Induced trail

Mechanics of the fluids

Aerodynamic, Hydrodynamic.

The complete expression is trailed induced by the Portance (of a Aile).

The induced trail IH is a force of resistance to the advance which depends on the characteristics of the wing:

of its form in plan,
of its twist (which modifies the distribution of bearing pressure in Envergure),
and especially of sound Allongement.

  • calculation of IH

IH = Q. S. Ci
Q: dynamic Pressure = 1/2. rho. V2
rho: density of the fluid, V = speed in m/s
Ci: coefficient of drag induced

  • Calculation of Ci

Ci = Cz2/(π. λ. E)
Cz: Coefficient of bearing pressure of the wing
π (pi): 3.1416
λ: effective Lengthening; λ can be higher than geometrical lengthening (partitions in end of wing, marginal vertical wings (English winglets))
E: coefficient (lower than 1) which depends on the shape of the wing and of the distribution of bearing pressure in envergure.
E could be equal to 1 for a distribution of bearing pressure " idéale" (elliptic). In practice E is about 0.75 to 0.85.

Distribution of the bearing pressure

Distribution of optimal bearing pressure
form in plan, arrow, twist, interaction of the fuselage, blows propeller, to develop

Value of the induced trail

  • the induced trail is null:
if the bearing pressure is null
if lengthening is infinite

  • the induced trail is small:

if lengthening is large and if the Cz is small (Cz 0.1 to 0.3, fast plane)

  • the induced trail is large:

if lengthening is small and strong Cz (Delta wing on takeoff).

Bonds

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