Dear all,

I don't understand the exact definition of structured mesh and unstructured mesh. When do you call it structured mesh and when you don't? Could anyone help explain this to me?

A structured mesh has implicit ordering for each cell. Thus if we take a cell, let's say with index i, its neighbour must be i-1 in one direction and i+1 in other direction. In other word the cells are regularly stacked. Therefore in 3D, structured mesh can only have hexahedral cell that allows three 'logically' independent directions to be define, the i,j,k directions.

An unstructured mesh has no implicit ordering. If we take a cell with index 100, say, its neighbours can have any index between 1 to Nmax. The cell itself can be any polygon. However, thanks to Finite Element, tetrahedra and triangles are often seen as identical to unstructured meshes, eventhough it is possible to have an unstructured mesh consist of regularly stacked hexa that looks like a typical structured mesh.

BTW, Fluent 5/6 mesh is unstructured, even if the mesh appears like a typical structured mesh. On the other hand Fluent 4 mesh is multiblock structured.

Dear Indi, Thanks a lot for your detailed explanation.I always use Fluent 5/6 so I guess all my mesh is unstructured.