# Prism Layer Thickness

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June 2, 2011, 00:12
Prism Layer Thickness
#1
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Hey,

I met a problem when working on the prism layer thickness. As shown in the picture, at the left part, there is an area with no prism layer because of the narrowing geometry. And the meshes themselves are not complete. The skewness angle in that area are pretty large.

A.So what should I do? Decreasing the base size in that narrowed area?

B.Is the prism layer thickness needed to be smaller than the geometry dimmension or there is no need to do that?

C. If I decrease the base size there, so the base size + the prism layer thickness should be equal or smaller than the geometry dimmension?

Any help would be appreciated!

Famerfamer
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 June 2, 2011, 04:23 #2 Member   Join Date: May 2010 Posts: 38 Rep Power: 9 You should try increase the # of points in gap in the surface proximity node. But your prism layer seems too thick, or the geometry is very small. In that case it can maybe be simplified by removing the gaps.

June 2, 2011, 08:21
#3
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Ryne Whitehill
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Quote:
 Originally Posted by famerfamer Hey, I met a problem when working on the prism layer thickness. As shown in the picture, at the left part, there is an area with no prism layer because of the narrowing geometry. And the meshes themselves are not complete. The skewness angle in that area are pretty large. A.So what should I do? Decreasing the base size in that narrowed area? B.Is the prism layer thickness needed to be smaller than the geometry dimmension or there is no need to do that? C. If I decrease the base size there, so the base size + the prism layer thickness should be equal or smaller than the geometry dimmension? Any help would be appreciated! Famerfamer
Under Continua->Mesh->Models->Prism Layer Mesher:

1) change layer reduction percentage to 99.
2) change minimum thickness percent to .5
3) change gap fill to 45

These three values are at the extreme end of the spectrum. If this fixes your problem, you can likely play with their values (lower layer reduction percentage, raise minimum thickness percent, lower gap fill) and get it to still work

June 2, 2011, 14:06
#4
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Quote:
 Originally Posted by rwryne Under Continua->Mesh->Models->Prism Layer Mesher: 1) change layer reduction percentage to 99. 2) change minimum thickness percent to .5 3) change gap fill to 45 These three values are at the extreme end of the spectrum. If this fixes your problem, you can likely play with their values (lower layer reduction percentage, raise minimum thickness percent, lower gap fill) and get it to still work
Thank you very much. But I'm still wondering if the thickness of prism layer should be smaller than the geometry gap. Because I'm using volumetric control to deal with this area or I don't need it at all? The prism layer thickness for areas around that gap is pretty large.

Famerfamer

June 2, 2011, 14:16
#5
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Ryne Whitehill
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Quote:
 Originally Posted by famerfamer Thank you very much. But I'm still wondering if the thickness of prism layer should be smaller than the geometry gap. Because I'm using volumetric control to deal with this area or I don't need it at all? The prism layer thickness for areas around that gap is pretty large. I appreciate your help. Famerfamer

With those settings, the mesher should chop the prism layer thickness down to fill the gap with mostly prism cells.

I have numerous areas like this in my geometry. They do not always come out with the highest quality, but a prism mesh usually does get generated there.

 June 2, 2011, 15:59 #6 Member   Join Date: Apr 2011 Location: US Posts: 43 Rep Power: 8 Thanks! How about the core mesh size in those narrowed areas? For my case as shown in the priture, in that narrowed area, there are three parameters should be set properly, the prism layer thickness (Denoting a) for walls at each side and the core meshes in the middle (denoting b as the width or thickness of the mesh), correct? Denoting the distance of the gap is c. Q: A. So what's a proper relationship among a, b and c? 2a+b=c? B. When I paly those three values you mentioned above, everytime I need to do the surface mesh repair and volume mesh for the whole big geometry when I change one value. So do you know have some better ideas dealing with this? Like only mesh those problematic areas and leave other area with a coarse mesh or something esle? Thanks!

 June 2, 2011, 21:00 #7 Member   Join Date: Apr 2011 Location: US Posts: 43 Rep Power: 8 oh, man, the total surface size increased from 5 million to more than 50 million after I adjusted those values although I also decreased base size of that area. It seems that the 0.5 pecent is too small?

June 3, 2011, 08:26
#8
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Ryne Whitehill
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Quote:
 Originally Posted by famerfamer oh, man, the total surface size increased from 5 million to more than 50 million after I adjusted those values although I also decreased base size of that area. It seems that the 0.5 pecent is too small?
Those values I suggested for you to change should not affect surface size. They will only affect the prism layer.

June 3, 2011, 14:41
#9
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Quote:
 Originally Posted by rwryne Those values I suggested for you to change should not affect surface size. They will only affect the prism layer.
Got you. That is, it only affects the # of cells for the volume mesh but not the # of of surface faces, correct? Thanks for your help!

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