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[Gmsh] Using Bump with Extrude, layers in GMSH??

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Old   October 26, 2016, 07:08
Default Using Bump with Extrude, layers in GMSH??
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Hi there,

I have been building a basic wave tank in GMSH and used the extrude command to create the 3d volume. I now want to "bump" the vertical lines to coarsen the cells towards the top and bottom (towards +z and -z) and refine the mesh towards the centre of the z axis (where the free surface would be if the vertical mesh is divided evenly between fluid and air).

Using, for example, this snippet of code (not an mwe but hopefully gives enough info):

Code:
Physical Volume("water") = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; // volume numbers
Extrude{0,0,10} {
Surface{11, 12, 13, 14, 15, 16, 17, 18, 19, 20};
Layers{10};
Recombine:
}

Transfinite Line{Line connecting +z point of surfaces to -z point} = 10 Using Bump 5.00;
Probably not surprising that this doesn't work... is there a way to include a bump expression in with layers? I was reading in the guide and didn't understand the explanation of layers enough to apply it.

Any advice would be greatly appreciated, thank you in advance!
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Old   October 30, 2016, 14:06
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Quote:
Originally Posted by arieljeds View Post
Hi there,

I have been building a basic wave tank in GMSH and used the extrude command to create the 3d volume. I now want to "bump" the vertical lines to coarsen the cells towards the top and bottom (towards +z and -z) and refine the mesh towards the centre of the z axis (where the free surface would be if the vertical mesh is divided evenly between fluid and air).

Using, for example, this snippet of code (not an mwe but hopefully gives enough info):

Code:
Physical Volume("water") = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; // volume numbers
Extrude{0,0,10} {
Surface{11, 12, 13, 14, 15, 16, 17, 18, 19, 20};
Layers{10};
Recombine:
}

Transfinite Line{Line connecting +z point of surfaces to -z point} = 10 Using Bump 5.00;
Probably not surprising that this doesn't work... is there a way to include a bump expression in with layers? I was reading in the guide and didn't understand the explanation of layers enough to apply it.

Any advice would be greatly appreciated, thank you in advance!
The snipped code is not in the right order. This might do the trick

Example

Extrude {0, 0, 1} {
Surface{12, 14, 16};
Layers{1};
Recombine;
}
Transfinite Line {1, 2, 3, 4, 5, 6} = 10 Using Bump 0.4;
Transfinite Surface "*";
Recombine Surface "*";

Best,
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Old   November 3, 2016, 08:00
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Hi tareqkh,

Thanks for your reply, somehow I missed this so sorry for the delay... Ok so I tried your suggestion but oddly it didn't seem to do anything at all?

Here's the full .geo code:
Code:
// Gmsh project created on Wed Oct 26 18:11:53 2016

L = 50;
Lx = 2.5*50;
Ly = L; 
depth = -15;

Nx = 100; Rx = 1.00;
Ny = 40;  Ry = 1.00;

Point(1) = {-Lx, -Ly, depth, 1.0};
Point(2) = { Lx, -Ly, depth, 1.0};
Point(3) = { Lx,  Ly, depth, 1.0};
Point(4) = {-Lx,  Ly, depth, 1.0};
Line(1) = {1, 2};
Line(2) = {4, 3};
Line(3) = {1, 4};
Line(4) = {2, 3};

Transfinite Line {1} = Nx Using Progression Rx;
Transfinite Line {2} = Nx Using Progression Rx;
Transfinite Line {3} = Ny Using Progression Ry;
Transfinite Line {4} = Ny Using Progression Ry;

Line Loop(5) = {3, 2, -4, -1};
Plane Surface(6) = {5};
Transfinite Surface {6}; Recombine Surface{6};

Physical Volume("water") = {1};
Extrude {0, 0, 25} {
  Surface{6};
  Layers{20};
  Recombine;
}

Geometry.LineNumbers =1 ;
Transfinite Line {13,14,22,18} = 10 Using Bump 0.4;
Transfinite Surface "*";
Recombine Surface "*";


Physical Surface("inlet") = {15}; //inlet
Physical Surface("outlet") = {23}; // outlet
Physical Surface("topAndBottom") = {27, 19}; // topAndBottom
Physical Surface("atmosphere") = {28}; // atmosphere
Physical Surface("seaFloor") = {6}; // seaFloor
It makes the mesh properly but then I can't see any "bump"?
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Old   November 3, 2016, 10:27
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Try this;

Code:
L = 50;
Lx = 2.5*50;
Ly = L;
depth = -15;

Nx = 100; Rx = 1.00;
Ny = 40;  Ry = 1.00;

Point(1) = {-Lx, -Ly, depth, 1.0};
Point(2) = { Lx, -Ly, depth, 1.0};
Point(3) = { Lx,  Ly, depth, 1.0};
Point(4) = {-Lx,  Ly, depth, 1.0};
Line(1) = {1, 2};
Line(2) = {4, 3};
Line(3) = {1, 4};
Line(4) = {2, 3};

Transfinite Line {1,2} = Nx Using Progression Rx;
Transfinite Line {3,4} = Ny Using Progression Ry;
Transfinite Line {3,4} = 10 Using Bump 0.4;

Line Loop(5) = {3, 2, -4, -1};
Plane Surface(6) = {5};

Extrude {0, 0, 25} {
  Surface{6};
  Layers{20};
  Recombine;
}
Transfinite Surface "*";
Recombine Surface "*";


Physical Surface("inlet") = {15}; //inlet
Physical Surface("outlet") = {23}; // outlet
Physical Surface("topAndBottom") = {27, 19}; // topAndBottom
Physical Surface("atmosphere") = {28}; // atmosphere
Physical Surface("seaFloor") = {6}; // seaFloor
Physical Volume("water") = {1};
You can also send what are tying to do.

Best,
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Old   November 5, 2016, 15:26
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@ArielJ

You can just remove Layers and Recombine from Extrude command; determine new lines IDs using, for example, GUI and then make them Transfinite. There is an example

Code:
Point(1) = {0, 0, 0};
Point(2) = {1, 0, 0};
Point(3) = {1, 1, 0};
Point(4) = {0, 1, 0};

Line(1) = {1, 2};
Line(2) = {4, 3};
Line(3) = {1, 4};
Line(4) = {2, 3};
Line Loop(5) = {3, 2, -4, -1};
Plane Surface(6) = {5};
Extrude {0, 0, 1} {
  Surface{6};
}

Transfinite Line {1, 2, 3, 4} = 11;

// New lines due to extrusion in the new surface
Transfinite Line {8, 9, 10, 11} = 11;

// New vertical lines due to extrusion
Transfinite Line {13, 14, 18, 22} = 51 Using Bump 0.1;

Transfinite Surface "*";
Recombine Surface "*";
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Old   March 1, 2017, 06:22
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Quote:
Originally Posted by alexeym View Post
@ArielJ

You can just remove Layers and Recombine from Extrude command; determine new lines IDs using, for example, GUI and then make them Transfinite. There is an example

Code:
Point(1) = {0, 0, 0};
Point(2) = {1, 0, 0};
Point(3) = {1, 1, 0};
Point(4) = {0, 1, 0};

Line(1) = {1, 2};
Line(2) = {4, 3};
Line(3) = {1, 4};
Line(4) = {2, 3};
Line Loop(5) = {3, 2, -4, -1};
Plane Surface(6) = {5};
Extrude {0, 0, 1} {
  Surface{6};
}

Transfinite Line {1, 2, 3, 4} = 11;

// New lines due to extrusion in the new surface
Transfinite Line {8, 9, 10, 11} = 11;

// New vertical lines due to extrusion
Transfinite Line {13, 14, 18, 22} = 51 Using Bump 0.1;

Transfinite Surface "*";
Recombine Surface "*";
Hi Alexey.

This script seems to produce the desired result only on the surface (structured quadrilaterals). The domain is meshed using tetrahedrals. Can you please confirm this or am I missing something?
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Old   July 27, 2017, 23:20
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Quote:
Originally Posted by alexeym View Post
@ArielJ

You can just remove Layers and Recombine from Extrude command; determine new lines IDs using, for example, GUI and then make them Transfinite. There is an example

Code:
Point(1) = {0, 0, 0};
Point(2) = {1, 0, 0};
Point(3) = {1, 1, 0};
Point(4) = {0, 1, 0};

Line(1) = {1, 2};
Line(2) = {4, 3};
Line(3) = {1, 4};
Line(4) = {2, 3};
Line Loop(5) = {3, 2, -4, -1};
Plane Surface(6) = {5};
Extrude {0, 0, 1} {
  Surface{6};
}

Transfinite Line {1, 2, 3, 4} = 11;

// New lines due to extrusion in the new surface
Transfinite Line {8, 9, 10, 11} = 11;

// New vertical lines due to extrusion
Transfinite Line {13, 14, 18, 22} = 51 Using Bump 0.1;

Transfinite Surface "*";
Recombine Surface "*";
Hi Alexey,

I wonder how did you come with the number 0.1 for 51 nodes? Could you please give a little explanation?

Thank you,
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Old   June 15, 2018, 00:22
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Quote:
Originally Posted by Jibran View Post
Hi Alexey.

This script seems to produce the desired result only on the surface (structured quadrilaterals). The domain is meshed using tetrahedrals. Can you please confirm this or am I missing something?

Just a small message for anybody who finds this thread:
Adding Transfinite Volume "*"; to the script means that the volume is meshed correctly as well.
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