[firedrake] RectangleMesh

[Floriane Gidel [RPG]]

Hi David,


Great, thanks a lot.


Best regards,

Floriane

________________________________
De : firedrake-bounces at imperial.ac.uk <firedrake-bounces at imperial.ac.uk> de la part de David Ham <David.Ham at imperial.ac.uk>
Envoyé : vendredi 24 février 2017 12:58:16
À : firedrake
Objet : Re: [firedrake] RectangleMesh

Hi Floriane,

you can do this using a par_loop with a custom kernel. I don't have time to work out the precise syntax for this today so I've raised an issue on GitHub so we don't lose this question. See: https://github.com/firedrakeproject/firedrake/issues/1022 I hope to get back to this next week, or maybe someone else will get to it faster.

Regards,

David

On Thu, 23 Feb 2017 at 15:03 Floriane Gidel [RPG] <mmfg at leeds.ac.uk<mailto:mmfg at leeds.ac.uk>> wrote:


Dear David,


Thanks for your fast answer.


I change the coordinates for saving purpose only (once the WF are solved).

So my objective is to solve the WF in a fixed 2D RectangleMesh, and then save the functions in a 3D mesh in which I apply the coordinate transforms to get moving boundaries.

I managed to do this when Ny>1, and I changed my code so that it works for Ny=1, but I would like a general command that works whatever the value of Ny.


So my question would be : how can I make the link between the x-coordinates in a RectangleMesh, and the x-coordinates in the 3D mesh obtained by extrusion of the RectangleMesh ?


For instance, for a function h_2D defined in the RectangleMesh, if I want to change the z-coordinate of the extruded mesh as z_new = z*h_2D/H0 so that the top boundary of the 3D domain for a given (xi,yi) coordinates moves as h_2D(xi,yi), how can I find the indices "..." to substitute into the following expression :


mesh_3D.coordinates.dat.data[ ..., 2]*= h_2D.dat.data[ ... ]/H0 ?


Thank you very much,

Floriane










________________________________
De : firedrake-bounces at imperial.ac.uk<mailto:firedrake-bounces at imperial.ac.uk> <firedrake-bounces at imperial.ac.uk<mailto:firedrake-bounces at imperial.ac.uk>> de la part de David Ham <David.Ham at imperial.ac.uk<mailto:David.Ham at imperial.ac.uk>>
Envoyé : jeudi 23 février 2017 14:16:06
À : firedrake
Objet : Re: [firedrake] RectangleMesh

Dear Floriane,

The thing to understand is that there is no guaranteed relationship between vertex number and the location of that vertex. Vertex numbers are (as far as the user is concerned), completely arbitrary. This is fine because none of the correct ways to access vertices  depend on what the order is.

When you say that you are applying a change of coordinates, what do you mean? Do you mean that you are changing the coordinate values before you compute? If so, please tell us mathematically what you are attempting to do and we can tell you the right way to do it.

Regards,

David

On Thu, 23 Feb 2017 at 14:08 Floriane Gidel [RPG] <mmfg at leeds.ac.uk<mailto:mmfg at leeds.ac.uk>> wrote:

Dear all,


I have a question concerning the mesh definition with RectangleMesh:


I define my  mesh as a Rectangle mesh, with quadrilaterals as:

hor_mesh = RectangleMesh(Nx, Ny, 10.0, 1.0, quadrilateral=True).


As my functions are only (x,t) dependent, I'd like to get only one element in y, i.e. Ny=1.

However I noticed that if I set Ny=1, then the x-coordinates are swapped from 10.0 to 0.0 . Basically, I obtain

hor_mesh.coordinates.dat.data[:,0] = [10.0 10.0 9.9 9.9 ...... 0.0]

instead of

hor_mesh.coordinates.dat.data[:,0] = [0.0 0.0 0.1 0.1 ........ 10.0] (that I obtain for Ny>1)


Can someone explain me what happens there ? Is there a way to avoid that ?

And if I use the integral on ds(1), will it be at x=0 of x=10 in that case?


The reason why I want to understand this is because I apply a change of coordinate in some part of the domain (let's say for x<L<Lx) and the coordinate transform does not give the right result for Ny=1 (while it does for Ny>1).


Thanks in advance for your help,

Floriane



--
Dr David Ham
Department of Mathematics
Imperial College London
--
Dr David Ham
Department of Mathematics
Imperial College London
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