# Inverted growth ratio in Boundary Layer generation

**URL:** <https://discourse.slicer.org/t/inverted-growth-ratio-in-boundary-layer-generation/36857>\
**Category:** VMTK\
**Created:** [June 18, 2024, 7:45am UTC](https://discourse.slicer.org/t/inverted-growth-ratio-in-boundary-layer-generation/36857 "2024-06-18T07:45:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![fil\_ita](https://avatars.discourse-cdn.com/v4/letter/f/a183cd/32.png) [@fil\_ita](https://discourse.slicer.org/u/fil_ita)\
**Post date:** [June 18, 2024, 7:45am UTC](https://discourse.slicer.org/t/inverted-growth-ratio-in-boundary-layer-generation/36857/1 "2024-06-18T07:45:18Z")

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Good morning,  
I am trying to use VMTK to genera the boundary layer of some TPMS geometries, as it is the only software that seems to have a good BL creation algorithm.

However, I have noticed that along my geometry, there are some regions where the growth ratio is “decreasing” rather than increasing:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/e/4/e4a46f5c236860d2d93207af8e4572dcb291c084.jpeg)  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/7/5/75efc68ef61a7cf1cf2627f3339fb3565883bab7.jpeg)

I was wondering if you would be able to help me in identifying the problem or suggest a workflow to bypass it.  
At the moment, I use the following command:

vmtkmeshgenerator -ifile ./cfd\_mesh/fluid1.stl -minedgelength 1e-4 -maxedgelength 5e-3 -skipcapping 1 -boundarylayer 1 -thicknessfactor 8e-1 -sublayers 9 -sublayerratio 0.917 -ofile f1\_vmtk.vtk -skipremeshing 1

Thank you in advance!

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<div class="post-metadata">

**Author:** ![fil\_ita](https://avatars.discourse-cdn.com/v4/letter/f/a183cd/32.png) [@fil\_ita](https://discourse.slicer.org/u/fil_ita)\
**Post date:** [September 23, 2024, 9:01pm UTC](https://discourse.slicer.org/t/inverted-growth-ratio-in-boundary-layer-generation/36857/2 "2024-09-23T21:01:07Z")

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Hello,

would anyone be able to help me with this?