Darcy-Weisbach Pressure Drop mechanism

Model scope

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.

• 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.

Units and conventions

• 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.

Inspectable vector

One of 4 source-bound review vectors:

{
  "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."
}

Failure boundary

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.

Other records

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
• BOUNDARY_HAZARD_CATALOG.json