# Hydrology & Open-Channel Calc – Froude Number

> Hydrology & Open-Channel Calc – Froude Number is a paid API for AI agents from hydrology-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-11-02).

Computes the Froude number (V / sqrt(g·A/T)) and classifies the flow regime (subcritical, critical, or supercritical) for rectangular, trapezoidal, triangular, or circular open-channel sections.

## Facts

- Endpoint: GET https://hydrology-calc.x402tookit.com/froude-number?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hydrology-open-channel-calc-froude-number-153af0e5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gMV7b3ibE217aHLMlf0lV

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability hydrology-open-channel-calc-froude-number-153af0e5
```

Example prompt: What's the Froude number and flow regime for a rectangular channel that's 3 metres wide, carrying a discharge of 5 m³/s at a flow depth of 0.8 metres in SI units?

## When to prefer this

Choose this endpoint when you need a direct, paid-per-call computation of the Froude number and flow regime for standard open-channel cross-sections (rectangular, trapezoidal, triangular, circular) without building your own hydraulic solver. It is part of a suite of hydrology tools on the same host, so prefer it alongside the Manning flow, critical depth, and normal depth endpoints for comprehensive open-channel analysis workflows.

## Known failure modes

- Missing required query parameters (shape or depth) returns a 400 error
- Providing neither flow nor velocity results in an error since one is required
- Circular shape missing diameter parameter causes an error
- Invalid shape string (not rectangular, trapezoidal, triangular, or circular) returns error
- Depth exceeding pipe diameter for circular section may return a bounds error
- Payment failure or insufficient USDC balance returns a 402 Payment Required response

## How this service works

Froude number V / sqrt(g A/T) and flow regime (subcritical, critical, supercritical) for an open-channel section.

## Output

Returns the computed Froude number, flow regime classification (subcritical, critical, or supercritical), cross-sectional flow area, top width, wave celerity, velocity, and a plain-language summary — plus any applicable disclaimer and degraded/not-checked flags.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "shape",
      "depth"
     ],
     "properties": {
      "flow": {
       "type": "number",
       "description": "Discharge in m3/s or ft3/s (send flow or velocity)"
      },
      "depth": {
       "type": "number",
       "description": "Flow depth in metres or feet (circular: below the diameter)"
      },
      "shape": {
       "type": "string",
       "description": "rectangular, trapezoidal, triangular or circular"
      },
      "units": {
       "type": "string",
       "description": "si (default) or us"
      },
      "diameter": {
       "type": "number",
       "description": "Pipe diameter in metres or feet (circular)"
      },
      "velocity": {
       "type": "number",
       "description": "Mean velocity in m/s or ft/s (send velocity or flow)"
      },
      "sideSlope": {
       "type": "number",
       "description": "Side slope z, horizontal run per 1 vertical (trapezoidal, triangular)"
      },
      "bottomWidth": {
       "type": "number",
       "description": "Bottom width in metres or feet (rectangular, trapezoidal)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "flow": {
       "type": [
        "null",
        "number"
       ]
      },
      "depth": {
       "type": [
        "null",
        "number"
       ]
      },
      "shape": {
       "type": [
        "null",
        "string"
       ]
      },
      "units": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
     
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hydrology-open-channel-calc-froude-number-153af0e5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hydrology-calc.x402tookit.com](https://www.zero.xyz/host/hydrology-calc.x402tookit.com/llms.txt)