Source: https://guthlabs.ai/docs/instruments/venturi-flow-meter-calculator/
instrument / verified-clean
# Venturi Flow Meter Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## 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**: t4-284
**Ledger rows**: 1
No ledger note is attached.
## Review findings
NEEDS_REVIEW because the exact velocity definition and the definitions of beta and A2 are absent. The honest label is empty even though the instrument should disclose its incompressible-flow limitation and that gas/compressible-flow applications require a different model or correction.
### Formula and scope findings
- The stated flow formula is standard for steady, incompressible flow when beta=d2/d1 and A2 is the throat area, but beta and A2 are not defined in the specification.
- The specification promises a velocity output but provides no velocity formula or definition of which velocity is intended. Throat velocity would be v2=Q/A2; pipe inlet velocity would be v1=Q/A1, and these are different.
- The formula's applicability to compressible fluids, especially gases at substantial pressure differences, is not stated; the incompressible formula must not be presented as universally valid.
### Unit assumptions
- Diameters are assumed to be in metres, producing A2 in m^2.
- Differential pressure DeltaP is assumed to be in pascals.
- Density rho is assumed to be in kg/m^3.
- The resulting volumetric flow Q is in m^3/s and throat velocity is in m/s.
- beta is assumed to be the dimensionless diameter ratio d2/d1, with d2 as throat diameter and d1 as upstream pipe diameter.
- Cd is dimensionless.
## Boundary hardening
### Recorded hazards
- 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.
## 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": {
"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."
}
````
## Related workflows
[Pipe & Pump Benchmeter 2]()
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json ยท VERIFIED_CLEAN`
- `evidence-tranche4/tranche4-results.json`