[ginop]

Hi,
I have generated a set of meshes with a commercial grid generator, and exported to openfoam successfully. Now I would like to modify those meshes to simulate different conditions. The changes "simply" require cutting off part(s) of the domain.

As such I am looking for options to obtain this, if even possible.

- cut(s) would be made through planes. So I initially thought about using snappyHexMesh, but it doesn't seem to work using searchablePlane

- it also popped to my mind to use topoSet and subsetMesh. While I haven't tried it yet, I fear that it would require fiddling around with boundary patches for the exposed cells

- alternatively, I thought of using paraview filters, then export as VTK, and convert such VTK to foam

Sooo... in your experience, what approach would you pursuit? is it even doable at all?

previous threads on the topic went unanswered, here and here.

Thanks


EDIT: using the paraview approach all boundary patches are lost, i.e. all cells/faces are either internal or default

[AtoHM]

This is untested territory for me, but knowing a few things about how snappy works, I might have a lead for you:


When using any of the searchable regions, you can use them for refinement which is probably the usual way people use them. However, if you add these parts inside the surfaceRefinement { } subdict, create a faceZone, snappy will snap the cells to them. Additionally, if you add a cellZone, you can create regions this way. Once you have regions, you can extract them separately.


Now, yet an easier way might be possible in the ESI version of OF. There we have the possibility to provide inside and outside points. So I would go about this by adding the plane as you did. Add an entry for the plane inside the refinementSurfaces subdict and create a faceZone for it to snap the cells which are cut, while supplying a locationInMesh inside the part you want to preserve. Usually, snappy cuts away separate regions which do not have a locationInMesh, so this might be all thats needed. If its remains there, you can try to explicitly remove it: https://www.openfoam.com/documentati...onsOutsideMesh

[ginop]

Thanks AtoHM

ok, so I tested the suggestions on a simple mesh, and it works there.

I define a searchablePlane as

plane1
{
	type          searchablePlane;
	planeType    pointAndNormal;
	pointAndNormalDict
	{
	    point	(0 0 -1.);
	    normal	(0.1 0 0.9);
	}
}

then use it within the refinementSurfaces as

plane1
{
	level (0 2);
	patchInfo
	{
	    type patch;
	}
	faceZone aaa;
	faceType boundary;  //internal;
	cellZone bbb;
	cellZoneInside inside;
	insidePoint (0.1 0.2 -3.3);
}

I do obtain sets for the two regions, and also the faceZone. For some reasons the cellZone is empty, but I am not really bothered.

After running snappyHexMesh, I run subsetMesh using the region of interest (cellSet) to obtain the new domain.

I will try the approach on the actual mesh (much larger in size), and keep you posted about the outcome.

Again, thanks a lot for your help!