Bernoulli's Principle: As flow speeds up over a convex surface (such as the upper camber of an airfoil), fluid kinetic energy increases while local static pressure drops (ΔP = ½ρ(v₁² - v₂²)). This static pressure differential generates net lift.
Coandă Effect & Boundary Layer Attachment: Viscous forces cause fluid streams to stay attached to adjacent curved solid surfaces. Higher angles of attack increase adverse pressure gradients, eventually triggering boundary layer separation and stall turbulence in the wake.
Choose the cylinder preset in this source simulator. Its drag is a prescribed coefficient model, not a fluid solution. Fix density at one point two two five kilograms per cubic metre, and reference area at zero point two five square metres. The cyan point begins at speed five metres per second and drag one point seven two newtons. Increase incoming speed from five to fifty metres per second. The source multiplies one half density, speed squared, reference area and a fixed cylinder coefficient of zero point four five. Watch the marker rise along the quadratic curve. Ten times the speed therefore multiplies this drag fixture by one hundred. The endpoint is about one hundred seventy two point two seven newtons. The equation explains this particular response. It does not validate the coefficient across Reynolds numbers, resolve a wake, or measure an actual cylinder. Now choose the curved spoon preset and hold incoming speed at twenty five metres per second. The source prescribes top speed as one point seven times incoming speed and bottom speed as zero point eight times incoming speed. Its signed pressure difference is one half density times bottom speed squared minus top speed squared. Increase density from zero point five to two kilograms per cubic metre while keeping both prescribed speeds fixed. The formula becomes minus seven hundred three point one two five times density, in pascals. Follow the point downward from minus three hundred fifty one point five six to minus fourteen hundred six point two five pascals. Four times the density makes the magnitude four times larger. The negative sign follows this source subtraction convention. The velocity multipliers and spoon shape are illustrative assumptions; this curve is not a computed surface pressure distribution. Keep the curved spoon preset, speed twenty five and density one point two two five. The source separately computes lift from dynamic pressure, the same reference area, and two pi times sine of angle plus zero point zero five radians. Negative calculated lift is explicitly clipped to zero. Increase the angle from minus ten to twenty five degrees. Convert degrees to radians inside the sine. The marker initially stays on the zero plateau, then rises once the sine becomes positive near minus two point eight six degrees. At twenty five degrees the source lift is about two hundred eighty one point zero five newtons. This is the source clipped force fixture, separate from its displayed pressure difference. It does not integrate pressure over the spoon or model stall. The original default airfoil also uses an explicit representative override; these three scenes deliberately use the cylinder and spoon branches instead.