Darcy-Weisbach Pressure Drop

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Mechanical, Civil & Structural Engineering — Statics/Dynamics, Strength of Materials, Machine Design, Civil, HVAC, Vibration

Tranche

tranche-6

Evidence ID

t6-132

Ledger rows

1

No ledger note is attached.

Review findings

The direct Darcy-Weisbach arithmetic is standard under the stated SI assumptions and is demonstrated by all four vectors. The overall specification needs review because the declared Colebrook algorithm cannot be verified from the declared input set, and the required Colebrook inputs, convergence policy, friction-factor convention, and gravitational constant are unspecified.

Formula and scope findings

• The Darcy-Weisbach formulas are not explicitly provided. The standard formulas assumed here are ΔP = f(L/D)(ρV²/2) and h_f = f(L/D)(V²/(2g)).
• The declared Colebrook iteration cannot be performed from the listed inputs f, L, D, V, and ρ alone. Colebrook requires Reynolds number Re and relative roughness ε/D, or viscosity μ plus ε. The spec also omits the initial guess, iteration equation details, and convergence tolerance.
• The friction-factor convention is unspecified: f must be the Darcy friction factor, not the Fanning friction factor. Using a Fanning factor directly would produce a result four times too small.
• The gravitational acceleration g is not listed; the head-loss output requires an explicit value or stated default.

Unit assumptions

• f is dimensionless Darcy friction factor.
• L and D are in metres, V is in metres per second, ρ is in kilograms per cubic metre, ΔP is in pascals, and h_f is in metres of fluid.
• g = 9.81 m/s² is assumed for all head-loss calculations.
• The listed f values are treated as already-known friction factors; no Colebrook iteration is possible without Re and ε/D.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

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.

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": {
    "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."
}

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