I’m sorry, I should have remembered that the “Build type” control is not present in the Windows version of MFiX. I will address this in the next release. In the meanwhile you can try to build a debug-enabled mfixsolver using the build_mfixsolver.py command as described above (and in the user manual)
Thank you Jeff. I want to know whether the size of each cell everywhere should be smaller than the smallest geometries, that means apart from the uniform meshing, even if I use control points, the size of largest cell should be smaller than the smallest geometries. Otherwise, can I only control the largest cell size of background mesh around the geometries with the smallest scale smaller than the smallest geometries? Thank you.
I use control point method this time, and this type is error is persistent. I hereby attach the .mfx file. Could you please help me have a look at it (the .stl does not change)? I am not sure whether I have missed anything related to the method. Thank you.
chamber_delicate_structure1.mfx (8.8 KB)
The mesh needs to be smaller than the geometric detail near that detail. It can be larger elsewhere.
You missed the following steps:
- Inspecting the stl file. Is there any collapsed triangle, duplicate edge/vertex, missing triangles? Are all the normals pointing in the correct direction?
- Be aware of smallest geometry. I still see some areas where the mesh is larger or about the same size of the internal tubes.
You will not be able to proceed until to spend some time on the above.
Hey Jeff, Thank you for your reply and reminder. I have checked the above two steps as you said. And they are both fine. But the “index dimension1, above upper bounds” error persistent, so then I adjusted slightly the paras such as increasing dot product tol, etc, and obtained the following result, which gives better meshing quality for the small geometries than previous attempts. So I want to know whether there exists a systematic tutotial instead of trial&error to let us know how to coordinate the paras of cut cell method and cell numbers/control point positions. Thank you.
Hi Jeff, could you please help me figure out how to fix the tiny defects that can not be detected without zooming. I have tried different set of paras for cut-cell method but not obtain a perfect mesh. And @cgw also has helped to fix a bug with bug report I uploaded. Thank you.
And when I slightly adjust the sets of related parameters of cut cell method, I found out some of them are self-contradict, that means one specific param is suitable for one part of geometry while incurred defects in the other parts of the geometry.
So I want to know 1. whether there exists a standard procedure to generate acceptable and convergent mesh when the .stl model has already satisfied the two key points you mentioned above. 2. whether there exists meshing methods available for the MFIX apart from cut-cell method. 3. how can I thoroughly inspect the stl file. to find out the existence of any collapsed triangle, duplicate edge/vertex, missing triangles? Thank you.
It turns out your STL file is not clean. There are many duplicate vertices/triangles. Please see attached. My recommendation is you start with much simpler models to get familiar with the procedure. See 3. Tutorials — MFiX 21.3 documentation for some examples. For non-rectangular geometries, the cut-cell method is the only option. To clean your STL file, use the CAD sofware you used to generate the file, it should have options to remove duplicates and recompute normals.
What worries me in your simulation is that the inlet velocity is quite high (around 9 m/s) for the size of the inlet tube (around 2.5 mm), and you have many other tubes smaller than 1 mm, so you will end up with very large velocities that require tiny time steps (see picture below). In the attached, I used a grid spacing that will get you the bare minimum to resolve the internal tubes, and I had to use fairly large values of the snap and small cell tolerances to get it to run (you may be able to find a better combination that work too). I also removed duplicates in the stl file, which went from 2894 triangles to 1298. It still has many stretched triangles, and you need to set a facet angle tolerance to zero or close to zero so no facet is excluded. You want to see this
Total number of facets read = 1298
Number of valid facets = 1298
Number of ignored facets = 0
If you have ignored facets, this will create holes in the stl and the meshing will likely fail.
chamber_delicate_structure2_clean.mfx (15.3 KB)
chamber_delicate_structure2_clean.STL (63.5 KB)
Thank you Jeff, but when I load your updated .mfx and .stl, the “index, dimension 1, above upper bounds” type error happened again, and I did not change your settings and the .stl file. So I wonder whether there exists some stochastic effects to incur error in one computer while run meshing normally in another computer? Thank you.
And when I just copied and pasted your clean .mfx and .stl files into a new project and open the project by clicking its .mfx file, the error reported in the following link happened. I remembered this kind of problem happened just after I deleted the mfix21.2 and installed 21.3 version. And there is no bug report generated currently. Thank you.
We are looking into it. We will let you know when we have an update to share. This will most likely take a few days. Thank you for you patience.
Thank you Jeff, I tested the files you attached above, and the “index, dimension 1, above upper bounds” type error as follows is persistent. I want to know whether the above attached project modified by you can successfully run in your computers. Thank you.
And another question referring to the following quote is that if the reason for the quoted problem is unclean .stl file, why the “index, dimension 1, above upper bounds” type error still appeared when I replaced the origin .stl with the clean one uploaded. Thank you.
And could you please recommend me a software to remove the duplicate entities including facets, vortexs and lines? Since I can not find the tools and commands in solidworks to do the above job and flip their norm (if you know, could you please tell me)? It would be better if it is open-sourced. Thank you.
Hey Jeff, I hope I am not bothering you too frequently, I am willing to know whether you have any updates for the problem I have posted. Now that you have posted the gas velocity distribution across the chamber, could you please tell me how long you have simulated in that case and can you give me the evolution of bulk density, volume fraction and outlet mass flowrate as well? Thank you for your consideration. I need your help.
We have a potential fix for the meshing issue on Windows that we will make available in the next few days (21.3.1 point release). Even if you can mesh, it will take too long to run on a PC, you will need access to a cluster. I only ran for 0.1s to troubleshoot and I did not analyze any data.
Thanks for your reply, but when I encountered the “index, dimension1, above upper bounds” problem when I mesh the cleaned files provided by you.
Why my PC can not even build that? due to RAM, Algo Lib, stochastic effect, version difference from you, windows operation systems?
I really want to know the reason. Thank you.
Hi Jeff this info is very important for me. Could you please answer me? Thank you.
Ju Wu - please understand that we all have full-time jobs and MFiX support is provided on a best-effort basis. We are all working on our own research and development of MFiX. Please be patient when asking questions on the forum and do not repeat the same questions in different threads. Thanks.
I am personally using Blender right now, but I have used meshlab in the past. I don’t know about solidswork, but I imagine they have some clean up tools.
Regarding the out of bound error while meshing on Windows, please try the 21.3.2 point release. I hope this fixes your issue.