Surface reference

In Mechanical of the fluids, the surface of reference is surface chosen to quantify a force (Portance, Traînée) or a moment of force.

Forces

An example of calculation utilizing the surface of reference is that of the trail. The force of Fx trail is calculated starting from surface S and of the Coefficient of drag Cx :
Fx = Q. S. Cx
with Q the dynamic Pressure = 1/2. ρ. V ²
and ρ the Density of the fluid

Examples of surfaces of references:

  • quite shaped body wing or fuselage (Cx < 0,05):
the surface of reference for the vertical bearing pressure in Z and the trail in X is the airfoil projected in plan X there (seen in plan),
the surface of reference for the side bearing pressure in is there the surface projected in the plan x-z (seen profile),
recall of notation X, there, Z: X into longitudinal, there of transverse and Z into vertical.

  • body less quite shaped (Cx > 0,10): the surface of reference for the trail is frontal surface (front view).

automobile, ships (Master-couple)
element of structure (stay, mast, leg, pylon, etc)

Moments

To quantify one moment (produced: force X length): one needs a force (related to the surface of reference) and a reference length, generally the aerodynamic average Corde (CMA) for a wing in aéro or hydrodynamics.

Internal bonds

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