Linear drag law for high-Reynolds-number flow past an oscillating body

Abstract

Flying is a delicate balance of lift versus weight and thrust versus drag. But the flapping wings of animals do not seem to abide by the aerodynamic laws of airplane wings. A new study shows that fast wing oscillations -- like that used by flying insects -- lead to fundamental changes in the physics of drag or wind resistance. The steady motion of airplane wings leads to a resistance that increases as the square of speed. The new research shows that flapping wings instead have a drag that increases in direct proportion to their speed through air. This means that, to go twice as fast, an airplane must generate four times the thrust, while an insect only needs to produce twice the thrust.