Unable to collect periodic faces

[vachanpo...@gmail.com]

Dear all,

I have a simple cube gmsh file (annexed) which I want to read, and assign a periodic BC to it. I export the mesh to 'msh2' format and then read it using GridIn. I then call collect_periodic_faces() at which point, the code crashes with the error

The violated condition was:
    pairs1.size() > 0
Additional information:
    No new periodic face pairs have been found. Are you sure that you've selected the correct boundary id's and that the coarsest level mesh is colorized?

The above error was generated when the function was called with bid=2 and direction=2. I have checked using gmsh gui that the boundary ids have been correctly assigned. What is causing this error? Am I missing a step somewhere?

Thanking in anticipation,

Vachan

-----------------------------------------------------------------------------------------

// gmsh file

// Simple cube geometry

lc=0.1;

l=1;

// 2D geometry

p1=newp; Point(p1) = {0,0,0,lc};

p2=newp; Point(p2) = {l,0,0,lc};

p3=newp; Point(p3) = {l,l,0,lc};

p4=newp; Point(p4) = {0,l,0,lc};

l1=newl; Line(l1) = {1,2};

l2=newl; Line(l2) = {2,3};

l3=newl; Line(l3) = {3,4};

l4=newl; Line(l4) = {4,1};

Transfinite Curve{l1,l2,l3,l4} = 10;

ll1=newll; Curve Loop(ll1) = {l1,l2,l3,l4};

s1=news; Plane Surface(s1) = {ll1};

Transfinite Surface{s1} = {p1,p2,p3,p4};

Recombine Surface{s1};

// 3D extrusion

out[] = Extrude {0,0,l} {

    Surface{s1}; Layers{10}; Recombine;

};

// Physical entities

// periodic BCs must have same boundary id

Physical Volume(1) = {out[1]};

Physical Surface(2) = {s1,out[0]}; // z dir faces

Physical Surface(1) = {out[2],out[4]}; // y dir faces

Physical Surface(0) = {out[3],out[5]}; // x dir faces

[Daniel Arndt]

Vachan,

Maybe the boundary information is not transferred to the deal.II Triangulation when calling GridIn::read_msh. I would recommend checking the triangulation after reading it in and modify the boundary indicators manually if necessary.

Best,

Daniel

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[vachanpo...@gmail.com]

Daniel,

Thanks for your reply. I had previously used GridIn::read_msh() in 2d in which case the boundary ids were also correctly read. Isn't it unexpected behaviour then, if the data is not getting transferred in 3d? Manually setting the ids will work for now, but eventually I wish the transfer of boundary id information also happens.