[snappyHexMesh] Internal and External flow in SnappyHexMesh

selvavm · September 11, 2015, 05:25

Dear Friends,

I am new to OpenFOAM and I have doubt.

My case is a thick hollow cylinder rotating around an axis. I added the cylinder.stl to refinement surface in snappyhexmesh dict and after meshing I could see that only the outer surface of the cylinder is meshed with block mesh and internal channel is void (no cells)

So, I created one more channel.stl (same dimension as the inside of the cylinder), and added that to refinement region. Then, Only one face of the channel.stl exposed to free stream is meshed but the channel region is still not meshed

Could you please help me in this?

Also, If there is any other way to mention both Internal and External flow in snappyhexmesh please let me know.

I will be waiting for your replies.

EDIT: From guide, I found that cell removal depends on locationinmesh parameter. Now, I am confused what value to give

Is there any way to give two locationinmesh so that cells are removed from the cylinder except on the channel?

Thanks,
Selva

student666 · September 12, 2015, 05:02

Can you post a picture or two of your domain?
Can you give more details about the simulation you're planning to run?

selvavm · September 12, 2015, 21:42

Hey,

Thanks for replying. I don't have my case data now, but I can explain the same thing with motorbike tutorial.

When I ran the snappyhexmesh in motorbike tutorial, I am able to see there is void space in bike's wheel rim (with paraview's wireframe view on Bike).

Now my doubt is, whether the grid missing in the rim, is due to my setting in paraview to display only bike?

I mean, if the enclosing object (in my case a box surrounding the motorbike) has grids in it (assuming very fine grid), then that means gaps in model also has grid? That is, does fluid can flow through the rim gap?

Thanks a lot

Regards,
Selva

student666 · September 13, 2015, 05:39

Ok, is it right to say that you have meshing problem on small gaps?
In any case, before we go further with discussion is better to discuss within your case?
It's already hard to understand sometimes others people problem, and speaking about a case to relate to one other: I think it's crazy.

For example: I could suggest you to merge two meshes (look at sourceflux for a tutorial) and create interfaces between them (cyclic or cyclic AMI), but I don't know if you really need it and I can lead you to the wrong way, not allowing you to solve the problem.

the more specific you are, the more you can get help from other people in the forum.

Regards

September 11, 2015, 05:25	Internal and External flow in SnappyHexMesh	#1
selvavm New Member Join Date: Aug 2015 Posts: 10 Rep Power: 11	Dear Friends, I am new to OpenFOAM and I have doubt. My case is a thick hollow cylinder rotating around an axis. I added the cylinder.stl to refinement surface in snappyhexmesh dict and after meshing I could see that only the outer surface of the cylinder is meshed with block mesh and internal channel is void (no cells) So, I created one more channel.stl (same dimension as the inside of the cylinder), and added that to refinement region. Then, Only one face of the channel.stl exposed to free stream is meshed but the channel region is still not meshed Could you please help me in this? Also, If there is any other way to mention both Internal and External flow in snappyhexmesh please let me know. I will be waiting for your replies. EDIT: From guide, I found that cell removal depends on locationinmesh parameter. Now, I am confused what value to give Is there any way to give two locationinmesh so that cells are removed from the cylinder except on the channel? Thanks, Selva

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September 12, 2015, 05:02		#2
student666 Senior Member M. C. Join Date: May 2013 Location: Italy Posts: 286 Blog Entries: 6 Rep Power: 17	Can you post a picture or two of your domain? Can you give more details about the simulation you're planning to run?

September 12, 2015, 21:42		#3
selvavm New Member Join Date: Aug 2015 Posts: 10 Rep Power: 11	Hey, Thanks for replying. I don't have my case data now, but I can explain the same thing with motorbike tutorial. When I ran the snappyhexmesh in motorbike tutorial, I am able to see there is void space in bike's wheel rim (with paraview's wireframe view on Bike). Now my doubt is, whether the grid missing in the rim, is due to my setting in paraview to display only bike? I mean, if the enclosing object (in my case a box surrounding the motorbike) has grids in it (assuming very fine grid), then that means gaps in model also has grid? That is, does fluid can flow through the rim gap? Thanks a lot Regards, Selva

September 13, 2015, 05:39		#4
student666 Senior Member M. C. Join Date: May 2013 Location: Italy Posts: 286 Blog Entries: 6 Rep Power: 17	Ok, is it right to say that you have meshing problem on small gaps? In any case, before we go further with discussion is better to discuss within your case? It's already hard to understand sometimes others people problem, and speaking about a case to relate to one other: I think it's crazy. For example: I could suggest you to merge two meshes (look at sourceflux for a tutorial) and create interfaces between them (cyclic or cyclic AMI), but I don't know if you really need it and I can lead you to the wrong way, not allowing you to solve the problem. the more specific you are, the more you can get help from other people in the forum. Regards