gmsh BoundaryLayer Field

mhollander · October 29, 2020, 09:54

I have been attempting to use the BoundaryLayer size field in gmsh in order to produce a boundary layer around an airfoil. I'm trying to figure this out hoping that being able to utilize the 'BoundaryLayer' size field will be more efficient than dividing, offsetting curves and manually playing with the 'transfinite' curve settings.

I haven't been able to find any resources that go through how to properly utilize 'BoundaryLayer'. Has anyone here had any luck? Would they be willing to share screenshots and/or .geo files?

Cheers,
Moshe.

jmkouglas · December 1, 2020, 17:48

I had the same question, and ran across a gmsh thread (that I can't find now) that said the BoundaryField was a) experimental, and b) only worked on 2D geometry.

I ended up using Distance fields, see below.

If you've found a better solution, I'd appreciate hearing about it.

What I ended up doing is to set the minimum mesh size to what I wanted at the surface. Bigger surfaces need more NumPointsPerCurve or you get periodic mesh sizes across the surface. Then a final Min field to create the background field.

Field[1] = Distance;
Field[1].SurfacesList = { 2, 4};
Field[1].NumPointsPerCurve = 20;

Field[2] = Distance;
Field[2].SurfacesList = { 3 };
Field[2].NumPointsPerCurve = 40;

Field[3] = Distance;
Field[3].SurfacesList = { 6, 7 };
Field[3].NumPointsPerCurve = 80;

// take min
Field[4] = Min;
Field[4].FieldsList = {1, 2, 3};

mhollander · December 1, 2020, 18:05

Thanks! I'll give it a shot.

I'd be really curious to see a screenshot of the mesh that this produced.

Also, what surfaces are surfaces 2, 4, 3, 6 & 7? (airfoil surfaces? far-field boundaries? Internal flow surfaces...?)

jmkouglas · December 1, 2020, 19:35

The surfaces are just the walls of my duct that I wanted higher resolution on.

ari003 · July 5, 2021, 14:56

Quote:

Originally Posted by mhollander

Thanks! I'll give it a shot.

I'd be really curious to see a screenshot of the mesh that this produced.

Also, what surfaces are surfaces 2, 4, 3, 6 & 7? (airfoil surfaces? far-field boundaries? Internal flow surfaces...?)

Did you get anything better for refinement around the airfoil. Will be very helpful if you share.

mhollander · July 7, 2021, 16:14

Unfortunately, I haven't had a chance to play around with it all that much since I last posted.

October 29, 2020, 09:54	gmsh BoundaryLayer Field	#1
mhollander New Member Moshe Hollander Join Date: Dec 2018 Posts: 20 Rep Power: 7	I have been attempting to use the BoundaryLayer size field in gmsh in order to produce a boundary layer around an airfoil. I'm trying to figure this out hoping that being able to utilize the 'BoundaryLayer' size field will be more efficient than dividing, offsetting curves and manually playing with the 'transfinite' curve settings. I haven't been able to find any resources that go through how to properly utilize 'BoundaryLayer'. Has anyone here had any luck? Would they be willing to share screenshots and/or .geo files? Cheers, Moshe.

December 1, 2020, 17:48	gmsh BoundaryLayer Field	#2
jmkouglas New Member Jason Douglas Join Date: Sep 2020 Posts: 2 Rep Power: 0	I had the same question, and ran across a gmsh thread (that I can't find now) that said the BoundaryField was a) experimental, and b) only worked on 2D geometry. I ended up using Distance fields, see below. If you've found a better solution, I'd appreciate hearing about it. What I ended up doing is to set the minimum mesh size to what I wanted at the surface. Bigger surfaces need more NumPointsPerCurve or you get periodic mesh sizes across the surface. Then a final Min field to create the background field. Field[1] = Distance; Field[1].SurfacesList = { 2, 4}; Field[1].NumPointsPerCurve = 20; Field[2] = Distance; Field[2].SurfacesList = { 3 }; Field[2].NumPointsPerCurve = 40; Field[3] = Distance; Field[3].SurfacesList = { 6, 7 }; Field[3].NumPointsPerCurve = 80; // take min Field[4] = Min; Field[4].FieldsList = {1, 2, 3};

December 1, 2020, 19:35	gmsh BoundaryLayer Field	#4
jmkouglas New Member Jason Douglas Join Date: Sep 2020 Posts: 2 Rep Power: 0	The surfaces are just the walls of my duct that I wanted higher resolution on.

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December 1, 2020, 18:05		#3
mhollander New Member Moshe Hollander Join Date: Dec 2018 Posts: 20 Rep Power: 7	Thanks! I'll give it a shot. I'd be really curious to see a screenshot of the mesh that this produced. Also, what surfaces are surfaces 2, 4, 3, 6 & 7? (airfoil surfaces? far-field boundaries? Internal flow surfaces...?)

July 7, 2021, 16:14		#6
mhollander New Member Moshe Hollander Join Date: Dec 2018 Posts: 20 Rep Power: 7	Unfortunately, I haven't had a chance to play around with it all that much since I last posted.