Heavy Airfoil in a Freestream

Horizontal vortex theory

One computer model of the typical bathroom found that the spray from the shower-head drives a horizontal vortex. This vortex has a low-pressure zone in the centre, which sucks the curtain.

David Schmidt of University of Massachusetts was awarded the 2001 Ig Nobel Prize in Physics for his partial solution to the question of why shower curtains billow inwards. He used a computational fluid dynamics code to achieve the results. Professor Schmidt is adamant that this was done "for fun" in his own free time without the use of grant or other public monies.

The Coandă Effect

he Coandă effect is a result of entrainment of ambient fluid around the fluid jet. When a nearby wall does not allow the surrounding fluid to be pulled inwards towards the jet (i.e. to be entrained), the jet moves towards the wall instead. The fluid of the jet and the surrounding fluid should be essentially the same substance (a gas jet into a body of gas or a liquid jet into a body of liquid). In one application, a jet of air is blown over the upper surface of an airfoil, which can have a strong influence on the overall lift, especially at high angles of attack when the flow would otherwise separate (stall). See Blown flap.


Flight

According to 20th century folklore, the laws of aerodynamics prove that the bumblebee should be incapable of flight, as it does not have the capacity (in terms of wing size or beats per second) to achieve flight with the degree of wing loading necessary. Not being aware of scientists "proving" it cannot fly, the bumblebee succeeds under "the power of its own ignorance".[26] The origin of this myth has been difficult to pin down with any certainty. John McMasters recounted an anecdote about an unnamed Swiss aerodynamicist at a dinner party who performed some rough calculations and concluded, presumably in jest, that according to the equations, bumblebees cannot fly.[27] In later years McMasters has backed away from this origin, suggesting that there could be multiple sources, and that the earliest he has found was a reference in the 1934 French book Le vol des insectes; they had applied the equations of air resistance to insects and found that their flight was impossible, but that "One shouldn't be surprised that the results of the calculations don't square with reality".[28]

Some credit physicist Ludwig Prandtl (18751953) of the University of Göttingen in Germany with popularizing the myth. Others say it was Swiss gas dynamicist Jacob Ackeret (18981981) who did the calculations.

In 1934, French entomologist Antoine Magnan included the following passage in the introduction to his book Le Vol des Insectes: Tout d'abord poussé par ce qui fait en aviation, j'ai appliqué aux insectes les lois de la résistance de l'air, et je suis arrivé avec M. SAINTE-LAGUE a cette conclusion que leur vol est impossible.

This means: First prompted by the fact of aviation, I have applied the laws of the resistance of air to insects, and I arrived, with Mister Sainte-Lague, at the conclusion that their flight is impossible.

Magnan refers to his assistant André Sainte-Laguë who was, apparently, an engineer.

It is believed that the calculations which purported to show that bumblebees cannot fly are based upon a simplified linear treatment of oscillating aerofoils. The method assumes small amplitude oscillations without flow separation. This ignores the effect of dynamic stall, an airflow separation inducing a large vortex above the wing, which briefly produces several times the lift of the aerofoil in regular flight. More sophisticated aerodynamic analysis shows that the bumblebee can fly because its wings encounter dynamic stall in every oscillation cycle.[29]

Another description of a bee's wing function is that the wings work similarly to helicopter blades, "reverse-pitch semirotary helicopter blades".


Vector Fields and Hydrodynamics Force fields have definite properties of their own suitable for scientific study. This series helps teachers demystify physics by showing students what it looks like. Field trips to hot-air balloon events, symphony concerts, bicycle shops, and other locales make complex concepts more accessible. Inventive computer graphics illustrate abstract concepts such as time, force, and capacitance, while historical reenactments of the studies of Newton, Leibniz, Maxwell, and others trace the evolution of theories. The Mechanical Universe helps meet different students' needs, from the basic requirements of liberal arts students to the rigorous demands of science and engineering majors. This series is also valuable for teacher professional development. Produced by the California Institute of Technology and Intelecom. 1985.

http://video.google.com/videoplay?docid=4532767129040787318&ei=NixUSveREY...

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