Venturi Flow Meter Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-284

Effect

Computation or source lookup only

Input and validation requirements

• Division by zero or invalid results occur if density is zero or negative.
• The denominator factor 1-beta^4 must be positive; beta=1 causes division by zero and beta>1 makes the square-root argument negative.
• Negative DeltaP produces an invalid square root unless signed/reverse-flow handling is explicitly implemented.
• Diameters must be positive, and the throat diameter must be smaller than the pipe diameter.
• The velocity output is ambiguous unless the instrument specifies throat velocity versus upstream pipe velocity.
• Using this incompressible formula for gases or large pressure ratios can produce materially incorrect results.
• Cd must be constrained to a physically appropriate positive range and should not be silently assumed to be 0.95-0.98 for every venturi and Reynolds-number regime.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "pipe_diameter_d1_m": 0.1,
    "throat_diameter_d2_m": 0.05,
    "deltaP_Pa": 20000,
    "Cd": 0.97,
    "density_kg_m3": 998
  },
  "expected_outputs": {
    "Q_m3_s": 0.0124532,
    "throat_velocity_m_s": 6.34236
  },
  "working": "beta=d2/d1=0.05/0.1=0.5; beta^4=0.5^4=0.0625; 1-beta^4=0.9375. A2=pi*d2^2/4=pi*(0.05^2)/4=0.00196350 m^2. sqrt(2*DeltaP/(rho*(1-beta^4)))=sqrt(40000/(998*0.9375))=sqrt(40000/935.625)=sqrt(42.7522)=6.53851 m/s. Q=Cd*A2*sqrt(...)=0.97*0.00196350*6.53851=0.0124532 m^3/s. Throat velocity=Q/A2=0.0124532/0.00196350=6.34236 m/s."
}

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-tranche4/tranche4-results.json