What we all know to be true in practice is that a good mesh helps the computational fluid dynamics (CFD) solver converge to the correct answer while minimizing the computer resources expended. Stated differently, most every decent solver will yield an accurate answer with a good mesh, but it takes the most robust of solvers to get an answer on a bad mesh.
The crux of the issue is what precisely is meant by “a good mesh.” What matters is how accurately the CFD solution reflects reality. Therefore, the solver’s numerical algorithm and the physics of the flow to be computed also have to be accounted for in the evaluation of a mesh.
In HPDC the phyisics of the flow is strictly related to the geometry complexity: parts are often very thin walled and some important details need to be modelled with a very high degree of accuracy using enough mesh resolution to correctly calculate the flow.
Currently kinds of mesh can be divided into:
- Structured cubic mesh
- High calculation accuracy
- Poor geometry representation
- Long calculation time
- Tethraedral mesh
- Low calculation accuracy
- Good geometry representation
Castle uses an hybrid mesh which is the “third way” and combines the main benefits of the other kinds of mesh:
- Structured hexaedral mesh inside the part
- Unstructured tethraedral mesh outside
- Auto-refined mesh to get the necessary number of elements only where they are needed.
Therefore the hybrid mesh is:
- Fast and easy to prepare (in a few minutes)
- Fast to calculate
- Very accurate to follow the real part shape
- Matching perfectly the requests of the solver’s numerical algorithm