aero · lab.corentinbel.com how things fly — 2D potential-flow intuition, not CFD

STALL!

air over the top travels faster → lower pressure → the wing is sucked upward, not pushed from below

myth check: the two parcels do not reunite at the trailing edge — “equal transit time” is false; the top air arrives earlier

stall = the flow gives up following the curve — lift collapses, drag explodes

water is ~840× denser than air: the same lift needs a tiny foil at walking-pace speed — that’s why a wing-foil front wing is pocket-sized next to a glider wing

Readouts (chord 1 m, per m span)

Cl–

L/D–

lift L′–

drag D′–

ρ–

½ρv²–

wing area to hold 80 kg–

Pressure along the chord

Controls

angle of attack 6°

camber 4%

thickness 12%

flow speed 30 m/s

Fluid

ρ_water / ρ_air ≈ 840 — same field shape, wildly different forces

Presets

✨ particles

count –

visual speed 1.0×

focus on the foil 65%

trail length 60%

colour by

🪂 could you fly?

with this foil at this angle (Cl –): wing area S = m·g / (½ρv²·Cl), at your speed below — not the flow slider.

your weight 75 kg

your speed 10 m/s

✈️ air – — –

🌊 water – — –

–

Explain

2D potential-flow intuition, not CFD. Field = uniform flow + thin-airfoil bound circulation (5 vortices on the camber line, Γ = π·U·c·(α + 2h/c)) + thickness sources. Cl = 2π(α + 2h/c), faded smoothly past ~15° effective AoA (post-stall floor 0.3). Drag = profile + induced (AR 8, e 0.85) + separation term. Lift/drag magnitudes come from these formulas at chord 1 m, per metre of span. Particles colour by local speed or by Cp = 1 − (v/U)² (Bernoulli) — fast = low pressure. “Could you fly?” inverts the lift equation: S = m·g / (½ρv²·Cl), with the same Cl (and stall fade) as everything else.