Look what Finding Nemo puts Marlin through, just because he stopped concentrating on survival for a second:
1) His wife and 99 percent of his children are eaten alive by a barracuda. 2) His son, on his first day of school, ventures away from the class and is kidnapped by an Australian dentist (Parents: Beware). 3) He is pressed into joining a “Fish Are Friends” AA-style club run by sharks, who are not sticking to the program. 4) Said club’s leader, Bruce, tries to eat him. 5) He is almost blown up by underwater mines. 6) He is eaten, but not digested, by an angler fish. 7) He is shocked unconscious by jellyfish. 8) Again he is eaten, but not digested, this time by a whale. 9) He survives a spinning “vortex of terror.” 10) Once more, he is eaten, but not digested, by a pelican (for a change).
Flow visualization can be a valuable tool for understanding fluid dynamics. In this video, we see how it can help elucidate the mechanisms of flapping flight. By dyeing vortices from the leading edge in red rhodamine and vortices from the trailing edge in green fluorescein, it’s possible to distinguish their competing effects for wings of different size. The speed and efficiency of a flapping wing depends on the vortices it sheds–these provide its lift and thrust. On a short wing, the leading edge vortex is significant and spins in a counter-clockwise (positive) direction. When it reaches the trailing edge, it meets a vortex spinning clockwise (negative). The interference of the two vortices weakens the shed vortex, thereby slowing the wing. Lengthening the wing weakens the leading edge vortex, which reduces its interference at the trailing edge and makes the longer wings more efficient. (Video credit: T. Mitchel et al.; via @AlbanSauret)