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Air Particles
The concept of an air particle, or particles of air is fundamental to the mathematical treatment of aerodynamics. It is the element of air whose velocity gives rise to the aerodynamic force that provides lift and contributes to the drag of aircraft wings, propellers, wind turbines and, of course, sailboat sails. The particle velocity is also the source of the destructive blast wind generated from a chemical or nuclear explosion.

Historical perspective
The concept of fluid velocity was clearly established by 1850 with the development of the Navier Stokes equations, where fluid velocity "u" is a key parameter in all four equations. In 1869 Rankine ,identifies air particles and includes particle velocity in equations. Lanchester, 1907 used the concept of fluid particles and their velocity in the development of his circulation theory of flight which is the regarded as the basis of aerodynamics and the foundation of modern aerofoil theory. In 1923 NACA (the predecessor of NASA) invited Ludwig Prandtl to prepare his report in which he invokes the concept of fluid and air particles to develop his circulation theory of lift. In the 1940's the development of the atomic bom spawned a number of papers Taylor, Sedov, Von Neuman which developed methods of evaluating the yield of explosions by using equations involving the velocity of air particles, gas particles or fluid particles.