A kite on a tether in a sheared, gusty wind. Arrows show lift, drag, weight and line tension; the graph follows tension and wind speed at the kite.
The kite is a point mass at the end of a line of length L anchored at the origin. In the relative wind vr = u(z) - v a fixed angle of attack α gives, per unit dynamic pressure, CL = 1.5 sin 2α and CD = 0.08 + 1.2 sin²α (a flat-plate style model with stall near 45 °). Lift acts perpendicular to vr, drag along it: F = ½ ρ A |vr|² (CL n + CD t).
The wind follows the atmospheric boundary-layer power law u(z) = u10 (z/10 m)0.143 with sinusoidal gusts. The line is a stiff one-way spring (it pulls only when stretched) with damping. In steady uniform wind the kite rests where the line balances aerodynamics and weight: T cosγ = D, T sinγ = L - mg, so tanγ = (L - mg)/D, which the checks panel compares with the simulation.
Simplifications: 2D motion in the wind plane, constant angle of attack (a real kite trims itself with its bridle), no line weight or sag, no kite rotation dynamics, constant air density. Educational model only, not a flight-safety tool.