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API · /darcy-api

Pipe Pressure Drop API

healthy 3,136 Subscribers

Darcy-Weisbach pipe pressure-drop and head-loss as an API, computed locally and deterministically. The friction endpoint gives the Darcy friction factor: laminar flow uses f = 64/Re, and turbulent flow uses the explicit Swamee-Jain approximation of the Colebrook-White equation, f = 0.25/[log₁₀(ε/3.7D + 5.74/Re⁰·⁹)]², from a Reynolds number (given directly, or computed from velocity, diameter and fluid) and the relative roughness, classifying the flow as laminar, transitional or turbulent. The headloss endpoint computes the major head loss hf = f·(L/D)·v²/(2g) from a friction factor (given or derived) and the pipe length, diameter and velocity, and — given the fluid density — the pressure drop Δp = ρ·g·hf in pascals, kilopascals and bar. The pipe endpoint does the whole calculation end to end: from a flow rate or velocity, the pipe diameter, length, fluid (water, seawater, air, oil and more, or a custom density and viscosity) and roughness material, it returns the velocity, Reynolds number, friction factor, head loss, pressure drop and the pumping power needed to overcome friction. Everything is computed locally and deterministically, so it is instant and private. Ideal for plumbing, HVAC and process-piping tools, hydraulics and pump-sizing apps, irrigation and fire-protection design, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is pipe friction pressure drop; for the continuity relation and Reynolds number use a pipe-flow API and for pump power and head use a pump API.

#darcy-weisbach #pressure-drop #head-loss #fluid-mechanics #piping #developer-tools
api.oanor.com/darcy-api
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/api/darcy-api/openapi.json
/api/darcy-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
99 ms
Server probes · 24h
Subscribers
3,136
active
Total calls
36
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 2,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • Darcy-Weisbach pressure-drop endpoint
  • Friction factor (laminar + turbulent)
  • SI units
  • 2000 calls/month
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Starter

€9.00 /month

  • 25,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • Pressure drop + head loss endpoints
  • Colebrook-White & laminar friction factor
  • Roughness presets for common pipe materials
  • 25k calls/month
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Pro

€24.00 /month

  • 150,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • All endpoints incl. Reynolds & flow-regime
  • SI + imperial unit output
  • Batch pipe-segment evaluation
  • 150k calls/month, priority support
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Mega

€75.00 /month

  • 758,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • Full fluid-mechanics suite, unmetered endpoints
  • High-throughput batch sizing for pipe networks
  • 99.9% uptime SLA
  • 750k calls/month, dedicated support
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Viscosity API

Fluid-viscosity physics as an API, computed locally and deterministically. The sutherland endpoint gives the dynamic viscosity of a gas at any temperature from Sutherland’s law, μ(T) = μ_ref·(T/T_ref)^1.5·(T_ref+S)/(T+S), with built-in constants for air, nitrogen, oxygen, carbon dioxide, hydrogen, helium and argon (or your own μ_ref, T_ref and S) — air comes out at about 1.72×10⁻⁵ Pa·s at 0 °C, 1.84×10⁻⁵ at 25 °C and 2.17×10⁻⁵ at 100 °C, returned in Pa·s, micro-Pa·s and centipoise. The kinematic endpoint converts between dynamic viscosity μ and kinematic viscosity ν through the density, ν = μ/ρ and μ = ν·ρ, so water at 1.002 cP and 998 kg/m³ becomes about 1.004 cSt. The convert endpoint handles viscosity units both ways — dynamic between Pa·s, centipoise and poise (1 Pa·s = 1000 cP = 10 P) and kinematic between m²/s, centistokes and stokes (1 m²/s = 10⁶ cSt = 10⁴ St). Temperatures are in °C or kelvin. Everything is computed locally and deterministically, so it is instant and private. Ideal for fluid-mechanics, CFD, process-engineering, lubrication, HVAC and chemical-engineering app developers, viscosity-correlation and unit-conversion tools, and simulation software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This computes viscosity; for the Reynolds number that uses it use a Reynolds API.

api.oanor.com/viscosity-api

Particle Settling API

Particle settling-velocity maths as an API, computed locally and deterministically. The stokes endpoint computes the terminal settling velocity of a small spherical particle by Stokes' law, vt = (ρp − ρf)·g·d²/(18·μ), from the particle diameter and density, the fluid density and the dynamic viscosity, and checks the particle Reynolds number to tell you whether the creeping-flow assumption (Re < 1) still holds — a negative velocity means a buoyant particle that rises. The terminal endpoint computes the drag-based terminal velocity for larger, faster particles, vt = √(4·g·d·(ρp − ρf)/(3·Cd·ρf)), from a drag coefficient (≈0.44 in the turbulent Newton regime). The time endpoint computes the time for a particle to settle through a given depth, t = height/vt, taking the velocity directly or deriving it from the particle properties via Stokes. Everything is computed locally and deterministically, so it is instant and private. Ideal for water- and wastewater-treatment, mineral-processing and environmental-engineering tools, clarifier and settling-tank design, sediment and aerosol analysis, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is particle sedimentation; for pipe-flow Reynolds/Froude/Mach numbers use a Reynolds API.

api.oanor.com/settling-api

Reynolds Number API

Dimensionless flow-number maths for fluid-mechanics similitude as an API, computed locally and deterministically. The reynolds endpoint computes the Reynolds number, Re = v·L/ν = ρvL/μ — the ratio of inertial to viscous forces — from the velocity, a characteristic length (pipe diameter) and either the kinematic viscosity or the density and dynamic viscosity, and classifies the flow as laminar (< 2300), transitional (2300–4000) or turbulent (> 4000). The froude endpoint computes the Froude number, Fr = v/√(g·L) — the ratio of inertia to gravity used for open-channel and ship flows — together with the critical velocity, and tells you whether the flow is subcritical (tranquil), critical or supercritical (shooting). The mach endpoint computes the Mach number, M = v/c, with the sound speed taken directly or worked out from the air temperature, c = √(γRT), and classifies the speed as subsonic, transonic, supersonic or hypersonic. Everything is computed locally and deterministically, so it is instant and private. Ideal for fluid-mechanics, aerodynamics and hydraulics tools, model-scaling and wind-tunnel similitude, pipe-flow and open-channel analysis, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is dimensionless-number similitude; for pipe friction pressure drop use a Darcy-Weisbach API and for open-channel uniform flow use a Manning API.

api.oanor.com/reynolds-api

Valve Flow Coefficient API

Control-valve flow-coefficient (Cv / Kv) maths as an API, computed locally and deterministically. The liquid endpoint sizes a control valve for liquid service using Q = Kv·√(ΔP/SG): give any two of the flow rate (m³/h), the pressure drop across the valve (bar) and the flow coefficient Kv, and it returns the third — the required Kv to size a valve, the flow a valve passes, or the pressure drop it develops — together with the equivalent Cv. The convert endpoint converts between the three flow coefficients in use around the world: the metric Kv, the US Cv = 1.156·Kv, and the SI Av = 2.4e-5·Cv. The opening endpoint computes how far a valve must open to pass an operating Kv against its rated Kvs, for both a linear trim (opening = Kv/Kvs) and an equal-percentage trim (opening = 1 + ln(Kv/Kvs)/ln(R) for a rangeability R), so you can keep the valve in its controllable 20–80 % travel band. Everything is computed locally and deterministically, so it is instant and private. Ideal for process, instrumentation and HVAC engineering tools, control-valve selection and commissioning, hydronic-balancing and plant-design apps, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is control-valve sizing; for pump power and head use a pump API and for orifice-plate metering use an orifice API.

api.oanor.com/valveflow-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Pipe Pressure Drop API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Pipe Pressure Drop API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Pipe Pressure Drop 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 Pipe Pressure Drop API cost?
Pipe Pressure Drop API has a free tier with 100 calls / month. Paid plans start at €9.00 / 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 Pipe Pressure Drop API GDPR-compliant?
All requests to Pipe Pressure Drop 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.

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