[Gmsh] separate boundary layer settings

[Felix Salazar]

Forwarding this thread to the mailing list. At some points I clicked Reply
instead of Reply-All and left out the mailing list address

Thanks

On Mon, May 20, 2019, 8:58 PM Ziad Boutanios <ziad at binkz.ca> wrote:

> Don't worry about it. I'll take a look at background fields, but off the
> bat it seems like a substantial detour for additional boundary layers,
> assuming it works.
>
> Maybe one of the developers can comment whether separate instances of
> BoundaryLayer can be implemented in a mesh at all?
> On 2019-05-20 3:29 p.m., Felix Salazar wrote:
>
> Sorry for not replying sooner. I'm using my phone to read your messages
> and couldn't open gmsh. But you're right, the extrusion lines were
> commented. My bad.
>
> You need to specify a background field. That field needs to somehow
> integrate the effect of your 3 boundary layers. Take a look at this example
> http://gmsh.info/doc/texinfo/gmsh.html#t10_002egeo
>
> Several fields are computed, and the background field used for meshing is
> the minimum of all of them
>
> Not sure if it will work on your version of gmsh
>
> Hope that helps
>
> On Mon, May 20, 2019, 1:16 PM Ziad Boutanios <ziad at binkz.ca> wrote:
>
>>
>> On 2019-05-20 11:59 a.m., Ziad Boutanios wrote:
>>
>>
>> On 2019-05-20 11:26 a.m., Felix Salazar wrote:
>>
>> Based on the .geo file, what you're seeing on the top and bottom surfaces
>> is due to the extrusions. The combination of these plus the BL fields
>> creates more layers than the 5 specified in the extrusions.
>>
>> Try disabling (commenting) either the extrude or the BL field and remesh.
>>
>>
>> The Extrude sections in the bottom of the provided geo file are already
>> commented.
>>
>>
>> Around the cylinder, there's a BL. You have smaller quads there. If you
>> want finer control, try using an O-grid mesh
>> <https://www.researchgate.net/figure/O-grid-around-the-circular-cylinder_fig11_280028215>,
>> similar to the one on the previous link.
>>
>> Thanks for the suggestion but it doesn't help me. I'm looking for a way
>> to implement different instances of BoundaryLayer, each with its own
>> settings. Any idea how this can be done?
>>
>> BTW, I have to use gmsh 3.0.6 for compatibility reasons.
>>
>> Forgot to mention that what you see in the original snapshot around the
>> cylinder is not a BoundaryLayer. That's just the unstructured quad result
>> of Recombine. If you comment lines 53-61 you can see what the cylinder BL
>> looks like. I attached a snapshot of it.
>>
>> The problem is that when I use successive instances of BoundaryLayer,
>> only the last one in the geo file is produced. I need to have them all work
>> so I can customize each with its own settings.
>>
>>
>> ------------------------------------
>>
>> * Félix Salazar **felix.salazar at polymtl.ca <felix.salazar at polymtl.ca>*
>> ------------------------------------
>>
>>
>> On Sun, May 19, 2019 at 11:11 AM Ziad Boutanios <ziad at binkz.ca> wrote:
>>
>>> Hi,
>>>
>>> The geometry I'm meshing is that of a cylinder in a straight rectangular
>>> channel in 2D. The geo file is attached, as well as a screenshot of the
>>> result. I would like to use separate settings for the boundary layer
>>> around the cylinder and at the top and bottom surfaces. To do this I
>>> implemented two BoundaryLayer Field sections (lines 40-48 and 53-61).
>>> Unfortunately only the boundary layer corresponding to the last section
>>> is produced. Can that be fixed using BoundaryLayer?
>>>
>>> Thanks,
>>>
>>> Ziad
>>>
>>>
>>> _______________________________________________
>>> gmsh mailing list
>>> gmsh at onelab.info
>>> http://onelab.info/mailman/listinfo/gmsh
>>>
>>
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