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0.2.7 Mesh Quality and Distortion Contract

WP06 status is PASS for the additive common diagnostic contract in solveur.mesh.quality_contract. It covers TET4, TET10, HEX8 and HEX20, integrates invalid-geometry reporting with the WP03 preflight, and does not alter existing element integration or solver validation behavior.

Principle

Mesh quality is a multidimensional diagnostic. No universal acceptance rule based only on nominal aspect ratio is proposed. A quality decision must retain the actual geometry, Jacobian samples, orientation, volume, distortion, conditioning and relevant response metrics.

Metrics

For every controlled mesh level, record:

  • element count, node count, active DOF and connectivity hash;
  • signed Jacobian minimum/maximum and sampling locations;
  • volume/area and orientation signs;
  • edge/face measures and aspect-ratio indicators;
  • distortion/skew/warpage indicators appropriate to the family;
  • tangent or stiffness conditioning diagnostic when available;
  • displacement, reaction, energy and residual observables relevant to the case;
  • solver iterations, convergence status and deterministic replay digest.

Planned matrix

Each new element campaign should include a regular mesh, orientation changes, controlled distortion, near-invalid geometry and at least three compatible levels when a convergence statement is made. A mesh-sensitive result is reported as a limitation, not hidden by selecting the most favorable level.

Failure policy

Invalid Jacobian, non-positive volume, unsupported topology and non-finite metric must be rejected explicitly. A severe conditioning observation may explain a failure but is not itself a universal cutoff. Retry/cutback must not turn an invalid model into a silent PASS.

Implemented classification

The common contract reports VALID, VALID_WITH_WARNING or INVALID. A warning leaves calculation permitted; invalid geometry is reported fail-closed by preflight. Dimensionless diagnostics are invariant under rigid transforms and coordinate scaling in the controlled tests. See 0_2_7_mesh_quality_contract.md and qualification/0_2_7/vnv_v2/mesh_quality_cases.json.

Owner review items

Numerical thresholds, family-specific quality bands and any use of a conditioning indicator remain PROPOSED_OWNER_REVIEW until justified by predeclared mechanics, reproducible evidence and an explicit decision.