[snappyHexMesh] Can snappyHexMesh handle intersecting geometries?

Attesz · January 14, 2015, 14:03

Hi all,

can snappyHexMesh handle geometries (closed STL/OBJ shells), that intersect each other? Will the algorithm identify these geometries as one and create a mesh around them, or I need to unite the two geometries?

Also, what happens when the geometry "sticks out" of the domain of the background mesh?

Thanks in advance!

P Greene · January 20, 2015, 17:57

If part of your geometry sticks out of the background mesh, that part will simply be cut off.

As for your question about intersecting geometries, I'm not sure what you're referring to. If, as I think, you mean that some part of your geometry overlaps, I'm not sure what sHM will do. I suspect you are correct in that it will consider only those regions which are unambiguously "outside" your geometry as outside, and anything else as "inside". But there's only really one way to find out. Try it! Let me know your result.

Attesz · January 21, 2015, 07:06

Hi Patrick, thanks for your input.
On intersecting I mean not only overlapping, but penetrating geometries (e.g. a cylinder goes into a cube). What will be meshed in this case? The union of the geometries, or the mesh will go inside somehow?
Hope somebody else can also make an input. Nevertheless, I will try it out on a simple geometry!

ameyer · January 16, 2022, 06:27

Hi Attesz,
old thread for sure, but i have the exact same question right now - so... beeing lazy to try my self (and for the sake of thread-completeness): Do you remember what your final conclusions were? Did you try it?

Attesz · January 16, 2022, 16:38

Yes - snappy handles intersecting geometries as they were united. The intersection will not necessarily be captured properly however. It is better to avoid intersection if possible and use one high quality closed surface mesh.

ameyer · January 16, 2022, 19:39

Thank you for the quick reply! So it seems that this is not a use-case of snappy and merely works by accident but may produce artifacts. Then I have to think of another solution, thanks again!

January 14, 2015, 14:03	Can snappyHexMesh handle intersecting geometries?	#1
Attesz Senior Member Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17	Hi all, can snappyHexMesh handle geometries (closed STL/OBJ shells), that intersect each other? Will the algorithm identify these geometries as one and create a mesh around them, or I need to unite the two geometries? Also, what happens when the geometry "sticks out" of the domain of the background mesh? Thanks in advance! __________________ I am doing CFD Consulting Services. Ich biete CFD Strömungssimulationen an.

January 20, 2015, 17:57		#2
P Greene New Member Patrick Greene Join Date: Aug 2014 Location: New Hampshire Posts: 7 Rep Power: 12	If part of your geometry sticks out of the background mesh, that part will simply be cut off. As for your question about intersecting geometries, I'm not sure what you're referring to. If, as I think, you mean that some part of your geometry overlaps, I'm not sure what sHM will do. I suspect you are correct in that it will consider only those regions which are unambiguously "outside" your geometry as outside, and anything else as "inside". But there's only really one way to find out. Try it! Let me know your result. Last edited by P Greene; January 20, 2015 at 18:03. Reason: Clarification and omition of unnecessary detail

January 21, 2015, 07:06		#3
Attesz Senior Member Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17	Hi Patrick, thanks for your input. On intersecting I mean not only overlapping, but penetrating geometries (e.g. a cylinder goes into a cube). What will be meshed in this case? The union of the geometries, or the mesh will go inside somehow? Hope somebody else can also make an input. Nevertheless, I will try it out on a simple geometry! __________________ I am doing CFD Consulting Services. Ich biete CFD Strömungssimulationen an.

January 16, 2022, 16:38		#5
Attesz Senior Member Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17	Yes - snappy handles intersecting geometries as they were united. The intersection will not necessarily be captured properly however. It is better to avoid intersection if possible and use one high quality closed surface mesh. __________________ I am doing CFD Consulting Services. Ich biete CFD Strömungssimulationen an.

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January 16, 2022, 06:27		#4
ameyer New Member Join Date: Jan 2015 Location: Berlin Posts: 5 Rep Power: 11	Hi Attesz, old thread for sure, but i have the exact same question right now - so... beeing lazy to try my self (and for the sake of thread-completeness): Do you remember what your final conclusions were? Did you try it?

January 16, 2022, 19:39		#6
ameyer New Member Join Date: Jan 2015 Location: Berlin Posts: 5 Rep Power: 11	Thank you for the quick reply! So it seems that this is not a use-case of snappy and merely works by accident but may produce artifacts. Then I have to think of another solution, thanks again!