The Coandă Effect

This concept has been mentioned by Mr. Thomas in Physics tutorial last week.

Henri Marie Coandă (June 7, 1886 – November 25, 1972) was a Romanian inventor, aerodynamics pioneer and the parent of the modern jet aircraft.

The Coandă effect (IPA: 'kwand[schwa]) is the tendency of a stream of fluid to stay attached to a convex surface, rather than follow a straight line in its original direction. The principle was named after Romanian inventor Henri Coandă, who was the first to understand the practical importance of the phenomenon for aircraft development. He made the discovery during experiments with his Coandă-1910 aircraft, which is the first aircraft based on an early type of jet engine.

It has important applications in various high-lift devices on aircraft, where air moving over the wing can be "bent down" towards the ground using flaps and a jet blowing over a curved surface. The flow from high speed jet produces enhanced lift through turbulent mixing that does not occur above a normal wing. [...]

Closely following the work of Coandă on applications of his research, and in particular the work on Aerodina Lenticulara, John Frost of Avro Canada also spent considerable time researching the effect, leading to a series of "inside out" hovercraft-like aircraft where the air exited in a ring around the outside of the aircraft and was directed by being "attached" to a flap-like ring. This is as opposed to a traditional hovercraft design, in which the air is blown into a central area, the plenum, and directed down with the use of a fabric "skirt". [...]

Some people have attempted to explain how a wing generates lift, by invoking the Coandă effect. However, this theory does not produce quantifiable data, and so it is unable to predict such things as the thickness of the boundary layer. Professional aerodynamicists regard this theory as a fallacy. For example, the theory states that air “sticks” to the surface because of its viscosity. This implies that if the viscosity of the fluid changes, the amount of lift an airfoil produces should change in proportion. Experiments show that the amount of lift produced by a real wing is independent of viscosity over a wide range. The real Coandă effect requires turbulence, so it occurs only if the viscosity is sufficiently low. Furthermore, the air speeds up above a wing's upper surface. The theory assumes that the relative air-flow meets the wing at the same velocity as in free air and then follows the curve. This understates the pressure gradients by an order of magnitude.

-- Wikipedia.com

Ok that was really random and stuff, and anyway just find some time for the class photo to be taken k...