Script | Spoken-Tutorial - User contributions [en]

OpenFOAM/C3/Unstructured-mesh-generation-using-Gmsh/English

2015-08-17T13:56:05Z

Mehtapavanp: Created page with "Tutorial: Unstructured Mesh generation using GMSH Script and Narration: Pavan Mehta Keywords: Video tutorial, CFD, GMSH, unstructured mesh, curved lines, circular arc, rul..."

Tutorial: Unstructured Mesh generation using GMSH

Script and Narration: Pavan Mehta

Keywords: Video tutorial, CFD, GMSH, unstructured mesh, curved lines, circular arc, ruled surface

{| style="border-spacing:0;"
| style="border-top:0.05pt solid #000000;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| <center>'''Visual Cue'''</center>
| style="border:0.05pt solid #000000;padding:0.0382in;"| <center>'''Narration'''</center>

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 1
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Hello and welcome to the spoken tutorial on '''Unstructured Mesh generation using GMSH.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 2: Learning Objective
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial we will learn to

* Create an '''unstructured mesh '''in '''GMSH'''
* Create plane''' surfaces'''
* Basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 3: System requirement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To record this tutorial I am using

* '''Ubuntu Linux Operating system 14.04'''
* '''GMSH version 2.8.5'''
* '''OpenFOAM version 2.4.0'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 4: Pre-requisite
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This tutorial is a continuation of:

Creation of sphere using GMSH

We have already learnt to create a sphere using GMSH earlier.

If you don't know how to do so, refer to the '''GMSH '''spoken tutorials in the '''OpenFOAM '''series on this website.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 5: Sphere Geometry and Domain
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Here is our problem statement.

This picture shows the flow direction and boundary faces.

We will now learn how to create an '''unstructured mesh '''using '''GMSH'''.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 6: Points for Domain (slide)
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Note that the size of the domain is 45 X 30 X 30, and the radius of the sphere is 1.

However, these dimensions can vary from problem to problem.

The points for the domain are as shown here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us switch to '''GMSH '''now.

Here is the sphere we created earlier.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create the points and lines of the domain.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I have also created all the points and lines of the domain.

To create the points of the domain, kindly refer to the tutorial mentioned earlier.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Selecting the option plane surface

Using this option, selecting the edges
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, select the option '''plane surface. '''

Then select the respective edges for the surface. The selection will be displayed in red.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Press '''E'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Press '''E''' on the keyboard to execute the selection.

On doing so, we can see the dotted lines.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the surfaces.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process until all surfaces are created.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select''' Physical Groups '''>> Add >> '''surface'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, select the option '''Physical Groups''', then '''Add''' and then '''surface.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select the four faces for wall >> Press '''E'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, select these four faces for the '''wall''' and press '''E '''on the keyboard.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select the face for inlet >> Press '''E'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Select the front face for '''inlet '''and press '''E. '''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select the face for outlet >> Press '''E'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Select the back face for''' outlet''' and press '''E. '''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Close '''GMSH'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now close '''GMSH.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Open sphere1.geo file >> go to the bottom
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, open the '''sphere1.geo '''file in '''gEdit Text Editor.'''

Note that there are additions to this file.

Also note that the identification numbers for the entities is in continuation of the earlier series.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replace the numerical values to a variable d
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As done earlier, replace the numerical values.

Use the letter''' d''' for the domain''' mesh''' variable.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Typing d = 0.5; at the beginning of the document
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Then, at the beginning of the file type

'''d = 0.5;'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To name the boundaries, change the numerical value with your desired name, as demonstrated.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the integer with “wall”
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The first physical surface, we made in the interface was '''wall'''.

So, here, we will replace it with '''wall.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the integer with “inlet”
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The second physical surface, we made in the interface was '''inlet'''.

Hence, here, we will replace it with '''inlet.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the integer with “outlet”
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The third physical surface, we made in the interface was '''outlet.'''

So, here, we will replace it with '''outlet.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Typing Surface Loop()={};

and highlighting
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now type''', Surface Loop''',''' ID''' which is the next integer in round brackets

equals the IDs of all surfaces of the domain in braces

which is 43, 45, 47, 49, 51 and 53

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Typing Volume()={};

and highlighting
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For definition of volume, use '''Volume, ID''' which is the next integer in round brackets

equals the IDs of the two surfaces in braces

Which is 29 and 56

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Typing Physical Volume();

and highlighting
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For physical volume, use '''Physical Volume''', '''ID''' which is the next integer in round brackets

equals the IDs of the volume in braces

which is 58

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Save and close sphere1.geo
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Save this file and close it.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| In the terminal >> type '''gmsh sphere1.geo'''

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, using the terminal reopen '''GMSH '''by''' '''typing:

'''gmsh sphere1.geo '''and press '''Enter'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In '''GMSH''', a bottom to top approachis followed

* That is, first '''1D mesh''' is created
* Using '''1D mesh, 2D mesh '''is created
* Using '''2D mesh, 3D mesh''' is created

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| 1D mesh creation, by pressing F1 key
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For 1D mesh creation, press '''F1''' key.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| 2D mesh creation, by pressing F2 key
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For 2D mesh creation, press '''F2''' key.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| 3D mesh creation, by pressing F3 key
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For 3D mesh creation, press '''F3''' key.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Point to the status bar.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This may take a while. Watch the progress in the status bar.

It shows '''Done '''now.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"|
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Once the '''mesh '''is created, we need to optimize it

to remove faulty cells.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Optimizing mesh using Optimize 3d Netgen option
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For optimization click on Modules , then Mesh and then on '''Optimize 3d Netgen '''option

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Point to the status bar.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This may also take a while.

Once again, watch the progress in the status bar.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Saving mesh and closing terminal
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To save the '''mesh''' go to file, '''save mesh''' and close the '''terminal.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 7: Importing mesh in OpenFOAM
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Create '''OpenFOAM''' '''case''' directory without the '''constant '''folder

In the '''case''' directory, copy the newly created file '''sphere1.msh'''

Using the '''terminal''' window, go to the '''case''' directory of this problem.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Open a new terminal >> type '''gmshToFoam sphere.msh'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Once you are in the '''case''' directory,

Type: '''gmshToFoam sphere1.msh '''and press '''Enter'''

To convert the '''mesh'''

Ensure that the same '''boundary names''' are there in the files of folder 0, before proceeding to the next step.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 8: Summary
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us summarise.

In this tutorial we have learnt to:

* Create an '''unstructured mesh '''in '''GMSH'''
* Create plane''' surfaces'''
* Basic manipulations using the file with''' '''extension''' .geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 9: Assignment
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As an assignment,

Make refinement in the''' mesh''' by changing the values of:

'''s, d '''and

'''Mesh.CharacteristicLengthFromCurvature'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 10: About FOSSEE
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| '''OpenFOAM''' series is created by the '''FOSSEE Project, IIT Bombay'''.

'''FOSSEE''' stands for Free and Open Source Software for Education.

This project promotes the use of free and open source software tools.

For more details, please visit: [http://fossee.in/ http://fossee.in/]

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 11: About Spoken tutorials

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The video at this link summarises the Spoken Tutorial project.

Please download and watch it.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 12:

About Spoken tutorials

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The Spoken Tutorial Project Team conducts workshops and gives certificates on passing online tests.

For more details, please write to us.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 13: Acknowledgement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this Mission is available at this link.

This is Pavan Mehta from FOSSEE Project, IIT BOMBAY signing off.

Thanks for joining.

|}

OpenFOAM/C3/Creating-a-sphere-in-GMSH/English

2015-08-08T15:09:57Z

Mehtapavanp:

Tutorial: Creating a sphere in GMSH

Script and Narration: Pavan Mehta

Keywords: Video tutorial, CFD, GMSH, unstructured mesh, curved lines, circular arc, ruled surface

{| style="border-spacing:0;"
| style="border-top:0.05pt solid #000000;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| <center>'''Visual Cue'''</center>
| style="border:0.05pt solid #000000;padding:0.0382in;"| <center>'''Narration'''</center>

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 1
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Hello and welcome to the spoken tutorial on '''Creating a sphere in GMSH.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 2: Learning Objective
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial, we will learn to

* Create a '''circular arc'''
* Create '''ruled surfaces'''
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 3: System requirement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To record this tutorial I am using

* '''Ubuntu Linux Operating system 14.04'''
* '''GMSH version 2.8.5'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 4: Pre-requisite
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As a pre-requisite, user should have basic knowledge of creating points.

If not, refer to the '''GMSH '''spoken tutorials in the '''OpenFOAM '''series on this website.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 5: Points for sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us begin.

* The origin of the sphere is at (0,0,0).
* And the other points of the sphere are as displayed.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to terminal

In terminal type gmsh sphere1.geo and press enter
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now open '''GMSH''' from the '''terminal.'''

To open the '''terminal, '''press '''Ctrl+Alt+T '''keys.

Now type''' gmsh sphere1.geo'''

and Press''' Enter '''

'''GMSH''' is opened.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I have already created 7 points for the sphere, as shown here.

To create the points of the sphere, kindly refer to the tutorial mentioned earlier.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| In GMSH's interface, selecting circle arc option
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I'll now demonstrate how to make a circular arc.

In '''GMSH, '''a circular arc is strictly created less than '''Pi.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select '''circle arc '''in LHS menu
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To create an arc, select '''circle arc''' option in the left-hand-side menu.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Creating curved lines by selecting 1st , 2nd and then 3rd point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, I will select the right-most point as the starting point of the arc.

Then, select this point here as the center point. Please note: This is the point with the coordinates (0,0,0).

And finally, I will select a point on the top-side as the end point of the arc.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the arcs and complete the sphere.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process till all arcs are created.

Remember to keep the same centre point for all the arcs.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Selecting the option ruled surface

and then selecting respective edges
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now select '''ruled surface '''option from the left-hand side menu, to create the curved surface.

Select the bounding edges for the surface, as demonstrated here.

Notice that the selected edges are now in red colour.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Press E

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Press E on the keyboard to execute this selection.

You can see that the surface has been created.

This is indicated by the dotted line, as shown here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the surfaces

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process and create all 8 surfaces of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Show the completed sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| On completion, your sphere should look like this.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Going to home folder and opening sphere1.geo text file, by double clicking
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, go to the '''Home''' folder.

Locate and open the file '''sphere1.geo''' using '''gedit Text Editor.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Information related to the geometrical entities that we just created, are stored here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining general syntax of GMSH
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In '''GMSH, '''the general syntax is

'''Geometrical entity, identification number''' inside the parenthesis

which equals to an expression.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining syntax of point

Simultaneously highlighting the syntax
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Here, for point, the expression is

'''Point, identification number '''inside parenthesis, which is usually the next integer starting from 1

equals to X,Y,Z coordinates and the value of '''mesh element size '''inside braces.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining further on syntax of point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This value is the desired '''mesh element size'''.

The size of the mesh elements will then be computed by linearly interpolating these values on the initial mesh.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the numerical value to a variable, s
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now replace the numerical value of the points of the sphere, to a variable, '''s.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type s=0.1; at the beginning of the document
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| At the beginning, type '''s = 0.1; '''

This is for specifying the value of''' mesh element size''' of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the necessity of refinement

and typing Mesh.CharacteristicLengthFromCurvature = 0.05;
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To capture the boundary layer, we will refine the mesh near the sphere.

For this purpose, we shall use the line,

'''Mesh.CharacteristicLengthFromCurvature = 0.05;'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the syntax Mesh.CharacteristicLenghtFromCurvature
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The syntax '''Mesh.CharacteristicLengthFromCurvature'''

will adapt the''' mesh''' with respect to the curvature of the geometrical entities.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type '''Surface Loop'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For volume creation, we require all the bounding surfaces.

For this, at the end of the file, type

'''Surface Loop '''followed by its identity

which is the next integer inside parenthesis

Which equals the identities of all the surfaces of the sphere within braces.

Here, the identities are 14, 16, 18, 20, 22, 24, 26 and 28.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Saving and Closing the text file
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the '''sphere1.geo''' file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface

Select Physical Groups >> Add >> Surface option --> select all the surfaces --> Press E
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let's switch to the '''GMSH''' interface.

In the left-hand-side menu, click on '''Physical Groups''', then '''Add''', and then '''Surface '''option.

Select all the surfaces of the sphere.

Press '''E''' on the keyboard to execute this selection.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Double-click to open sphere1.geo file >> go to the last line of the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, again open '''sphere1.geo '''file in the '''Text Editor'''.

Right at the bottom, notice that a new line of code has been added.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replace this number with sphere in double inverted commas and explaining it's importance
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Replace this number with '''sphere''' within quotes.

This will help us to easily identify the boundaries of the sphere while post processing or otherwise.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Save and close the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This completes this tutorial. Let us summarize.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 6: Summary
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial we learnt to

* Create curved lines and surfaces
* Create a sphere and
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 7: Assignment
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As an assignment,

Create a '''sphere '''with a larger radius.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 8: About FOSSEE
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| '''OpenFOAM''' series is created by the '''FOSSEE Project, IIT Bombay'''.

'''FOSSEE''' stands for Free and Open Source Software for Education.

This project promotes the use of free and open source software tools.

For more details, please visit: [http://fossee.in/ http://fossee.in/]

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 9: About the Spoken tutorial project

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The video at this link summarises the Spoken Tutorial project.

Please download and watch it.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 10:

Spoken tutorials Workshops

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The Spoken Tutorial Project Team conducts workshops and gives certificates on passing online tests.

For more details, please write to us.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 11: Acknowledgement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this Mission is available at this link.

This is Pavan Mehta from FOSSEE Project, IIT BOMBAY signing off.

Thanks for joining.

|}

OpenFOAM/C3/Creating-a-sphere-in-GMSH/English

2015-08-08T15:05:26Z

Mehtapavanp:

Tutorial: Creating a sphere in GMSH

Script and Narration: Pavan Mehta

Keywords: Video tutorial, CFD, GMSH, unstructured mesh, curved lines, circular arc, ruled surface

{| style="border-spacing:0;"
| style="border-top:0.05pt solid #000000;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| <center>'''Visual Cue'''</center>
| style="border:0.05pt solid #000000;padding:0.0382in;"| <center>'''Narration'''</center>

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 1
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Hello and welcome to the spoken tutorial on '''Creating a sphere in GMSH.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 2: Learning Objective
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial, we will learn to

* Create a '''circular arc'''
* Create '''ruled surfaces'''
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 3: System requirement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To record this tutorial I am using

* '''Ubuntu Linux Operating system 14.04'''
* '''GMSH version 2.8.5'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 4: Pre-requisite
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As a pre-requisite, user should have basic knowledge of creating points.

If not, refer to the '''GMSH '''spoken tutorials in the '''OpenFOAM '''series on this website.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 5: Points for sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us begin.

* The origin of the sphere is at (0,0,0).
* And the other points of the sphere are as displayed.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to terminal

In terminal type gmsh sphere1.geo and press enter
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now open '''GMSH''' from the '''terminal.'''

To open the '''terminal, '''press '''Ctrl+Alt+T '''keys.

Now type''' gmsh sphere1.geo'''

and Press''' Enter '''

'''GMSH''' is opened.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I have already created 7 points for the sphere, as shown here.

To create the points of the sphere, kindly refer to the tutorial mentioned earlier.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| In GMSH's interface, selecting circle arc option
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I'll now demonstrate how to make a circular arc.

In '''GMSH, '''a circular arc is strictly created less than '''Pi.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select '''circle arc '''in LHS menu
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To create an arc, select '''circle arc''' option in the left-hand-side menu.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Creating curved lines by selecting 1st , 2nd and then 3rd point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, I will select the right-most point as the starting point of the arc.

Then, select this point here as the center point. Please note: This is the point with the coordinates (0,0,0).

And finally, I will select a point on the top-side as the end point of the arc.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the arcs and complete the sphere.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process till all arcs are created.

Remember to keep the same centre point for all the arcs.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Selecting the option ruled surface

and then selecting respective edges
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now select '''ruled surface '''option from the left-hand side menu, to create the curved surface.

Select the bounding edges for the surface, as demonstrated here.

Notice that the selected edges are now in red colour.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Press E

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Press E on the keyboard to execute this selection.

You can see that the surface has been created.

This is indicated by the dotted line, as shown here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the surfaces

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process and create all 8 surfaces of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Show the completed sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| On completion, your sphere should look like this.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Going to home folder and opening sphere1.geo text file, by double clicking
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, go to the '''Home''' folder.

Locate and open the file '''sphere1.geo''' using '''gedit Text Editor.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"|
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Information related to the geometrical entities that we just created, are stored here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining general syntax of GMSH
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In '''GMSH, '''the general syntax is

'''Geometrical entity, identification number''' inside the parenthesis

which equals to an expression.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining syntax of point

Simultaneously highlighting the syntax
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Here, for point, the expression is

'''Point, identification number '''inside parenthesis, which is usually the next integer starting from 1

equals to X,Y,Z coordinates and the value of '''mesh element size '''inside braces.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining further on syntax of point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This value is the desired '''mesh element size'''.

The size of the mesh elements will then be computed by linearly interpolating these values on the initial mesh.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the numerical value to a variable, s
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now replace the numerical value of the points of the sphere, to a variable, '''s.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type s=0.1; at the beginning of the document
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| At the beginning, type '''s = 0.1; '''

This is for specifying the value of''' mesh element size''' of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the necessity of refinement

and typing Mesh.CharacteristicLengthFromCurvature = 0.05;
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To capture the boundary layer, we will refine the mesh near the sphere.

For this purpose, we shall use the line,

'''Mesh.CharacteristicLengthFromCurvature = 0.05;'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the syntax Mesh.CharacteristicLenghtFromCurvature
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The syntax '''Mesh.CharacteristicLengthFromCurvature'''

will adapt the''' mesh''' with respect to the curvature of the geometrical entities.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type '''Surface Loop'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For volume creation, we require all the bounding surfaces.

For this, at the end of the file, type

'''Surface Loop '''followed by its identity

which is the next integer inside parenthesis

Which equals the identities of all the surfaces of the sphere within braces.

Here, the identities are 14, 16, 18, 20, 22, 24, 26 and 28.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Saving and Closing the text file
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the '''sphere1.geo''' file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface

Select Physical Groups >> Add >> Surface option --> select all the surfaces --> Press E
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let's switch to the '''GMSH''' interface.

In the left-hand-side menu, click on '''Physical Groups''', then '''Add''', and then '''Surface '''option.

Select all the surfaces of the sphere.

Press '''E''' on the keyboard to execute this selection.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Double-click to open sphere1.geo file >> go to the last line of the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, again open '''sphere1.geo '''file in the '''Text Editor'''.

Right at the bottom, notice that a new line of code has been added.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replace this number with sphere in double inverted commas and explaining it's importance
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Replace this number with '''sphere''' within quotes.

This will help us to easily identify the boundaries of the sphere while post processing or otherwise.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Save and close the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This completes this tutorial. Let us summarize.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 6: Summary
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial we learnt to

* Create curved lines and surfaces
* Create a sphere and
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 7: Assignment
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As an assignment,

Create a '''sphere '''with a larger radius.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 8: About FOSSEE
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| '''OpenFOAM''' series is created by the '''FOSSEE Project, IIT Bombay'''.

'''FOSSEE''' stands for Free and Open Source Software for Education.

This project promotes the use of free and open source software tools.

For more details, please visit: [http://fossee.in/ http://fossee.in/]

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 9: About the Spoken tutorial project

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The video at this link summarises the Spoken Tutorial project.

Please download and watch it.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 10:

Spoken tutorials Workshops

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The Spoken Tutorial Project Team conducts workshops and gives certificates on passing online tests.

For more details, please write to us.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 11: Acknowledgement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this Mission is available at this link.

This is Pavan Mehta from FOSSEE Project, IIT BOMBAY signing off.

Thanks for joining.

|}

OpenFOAM/C3/Creating-a-sphere-in-GMSH/English

2015-08-08T14:55:22Z

Mehtapavanp:

Tutorial: Creating a sphere in GMSH

Script and Narration: Pavan Mehta

Keywords: Video tutorial, CFD, GMSH, unstructured mesh, curved lines, circular arc, ruled surface

{| style="border-spacing:0;"
| style="border-top:0.05pt solid #000000;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| <center>'''Visual Cue'''</center>
| style="border:0.05pt solid #000000;padding:0.0382in;"| <center>'''Narration'''</center>

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 1
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Hello and welcome to the spoken tutorial on '''Creating a sphere in GMSH.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 2: Learning Objective
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial, we will learn to

* Create a '''circular arc'''
* Create '''ruled surfaces'''
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 3: System requirement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To record this tutorial I am using

* '''Ubuntu Linux Operating system 14.04'''
* '''GMSH version 2.8.5'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 4: Pre-requisite
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As a pre-requisite, user should have basic knowledge of creating points.

If not, refer to the '''GMSH '''spoken tutorials in the '''OpenFOAM '''series on this website.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 5: Points for sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us begin.

* The origin of the sphere is at (0,0,0).
* And the other points of the sphere are as displayed.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to terminal

In terminal type gmsh sphere1.geo and press enter
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now open '''GMSH''' from the '''terminal.'''

To open the '''terminal, '''press '''Ctrl+Alt+T '''keys.

Now type''' gmsh sphere1.geo'''

and Press''' Enter '''

'''GMSH''' is opened.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I have already created 7 points for the sphere, as shown here.

To create the points of the sphere, kindly refer to the tutorial mentioned earlier.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| In GMSH's interface, selecting circle arc option
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I'll now demonstrate how to make a circular arc.

In '''GMSH, '''a circular arc is strictly created less than '''Pi.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select '''circle arc '''in LHS menu
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To create an arc, select '''circle arc''' option in the left-hand-side menu.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Creating curved lines by selecting 1st , 2nd and then 3rd point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, I will select the right-most point as the starting point of the arc.

Then, select this point here as the center point. Please note: This is the point with the coordinates (0,0,0).

And finally, I will select a point on the top-side as the end point of the arc.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the arcs and complete the sphere.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process till all arcs are created.

Remember to keep the same centre point for all the arcs.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Selecting the option ruled surface

and then selecting respective edges
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now select '''ruled surface '''option from the left-hand side menu, to create the curved surface.

Select the bounding edges for the surface, as demonstrated here.

Notice that the selected edges are now in red colour.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Press E

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Press E on the keyboard to execute this selection.

You can see that the surface has been created.

This is indicated by the dotted line, as shown here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the surfaces

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process and create all 8 surfaces of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Show the completed sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| On completion, your sphere should look like this.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Going to home folder and opening sphere1.geo text file, by double clicking
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, go to the '''Home''' folder.

Locate and open the file '''sphere1.geo''' using '''gedit Text Editor.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"|
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Information related to the geometrical entities that we just created, are stored here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining general syntax of GMSH
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In '''GMSH, '''the general syntax is

'''Geometrical entity, identification number''' inside the parenthesis

which equals to an expression.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining syntax of point

Simultaneously highlighting the syntax
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Here, for point, the expression is

'''Point, identification number '''inside parenthesis, which is usually the next integer starting from 1

equals to X,Y,Z coordinates and the value of '''mesh element size '''inside braces.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining further on syntax of point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This value is the desired '''mesh element size'''.

The size of the mesh elements will then be computed by linearly interpolating these values on the initial mesh.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the numerical value to a variable, s
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now replace the numerical value of the points of the sphere, to a variable, '''s.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type s=0.1; at the beginning of the document
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| At the beginning, type '''s = 0.1; '''

This is for specifying the value of''' mesh element size''' of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the necessity of refinement

and typing Mesh.CharacteristicLengthFromCurvature = 0.05;
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To capture the boundary layer, we will refine the mesh near the sphere.

For this purpose, we shall use the line,

'''Mesh.CharacteristicLengthFromCurvature = 0.05;'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the syntax Mesh.CharacteristicLenghtFromCurvature
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The syntax '''Mesh.CharacteristicLengthFromCurvature'''

will adapt the''' mesh''' with respect to the curvature of the geometrical entities.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type '''Surface Loop'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For volume creation, we require all the bounding surfaces.

For this, at the end of the file, type

'''Surface Loop '''followed by its identity

which is the next integer inside parenthesis

Which equals the identities of all the surfaces of the sphere within braces.

Here, the identities are 14, 16, 18, 20, 22, 24, 26 and 28.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"|
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the '''sphere1.geo''' file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface

Select Physical Groups >> Add >> Surface option --> select all the surfaces --> Press E
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let's switch to the '''GMSH''' interface.

In the left-hand-side menu, click on '''Physical Groups''', then '''Add''', and then '''Surface '''option.

Select all the surfaces of the sphere.

Press '''E''' on the keyboard to execute this selection.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Double-click to open sphere1.geo file >> go to the last line of the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, again open '''sphere1.geo '''file in the '''Text Editor'''.

Right at the bottom, notice that a new line of code has been added.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replace this number with sphere in double inverted commas and explaining it's importance
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Replace this number with '''sphere''' within quotes.

This will help us to easily identify the boundaries of the sphere while post processing or otherwise.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Save and close the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This completes this tutorial. Let us summarize.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 6: Summary
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial we learnt to

* Create curved lines and surfaces
* Create a sphere and
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 7: Assignment
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As an assignment,

Create a '''sphere '''with a larger radius.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 8: About FOSSEE
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| '''OpenFOAM''' series is created by the '''FOSSEE Project, IIT Bombay'''.

'''FOSSEE''' stands for Free and Open Source Software for Education.

This project promotes the use of free and open source software tools.

For more details, please visit: [http://fossee.in/ http://fossee.in/]

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 9: About the Spoken tutorial project

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The video at this link summarises the Spoken Tutorial project.

Please download and watch it.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 10:

Spoken tutorials Workshops

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The Spoken Tutorial Project Team conducts workshops and gives certificates on passing online tests.

For more details, please write to us.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 11: Acknowledgement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this Mission is available at this link.

This is Pavan Mehta from FOSSEE Project, IIT BOMBAY signing off.

Thanks for joining.

|}

OpenFOAM/C3/Creating-a-sphere-in-GMSH/English

2015-08-08T14:42:28Z

Mehtapavanp: Created page with " {| style="border-spacing:0;" | style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| <center>'''Vis..."

{| style="border-spacing:0;"
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| <center>'''Visual Cue'''</center>
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| <center>'''Narration'''</center>

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 1
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Hello and welcome to the spoken tutorial on '''Creating a sphere in GMSH.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 2: Learning Objective
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial, we will learn to

* Create a '''circular arc'''
* Create '''ruled surfaces'''
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 3: System requirement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To record this tutorial I am using

* '''Ubuntu Linux Operating system 14.04'''
* '''GMSH version 2.8.5'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 4: Pre-requisite
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As a pre-requisite, user should have basic knowledge of creating points.

If not, refer to the '''GMSH '''spoken tutorials in the '''OpenFOAM '''series on this website.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 5: Points for sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us begin.

* The origin of the sphere is at (0,0,0).
* And the other points of the sphere are as displayed.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to terminal

In terminal type gmsh sphere1.geo and press enter
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now open '''GMSH''' from the '''terminal.'''

To open the '''terminal, '''press '''Ctrl+Alt+T '''keys.

Now type''' gmsh sphere1.geo'''

and Press''' Enter '''

'''GMSH''' is opened.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I have already created 7 points for the sphere, as shown here.

To create the points of the sphere, kindly refer to the tutorial mentioned earlier.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| In GMSH's interface, selecting circle arc option
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| I'll now demonstrate how to make a circular arc.

In '''GMSH, '''a circular arc is strictly created less than '''Pi.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Select '''circle arc '''in LHS menu
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To create an arc, select '''circle arc''' option in the left-hand-side menu.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Creating curved lines by selecting 1st , 2nd and then 3rd point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, I will select the right-most point as the starting point of the arc.

Then, select this point here as the center point. Please note: This is the point with the coordinates (0,0,0).

And finally, I will select a point on the top-side as the end point of the arc.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the arcs and complete the sphere.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process till all arcs are created.

Remember to keep the same centre point for all the arcs.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Selecting the option ruled surface

and then selecting respective edges
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now select '''ruled surface '''option from the left-hand side menu, to create the curved surface.

Select the bounding edges for the surface, as demonstrated here.

Notice that the selected edges are now in red colour.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Press E

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Press E on the keyboard to execute this selection.

You can see that the surface has been created.

This is indicated by the dotted line, as shown here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Pause recording and create all the surfaces

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Repeat the process and create all 8 surfaces of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Show the completed sphere
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| On completion, your sphere should look like this.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Going to home folder and opening sphere1.geo text file, by double clicking
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, go to the '''Home''' folder.

Locate and open the file '''sphere1.geo''' using '''gedit Text Editor.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"|
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Information related to the geometrical entities that we just created, are stored here.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining general syntax of GMSH
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In '''GMSH, '''the general syntax is

'''Geometrical entity, identification number''' inside the parenthesis

which equals to an expression.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining syntax of point

Simultaneously highlighting the syntax
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Here, for point, the expression is

'''Point, identification number '''inside parenthesis, which is usually the next integer starting from 1

equals to X,Y,Z coordinates and the value of '''mesh element size '''inside braces.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining further on syntax of point
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This value is the desired '''mesh element size'''.

The size of the mesh elements will then be computed by linearly interpolating these values on the initial mesh.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replacing the numerical value to a variable, s
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let us now replace the numerical value of the points of the sphere, to a variable, '''s.'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type s=0.1; at the beginning of the document
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| At the beginning, type '''s = 0.1; '''

This is for specifying the value of''' mesh element size''' of the sphere.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the necessity of refinement

and typing Mesh.CharacteristicLengthFromCurvature = 0.05;
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| To capture the boundary layer, we will refine the mesh near the sphere.

For this purpose, we shall use the line,

'''Mesh.CharacteristicLengthFromCurvature = 0.05;'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Explaining the syntax Mesh.CharacteristicLenghtFromCurvature
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The syntax '''Mesh.CharacteristicLengthFromCurvature'''

will adapt the''' mesh''' with respect to the curvature of the geometrical entities.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Type '''Surface Loop'''
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| For volume creation, we require all the bounding surfaces.

For this, at the end of the file, type

'''Surface Loop '''followed by its identity

which is the next integer inside parenthesis

Which equals the identities of all the surfaces of the sphere within braces.

Here, the identities are 14, 16, 18, 20, 22, 24, 26 and 28.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"|
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the '''sphere1.geo''' file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Switch to GMSH's interface

Select Physical Groups >> Add >> Surface option --> select all the surfaces --> Press E
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Let's switch to the '''GMSH''' interface.

In the left-hand-side menu, click on '''Physical Groups''', then '''Add''', and then '''Surface '''option.

Select all the surfaces of the sphere.

Press '''E''' on the keyboard to execute this selection.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Double-click to open sphere1.geo file >> go to the last line of the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now, again open '''sphere1.geo '''file in the '''Text Editor'''.

Right at the bottom, notice that a new line of code has been added.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Replace this number with sphere in double inverted commas and explaining it's importance
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Replace this number with '''sphere''' within quotes.

This will help us to easily identify the boundaries of the sphere while post processing or otherwise.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Save and close the file.
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Now save and close the file.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Narration
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| This completes this tutorial. Let us summarize.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 6: Summary
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| In this tutorial we learnt to

* Create curved lines and surfaces
* Create a sphere and
* and basic manipulations using the file with extension '''.geo'''

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 7: Assignment
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| As an assignment,

Create a '''sphere '''with a larger radius.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 8: About FOSSEE
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| '''OpenFOAM''' series is created by the '''FOSSEE Project, IIT Bombay'''.

'''FOSSEE''' stands for Free and Open Source Software for Education.

This project promotes the use of free and open source software tools.

For more details, please visit: [http://fossee.in/ http://fossee.in/]

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 9: About the Spoken tutorial project

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The video at this link summarises the Spoken Tutorial project.

Please download and watch it.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 10:

Spoken tutorials Workshops

| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| The Spoken Tutorial Project Team conducts workshops and gives certificates on passing online tests.

For more details, please write to us.

|-
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:none;padding:0.0382in;"| Slide 11: Acknowledgement
| style="border-top:none;border-bottom:0.05pt solid #000000;border-left:0.05pt solid #000000;border-right:0.05pt solid #000000;padding:0.0382in;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this Mission is available at this link.

This is Pavan Mehta from FOSSEE Project, IIT BOMBAY signing off.

Thanks for joining.

|}

File:Creating-sphere-GMSH.pdf

2015-08-06T14:14:32Z

Mehtapavanp: