Mesh families and topology
Structured, unstructured and hybrid grids serve different geometric and numerical needs.
Connectivity and cell shape are separate
A structured block has logically indexed cells, often quadrilateral in 2D or hexahedral in 3D. A multiblock grid joins several such regions. An unstructured grid stores connectivity explicitly and can use tetrahedra, prisms, hexes, polyhedra or a mix. A Cartesian core is a particular arrangement of cells, and a hybrid grid can combine a prism layer with an unstructured or Cartesian core.
| Family | Where it helps | What to inspect |
|---|---|---|
| Structured O-grid | Wraps the body, with orderly surface-normal spacing. | Trailing-edge treatment and how well the wake is resolved outside the near-body block. |
| Structured C-grid | Wraps from a downstream cut around the airfoil and can extend a refined block into the wake. | The wake cut, block interfaces and cell quality near the trailing edge. |
| Multiblock H-type / mixed topology | Fits selected passages or larger aircraft assemblies using connected blocks. | Effort to maintain quality at block joins, junctions and sharply curved surfaces. |
| Unstructured tet or poly core with prisms | Fits complex wing-body geometry, flap gaps and assemblies. | Layer collapse, size transitions, curvature and solver-specific mesh quality. |
| Cartesian or octree core | Supports local refinement and automated grid generation. | Wall representation, tiny cut cells or poor geometry conformity, depending on the method. |
High aspect ratio can be useful in a boundary layer when cells align with the dominant gradients. The same stretching can be a problem in an eddy-resolving wake. Judge quality against the flow, the discretization and the wall treatment together.