Colebrook-White / Moody Friction Factor Solver

Inspectable records

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