[daniel1030]

Hello,

I am a young engineer who has minimal experiences in CFD. I have started self-teaching myself how to use CCM+ by going through the tutorials provided by CD-adapco. There are some questions that came to my mind while I was doing these tutorials and I feel like they are almost 'too simple' that I cant even find the answers on google (as no one asks them..). Please bear with me!

1. My understanding of surface/volume mesh is that surface meshing only covers the surface of the material and volume meshing covers the entire bulk of the object, hence computationally expensive compared to surface meshing. What is, then, the point of doing both surface meshing and volume meshing? I have seen countless times in the tutorial where both surface and volume mesh was done. Precisely, they would do surface meshing first, then do volume mesh. Isn't volume meshing just overwriting the existing mesh?(Tutorials->Tutorial Guide->Mesh->Region Based Meshing Imported Control Valve->Polyhedral Meshing Example->Selecting the Meshing Models)

2. In the tutorial, the 'surface remesher' was used as a mesher. However my understanding is that surface remesher is used to improve the quality of the initial meshing. Is this not always true? (Same tutorial as the above)

3. What is the purpose of the tool 'Compute Part Curves'? It was done in the tutorial but not actually used. (Tutorials->Tutorial Guide->Mesh->Region Based Meshing Imported Control Valve->Polyhedral Meshing Example->Extracting Feature Curves)

If I just ask the questions I thought it might be hard to answer, so I included the section of the tutorial that I am referring to.

Also, I am interested in modelling fluid flow (ie.water) across pipes with nonspherical particles being carried around. If anyone knows any relevant tutorials or practices could they please let me know? I need practice but it would also be great if there are any explained examples so I can gain a greater understanding in this field.

Thank you very much and I hope you all have a Merry Christmas!

[Nealcaffrey]

You can also do the volume mesh directly, no need for surface mesh...but surface mesh as far I know needs to be done because of two reasons.... if you are doing solid fluid interactive problems like conductive convective hear transfer u need conformal mesh.. hence the volume mesh needs to be grown from surface mesh.... 2nd is when u do surface re me sher it fixes sometimes bad surfaces automatically which create singularity

[AntonZ44]

1) The volume mesh grows from the surface mesh - that is, the size of 3D cells near a boundary is related to the surface mesh at that location. The surface mesh controls the volume mesh.

This also ties in to the surface remesher. Consider the case of trying to volume mesh around some imported CAD file.

CAD files (e.g STL) are just sets of points/faces describing what something looks like - typically triangular faces. If you have a 1m x 1m flat square face in a CAD file, it could be represented using triangles by just two faces. You probably want more than two volume mesh faces touching a 1m x 1m flat square plate, so remesher will break up that surface, in preparation for the volume mesher to grow volume cells from the new, improved surface.

Confusingly, the initial imported/created CAD geometry is sometimes referred to as a "geometry mesh", I think that is the "initial mesh" you speak of. It is a collection of something like triangular faces describing what a geometry looks like.

The remesher is most commonly used to take an imported CAD geometry "mesh", which contains the minimum amount of information required for CAD purposes - far too coarse for CFD - and break up big surfaces in to something that a volume mesh can grow from.