I set a mesh control on a body, for example, cylinder control with circumferential setting and axial setting. For 3D mesh, there is also a setting for element size. I am wondering which one has a higher proirty during the meshing. For example, i use the default element size in 3D mesh setting window. But my mesh control define a smaller element size. I tried to mesh the body, and it seems that the samller one defined by mesh control is respected. Could you please give some comments for how SC takes into account the mesh control and the element size setting.
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This is a question worth reviewing again after getting Simcenter 3D version 2019.1. That version updated the manner in which element sizes are applied to geometry. The images below illustrate behavior in current releases and the updated behavior to be available in version 2019.1. The model contains mesh controls (size on face) that lead to much smaller element sizes than the global element size on the 3D mesh. Simcenter 3D processes all of the faces, then assigns element sizes to related edges.
However, in the first image, you don't see small element sizes on all of the mesh control faces. That is because of the way faces are processed when assigning element sizes to them. Previous versions would sort faces by internal face IDs, which tend to be random in nature. That randomness depicts itself in the first image where large element sizes are associated with edges whose face is assigned the mesh control. In those situations the edge was sized based upon a face that obtained its element size from the 3D mesh (i.e. a large element size). Then the mesh control face was processed, but since some of its edges were already sized, the mesh control may not have influenced the size at all.
Now counter that with version 2019.1, which processes edges and faces based upon element size assignments. The geometry is sorted and processed from smallest element size to the largest element size. Therefore one should see more consistent applications of mesh controls and smoother transitions between small and larger element sizes. The next image is taken from the same model, but meshed in version 2019.1.
Now it is clear that the mesh control faces all obtained the smaller element size per the mesh control. Neighboring faces obtained larger element sizes from the 3D mesh dialog, while transitioning from the small elements on the edges to larger ones on the interior of the faces.
There is control for transition rate too, both on the surface and into the solid.The surface element size transition is embedded as part of the curvature based mesh refinement option. As you increase the curvature based refinement, you also reduce the size transition rate. There's no independent control for the size transition rate on the surface, but that is likely to be a topic for development in the future.
Another aspect of transition is that it achieves transition across multiple faces according to how the adjacent edges transition. This can be a challenge when faces are narrow relative to the largest possible element size. The mesher doesn't use proximity to a small element region completely through to an opposite edge of a face. If a face is narrow, you can still see quicker than desired transitions across the narrow width. I hope this explanation makes sense.
Thanks for your explanation. This is really helpful.
For the case in which a narrow face having a small element size is adjacent to a wide face having a large element size, here i mean two faces are belong to tow touching bodies where MMC is applied. The transition seems too quick. As you explain, this is really a challege, but in some physics, a smooth tranisiton will be needed in some critical regions to help improving accuracy of the simulation.