Open-channel discharge & velocity
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.
api.oanor.com/manning-api
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 80 ms
- Server probes · 24h
- Subscribers
- 3,289
- active
- Total calls
- 76
- last 7 days
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
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
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
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
Built by
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
Water Hammer API
Water-hammer (hydraulic-transient) maths as an API, computed locally and deterministically — the surge-pressure, wave-speed and valve-timing numbers a piping or plumbing engineer guards a system with. The surge endpoint applies the Joukowsky equation Δp = ρ · a · Δv: a sudden stop of the flow spikes the pressure by the fluid density × the pressure-wave speed × the velocity change — stopping 2 m/s of water at a ≈ 1200 m/s adds about 24 bar (348 psi), far above the line pressure, which is what bangs the pipes and can split fittings. The wave-speed endpoint gives that pressure-wave speed: a = √(K/ρ) in a rigid pipe (≈ 1,480 m/s for water), slowed in a real elastic pipe to √(K/ρ) ÷ √(1 + (K·D)/(E·t)) — a thin or plastic pipe gives a lower wave speed and a gentler surge, which is why PVC tolerates hammer better than steel. The critical-time endpoint gives 2L/a, the round-trip time of the wave: close a valve faster than this and you get the full Joukowsky surge, slower and the returning relief wave eats into it, so sizing closure times (or fitting a surge tank or air chamber) above the critical time is the standard cure. Everything is computed locally and deterministically, so it is instant and private. Ideal for piping- and plumbing-design tools, pump-station and pipeline-surge analysis, and hydraulic-engineering utilities. Pure local computation — no key, no third-party service, instant. Idealised single-pipe transient. 3 compute endpoints. For steady pipe pressure drop use a Darcy API; for pump head and affinity a pump API.
api.oanor.com/waterhammer-api
Hydraulic Cylinder API
Hydraulic-cylinder engineering maths as an API, computed locally and deterministically — the force, speed and oil-volume numbers a fluid-power designer, machine builder or hydraulics technician sizes a cylinder with. The force endpoint gives the push and pull from the bore, rod diameter and working pressure: extending, the oil acts on the full bore area, so the cylinder is strongest pushing out; retracting, it acts only on the annulus left by the rod, giving less force — a 100 mm bore with a 56 mm rod at 160 bar pushes about 125.7 kN out but pulls only 86.3 kN back, which is why a press or an excavator does its hard work on the extend stroke. The speed endpoint gives the piston speed from the pump flow (speed = flow ÷ area), so extending is the slower stroke and retracting the faster, the trade-off every circuit designer balances against force. The volume endpoint gives the swept oil volume per stroke for extend and retract, the rod displacement and the bore-to-annulus area ratio — the differential (regeneration) ratio used to speed the extend stroke in a regen circuit — so the pump, tank and lines can be sized for the larger volume. Everything is computed locally and deterministically, so it is instant and private. Ideal for fluid-power and machine-design tools, hydraulics-sizing calculators, mobile- and industrial-equipment utilities, and engineering apps. Pure local computation — no key, no third-party service, instant. Ideal-area estimates — allow for friction, back-pressure and efficiency. 3 compute endpoints. For Pascal force-multiplication use a hydraulics API; for valve sizing a valve-flow (Cv/Kv) API.
api.oanor.com/hydrauliccylinder-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())Ratings
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