[Gmsh] Extrude 2-D curved boundary layer mesh: Could not orient normal of surface

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Dear gmsh list,

firstofall, thanks for your help in the past. Currently I am working on a 2-D curved surface with a low-Re boundary layer mesh. When I am trying to extrude it in the third dimension I keep getting the error " Warning: Could not orient normal of surface 37". This occurs only when I have a huge amount of cells (like 40) in the normal direction. Below you can see the minimal example. I would appreciate any advice.

Best regards,

Kate



//Gmsh

radius=1;
outerradius=1.5;
extr=0.1; // Extrusion-length

// Points
Point(1)={radius,0,0};
Point(2)={radius*Cos(45*Pi/180),radius*Sin(45*Pi/180),0};
Point(3)={outerradius,0,0};
Point(4)={outerradius*Cos(45*Pi/180),outerradius*Sin(45*Pi/180),0};
Point(5)={0,0,0}; // Center

// Normal Lines:
Line(10)={1,3};
Line(11)={2,4};

/////////////////////////////////////////////////////////////////////////////////
Transfinite Line {10,11} = 40 Using Progression 1.2; // 10 layers: working // 40 layers: Warning: Could not orient normal of surface 37
/////////////////////////////////////////////////////////////////////////////////

// Curved Lines:
Circle(12) = {1, 5, 2};
Circle(13) = {3, 5, 4};
Transfinite Line {12,13} = 10;

// Transfinite Surface:
Line Loop(14) = {10, 13, -11, -12};
Plane Surface(15) = {14};
Transfinite Surface {15};
Recombine Surface {15};

//Extrusion:
Extrude {0, 0, extr} {Surface{15}; Layers{1}; Recombine;}

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