a frosted superhydrophobic surface (bottom). (via Gizmodo) #
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 to conventional designs. See Scientific American for more. #
Pterosaur Aerodynamics
The pterosaur was an enormous prehistoric reptile that flew with wings of living membrane stretched over a single long bone, unlike any of today’s flying creatures. New research using carbon fiber wing analogues and wind tunnel testing suggests that the pterosaur would have been a slow, soaring flyer well adapted to using thermals for lift. Once on a thermal, the pterosaur could coast, perhaps for hours at a time, with little to no flapping necessary. See the research paper or the Scientific American article for more. #
Flying Snakes Draft off Themselves
Some snakes in Southeast and South Asia are known to glide some 100 m between trees. Researchers filmed snakes, constructed computational models of their flights, and tested plastic models in a water tunnel. They found that the snakes angled their bodies such that they generate lift to counteract their fall and that the S-configuration they assume increases lift much the way flying in a V-formation does for geese. The wake from the forward portion of the snake interacts with the flow around the back of the snake and reduces downwash, which increases lift. In effect, the back of the snake is drafting off the front. #
Bell’s Powered Kite
Inventor Alexander Graham Bell is best known for the telephone but also made many contributions to early aeronautics. This man-carrying kite, the Cygnet III, was a powered kite with a “wing” made of 3,393 tetrahedral cells; it managed enough lift to fly on March 1, 1912. National Geographic is featuring photos from the early days of flight courtesy of the Smithsonian National Air and Space Museum. They’re well worth checking out. #
Jet-Based Control
Researchers have flown the first aircraft designed to maneuver without conventional control surfaces like ailerons and flaps. Instead of changing the wing geometry to alter the lift on different parts of the craft, the UAV uses strategically placed jets of air along the wing to control its flight. The plane can also alter the direction of its thrust, not by turning the nozzle as is conventionally done, but by modifying the thrust vector by directing and firing a secondary jet into the exhaust. #
Human-Powered Ornithopter
A team at the University of Toronto has flown the world’s first human-powered ornithopter, an aircraft that flies by flapping its wings like a bird. The concept dates back all the way to Da Vinci in the 15th century. Part of why it’s taken centuries to realize the dream is that bird flight is much more complicated than simply flapping up and down. Flapping a wing up and down will produce lift equally upward and downward. In order to create usable lift and thrust, it’s necessary to change the angle of attack during each stroke by twisting the wing while flapping. Watch the U of T craft carefully, and you can see this happening. #
Flying Fish Aerodynamics
New research using wind tunnel measurements of (dead) flying fish is giving new insight into how these fish are able to fly over the waves. Lift and drag data indicates that flying fish have a gliding ability comparable to soaring birds like hawks! #