1. Sphere example
The results of the structured mesh around the sphere flow are shown in:
https://mp.weixin.qq.com/s/HhB5Pdzwdl-kKDDgnGA3qA (previous public account articles)
The main idea of the overlapping mesh is to divide the boundary layer mesh in the near-wall area, and fill it with a Cartesian mesh as the background mesh for the rest of the computational domain, which together form the final computational Final Mesh. Boundary layer meshes can be generated by surface mesh extrusion or divided in the form of structured block meshes, making them very flexible.
For the sphere example, we can use the Quad Mesher tool to divide the sphere into a quadrilateral face mesh, and then use the Mesh Extrude function to stretch a whole Near Wall Mesh.
Spheres are a whole Near Wall Mesh
When the model is complex, even if the entire model can be fully quadrilateral, it is extremely challenging to extrude into a continuous and complete near-wall mesh with the required quality, so you can try a multi-block overset mesh scheme.
Left hemisphere NW
Right Hemisphere NW
The profile is as follows: the green grid is the mesh that fills the gap between the NW in the left hemisphere and the NW in the right hemisphere, and the green grid is stretched from the side grid of the NW in the left hemisphere and forms a set of overset overlapping relationships with the NW grid in the right hemisphere.
Sectional view
The local encryption method is used in the computing domain to ensure the uniform transition of the grid size on the one hand, and the fine mesh in the wake region on the other hand. The total number of grids is 330,000, which is only about half of the previous structured grids.
The composition and overlap of multiple grids can be seen from the local zoomed-in image, which helps you understand the concept of multiple overset grids.
Overview of the sphere calculation grid
The sphere calculates the local enlargement of the grid
The calculation conditions and configuration are consistent with the previous examples, and the flow field results are as follows:
02
2. Rod Airfoil example
The Rod-Airfoil study consists of a cylinder and airfoil, with the cylinder upstream of the leading edge of the airfoil, which can be used to evaluate the ability of a CFD program to predict the frequency of shedding around the fluid vortex and to simulate the development of turbulent structures in the wake.
The near-wall mesh is generated by Mesh Extrude, and the mesh with a large aspect ratio at the trailing edge of the airfoil is encrypted by Element Divide, and the final mesh is 420,000.
Rod Alfoyle near-wall engrid
Grid encryption zone settings
Overview of the Rohde Elfoyle grid
Enlarged view of the overlap of the Rodern's grid with the background grid
Enlarged view of the overlap of the Airfoil NW grid with the background grid
The solver uses an incompressible solver, fourth-order precision calculation, 2 4090GPU cards, 10 hours per flow cycle, and the flow field results are as follows:
Transient results
Average results
3. Summary
The above cases show that Dimaxer has good adaptability to the calculation of Overset overlapping meshes, and the quantitative results are accurate, which can be further used in academic and engineering research.
This article focuses on the idea of multi-block Overset overlapping meshes, and will be expanded to more and more complex industrial verification cases in the future, so stay tuned!!
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