Source: https://guthlabs.ai/docs/instruments/colebrook-white-moody-friction-factor-solver/
instrument / verified-clean
# Colebrook-White / Moody Friction Factor Solver
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Thermodynamics, Fluids & Aero
**Tranche**: tranche-6
**Evidence ID**: t6-035
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The two supplied equations are standard within their respective regimes, but the instrument is not fully specified as an operational solver. Add explicit input validation, regime boundaries, a transitional-flow policy, Newton initialization and stopping rules, maximum iterations, convergence/failure reporting, and an unambiguous Darcy-friction-factor label before release.
### Formula and scope findings
- The Colebrook-White equation is standard for turbulent flow and the laminar formula f=64/Re is standard, but the specification does not define the transitional regime between the laminar and turbulent limits.
- Newton iteration is named but no iteration variable, initial guess, stopping criterion, maximum iteration count, or failure behavior is specified.
- Moody-chart region classification is claimed, but no regime boundaries or classification algorithm are specified.
- The solver must distinguish Darcy friction factor from Fanning friction factor; the supplied equations produce the Darcy friction factor.
### Unit assumptions
- Reynolds number Re is dimensionless and uses the same characteristic diameter D used in the relative roughness.
- Relative roughness ε/D is dimensionless, nonnegative, and should be computed from ε and D in consistent length units before being supplied.
- The logarithm is base 10.
- The Colebrook equation applies to fully developed turbulent pipe flow, conventionally Re greater than approximately 4000.
- The laminar equation f=64/Re applies to fully developed laminar pipe flow, conventionally Re less than approximately 2300.
- The reported friction factor is the Darcy-Weisbach friction factor, not the Fanning friction factor; the latter would be f_D/4.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
The Re = 0 input makes both the laminar formula and the Colebrook term undefined and must be rejected. In addition, the specification does not state the laminar/transitional/turbulent thresholds or how the transitional interval is handled, and it does not explicitly distinguish Darcy from Fanning conventions beyond the equation itself.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"Re": 2000,
"relative_roughness": "0.001",
"method": "laminar",
"newton_tolerance": 1e-10
},
"expected_outputs": {
"friction_factor": 0.032,
"flow_regime": "laminar"
},
"working": "Re=2000<2300, so use f=64/Re. 64/2000=0.032 exactly. The roughness is ignored for the laminar formula."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche6/tranche6-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`