[Gmsh] How to obtain small characteristic length in specific area of geometry?

[Ruth V. Sabariego]

Hi John,
The options you give to the BoundaryLayer Field are not correct.
You can use the GUI for defining a new BoundaryLayer Field you can go to 

Mesh->Size Fields->New->BoundaryLayer

You will see the following options:
EdgesList
NodesList
nfar
hwall_n
hwall_t
ratio
thickness

See the help of the menu for defining the values that suit your geometry.

HTH,
Ruth


Dr. Ir. Ruth V. Sabariego
University of Liege, Electrical Engineering & Computer Science, 
Applied & Computational Electromagnetics (ACE),
phone: +32-4-3663737 - fax: +32-4-3662910 - http://ace.montefiore.ulg.ac.be/



On 14 Oct 2011, at 03:50, Mikhail Artemiev wrote:

> Hi, John.
> When I load your .geo file to my Gmsh 2.5.0 for Windows, it sais that
> 
> Error   : 'John.geo', line 628 : Unknown option 'DistMax' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 629 : Unknown option 'DistMin' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 630 : Unknown option 'LcMax' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 631 : Unknown option 'LcMin' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 632 : Unknown option 'LcMax' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 633 : Unknown option 'LcMax' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 634 : Unknown option 'Sigmoid' in field 1 of type 'BoundaryLayer'
> Error   : 'John.geo', line 635 : Unknown option 'StopAtDistMax' in field 1 of type 'BoundaryLayer'
> 
> And I really didn't find these options in Gmsh documentation for BoundaryLayer type of field (only for Threshold).
> Anyway I can advise you to reduce your tolerance variable on "Options->Geometry->General".
> 
> Mikhail
> 
> 
>> Hi,
> 
>> I've been successfully using gmsh for some time, but now I would like to
>> specify a much denser mesh around one of the structures in my geometry. I
>> have tried using the boundary layer, box, and attractor fields to control
>> the characteristic length but they seem to be having no effect on the
>> generated mesh.
> 
>> Attached is my geometry, I would like to have a characteristic length in the
>> region of 1e-8 around the cantilever (or 'diving board') feature in the
>> centre of the geometry. Is this characteristic length too small I wonder?
>> How should I achieve the desired effect? The attached file has the boundary
>> layer that I would like to use, but it has no effect on the mesh density.
> 
>> Thank You in advance for any pointers you can share with me.
> 
>> Regards,
>> John Parkin
> 
> 
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