The geometry in STL is not well recongnized in OpenLB

[mwkim]

Hi all.

Recently, I have some problems with stlreader.

I am trying to simulate flow in a mixing pipe by modifying “aorta3D” case.

Before this case, I computed NACA0012 wing case. At that time, I used “cylinder3D” case as a reference.
OpenLB successfully read the geometry from the stl file, and materials are all well assigned as I want.

However, in this mixing pipe, the geometry in the stl file is not well recognized.

It is more clearly seen in a slice view.

It seems stlreader cannot resolve the junction part where the curved large pipe meets the straight small pipe.

I tried both options “0” and “1”, and “1” which is described as slow and stable option works better. Unfortunately, “1” gives above results…

Also, the additional problem is that material 3 region is not identified when I checked geometry in Paraview (as shown in above figures) while material 4 and 5 regions are well identified.

Could I get some helps or any comments to solve the current problems?
I don’t have ideas where should I start to improve it.

Sincerely,
MK

• This topic was modified 1 week, 2 days ago by mwkim.
• This topic was modified 1 week, 2 days ago by mwkim.
• This topic was modified 1 week, 2 days ago by mwkim.

[mwkim]

Sorry for the same figures in original post.

Cloud view of geometry can be seen below.

You can see a figure: Right click and Open Image in New Tap

[Adrian]

You can try the other modes of the STL reader (sorry for the hidden documentstion here, in the next release this will be an enum instead of integers).

enum class RayMode : int {
  FastRayZ  = 1,  /// Indicate function with ray in Z-direction(faster, less stable). Default option
  Robust    = 2,  /// Old indicate function (slower, more stable)
  FastRayX  = 3,  /// Indicate function with ray in X-direction(faster, less stable).
  FastRayY  = 4,  /// Indicate function with ray in Y-direction(faster, less stable).
  DoubleRay = 5   /// Indicate function with double ray
};

I recommend option 2.

The STL file is watertight?

[mwkim]

Thank you for kind answer.

Yes, it is watertight.

When I use option 2, openLB shows worse performance than 1. It cannot identify the small pipe, and material 3, 4, 5 are all not recognized.

Happily, I get the good geometry with option 5, except matarial 3 is not resolved. I follow totally same procedure to assign material 3 with 4 and 5. But, the indicator of material 3 does not work properly. I already several checked my code, but I cannot find any mistakes. I hope you also have comments for this material assignment problem..

Anyway, your answer makes really big improvement. So appreciate your comment.

[mathias]

According to https://www.openlb.net/forum/topic/material-assignment-indicator-is-changed-along-voxel-resolution/ I assume it is solve now — so it was not watertight!

[Author]

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