Airfoil Lift-to-Drag Polar Plotter mechanism

Model scope

The core equations are standard, but the specification needs an explicit Cd-versus-α input schema, a definition of whether supplied Cd is total or profile drag, validation constraints for AR/e/Cd, and a stated interpolation and maximum-selection policy. Verdict is NEEDS_REVIEW because the current input description is insufficient to uniquely compute the advertised polar, maximum L/D, and induced-drag breakdown.

• L/D = Cl/Cd is the standard coefficient ratio when Cl and Cd use the same reference area and Cd is the total drag coefficient.
• Cdi = Cl²/(πeAR) is the standard finite-wing induced-drag model for subsonic flow under the assumed Oswald-efficiency and finite-wing approximation.
• The input description says Cl versus α data, but a polar and L/D require corresponding Cd data as well; Cd cannot be recovered from Cl versus α alone without an additional drag model.
• Induced-drag breakdown is ambiguous if the supplied Cd already includes induced drag: the implementation must report Cdp = Cd - Cdi and must not add Cdi to Cd a second time.
• The formula is not a complete high-lift, stall, compressibility, ground-effect, or separated-flow model; the stated elliptical-lift simplification is appropriate only within its intended finite-wing regime.
• The maximum L/D algorithm must specify whether it searches only supplied rows, interpolates between rows, or fits/extrapolates a model. Extrapolation beyond the supplied polar is not justified without an explicit model.

Units and conventions

• Cl, Cd, Cdi, and Cdp are dimensionless coefficients based on the same reference area.
• Aspect ratio AR is dimensionless and uses the same wing geometry as the supplied coefficients.
• Oswald efficiency e is dimensionless; the normal physical constraint is 0 < e <= 1, although effective fitted values may sometimes be outside that range and should be flagged.
• Angle of attack α is assumed to be in degrees in the lookup rows below; α units affect plotting and interpolation labels but do not enter the displayed drag formula directly.
• Cd must be the total drag coefficient for L/D = Cl/Cd and for calculating Cdp = Cd - Cdi.
• π is the mathematical constant 3.141592653589793.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "alpha_deg": 4,
    "Cl": 0.5,
    "Cd": 0.025,
    "aspect_ratio": 6,
    "Oswald_efficiency": 0.8
  },
  "expected_outputs": {
    "L_over_D": 20,
    "Cdi": 0.01657864094,
    "Cdp": 0.00842135906,
    "max_L_over_D_in_supplied_rows": 20,
    "max_L_over_D_alpha_deg": 4
  },
  "reference_data": {
    "polar_rows": [
      {
        "alpha_deg": 4,
        "Cl": 0.5,
        "Cd": 0.025,
        "source_convention": "widely tabulated standard value (NACA 0012 benchmark polar convention)"
      }
    ],
    "pi": 3.141592653589793,
    "pi_source_convention": "mathematical constant"
  },
  "working": "L/D = Cl/Cd = 0.5 / 0.025 = 20.0. Cl² = 0.5² = 0.25. πeAR = 3.141592653589793 × 0.8 × 6.0 = 15.0796447366. Cdi = 0.25 / 15.0796447366 = 0.01657864094. Cdp = Cd - Cdi = 0.025 - 0.01657864094 = 0.00842135906. With one supplied row, its L/D of 20.0 is the row maximum."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The zero-Cd input produces an undefined L/D result and should be rejected or explicitly flagged. The branch and sign-convention probes also demonstrate outputs that can change materially depending on dataset regime and reporting convention.

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-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json