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Tony's Intertwingled Memex • Reference Manual

Airfoil Lift and Circulation

Formulas & Definitions

In aerodynamic wing theory, the lift force generated by air flowing past an aircraft wing profile is fundamentally linked to fluid circulation. According to the foundational Kutta-Joukowski Theorem in aerospace engineering, the aerodynamic lift force vector per unit wing span (F⃗L\vec{F}_LFL​) is directly proportional to the cross product of the free-stream airflow velocity vector (v⃗\vec{v}v) and the bound circulation vector (Γ⃗\vec{\Gamma}Γ):

F⃗L=ρ(v⃗×Γ⃗)\vec{F}_L = \rho (\vec{v} \times \vec{\Gamma})FL​=ρ(v×Γ)
where ρ\rhoρ is the ambient air density.

Consider an aircraft flying through cruising altitude where the air density is ρ=1.2 kg/m3\rho = 1.2\text{ kg/m}^3ρ=1.2 kg/m3. The relative wind velocity flowing horizontally past the wing chord is v⃗=⟨150,0,0⟩ m/s\vec{v} = \langle 150, 0, 0 \rangle\text{ m/s}v=⟨150,0,0⟩ m/s, and the bound circulation around the airfoil profile is oriented along the spanwise direction as Γ⃗=⟨0,4,0⟩ m2/s\vec{\Gamma} = \langle 0, 4, 0 \rangle\text{ m}^2/\text{s}Γ=⟨0,4,0⟩ m2/s.

  1. Compute the cross product v⃗×Γ⃗\vec{v} \times \vec{\Gamma}v×Γ.
  2. Determine the resulting lift force vector per unit span (F⃗L\vec{F}_LFL​) in Newtons per meter (N/m\text{N/m}N/m).
  3. State the spatial direction in which the lift force acts.