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Input Files

In this example we are going to use t3.geo, which we will edit slightly to obtain t3a.geo and t3b.geo.

All alterations are mentioned below the sample code:

t3a.geo

Include "t1.geo";

h = 0.1;

Extrude {0,0,h} {
  Surface{1}; Layers{h/(lc*2)}; Recombine;
}

Extrude { {0,1,0} , {-0.1,0,0.1} , -Pi/2 } {
  Surface{26}; Layers{9}; Recombine;
}

DefineConstant[ angle = {180, Min 0, Max 180, Step 1,
                         Name "Parameters/Twisting angle"} ];

out[] = Extrude { {-6*h,0,0}, {1,0,0} , {0,0.15,0.25} , angle * Pi / 180 } {
  Surface{news-1}; Layers{6*h/(lc*2)}; Recombine;
};

Geometry.PointNumbers = 1;
Geometry.Color.Points = Orange;
General.Color.Text = White;
Mesh.Color.Points = {255,0,0};
Geometry.Color.Surfaces = Geometry.Color.Points;

/* * * * * * * * * * * *
 * Dolfyn added lines: *
 * * * * * * * * * * * */

 // For decent outlet we need to extrude once again...

 Extrude {-4*h,0,0} {
   Surface{news-1}; Layers{4*h/(lc*2)}; Recombine;
 }

 // Boundaries (non-default)

 Physical Volume("Fluid") = {1, 2, 3, 4};
 Physical Surface("S1") = {1};
 Physical Surface("S2") = {92};

Note

We edited the following (line numbers according to original document):

  • line 22 – We define the extrude differently than the original file, using only 1 layer with subdivisions based on the characteristic length. Also we add the Recombine command to have the mesh produce prisms.
  • line 31 – We define 9 layers in the extrude
  • line 40 – You could remove this definition entirely, but we chose to set the variable to and increase the range to 180 degrees
  • line 43 – We define the extrude to translate -6h
  • line 44 – Changed the surface number to news-1, which returns the last created surface
  • line 44 – The number of subdivisions is again based on the characteristic length
  • Commented out lines:
    • line 55 – custom Physical Volume created later
  • Added lines (important!):
    • line 80-88 – added an extrude to obtain a decent outlet
    • line 89-94 – defined a new Physical Volume and Physical Surfaces for an In- and Outlet.

Visually the model will look like this:

Now we will also make t3b.geo, which is exaclty the same, except for the Recombine command.

t3b.geo

Note

We removed the Recombine commands on lines:

  • line 22
  • line 31
  • line 44
  • line 87

Visually, nothing has changed, but in the next step, we will see that the mesh will be different.

Lastly, we want to briefly talk about the t3ad.din and t3bd.din files.

> See the DINGuide (on the Downloads page) for reference.

t3d.din

title Test Gmsh t3.geo model
steps 200 1.e-3

density 1.2
vislam 20.e-6

opendx off
use gmsh fluid

relax 0.5 0.15 0.5
turbulence ke 0.01
init,field,0.0 0.0 0.0,,1.e-4,1e-4

scheme UVW  LUX 0.8
scheme KEPS LUD 0.8

slope UVW  vnf
slope P    vnf
slope KEPS vnf

#post p   vert
#post k   vert

#post k   cell
#post eps cell
#post vis cell

boundary,0
wall
noslip
0.0 0.0 0.0
adiabatic

boundary,S1
inlet
0.0 0.0 0.1
1.2
293
inle
0.05 0.01

boundary,S2
outlet
1.0

File t3ad.din and t3bd.din are exact copies of the file above. The reason will be to show the difference in mesh choice in the output.

Again use gmsh fluid is used (line 8), to produce a full *.msh file, but ommitting the results on the boudaries.

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