[Sanghera]

Hi community,

I am a new user to gmsh and have been trying to mesh a turbine blade.

I have been able to generate a .geo file with all the points/lines/surfaces that define the fluid domain and the blade. I have done this by first connecting the blade points using a B-spline whereas for the boundary points I have used straight lines. Following up, I have made separate line loops of the boundary lines and of the B-spline line. At last, I have generated a plane surface using the boundary line loop and the blade line loop.

To see if the geometry was fine, I tried to generate a 2D (without already defining physicals groups) mesh. I ran into the problem that gmsh does not seem to be forming a closed loop. The error is quite straightforward, however, I did not manage to fix it. I have looked in to the boundary line loop which seem perfectly fine and closed. The same applies for the blade line loop. I have even tried to generate the B-spline in different manners, such as making the end point equal to the starting point (with the same elementary IDs, and with different elementary IDs). The latter did not help either. The geometry seems to be too simple to mess up anything ... I'm sure my eyes have been on this for too long and I am overlooking a minor detail.

Please find attached the content of the .geo file that I use. Saving this in a simple text document using .geo and opening this file in gmsh will give you exactly what I have. Once it's uploaded, you can try to generate a mesh, however you will get the error:

Info : -------------------------------------------------------
Info : Reading 'gmshdat.geo'...
Info : Starting subloop 1 in Line Loop 10 (are you sure about this?)
Info : Done reading 'gmshdat.geo'
Info : Meshing 1D...
Info : Meshing curve 1 (Nurb)
Info : Meshing curve 2 (Line)
Info : Meshing curve 3 (Line)
Info : Meshing curve 4 (Line)
Info : Meshing curve 5 (Line)
Info : Meshing curve 6 (Line)
Info : Meshing curve 7 (Line)
Info : Meshing curve 8 (Line)
Info : Meshing curve 9 (Line)
Info : Done meshing 1D (0.034609 s)
Info : Meshing 2D...
Info : Meshing surface 1 (Plane, Delaunay)
Error : The 1D mesh seems not to be forming a closed loop
Info : Done meshing 2D (0.000354052 s)
Info : 789 vertices 798 elements
Error : ------------------------------
Error : Mesh generation error summary
Error : 0 warnings
Error : 1 error
Error : Check the full log for details
Error : ------------------------------

Does anyone know a fix for this? Help is much appreciated! (See content .geo file below)

Point(1) = {38.39000000000001,45.674,0,1.0};
Point(2) = {39.49000000000001,49.480000000000004,0,1.0};
Point(3) = {41.91000000000001,55.178,0,1.0};
Point(4) = {44.55000000000001,59.314,0,1.0};
Point(5) = {46.97000000000001,62.548,0,1.0};
Point(6) = {49.610000000000014,65.254,0,1.0};
Point(7) = {52.11800000000001,67.45400000000001,0,1.0};
Point(8) = {54.64800000000001,69.302,0,1.0};
Point(9) = {57.17800000000001,70.622,0,1.0};
Point(10) = {59.73000000000001,71.50200000000001,0,1.0};
Point(11) = {62.260000000000005,72.162,0,1.0};
Point(12) = {64.79,72.602,0,1.0};
Point(13) = {67.32000000000001,72.602,0,1.0};
Point(14) = {69.85000000000001,72.162,0,1.0};
Point(15) = {72.38000000000001,71.50200000000001,0,1.0};
Point(16) = {74.93200000000002,70.402,0,1.0};
Point(17) = {77.46200000000002,68.928,0,1.0};
Point(18) = {79.99200000000002,67.058,0,1.0};
Point(19) = {82.52200000000002,64.77,0,1.0};
Point(20) = {85.052,61.998000000000005,0,1.0};
Point(21) = {87.58200000000002,58.676,0,1.0};
Point(22) = {90.11200000000001,54.892,0,1.0};
Point(23) = {92.66400000000002,50.558,0,1.0};
Point(24) = {95.15,45.762,0,1.0};
Point(25) = {97.79000000000002,40.504,0,1.0};
Point(26) = {100.21000000000001,34.85,0,1.0};
Point(27) = {102.85000000000002,28.822,0,1.0};
Point(28) = {105.27000000000001,22.662,0,1.0};
Point(29) = {107.91000000000003,16.282,0,1.0};
Point(30) = {110.33000000000001,9.902000000000001,0,1.0};
Point(31) = {112.97000000000003,3.5219999999999985,0,1.0};
Point(32) = {114.51000000000002,-0.6580000000000013,0,1.0};
Point(33) = {114.07000000000002,-1.5380000000000038,0,1.0};
Point(34) = {113.19000000000003,-1.7580000000000027,0,1.0};
Point(35) = {112.09000000000003,-0.21800000000000352,0,1.0};
Point(36) = {109.01000000000002,4.401999999999994,0,1.0};
Point(37) = {106.15,8.802,0,1.0};
Point(38) = {103.29000000000002,12.982,0,1.0};
Point(39) = {100.43,16.502,0,1.0};
Point(40) = {97.57000000000002,20.022,0,1.0};
Point(41) = {94.798,23.102,0,1.0};
Point(42) = {91.93800000000002,26.006,0,1.0};
Point(43) = {89.07800000000002,28.58,0,1.0};
Point(44) = {86.19600000000001,30.89,0,1.0};
Point(45) = {83.33600000000001,32.936,0,1.0};
Point(46) = {80.47600000000001,34.74,0,1.0};
Point(47) = {77.61600000000001,36.302,0,1.0};
Point(48) = {74.756,37.644,0,1.0};
Point(49) = {71.87400000000001,38.766,0,1.0};
Point(50) = {69.01400000000001,39.646,0,1.0};
Point(51) = {66.15400000000001,40.306,0,1.0};
Point(52) = {63.29400000000001,40.768,0,1.0};
Point(53) = {60.43400000000001,41.032,0,1.0};
Point(54) = {57.55200000000001,41.076,0,1.0};
Point(55) = {54.69200000000001,40.944,0,1.0};
Point(56) = {51.83200000000001,40.592,0,1.0};
Point(57) = {48.95000000000001,40.042,0,1.0};
Point(58) = {46.09000000000001,39.294,0,1.0};
Point(59) = {43.23000000000001,38.326,0,1.0};
Point(60) = {41.470000000000006,38.084,0,1.0};
Point(61) = {39.71000000000001,38.744,0,1.0};
Point(62) = {38.39000000000001,40.174,0,1.0};
Point(63) = {38.17000000000001,42.0,0,1.0};
Point(64) = {38.39000000000001,45.674,0,1.0};
BSpline(1) = {1:64};
Point(65) = {0.0,0.0,0,1.0};
Point(66) = {76.34,0.0,0,1.0};
Point(67) = {95.425,-17.6729037745,0,1.0};
Point(68) = {152.68,-17.6729037745,0,1.0};
Point(69) = {152.68,66.3270962255,0,1.0};
Point(70) = {95.425,66.3270962255,0,1.0};
Point(71) = {76.34,84.0,0,1.0};
Point(72) = {0.0,84.0,0,1.0};
Line(2) = {65,66};
Line(3) = {66,67};
Line(4) = {67,68};
Line(5) = {68,69};
Line(6) = {69,70};
Line(7) = {70,71};
Line(8) = {71,72};
Line(9) = {72,65};
Line Loop(10) = {2,3,3,4,5,6,7,8,9};
Line Loop(11) = {1};
Plane Surface(1) = {10,11};

[mefseaff]

Hello Sanghera,
Were you able to solve your error? I am also getting the same error.
Thank you

[Sud075]

Okay so it just had minor issues.

1. Line Loop(10) = {2,3,3,4,5,6,7,8,9}; had line '3' repeated twice.
2. I added "Coherence" which removes the duplicate entities in the geometry I believe. You can also do this from the GUI.

3. OPTIONAL: I hope you are aware that gmsh surfaces expects the curves to be in same directional orientation to form a surface. Thus if in any case say for example your curves 5,7,8 were in opposite direction, then make sure you define your loop as {2,3,4,-5,6,-7,-8,9};

And now light her up and voila you got it.
I am also not sure why or where is the duplicate point produced or how exactly is the "Coherence" option is solving it. But I guess that is a problem for another day.

I am attaching the .geo file once again just in case. Ofc please rename the extension before using.
cfd_now.txt