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Hi All,

I am trying to generate a mesh for a model domain with a refined area (inner domain) and a high-resolution area within the refined area. The approach that I tried to use is first creating the high-res mesh and then use it as a sub-mesh to generate mesh for the inner domain. Eventually, the mesh of the inner domain was used as a sub-mesh to generate mesh for the overall/whole domain.

The issue that I encountered was that I was unable to generate a good mesh for the overall domain with the approach I mentioned, although it was successful to generate the mesh for the inner domain with high-res area as sub-mesh.

Feel free to see the attached photos and some technical details below:

For high-res area,
Edge length: 3 m
No. of nodes: 5746

For inner domain containing the high-res area,
Default edge length: 150 m
No. of nodes: 52792

For testing purposes, I tried to create the whole domain mesh by using the outer boundary of the inner domain as hardline, i.e. without using the inner domain mesh as sub-mesh, and then merge them together, which works perfectly fine with 99435 nodes created (see good mesh.jpg). However, this approach leads to another issue when adding boundary conditions (see boundary.jpg). A unwanted boundary was created automatically for the inner domain because I used it as the outline to generate mesh for the whole domain. Are there any ways to delete this boundary?

I also noticed one thing about the dialogue box and log while creating whole domain mesh that was bad (see allocating space for estimated max node count.jpg). The allocating space for estimated max node count was always 1000 for the bad meshes. My intuition was that the domain size was too large and the no. of nodes was too much. But the problem was not solved when I lowered the edge length of high-res mesh to 5m or even 10m, and to increase the growth rate from 1.05 to 1.2 for the inner domain.

Do you have any insights for solving this problem?

Sorry for this long message and thanks a lot.

Hi,

Just to add some more things to the trial and error, I tried to generate the inner domain mesh without having the high-res area and then use the mesh as sub-mesh to generate the whole domain mesh. Everything looked perfect...

I've also tried to extract points from the high-res mesh and use the point sets as hardpoints for generating the inner domain mesh, in other words, without using high-res mesh as sub-mesh. The inner domain mesh looked okay for me but when it was introduced as the sub-mesh of the whole domain, the mesh generated was as bad as shown from the screenshot - same issue as described.

Also, I tried to use the 'extract subset' method followed by 'extract edges' and 'merge meshes' to refine the high-res area locally. When I merge the high-res mesh to the outer domain mesh, a unwanted boundary - the common boundary between the high-res area and outer domain appears when I was setting new boundary conditions.

Hi,

Some nice images that you've created! Thanks for using BK, hope you find it helpful in your work...

Based on one of your screen snapshots I'm guessing you are using BK 3.3.4. And if that's so, then change the edge growth ratio by adding or subtracting an "epsilon". That is, instead of 1.2 try 1.200001

If that doesn't work to help generate a reasonable mesh, then try the most recent alpha... BK 3.12.6 or the soon-to-be created BK 3.12.7 that fixes a number of things.

Kindly,
Alan

a.barton wrote:


Hi Alan, thanks a lot. I managed to create a reasonably good mesh using the most recent alpha version. Yet, there are some bad spots in the domain where it did not mesh well. I created a set of hardpoints to guide the meshing process (see screenshot) but it did not seem to work after I dragged the point set to HardPoints.

I can't see where the points on the line are located. However, you could try resampling the outline in that area in order to have more points for the mesh to "grab onto"...

• remove the hard points if you try meshing after resampling the outline in that area
• this is so that you don't have too many issues involved all at the same time

Good luck!

Kindly,
Alan