Source: https://guthlabs.ai/docs/instruments/darcy-weisbach-pressure-drop/implementation/

instrument implementation / implementation-contract

# Darcy-Weisbach Pressure Drop implementation

A source-bound implementation contract for Darcy-Weisbach Pressure Drop; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t6-132

**Effect**: Computation or source lookup only

## Input and validation requirements

The listed inputs are insufficient to perform the stated Colebrook iteration: relative roughness and viscosity, or equivalently Reynolds number, are not provided. In addition, D=0 is an undefined input that must be explicitly rejected; returning a numeric result would be a failure.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "f": 0.02,
    "L_m": 100,
    "D_m": 0.1,
    "V_m_per_s": 2,
    "rho_kg_per_m3": 1000,
    "g_m_per_s2": 9.81
  },
  "expected_outputs": {
    "delta_P_Pa": 40000,
    "h_f_m": 4.077471967
  },
  "working": "L/D = 100/0.1 = 1000. V²/2 = 2²/2 = 2. ρV²/2 = 1000×2 = 2000 Pa. ΔP = f(L/D)(ρV²/2) = 0.02×1000×2000 = 40000 Pa. h_f = ΔP/(ρg) = 40000/(1000×9.81) = 40000/9810 = 4.077471967 m."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/darcy-weisbach-pressure-drop/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/darcy-weisbach-pressure-drop/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/darcy-weisbach-pressure-drop/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche6/tranche6-results.json`