Reynolds Number Calculator

Inspectable records

Ledger state

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

Area

Thermodynamics, Fluids & Aero

Tranche

tranche-4

Evidence ID

t4-216

Ledger rows

1

No ledger note is attached.

Review findings

The Reynolds-number formula is correct, but the instrument is not ready for an unqualified internal-or-external flow classification. The empty honest_label should be replaced with a statement of the selected characteristic-length definition, unit requirements, geometry-specific thresholds, and the fact that transition boundaries are approximate. Verdict remains NEEDS_REVIEW until these choices are explicit.

Formula and scope findings

• Re=ρVL/μ=VL/ν is the standard Reynolds-number formula when ρ, V, L, μ, and ν use mutually consistent units.
• The characteristic length L is underspecified: for internal flow it is commonly the pipe diameter, while for noncircular ducts it is commonly the hydraulic diameter; for external flow it depends on the geometry and stated reference length.
• Flow-regime thresholds are missing and are not universal. The commonly used internal smooth circular-pipe thresholds Re<2300 laminar, 2300≤Re≤4000 transitional, and Re>4000 turbulent do not generally apply to external flow.
• The declared plain-arithmetic engine can calculate Re but cannot by itself provide the requested categorical regime without comparison/branching logic.

Unit assumptions

• Use SI-consistent units: ρ in kg/m³, V in m/s, L in m, μ in Pa·s (kg/(m·s)), and ν in m²/s.
• The two formulas are equivalent only when ν=μ/ρ.
• For the test vectors, L is the pipe diameter and the classification basis is a smooth circular internal pipe using Re<2300 laminar, 2300≤Re≤4000 transitional, and Re>4000 turbulent.
• External-flow classification requires the geometry, reference length, and an explicitly selected transition criterion.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The specification leaves internal versus external classification thresholds and negative-velocity convention unspecified, and μ = 0 produces an undefined result that must be rejected rather than numerically evaluated.

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": {
    "flow_type": "internal_smooth_circular_pipe",
    "rho_kg_m3": 998,
    "velocity_m_s": 2,
    "characteristic_length_m": 0.05,
    "mu_Pa_s": 0.001
  },
  "expected_outputs": {
    "Re": 99800,
    "flow_regime": "turbulent"
  },
  "working": "Re=ρVL/μ=(998 kg/m³)(2 m/s)(0.05 m)/(0.001 Pa·s)=99.8/0.001=99,800. Since Re>4000, the regime is turbulent."
}

Related workflows

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-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json