[Gmsh] linear extrusion of quadratic quadrilaterals

[Triebenbacher Simon]

Dear Gmsh list members,

I am trying to model a boundary layer inside a circular pipe. Since I need a good resolution in radial direction I want save elements in circumferential direction. Therefore I am trying to use quite coarse quadratic quadrilaterals, which reproduce, the circular shape of a pipe much better, than bilinear quads. After I model the base plane of my pipe, I want to extrude, the mesh into 3D. This is where my problems starts, since only straight edges get extruded into 3D. The mid-side nodes are only placed properly if they are on the boundary surfaces. This is the case, even though the mid-side nodes are placed properly in the 2D base mesh. I have attached a simple example, that reproduces this behavior.

I would appreciate any help!

Simon Triebenbacher




Gmsh Script:

Mesh.Smoothing = 10;
//Mesh.SecondOrderLinear = 1;
//Mesh.SubdivisionAlgorithm = 0;
//Mesh.RemeshAlgorithm = 0;
//Mesh.RemeshParametrization = 1;
//Mesh.RecombineAll = 1;
Mesh.Algorithm3D = 6;
Mesh.ElementOrder = 2;
Mesh.Optimize = 1;
//Mesh 3;
Geometry.CopyMeshingMethod=1;

rad1=1.0;
midRad1=Sqrt(0.5);
rad2=0.5;
midRad2=Sqrt(0.125);

transLine = 10;
transCirc = 2;

cl1 = 1e+22;
Point(1) = {0, 0, 0};
Point(2) = {0, rad1, 0};
Point(3) = {midRad1, midRad1, 0};
Point(4) = {0, rad2, 0};
Point(5) = {midRad2, midRad2, 0};
Circle(1) = {4, 1, 5};
Circle(2) = {2, 1, 3};
Line(3) = {5, 3};
Line(4) = {4, 2};
Line Loop(6) = {4, 2, -3, -1};
Ruled Surface(6) = {6};

Transfinite Line {1,2} = transCirc Using Progression 0.5;
Transfinite Line {3,4} = transLine Using Progression 0.5;
Transfinite Surface{6};
Recombine Surface{6};
Physical Surface("arc") = {6};

Extrude {0, 0, 0.2} {
   Surface{6}; Layers{ 2 }; Recombine;
}


____________________________________________

E325 - Institute of Mechanics and Mechatronics
Measurement and Actuator Technology

Vienna University of Technology
Wiedner Hauptstrasse 8-10
A-1040 Wien, AUSTRIA

Dr.techn. M.Sc. Simon Triebenbacher
c/o Endress+Hauser GmbH+Co. KG
Am Lohmühlbach 12
85356 Freising - Germany

T: +49 8161 9972 74
F: +49 8161 9972 70
E: simon.triebenbacher at tuwien.ac.at
H: http://www.mec.tuwien.ac.at/
____________________________________________