Source: https://guthlabs.ai/docs/instruments/sphere-cylinder-drag-coefficient-vs-reynolds-correlation/implementation/

instrument implementation / implementation-contract

# Sphere/Cylinder Drag Coefficient vs Reynolds Correlation implementation

A source-bound implementation contract for Sphere/Cylinder Drag Coefficient vs Reynolds Correlation; 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**: t7-094

**Effect**: Computation or source lookup only

## Input and validation requirements

Re=0 produces division by zero and must be rejected or reported undefined. The exact value at Re=1 and all higher-Re outputs are also under-specified unless the instrument supplies a definite drag-curve table or fit; the representative higher-Re calculation is therefore only a reference check.

## 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": {
    "Re": 0.1,
    "shape": "sphere"
  },
  "expected_outputs": {
    "Cd": 240
  },
  "reference_data": {
    "drag_relation": {
      "value": "Cd=24/Re",
      "source_convention": "widely tabulated standard value: Stokes drag law for a sphere"
    },
    "validity_range": {
      "value": "Re much less than 1",
      "source_convention": "widely tabulated standard value: creeping-flow sphere regime"
    }
  },
  "working": "Use the Stokes sphere relation: Cd=24/Re. Substitute Re=0.1: Cd=24/0.1=240. Therefore Cd=240.0."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/sphere-cylinder-drag-coefficient-vs-reynolds-correlation/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/sphere-cylinder-drag-coefficient-vs-reynolds-correlation/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/sphere-cylinder-drag-coefficient-vs-reynolds-correlation/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-tranche7/tranche7-results.json`