Re: [Libmesh-users] Working with 1D mesh in 2D simulation

[John P. <jwp...@gm...>]

On Wed, Nov 28, 2018 at 3:58 PM Amneet Bhalla <mai...@gm...> wrote:

> Hi Folks,
>
> I have a question about using 1D mesh (of an immersed structure) in 2D
> (fluid domain) simulation.
> I am importing GMSH file to read linear elements (EDGE2) making the surface
> of a circle, such that I get
>
>         mesh.read_mesh(gmsh_filename);
>             and
>        int dim =  mesh.mesh_dimension; // dim == 1
>
> In my simulation I want to enquire the orientation of the normal vector of
> the edge elements.


In libMesh, the "normals" are always relative to the "face" of the element
(i.e. are computed by FE::reinit(elem, side), so in 1D the normals are
(perhaps paradoxically) tangential to the element itself.

If you are after a vector which is perpendicular to a given 1D element
(assuming it's not the side of a 2D parent element) you may be best of just
calculating it yourself as I don't think there's currently anything in the
library that does this.

--
John