#open-channel

Froude-number hydrodynamics as an API, computed locally and deterministically. The number endpoint computes the Froude number Fr = v/√(g·L) — the dimensionless ratio of inertial to gravitational forces — from a velocity and a characteristic length, classifies the flow as subcritical (Fr<1, tranquil), critical (Fr=1) or supercritical (Fr>1, rapid), and returns the critical velocity √(g·L) at which Fr=1; the velocity endpoint inverts it to v = Fr·√(g·L). The channel endpoint gives the open-channel Froude number from a flow velocity and depth, the flow regime, and the critical depth y_c = (q²/g)^(1/3) for the unit discharge q = v·y — the boundary between tranquil and shooting flow used in spillway and weir design. The hull-speed endpoint computes the displacement hull speed of a boat from its waterline length, v = 1.34·√(L_wl in ft) knots, the wave-making speed limit where the bow and stern waves equal the hull length, returned in knots, m/s and km/h with the corresponding Froude number — a 10 m waterline gives about 7.7 knots. Gravity defaults to 9.80665 m/s². Everything is computed locally and deterministically, so it is instant and private. Ideal for naval-architecture, marine, hydraulics, civil-engineering, river-modelling and fluid-mechanics-education app developers, spillway, weir and hull-design tools, and simulation software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is the Froude number and flow regime; for Manning open-channel discharge use a Manning API.

api.oanor.com/froude-api

Weir flow maths for open-channel discharge measurement as an API, computed locally and deterministically. The rectangular endpoint computes the flow over a rectangular sharp-crested weir, Q = (2/3)·Cd·b·√(2g)·H^1.5, from the crest width and the head of water above the crest — and solves the head back from a known discharge. The vnotch endpoint computes the flow over a triangular V-notch weir, Q = (8/15)·Cd·√(2g)·tan(θ/2)·H^2.5, from the notch angle and head, the most accurate weir for small flows because the discharge varies with the head to the power 2.5. The broadcrested endpoint computes the flow over a broad-crested weir, Q = Cd·(2/3)^1.5·√g·b·H^1.5 ≈ Cd·1.705·b·H^1.5, the rugged field structure used for river gauging. Each device carries its standard discharge coefficient (rectangular 0.62, V-notch 0.58, broad-crested 0.85) which you can override, and each solves either the discharge from a measured head or the head required for a target discharge. Everything is computed locally and deterministically, so it is instant and private. Ideal for hydrology, irrigation and civil-engineering tools, flow gauging in channels and treatment plants, stormwater and water-resource apps, and fluid-mechanics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is weir overflow discharge; for uniform open-channel flow use a Manning API and for differential-pressure pipe metering use an orifice API.

api.oanor.com/weir-api

Open-channel flow maths as an API, computed locally and deterministically with the Manning equation. The flow endpoint computes the discharge and velocity of water in an open channel — rectangular, trapezoidal, triangular or circular (a part-full pipe) — from the flow depth, the channel dimensions, the channel slope and the Manning roughness coefficient n: it works out the flow area, the wetted perimeter and the hydraulic radius, then applies Q = (1/n)·A·R^(2/3)·S^(1/2) and V = Q/A, reporting the discharge in cubic metres per second and hour, litres per second, cubic feet per second and US gallons per minute. The normal-depth endpoint reverses it: given a target discharge it solves for the normal depth by bisection and returns the resulting area, velocity and a discharge check. The roughness endpoint is a reference of typical Manning n values, from smooth PVC (0.009) and concrete (0.013) through earth and gravel to rocky natural streams (0.05); pass a material name or an explicit n. Dimensions are metric (metres by default, or cm, mm, ft, in). Everything is computed locally and deterministically, so it is instant and private. Ideal for civil and drainage engineering tools, stormwater and culvert design, irrigation and hydrology apps, and environmental modelling. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is open-channel (Manning) hydraulics; for full-pipe flow rate from diameter and velocity use a pipe-flow API.

api.oanor.com/manning-api