Re: [Getfem-users] Level set

[Andriy Andreykiv]

Dear Irene,

I understand that the surface of the sphere is not conforming to the mesh of the cube, right?

So you want to impose no-slip boundary conditions through the mesh of the cube. 

I know two ways to do it. 

 One through pure fictitious domain method, and the other through fictitious domain method with XFem. 

For the second you can look into implementation of contrib/xfem_contact/xfem_dirichlet.cc 

(you can find it in your Getfem installation).

Pure fictitious domain method (with LS integration, as you mentioned it) is described in detail in:

Legay A, Chessa J, Belytschko T. An Eulerian–Lagrangian method for fluid structure interaction based on level sets.

Computer Methods in Applied Mechanics and Engineering 2006; 195(17–18):2070–2087.

It's also possible to implement it in Getfem as well. A similar Level set based fictitious domain contact algorithm exists in Getfem and you can see the example of it usage in contrib/level_set_contact (it has a reference to the corresponding article inside)

Regarding the post-processing, I think you should use the technique of slices, as it's used in XFem examples of Getfem (although I've never used it myself).

Best regards,

                       Andriy

On 22 January 2014 10:30, ing.ire <address@hidden> wrote:

Hello,

I'm using getfem to solve Stokes problem in a cube (as in tests/stokes.cc), but I want to put a sphere inside the cube, as if it was a solid particle in a volume of fluid, so I don't want to solve stokes inside the sphere. I'm using level-sets to cut the mesh and the option INTEGRATE_OUTSIDE to solve the problem only outside the region cut by the level set function. 

How can I set no-slip boundary conditions on the sphere, i.e. Dirichlet condition?

Is there any way to export the cut mesh in vtk? I tried with

getfem::vtk_export vtkp("stokes.vtk");

vtkp.exporting(mfls);

vtkp.write_mesh();

where mfls is a mesh_fem_level_set object, but loading the stokes.vtk file in paraview I see the whole mesh, and no sign of the cut.

Thank you in advance.

Irene

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