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A site on Aerodynamics

Translated by BabelFish

 Theory Elementary theory Specific mass

rz = m/V. On the sea level (t=15°C) to rair = 1,225 Kg.m-3

Density
D = rz/r0 r0 = to rair with 15°C. The empirical formula is given: D = (20-Z)/(20+Z) with Z in km.

Pressure
P=F/S in a PASCAL corresponding to N.m-2. (If the fluid is at rest, the pressure is known as statics)

The temperature (in Kelvin or °C)
T(K) = T(°C) + 273(°C)

Compressibility
It is said that a fluid is compressible when its specific mass varies, for example, when the pressure P varies. Compressibility is characterized by the dr/dP report/ratio (has the dimension of the reverse a speed squared). Until V=100 m.s-1, one can neglect compressibility. If the fluid is moving, one preserves Pression, Température and Compressibility.

Speed
in m.s-1 or in nodes.

Dynamic pressure
(kinetic Energy per unit of volume) Pd=(1/2) * rz*(Vp)2 clean Vp~:vitesse, rz=m/V

Conservation of the mass of the flow Q
Q = rSV = Constant

Conservation of energy
Law of Bernouilli: p+(1/2)rV2 = constant Static pressure + dynamic Pressure = Total Pressure

Viscosity
Viscosity is translated only if the fluid meets an obstacle (the wing). One calls a fluid without viscosity a true fluid. The viscosity of the air is very low for v<100 m.s-1 Il exists in a real fluid of the tangential forces of viscosity which intensify with speed. One will find these forces of viscosity on the level of the boundary layer where they are dominating and generate the trail of friction noted h. to hair = 1,84.10-5 Kg.m-2 heau = 1,01.10-4 Kg.m-2           