[Gmsh] How to improve the quality of mesh generation

[Junhui Liu]

Hi All,

It appears that the quality of mesh generation depends on the version you use. I use Mesh.Algorithm3D = 1, and Mesh.Algorithm =5.

 For example, 

if I use gmsh-3.0.3, I got
Info    : Opti : (7594757,0,400672) =  1.34590E+03 QBAD  6.40230E-03 QAVG  6.92222E-01 ( 650.191 sec)
Info    : Opti : (7649463,0,408083) =  1.34590E+03 QBAD  6.40230E-03 QAVG  6.92316E-01 ( 965.826 sec)
Info    : Opti : 4 ill-shaped tets are still in the mesh
Info    : Opti : 0.00 < QUAL < 0.10 :         7 elements
I

But if I use gmsh-3.0.6, I got  
Info    : Opti : (7588653,0,400922) =  1.34590E+03 QBAD  1.05131E-02 QAVG  6.92189E-01 ( 561.789 sec)
Info    : Opti : (7643427,0,408262) =  1.34590E+03 QBAD  1.05131E-02 QAVG  6.92284E-01 ( 821.088 sec)
Info    : Opti : 4 ill-shaped tets are still in the mesh
Info    : Opti : 0.00 < QUAL < 0.10 :         5 elements
I

If I use the newest stable version gmsh-4.0.0, I got 
Info    : Opti : (5126023,0,163893) =  1.34579E+03 QBAD  6.22727E-04 QAVG  7.99073E-01 ( 556.652 sec)
Info    : Opti : (5145672,0,165902) =  1.34579E+03 QBAD  6.22727E-04 QAVG  7.99114E-01 ( 772.064 sec)
Info    : Opti : 6 ill-shaped tets are still in the mesh
Info    : Opti : 0.00 < QUAL < 0.10 :         9 elements

Although the newer version gave overall better quality, but it generated some very bad elements. Is there a way that I can improve the quality of the mesh, especially to eliminate the elements of poor quality?

Thanks a lot for your help.

Jun