Re: [Gmsh] Problems with structured meshing

[Christophe Geuzaine]

> On 15 Oct 2016, at 19:02, Kushagra Vidyarthi  
> wrote:
> 
> Dear Sir/Madam,
> 
> I am working on a CFD analysis around an ellipse. For this purpose, I have 
> created a circular domain around the geometry, and I am trying to create a 
> structured mesh around it, so that I can have some control over the boundary 
> layer. My .geo file is below:
> 
> // Gmsh project created on Fri Oct 14 10:40:40 2016
> 
> //geometry creation
> //ellipse: major axis 0.075, minor axis 0.009375
> // 1st arc
> Point(1) = {-0.0375, 0, 0, 0.01};
> Point(2) = {0, 0, 0, 0.01}; //global center
> Point(3) = {-0.02, 0, 0, 0.1};
> Point(4) = {-0.026516504, 0.003314563, 0, 0.01};
> Ellipse(1) = {1, 2, 3, 4};
> 
> //arc 2
> Point(5) = {0, 0.0046875, 0, 0.01};
> Point(6) = {0.02, 0, 0, 0.01};
> Ellipse(2) = {4, 2, 3, 5};
> 
> //arc3
> Point(7) = {0.026516504, 0.003314563, 0, 0.01};
> Ellipse(3) = {5, 2, 6, 7};
> 
> //arc4
> Point(8) = {0.0375, 0, 0, 0.01};
> Ellipse(4) = {7, 2, 6, 8};
> 
> //arc5
> Point(9) = {0.026516504, -0.003314563, 0, 0.01};
> Ellipse(5) = {8, 2, 6, 9};
> 
> //arc6
> Point(10) = {0, -0.0046875, 0, 0.01};
> Ellipse(6) = {9, 2, 6, 10};
> 
> //arc7
> Point(11) = {-0.026516504, -0.003314563, 0, 0.01};
> Ellipse(7) = {10, 2, 3, 11};
> 
> //arc8
> Ellipse(8) = {11, 2, 3, 1};
> 
> //circle
> Point(12) = {-1.7677669, -1.7677669, 0, 0.01};
> Point(13) = {-1.7677669, 1.7677669, 0, 0.01};
> Point(14) = {1.7677669, 1.7677669, 0, 0.01};
> Point(15) = {1.7677669, -1.7677669, 0, 0.01};
> 
> Circle(9) = {12, 2, 13};
> Circle(10) = {13, 2, 14};
> Circle(11) = {14, 2, 15};
> Circle(12) = {15, 2, 12};
> 
> //blocking lines
> Line(13) = {11, 12};
> Line(14) = {4, 13};
> Line(15) = {7, 14};
> Line(16) = {9, 15};
> 
> //splitting lines
> Transfinite Line {9} = 100 Using Progression 1;
> Transfinite Line {10} = 100 Using Progression 1;
> Transfinite Line {11} = 100 Using Progression 1;
> Transfinite Line {12} = 100 Using Progression 1;
> Transfinite Line {14} = 100 Using Progression 1;
> Transfinite Line {15} = 100 Using Progression 1;
> Transfinite Line {16} = 100 Using Progression 1;
> Transfinite Line {13} = 100 Using Progression 1;
> Transfinite Line {8} = 100 Using Progression 1;
> Transfinite Line {1} = 100 Using Progression 1;
> Transfinite Line {2} = 100 Using Progression 1;
> Transfinite Line {3} = 100 Using Progression 1;
> Transfinite Line {4} = 100 Using Progression 1;
> Transfinite Line {5} = 100 Using Progression 1;
> Transfinite Line {6} = 100 Using Progression 1;
> Transfinite Line {7} = 100 Using Progression 1;
> Line Loop(17) = {13, 9, -14, -1, -8};
> Plane Surface(1) = {17};
> Line Loop(19) = {15, -10, -14, 2, 3};
> Plane Surface(2) = {19};
> Line Loop(21) = {16, -11, -15, 4, 5};
> Plane Surface(3) = {21};
> Line Loop(23) = {13, -12, -16, 6, 7};
> Plane Surface(4) = {23};
> Transfinite Surface {1} = {4, 13, 12, 11};
> Transfinite Surface {2} = {7, 14, 13, 4};
> Transfinite Surface {3} = {9, 15, 14, 7};
> Transfinite Surface {4} = {11, 12, 15, 9};
> 
> Recombine Surface {1};
> Recombine Surface {2};
> Recombine Surface {3};
> Recombine Surface {4};
> 
> When I run this file in gmsh, I get errors like: "Error   : Surface 4 cannot 
> be meshed using the transfinite algo". I also get a warning stating: "Warning 
> : Cannot apply Blosson: odd number of triangles (15167) in surface 4". My 
> error log and .geo files are attached. Please advise on what I can do to fix 
> these errors.
> 

Transfinite Surface meshes require matching number of vertices on opposite 
sides. Add e.g. this to your file:

N = 10;
Transfinite Line {1:8} = N;
Transfinite Line {9:12} = 2*N-1;
Transfinite Line {13:16} = 50 Using Progression 1.2;


> Thanks and Regards,
> 
> Kushagra Vidyarthi
> 
>  (copy).geo>___
> gmsh mailing list
> gmsh@onelab.info
> http://onelab.info/mailman/listinfo/gmsh

-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

Free software: http://gmsh.info | http://getdp.info | http://onelab.info


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[Gmsh] Problems with structured meshing

[Kushagra Vidyarthi]

Dear Sir/Madam,

I am working on a CFD analysis around an ellipse. For this purpose, I 
have created a circular domain around the geometry, and I am trying to 
create a structured mesh around it, so that I can have some control over 
the boundary layer. My .geo file is below:


// Gmsh project created on Fri Oct 14 10:40:40 2016

//geometry creation
//ellipse: major axis 0.075, minor axis 0.009375
// 1st arc
Point(1) = {-0.0375, 0, 0, 0.01};
Point(2) = {0, 0, 0, 0.01}; //global center
Point(3) = {-0.02, 0, 0, 0.1};
Point(4) = {-0.026516504, 0.003314563, 0, 0.01};
Ellipse(1) = {1, 2, 3, 4};

//arc 2
Point(5) = {0, 0.0046875, 0, 0.01};
Point(6) = {0.02, 0, 0, 0.01};
Ellipse(2) = {4, 2, 3, 5};

//arc3
Point(7) = {0.026516504, 0.003314563, 0, 0.01};
Ellipse(3) = {5, 2, 6, 7};

//arc4
Point(8) = {0.0375, 0, 0, 0.01};
Ellipse(4) = {7, 2, 6, 8};

//arc5
Point(9) = {0.026516504, -0.003314563, 0, 0.01};
Ellipse(5) = {8, 2, 6, 9};

//arc6
Point(10) = {0, -0.0046875, 0, 0.01};
Ellipse(6) = {9, 2, 6, 10};

//arc7
Point(11) = {-0.026516504, -0.003314563, 0, 0.01};
Ellipse(7) = {10, 2, 3, 11};

//arc8
Ellipse(8) = {11, 2, 3, 1};

//circle
Point(12) = {-1.7677669, -1.7677669, 0, 0.01};
Point(13) = {-1.7677669, 1.7677669, 0, 0.01};
Point(14) = {1.7677669, 1.7677669, 0, 0.01};
Point(15) = {1.7677669, -1.7677669, 0, 0.01};

Circle(9) = {12, 2, 13};
Circle(10) = {13, 2, 14};
Circle(11) = {14, 2, 15};
Circle(12) = {15, 2, 12};

//blocking lines
Line(13) = {11, 12};
Line(14) = {4, 13};
Line(15) = {7, 14};
Line(16) = {9, 15};

//splitting lines
Transfinite Line {9} = 100 Using Progression 1;
Transfinite Line {10} = 100 Using Progression 1;
Transfinite Line {11} = 100 Using Progression 1;
Transfinite Line {12} = 100 Using Progression 1;
Transfinite Line {14} = 100 Using Progression 1;
Transfinite Line {15} = 100 Using Progression 1;
Transfinite Line {16} = 100 Using Progression 1;
Transfinite Line {13} = 100 Using Progression 1;
Transfinite Line {8} = 100 Using Progression 1;
Transfinite Line {1} = 100 Using Progression 1;
Transfinite Line {2} = 100 Using Progression 1;
Transfinite Line {3} = 100 Using Progression 1;
Transfinite Line {4} = 100 Using Progression 1;
Transfinite Line {5} = 100 Using Progression 1;
Transfinite Line {6} = 100 Using Progression 1;
Transfinite Line {7} = 100 Using Progression 1;
Line Loop(17) = {13, 9, -14, -1, -8};
Plane Surface(1) = {17};
Line Loop(19) = {15, -10, -14, 2, 3};
Plane Surface(2) = {19};
Line Loop(21) = {16, -11, -15, 4, 5};
Plane Surface(3) = {21};
Line Loop(23) = {13, -12, -16, 6, 7};
Plane Surface(4) = {23};
Transfinite Surface {1} = {4, 13, 12, 11};
Transfinite Surface {2} = {7, 14, 13, 4};
Transfinite Surface {3} = {9, 15, 14, 7};
Transfinite Surface {4} = {11, 12, 15, 9};

Recombine Surface {1};
Recombine Surface {2};
Recombine Surface {3};
Recombine Surface {4};

When I run this file in gmsh, I get errors like: "Error   : Surface 4 
cannot be meshed using the transfinite algo". I also get a warning 
stating: "Warning : Cannot apply Blosson: odd number of triangles 
(15167) in surface 4". My error log and .geo files are attached. Please 
advise on what I can do to fix these errors.


Thanks and Regards,

Kushagra Vidyarthi

Info: ---
Info: Gmsh version   : 2.10.1
Info: Build OS   : Linux
Info: Build options  : 64Bit Ann Bamg Bfgs Blas(Generic) Blossom Chaco 
DIntegration Dlopen Fltk Gmm Jpeg Kbipack Lapack(Generic) LinuxJoystick MPI 
MathEx Med Mesh Mmg3d Mpeg NativeFileChooser Netgen ONELAB ONELABMetamodel 
OpenCascade(OCE) OpenGL OptHom Parser Plugins Png Post Python Salome Solver 
Tetgen Voro3D Zlib
Info: Build date : 20160212
Info: Build host : lgw01-54
Info: Packager   : buildd
Info: Executable : /usr/bin/gmsh
Info: Home directory : /home/kushagra/
Info: Launch date: Sat Oct 15 18:59:00 2016
Info: Command line   : gmsh
Info: ---
Info: Reading '/home/kushagra/gmsh_work/ellipse+domain_geom_o-grid 
(copy).geo'...
Info: Done reading '/home/kushagra/gmsh_work/ellipse+domain_geom_o-grid 
(copy).geo'
Info: Meshing 1D...
Info: Meshing curve 1 (Ellipse)
Info: Meshing curve 2 (Ellipse)
Info: Meshing curve 3 (Ellipse)
Info: Meshing curve 4 (Ellipse)
Info: Meshing curve 5 (Ellipse)
Info: Meshing curve 6 (Ellipse)
Info: Meshing curve 7 (Ellipse)
Info: Meshing curve 8 (Ellipse)
Info: Meshing curve 9 (Circle)
Info: Meshing curve 10 (Circle)
Info: Meshing curve 11 (Circle)
Info: Meshing curve 12 (Circle)
Info: Meshing curve 13 (Line)
Info: Meshing curve 14 (Line)
Info: Meshing curve 15 (Line)
Info: Meshing curve 16 (Line)
Info: Done meshing 1D (0.012 s)
Info: 1583 vertices 1599 elements
Info: Meshing 2D...
Info: Meshing surface 1 (transfinite)
Error   : Surface 1 cannot be meshed using the transfinite algo
Info: Meshing