#aerodynamics

Mach-number and compressible-flow aerodynamics as an API, computed locally and deterministically. The mach endpoint computes the local speed of sound a = √(γ·R·T) (air γ = 1.4, R = 287.05 J/(kg·K)) and the Mach number M = v/a from a speed and a static temperature — given directly in °C or kelvin, or derived from a geopotential altitude through the International Standard Atmosphere (troposphere T = 288.15 − 0.0065·h up to 11 km, then the isothermal 216.65 K layer to 20 km) — and classifies the flight regime as subsonic, transonic, supersonic or hypersonic; the speed of sound is about 340.3 m/s at 15 °C and 295 m/s at 11 km. The speed endpoint inverts it, returning v = M·a in m/s, km/h and knots. The stagnation endpoint gives the isentropic total-to-static ratios T0/T = 1 + (γ−1)/2·M², P0/P = (T0/T)^(γ/(γ−1)) and ρ0/ρ = (T0/T)^(1/(γ−1)) — at Mach 2 the total pressure is about 7.82 times the static pressure — and will scale a supplied static temperature and pressure to their stagnation values. Everything is computed locally and deterministically, so it is instant and private. Ideal for aerospace, CFD, flight-simulation, wind-tunnel, UAV and aerodynamics-education app developers, compressible-flow and flight-envelope tools, and engineering software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is compressible aerodynamics; for viscous flow and the Reynolds number use a Reynolds API and for incompressible pressure/velocity a Bernoulli API.

api.oanor.com/machnumber-api

Aerodynamic drag and terminal-velocity maths as an API, computed locally and deterministically. The drag endpoint computes the drag force on a body moving through a fluid, F_d = ½·ρ·Cd·A·v² — half the fluid density times the drag coefficient, the reference area and the velocity squared — together with the dynamic pressure ½·ρ·v², from a fluid (air, water, seawater, oil and more, or a custom density), a drag coefficient (given directly or from a built-in shape table) the area and the speed. The terminal endpoint computes the terminal velocity of a falling object, v_t = √(2·m·g/(ρ·Cd·A)) — the steady speed at which drag balances gravity — from the mass and area, or for a sphere from its diameter and material density, in metres per second, km/h and mph (a belly-down skydiver reaches about 55 m/s, 200 km/h). The shapes endpoint lists typical drag coefficients for spheres, cubes, cylinders, flat plates, streamlined bodies, skydivers, cars, parachutes and more. Everything is computed locally and deterministically, so it is instant and private. Ideal for aerodynamics and ballistics tools, skydiving, model-rocketry and motorsport apps, sphere-settling and sedimentation calculators, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is drag and terminal velocity; for vacuum projectile and SUVAT kinematics use a physics API and for pipe friction pressure drop use a Darcy-Weisbach API.

api.oanor.com/drag-api