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See NeoVAD Mesh Convergence Results for the results of this study
This is a mesh convergence study for the modelled geometries in the NeoVAD (as defined in Creating the initial model).
Inlet and outlet meshes
The meshes for the inlet and outlet domains were less than 5% the size of the impeller and diffuser meshes and involved no significant flow interactions. Therefore, the default meshes were deemed appropriate.
The inlet (left) and outlet (right) meshes.
Impeller and diffuser meshes
The size and quality of the impeller and diffuser meshes were investigated.
Four meshes were investigated in total; one with the boundary layer refinement method as ‘Proportional to mesh size’, and three with the method based on a first element offset. The offset size was set to 0.69 mm for the impeller and 0.49 mm for the diffuser.
| Mesh number | Boundary layer refinement method | Number of elements |
|---|---|---|
| 1 | Proportional to mesh size | 427,181 |
| 2 | First element offset | 108,415 |
| 3 | First element offset | 300,780 |
| 4 | First element offset | 978,612 |
The pressure increase was monitored for each mesh and plotted against the number of elements. The following mesh statistics were recorded in each domain:
- Minimum and maximum face angles
- Maximum element volume ratio
- Minimum volume
- Maximum edge length ratio
- Maximum connectivity number
- Near-wall expansion rates
Each of these measures was monitored, and the percentage of mesh cells that had a value outside of the recommended bounds (according to Ansys CFX) was noted.
A mesh size that provided a suitable compromise between accuracy and computational resources was selected.