# [Gmsh] Pseudo 2-D unstructured Mesh

Eric Nutsch ericnutsch at gmail.com
Tue Jun 8 19:19:54 CEST 2010

```Emanuele,

Just leave your z dimension constant at say 0.1 regardless of your
characteristic length. Its 2D, so open foam doesn't care about that
dimension.

If it goes "full 3d" something is failing in your Recombine; command.
I doubt it is related to your characteristic length, but I could be
wrong.

Have a look at that and post back,

Eric

On Tue, Jun 8, 2010 at 9:46 AM, Emanuele T. <nuovodna at gmail.com> wrote:
> I solved using different values from z coordinates and lc.
> This .geo file works
> Point (1) = {0, 0, 0, 0.05};
> Point (2) = {3.2196, 0, 0, 0.05};
> Point (3) = {3.2196, 1.8, 0, 0.05};
> Point (8) = {0, 1.8, 0, 0.05};
> Point (9) = {1.2, 0, 0, 0.05};
> Point (12) = {1.2, 0.6, 0, 0.05};
> Point (13) = {0, 0.6, 0, 0.05};
> Line (1) = {8, 3};
> Line (2) = {3, 2};
> Line (3) = {2, 9};
> Line (4) = {9, 12};
> Line (5) = {12, 13};
> Line (6) = {13, 1};
> Line (7) = {1, 9};
> Line (8) = {13, 8};
> Line Loop (10) = {1, 2, 3, 4, 5, 8};
> Plane Surface (10) = {10};
> Line Loop (12) = {5, 6, 7, 4};
> Plane Surface (12) = {12};
> e1[] = Extrude {0, 0, 0.1} {Surface{10,12}; Layers{1}; Recombine;};
> Physical Surface(67) = {23};
> Physical Surface(68) = {43, 57};
> Physical Surface(69) = {61, 31};
> Physical Surface(70) = {27};
> Physical Volume(72) = {1, 2};
>
> A key role is covered by Layers{1} in Extrude function
>
> 2010/6/8 Emanuele T. <nuovodna at gmail.com>
>>
>> Hi, i d like to create a pseduo 2-D mesh but i have problems. If i use
>> characteristic length and z coordinates equal to 0.1 it works (i m using
>> gmshToFoam to import in OpenFOAM and solve a 2-d case using a 3-d mesh with
>> 1 cell in z direction). I'd like to make a mesh finer and i have set lc and
>> z coordinates to 0.04. Unfortunately in this way i don't obtain a pseudo 2-D
>> mesh but a full 3-D mesh (more than one cell in z direction). How can i
>> solve?? How can i obtain a fine mesh with low lc and 1 single cell in z
>> direction?