Source: https://guthlabs.ai/docs/instruments/boundary-layer-thickness-estimator-flat-plate/implementation/

instrument implementation / implementation-contract

# Boundary Layer Thickness Estimator (Flat Plate) implementation

A source-bound implementation contract for Boundary Layer Thickness Estimator (Flat Plate); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## 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**: t6-045

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification does not define the transition Reynolds number or equality convention, and it does not state whether velocity is signed or converted to speed. Zero viscosity produces undefined Reynolds number and must be rejected; without explicit validation, the arithmetic engine can return Infinity, NaN, or invalid plotted values.

## 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": {
    "U_m_per_s": 15,
    "x_m": 0.2,
    "rho_kg_per_m3": 1.2,
    "mu_Pa_s": 0.000018,
    "correlation": "laminar",
    "sampled_plot_point_x_m": 0.2
  },
  "expected_outputs": {
    "Re_x": 200000,
    "flow_regime": "laminar under the stated provisional criterion Re_x<500000",
    "delta_m": 0.00223606798,
    "sampled_plot_point": {
      "x_m": 0.2,
      "delta_m": 0.00223606798
    },
    "curve_features": {
      "root": "x=0 in the limiting sense, delta approaches 0",
      "finite_extrema": "none for either supplied correlation over x>0",
      "large_x_behavior": "delta increases monotonically as x^0.5 for laminar and x^0.8 for turbulent"
    }
  },
  "working": "Re_x=rho*U*x/mu=(1.2*15*0.2)/0.000018=3.6/0.000018=200000. sqrt(Re_x)=sqrt(200000)=447.2135955. delta=5*x/sqrt(Re_x)=5*0.2/447.2135955=1/447.2135955=0.00223606798 m."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/boundary-layer-thickness-estimator-flat-plate/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/boundary-layer-thickness-estimator-flat-plate/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/boundary-layer-thickness-estimator-flat-plate/qualification/>)

## 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`