aerodynamic

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Mostly Mute Monday: Volcanic Lightning

“During thunderstorms, approximately ten Coulombs of charge — some 10^20 electrons — are exchanged with every bolt, representing the release of an incredible build-up of energy.

During a volcanic eruption, however, the incredible heats cause neutral atoms to become ions, either positively or negatively charged, which then separate due to differences in masses, temperatures and physical cross-sections. The aerodynamics separates the particles even farther, and when the threshold of breakdown voltage is crossed, a lightning strike occurs.”

When it comes to lightning, you inevitably think of thunderstorms, rain, and the exchange of huge amounts of charge between the clouds above and the Earth. But there’s another sight that’s perhaps even more spectacular: volcanic lightning!

Nearly full span Krueger flaps is one of many things that makes the 747 a marvel to behold, even after all these years. Like the 727 and 737, the leading edge closest to the fuselage has a very similar folding bull-nose flat or rigid Krueger flap. Three on each side, in fact. But what looks like a Krueger flap outboard of the inboard engine nacelle is a variation that overcomes some of the aerodynamic limitations of a rigid Krueger flap- in what’s called a variable camber Krueger flap (VCK), the flap panel not only stands a bit away from the leading edge to form a slot, but the panel itself is a flexible fiberglass that stows flat but when extended, a four bar linkage bends the panel chord wise to form a curved Krueger flap with a folding bull nose. The 747-100/200/300 have 13 Krueger panels on each wing- 3 rigid and 10 VCK. The 747-400 has 14 panels- 3 rigid and 11 VCK, the extra variable camber Krueger flap on the outer wing. #Avgeek #aviation #aircraft #planeporn #kdfw #dfw #airport #igtexas #planespotting #airlines #boeing #747 #korean #koreanaircargo #dfwavgeek #instadfw #instagramaviation #HL7437 #avgeekery #avgeekschoolofknowledge #instaspotting (at DFW Founders Plaza)

Flying Snakes

The image of airborne snakes may seem like the stuff of nightmares, but in the jungles of South and Southeast Asia it is reality. Flying snake is a misnomer, since these animals can’t actually gain altitude. They’re gliders, using the speed of free fall and contortions of their bodies to catch air and generate lift.

To prepare for take-off, a flying snake will slither to the end of a branch, and dangle in a J shape. It propels itself from the branch with the lower half of its body, forms quickly into an S, and flattens to about twice its normal width, giving its normally round body a concave C shape, which can trap air. By undulating back and forth, the snake can actually make turns.

Knowledge of their behavior in the wild is limited, but they are thought to be highly arboreal, rarely descending from the canopy. The smallest species reach about 2 feet (61 centimeters) in length and the largest grow to 4 feet (1.2 meters).

Scientists don’t know how often or exactly why flying snakes fly, but it’s likely they use their aerobatics to escape predators, to move from tree to tree without having to descend to the forest floor, and possibly even to hunt prey. Although they are mildly venomous snakes, their tiny fixed rear fangs make them harmless to humans.

sources 1, 2

Designer Eleanor Lutz used high-speed video of five different flying species to create this graphic illustrating the curves swept out in their wingbeats. The curves are constructed from 15 points per wingbeat and are intended more as art than science, but they’re a fantastic visualization of several important concepts in flapping flight. For example, note the directionality of the curves as a whole. If you imagine a vector perpendicular to the wing curves, you’ll notice that the bat, goose, and dragonfly would all have vectors pointing forward and slightly upward. In contrast, the moth and hummingbird would have vectors pointing almost entirely upward. This is because the moth and hummingbird are hovering, so their wing strokes are oriented so that the force produced balances their weight. The bat, goose, and dragonfly are all engaged in forward flight, so the aerodynamic force they generate is directed to counter their weight and to provide thrust. (Image credit: E. Lutz; via io9)