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Aerofoil Forces and Moments - Coggle Diagram
Aerofoil Forces and Moments
Pressure distribution ifluences the aerodynamcis of an aerofoil more than shear
it determines tranistion, separation and strength of shockwaves
Pressure coefficient
q_inf = 0.5
rho_inf
V_inf^2
Cp = (p-p_inf)/q_inf
Cp = 1 - (V/V_inf)^2
At stagnation point Cp = 1
Freestream Cp = 0
When V> V_inf Cp<0
p = p__inf +Cp*q_inf
Roof- top pressure distribution is the closest thing
high lift to drag ratio
Aerfoil pressure distribution
y axis is reversed and shows the upper and lower surface pressure distribution
separation happens on the upper surface at the adverse pressure gradient
Would it be possible to design an aerofoil whose chordwise pressure distributuion is constant?
No, because there would have to be an instantaneous change at the trailing edge
this would cause flow separature and a lot of drag
Laminar flow aerofoils
Aerofoil design
Direct analysis
use an existing aerofoil
Inverse design
create a pressure distribution ans design around that
Aerofoil thickness
Aerodynamics
Higher Clmax
Gentler stall characteristic
following stall pitch is less agressive
More drag, but not that must more than a thin section
Structure
Increase the depth of the wing spar
Increase wing rigidity, same structural weight
Typical is 12-16% for lifitng surface and 6-12% for stabilisiers
Performance
cl = cn*cos(alpha)
