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API · /manning-api

Open Channel Flow API

healthy 3,289 Subscribers

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.

#open-channel #manning #hydraulics #drainage #civil-engineering #developer-tools
api.oanor.com/manning-api
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Machine-readable spec so AI agents can integrate this API.

/api/manning-api/openapi.json
/api/manning-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
88 ms
Server probes · 24h
Subscribers
3,289
active
Total calls
40
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 13,735 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 13,735 calls/month
  • 2 req/sec
  • Flow + normal depth + roughness
  • No credit card
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Starter

€15.35 /month

  • 23,450 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 23.45k calls/month
  • 8 req/sec
  • 4 channel shapes, roughness table
  • Email support
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Pro

€35.45 /month

  • 284,500 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 284.5k calls/month
  • 20 req/sec
  • Drainage / hydrology pipelines
  • Priority support
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Mega

€73.45 /month

  • 1,465,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 1.465M calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Froude Number API

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 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

O-Ring Seal API

O-ring seal-design maths as an API, computed locally and deterministically — the squeeze, gland and stretch numbers an engineer or maker designs a seal to. The squeeze endpoint gives the compression that makes the seal: squeeze = (cross-section − gland depth) ÷ cross-section, so a 0.139-inch cord in a 0.113-inch deep groove is squeezed 18.7 %, and it grades the result — roughly 10–16 % suits dynamic (reciprocating) seals and 15–30 % static ones — and, given the groove width, the gland fill percentage, which should stay under about 85 % so the rubber has room to expand from heat or fluid swell. The gland endpoint works the other way: from the cross-section and whether the seal is static or dynamic (or a target squeeze) it returns the groove depth and a width sized for about 70 % fill — typically 1.3 to 1.5 times the cross-section — plus a corner radius. The stretch endpoint checks installation: stretch = (mating diameter − o-ring ID) ÷ ID, which should stay under about 5 % on a rod because stretching thins the cross-section and steals squeeze. Everything is computed locally and deterministically, so it is instant and private. Ideal for mechanical-engineering, hydraulics, pneumatics, vacuum and product-design app developers, seal-selection and gland-design tools, and CAD plugins. Pure local computation — no key, no third-party service, instant. Inches or millimetres. Live, nothing stored. 3 compute endpoints.

api.oanor.com/oring-api

Torricelli Efflux API

Torricelli efflux and orifice-discharge maths as an API, computed locally and deterministically. The velocity endpoint applies Torricelli's law, v = √(2·g·h) — the speed at which fluid jets from an orifice under a head h equals that of a body that has fallen the same height — and returns the ideal and the actual jet velocity (corrected by a coefficient of velocity), and, if you give the orifice diameter or area, the ideal and actual volumetric discharge Q = Cd·A·√(2gh) in litres per second and minute, cubic metres per hour and US gallons per minute. The drain-time endpoint computes how long a vertical cylindrical tank takes to empty through an orifice, t = (2·A_tank)/(Cd·A_orifice·√(2g))·(√h0 − √h1), from the tank and orifice sizes, the starting head and an optional final head, with the initial flow rate. The range endpoint gives the horizontal distance a jet from a side orifice travels before it lands, x = 2·Cv·√(h·y), from the head above the orifice and the orifice's height above the ground, with the jet velocity and time of flight. The discharge and velocity coefficients default to 0.62 and 0.97 and can be overridden, as can gravity. Everything is computed locally and deterministically, so it is instant and private. Ideal for fluid-mechanics and hydraulics tools, tank-drainage, irrigation and process-engineering apps, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is orifice efflux and tank drainage; for pipe continuity Q = A·v use a flow-rate API and for tank volume and fill level use a tank API.

api.oanor.com/torricelli-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Open Channel Flow API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Open Channel Flow API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Open Channel Flow API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Open Channel Flow API cost?
Open Channel Flow API has a free tier with 100 calls / month. Paid plans start at €15.35 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Open Channel Flow API GDPR-compliant?
All requests to Open Channel Flow API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/manning-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/manning-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/manning-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/manning-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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