- Flow separation
All solid objects travelling through a
fluid (or alternatively a stationary object exposed to a moving fluid) acquire aboundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface.Boundary layer s can be either laminar or turbulent. A reasonable assessment of whether the boundary layer will be laminar or turbulent can be made by calculating theReynolds number of the local flow conditions.Flow separation occurs when the
boundary layer travels far enough against anadverse pressure gradient that the speed of the boundary layer falls almost to zero. The fluid flow becomes detached from the surface of the object, and instead takes the forms of eddies and vortices. Inaerodynamics , flow separation can often result in increased drag, particularlypressure drag which is caused by thepressure differential between the front and rear surfaces of the object as it travels through the fluid. For this reason much effort and research has gone into the design ofaerodynamic andhydrodynamic surfaces which delay flow separation and keep the local flow attached for as long as possible. Examples of this include the fur on a tennis ball, dimples on a golf ball,turbulator s on a glider,vortex generator s on light aircraft andleading edge extension s for high angles of attack on the wings of aircraft such as theF/A-18 Hornet .ee also
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Aerodynamics
*Boundary layer separation
*Stall (flight)
*Frost External links
* [http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml "Aerospaceweb"-Golf Ball Dimples & Drag]
*http://www.fi.edu/wright/again/wings.avkids.com/wings.avkids.com/Book/Sports/instructor/golf-01.html
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