CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Special Topics > Mesh Generation & Pre-Processing

Boundary layer in Gmsh with OpenCASCADE

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 13, 2017, 08:07
Default Boundary layer in Gmsh with OpenCASCADE
  #1
New Member
 
Malgorzata
Join Date: Jun 2017
Posts: 3
Rep Power: 8
chomikzimon is on a distinguished road
Dear All,

I am trying to create a boundary layer for a u-bend circular pipe. I have used the elements of OpenCASCADE, such as disk and wire; therefore, I cannot add a boundary layer through simple extrusion. I tried using Field[]=BoundaryLayer, but that also did not produce anything Could you please advise me on how to fix this issue? Please find my script below.

Thank you!

SetFactory("OpenCASCADE");

/* ** Choose general settings ** */

Mesh.CharacteristicLengthMin = 0.05;
Mesh.CharacteristicLengthMax = 0.05;
Geometry.NumSubEdges = 100; // nicer display of curve
General.Color.Text = Black;
Geometry.Color.Points = Purple;
General.Color.Background = White;

General.Color.Text = Black;
Mesh.Color.Points = {255,0,0};

//Mesh.Algorithm3D = 4;
//Mesh.Smoothing = 100;
//Mesh.Optimize=1;
//Mesh.OptimizeNetgen=1;
//Mesh.OptimizeNetgen=1;


/* ** Define constants ** */

DefineConstant[
npts = {16, Name "Number of points in the bend"}
r = {0.38, Name "Bend radius"}
rd = {0.125, Name "Radius of the cross-section"}
mes = {1e-2, Name "Mesh element size"}
lh = {1.49, Name "Length of the horizontal section"}
lv1 = {0.74, Name "Length of the 1st vertical section"}
lv2 = {2.07, Name "Length of the 2nd vertical section"}];


/* ** Create the first elbow ** */


For i In {0:npts}
theta = i * 0.5 * Pi/npts;
Point(i + 1) = {r * Cos(-theta), r * Sin(-theta), 0, mes};
EndFor

nr[] += 1;

Spline(nr[0]) = {1: npts+1};
Wire(nr[0]) = {1};
Disk(nr[0]) = {0,-r,0, rd};
Rotate {{0, -r, 0}, {0, 0, 0}, Pi/2} {Surface{nr[0]};}
my_volumes[] += Extrude { Surface{nr[0]}; } Using Wire {nr[0]};//pipe

/* ** Translate and duplicate the end point to create the horizontal section ** */


my_new_points[] += Translate {-lh, 0, 0} { Duplicata{ Point{npts+1}; }};
nr[] += newreg;
Spline(nr[1]) = {npts + 1, my_new_points[0]};
Wire(nr[1]) = {nr[1]};
Disk(nr[1]) = {0, -r, 0, rd};
Rotate {{0, -r, 0}, {0, 0, 0}, Pi/2} {Surface{nr[1]};}
my_volumes[] += Extrude { Surface{nr[1]}; } Using Wire {nr[1]};


/* ** Create the second elbow ** */


p1 = newp;
For i In {0:npts}
theta = i * 0.5 * Pi/npts;
Point(i + p1) = {-lh -r * Cos(-theta), r * Sin(-theta), 0, mes};
EndFor


p2 = newp;
nr[] += newreg;
Spline(nr[2]) = {p1: p2-1};
Wire(nr[2]) = {nr[2]};
Disk(nr[2]) = {-1.87, 0, 0, rd};
Rotate {{-(lh + r), 0, 0}, {0, 0, 0}, Pi/2} {Surface{nr[2]};}
my_volumes[] += Extrude { Surface{nr[2]}; } Using Wire {nr[2]};


/* ** Translate and duplicate a point to create the upstream vertical section ** */


my_new_points[] += Translate {0, lv1, 0} { Duplicata{ Point{p1}; }};
nr[] += newreg;
Spline(nr[3]) = {p1, my_new_points[1]};
Wire(nr[3]) = {nr[3]};
Disk(nr[3]) = {-(lh + r),0,0, rd};
Rotate {{-(lh + r), 0, 0}, {0, 0, 0}, Pi/2} {Surface{nr[3]};}
my_volumes[] += Extrude { Surface{nr[3]}; } Using Wire {nr[3]};


/* ** Translate and duplicate a point to create the downstream vertical section ** */


my_new_points[] += Translate {0, lv2, 0} { Duplicata{ Point{1}; }};
nr[] += newreg;
Spline(nr[4]) = {1, my_new_points[2]};
Wire(nr[4]) = {nr[4]};
Disk(nr[4]) = {r, 0, 0, rd};
Rotate {{0.38, 0, 0}, {0, 0, 0}, Pi/2} {Surface{nr[4]};}
my_volumes[] += Extrude { Surface{nr[4]}; } Using Wire {nr[4]};

//Printf("Surface id: %g", nr[0]);
Delete{ Surface{nr[]}; }
chomikzimon is offline   Reply With Quote

Old   October 5, 2017, 10:15
Default
  #2
New Member
 
Join Date: Jan 2015
Posts: 4
Rep Power: 11
ahab is on a distinguished road
Hi chomikzimon,
I stumbled upon the very same problem and can't find a solution. I have been working on it for a while now. As I am additionally using boolean operators, I am also not able to work around the issue through using only functions that work with the SetFactory "built-in". Were you able to solve your problem? I would be very glad for any kind of help!
ahab is offline   Reply With Quote

Old   October 5, 2017, 10:20
Default
  #3
New Member
 
Malgorzata
Join Date: Jun 2017
Posts: 3
Rep Power: 8
chomikzimon is on a distinguished road
Hi,

Unfortunately, I don't think there is an easy way to do it in Gmsh at the moment. I moved to Salome instead.

I am sorry for not being of much help.
chomikzimon is offline   Reply With Quote

Old   December 3, 2017, 08:50
Question Boundary in GMSH
  #4
New Member
 
Leonardo
Join Date: Dec 2017
Posts: 2
Rep Power: 0
Leoonardo is on a distinguished road
how can I make a duplicate mesh in the structure and not duplicate in the fluid in the GMSH?
Geometry is the cross section of the guitar, I'm having trouble putting just fluid in the sound hole of the guitar.

and I need the mesh to be triangular regular


between point(4) and point (5), it's the sound hole, and there I need it to be just fluid and the line(4) disappears.

help me please, i'm beginner of scientific research


msh code .geo

dim = 34;
gridsize = dim/4;

dim2 = 38.3;
gridsize2 = dim2/4;

dim3 = 48;
gridsize3 = dim3/4;


Point(1) = {0, 0, 0, gridsize};
Point(2) = {dim3 , 0, 0, gridsize3};
Point(3) = {dim3 , 10.5, 0, gridsize3};
Point(4) = {dim2, 10.5, 0, gridsize2};
Point(5) = {dim, 10.5, 0, gridsize};
Point(6) = {0, 10.5, 0, gridsize2};

//+
Line(1) = {1, 2};
//+
Line(2) = {2, 3};
//+
Line(3) = {3, 4};
//+
Line(4) = {4, 5};
//+
Line(5) = {5, 6};
//+
Line(6) = {6, 1};
//+
Line Loop(1) = {6, 1, 2, 3, 4, 5};
//+
Plane Surface(1) = {1};
Attached Images
File Type: jpg msh.jpg (30.7 KB, 36 views)
Leoonardo is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[snappyHexMesh] snappyHexMesh Boundary Layer at Corner panpanzhong OpenFOAM Meshing & Mesh Conversion 5 July 3, 2018 06:53
Problem in setting Boundary Condition Madhatter92 CFX 12 January 12, 2016 05:39
Wrong flow in ratating domain problem Sanyo CFX 17 August 15, 2015 07:20
Error finding variable "THERMX" sunilpatil CFX 8 April 26, 2013 08:00
[Gmsh] Default Faces on Boundary Layer axel OpenFOAM Meshing & Mesh Conversion 8 February 17, 2011 08:47


All times are GMT -4. The time now is 07:04.