[Tobi]

Hi all,

May I ask the experts of cfMesh about the difference between:

• cfMesh from sourceforge
• cfMesh+ coming from Creative Fields
• The main advantage of cfMesh compared to snappy (except memory usage, layer generation, meshing time and other input formats)

For me, it would be also interesting if cfMesh has a similar mesh quality dictionary and if one can choose the volume element types, e.g., for hex-dominant meshes only use hexahedral and polyhedral (or other cell types).

For me it seems, that cfMesh+ is commercial and comes with a GUI and I would expect, that the algorithm handles geometries better in terms of meshing results.

Tobi

[wyldckat]

Hi Tobi,

I don't work for Creative Fields, but I'm somewhat familiar with cfMesh and cfMesh+.
So here is what I know:

1. cfMesh was developed with performance and user simplicity in mind. I remember that in my first tests with it, I was able to generate a mesh with 10 million cells in what felt like 30s with a considerably low effort to configure and snap onto the geometry, while blockMesh+snappyHexMesh took something like 20 minutes.
2. cfMesh is able to mesh with either an hexahedral core or with a tetrahedral core mesh. That said, the tetrahedral core mesh feels like it's the hexahedrals sliced along one of the diagonals.
3. I don't remember how it handles the snapping on surfaces, so I don't remember if it will collapse faces in order to reduce hexahedral cells into prisms and tetrahedrals or not... but I do remember that snappyHexMesh usually tries (or has) to keep the whole mesh as hex-cells.
4. cfMesh is able to generate in parallel without decomposition, namely by using OpenMP for multi-threading, which can be faster in some situations when compared to using MPI. In other words, it can mesh with how many cores you have in your machine, without having to first create a base mesh and decompose it.
5. There were some discussions some years ago on providing a background mesh for cfMesh, but I don't remember if it was ever implemented/supported, given that cfMesh does a great job of generating its own background meshes.
6. cfMesh provides several utilities, among which improveMesh is a favorite of mine, given that it can iterate further to try and improve the mesh, after the mesher has ended. Mind you that sometimes it does not improve the mesh, when there are fairly complex situations in particular parts of the mesh. Using checkMesh to tell you which faces/cells are bad, can help you decide if you should try and refine the mesh in the troublesome locations.
7. If I remember correctly, cfMesh was developed during a PhD, which is why it's available to the public in its current form.
8. From what I know/remember, cfMesh+ is the product of the ongoing development that is sponsored by paying clients, which means that it has support for multi-region meshing and improved layered meshing (the ones I remember), along with any new features that clients ask/pay for.

As for which mesher is better, it's the same as usual: try it out yourself with the geometries and cases you need to mesh, because it can suit your needs, unless you need features it does not yet support.


The other scenario that comes to mind is if you need a fairly custom/hand-made mesh, but that's something that may require a more dedicated mesher either way.



Best regards,
Bruno

[franjo_j]

Originally Posted by wyldckat

Hi Tobi,

I don't work for Creative Fields, but I'm somewhat familiar with cfMesh and cfMesh+.
So here is what I know:

1. cfMesh was developed with performance and user simplicity in mind. I remember that in my first tests with it, I was able to generate a mesh with 10 million cells in what felt like 30s with a considerably low effort to configure and snap onto the geometry, while blockMesh+snappyHexMesh took something like 20 minutes.
2. cfMesh is able to mesh with either an hexahedral core or with a tetrahedral core mesh. That said, the tetrahedral core mesh feels like it's the hexahedrals sliced along one of the diagonals.
3. I don't remember how it handles the snapping on surfaces, so I don't remember if it will collapse faces in order to reduce hexahedral cells into prisms and tetrahedrals or not... but I do remember that snappyHexMesh usually tries (or has) to keep the whole mesh as hex-cells.
4. cfMesh is able to generate in parallel without decomposition, namely by using OpenMP for multi-threading, which can be faster in some situations when compared to using MPI. In other words, it can mesh with how many cores you have in your machine, without having to first create a base mesh and decompose it.
5. There were some discussions some years ago on providing a background mesh for cfMesh, but I don't remember if it was ever implemented/supported, given that cfMesh does a great job of generating its own background meshes.
6. cfMesh provides several utilities, among which improveMesh is a favorite of mine, given that it can iterate further to try and improve the mesh, after the mesher has ended. Mind you that sometimes it does not improve the mesh, when there are fairly complex situations in particular parts of the mesh. Using checkMesh to tell you which faces/cells are bad, can help you decide if you should try and refine the mesh in the troublesome locations.
7. If I remember correctly, cfMesh was developed during a PhD, which is why it's available to the public in its current form.
8. From what I know/remember, cfMesh+ is the product of the ongoing development that is sponsored by paying clients, which means that it has support for multi-region meshing and improved layered meshing (the ones I remember), along with any new features that clients ask/pay for.

As for which mesher is better, it's the same as usual: try it out yourself with the geometries and cases you need to mesh, because it can suit your needs, unless you need features it does not yet support.


The other scenario that comes to mind is if you need a fairly custom/hand-made mesh, but that's something that may require a more dedicated mesher either way.



Best regards,
Bruno

Hi Bruno, Tobias,


I want to add my 2 cents to this discussion.


Most of Bruno's statement are correct. There are a few details I wish to clarify to avoid any confusion.



cfMesh was NOT developed as part of my PhD studies. I started working on it afterwards. In addition, it was not funded by any organisation at all. It was developed as my research project in my spare time.


Back in 2014, I have decided to offer cfMesh under a GPL license with the assumption that it will attract developers and funding. These assumptions have proven false and that is the reason that we have decided to rewrite the code base to detach it from any other software and offer it as a closed-source commercial application CF-MESH+ that contains all of our latest developments.


The major differences between CF-MESH+ and cfMesh is in the quality of boundary layer generation, mesh-optimisation algorithms and automatic cell sizing. In addition, it comes with a GUI allowing quick setup and manipulation of patches and settings.


Franjo

[Gallienus]

CFMesh+ looks quite interesting. I 'm looking for a good hex/ polyhedral / hybrid meshing program for OpenFoam.

Running OpenFoam under Ubuntu Linux 18.04. Actually it's xUbuntu which is the same OS but uses the more modern XFCE Desktop instead of Gnome. My understanding is that OpenFoam v7 requires some libraries which Ubuntu doesn't supply, thus I'm using the dev version of OpenFoam 7 which seems to work okay.

From my past using commercial solvers, I have always been extremely limited on the number of processors and am used to commercial custom meshing programs which provided high details in high resolution regions while reducing the mesh count in areas that weren't. This is also a requirement for meshes for multiphase models.

I read somewhere that the binary of CFMesh does not work with OpenFoam 7, thus it must be compiled from source code. Before I do this, I was curious to know if CFMesh or CFMesh+ is capable of providing good custom meshes (hexes and hybrids ) for CFD / OpenFoam useage? If not, are there any meshing programs which you can advise?

I've corresponded a little with the folks at Salome but they seem interested in complete packages rather than just meshing. The SnappyHexMesh coming with OpenFoam seems too cumbersome to use for custom meshes.

For Tobi, I'll have to mention that I haven't forgotten about your book. No rush; you can send it whenever it is safe & convenient to do so.

[HPE]

Hi,

- Not objective being here, yet I think `snappyHex` is the most crucial and main reason why OpenFOAM has been being used so widely, so many years.
- I don't know cfMesh+, but in terms of the current state, snappyHex is superior to cfMesh in almost every aspect (subjective) although cfMesh is a very great work - among which the most important one is that cfMesh is not being supported any longer. No bug fix - no update - no nothing.
- Community support is larger for snappyHex than other open source CFD meshers.
- snappyHex is very powerful on arbitrary structures - but lots of tuning may be necessary: some documentation may help.
- If you have resources, I would go for Pointwise, though. That is the state of art and state of practice, in my opinion. It provides inherent OpenFOAM support as well, which is a big bonus.

Might I be wrong in each of my comments - but hope some of them may help in some way.

[Gallienus]

Thanks very much. I'll revisit the Snappy. I've seen a couple of videos on YouTube however was not happy with only automatic mesh generation.

I'll also contact the Pointwise people as well as seeing what CFMesh has to offer. I'm happy with Paraview for post-processing but it seems the pre-processing is more of a problem in the OpenFoam world. I can generate the stl files which it seems a lot of the Snappy videos assume as a prerequisite.

Actually the Pointwise meshing seems to be about $31,500 for one processor. That's a bit expensive so I was looking for something a bit more economical.

[HPE]

31k?! Geeez.. You can buy ~310 support hours from any OpenFOAM meshing support provider (OpenCFD/Wikki/CFDDirect)!

[Gallienus]

Originally Posted by HPE

31k?! Geeez.. You can buy ~310 support hours from any OpenFOAM meshing support provider (OpenCFD/Wikki/CFDDirect)!

Actually I just googled and found a pricing sheet uploaded by someone. Thus it may not be completely accurate but it seems priced for government or major industries. Also there are various creative ways to finance it which usually means: "paying more, but in smaller chunks".

I haven't gotten an official pricing quote from Pointwise yet. When I do so I'll update / edit my post. It apparently isn't cheap tho...

[Tobi]

If you wait 14 days more, you will have access to my videos which will show one how to use snappyHexMesh.

You can follow this link: https://holzmann-cfd.com/community/t...openfoam-usage