OpenFOAM/C2/Creating-simple-geometry-in-OpenFOAM/English

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Title of script: Creating simple geometry in OpenFOAM

Author: Rahul Ashok Joshi

Keywords: Video Tutorial,Computational Fluid Dynamics (CFD),OpenFOAM geometry


Visual Cue
Narration
Slide 1 Hello and welcome to the spoken tutorial on creating a simple geometry in OpenFOAM
Slide 2: Learning Objective In this tutorial I will show you
  • How to create a simple geometry
  • How to view the geometry in ParaView
Slide 3: System Requirement To record this tutorial I am using
  • Linux operating system Ubuntu 10.04
  • OpenFOAM version 2.1.0
  • ParaView version 3.12.0
Slide 4: System Requirement

The tutorials were recorded using the versions specified in previous slide.

Subsequently the tutorials were edited to latest versions.

To install latest system requirements go to Installation Sheet.

Only narration


run>> tutorials >> incompressible>> icoFoam >>cavity

In CFD the Pre-processing part consists of creating geometry and meshing it.

Let us take the Lid driven cavity case as an example.

I have already opened the command terminal and entered the path for lid driven cavity.

Slide 5: For OpenFOAM v 5.0

To source the OpenFOAM version 5, type:

$of5

To go to the run folder, type:

$cd $FOAM_RUN

To open the cavity case directory, type:

$cd tutorials/incompressible/icoFoam/cavity/cavity

To list the contents of case directory, type:

$ls

In the command terminal


constant>>polyMesh

There are three folders 0,constant and system.

Geometry is inside the polymesh folder of constant.

Terminal window: type cd constant In the command terminal type cd space constant and press Enter.
Type ls Now type ls and press Enter.


In this there is another folder called as polymesh.

Type cd polyMesh Type cd polymesh and press Enter.
Type ls Now type ls and press Enter.
Slide 6: For OpenFOAM v 5.0

To list the contents of the cavity directory, type: $ls 0 constant system

To open the system directory, type: $cd system

To list the contents of the system directory, type:

$ls blockMeshDict controlDict fvSchemes fvSolution

Open the blockMeshDict file.


This contains the geometry file called as blockMeshDict.

Open the blockMeshDict file with any editor of your choice.

Type gedit blockMeshDict


In the terminal type gedit blockMeshDict.

Note that M and D here are capital and press Enter.

Drag the window to the capture area


Let me drag this to the capture area.

Now minimise this.

Slides Let me switch back to the slides.
Hover over the diagram In OpenFoam the entire geometry is broken into blocks.
Block vertex starts from 0 The blocks are numbered starting from 0 as shown in the figure.
For 2D geometry enter a unit thickness cell in z axis Note that in OpenFOAM for creating a 2D geometry, you need to give cell thickness value in the z-axis.
Dimension of Cavity Lid driven cavity is of length 1 and height 1.


Minimise the slide.

Create empty file

right click >create document>empty file

On your Desktop create an empty file by right click > create document > Empty file
Name the file

right click >create document>empty file

Name this as block Mesh Dict.

(Note that M and D here are capital)

Copy data from old blockMeshDict file


upto convertToMeters


Paste

Open this.

Now copy the data from the original lid driven cavity blockMeshDict file to the new blockMeshDict file from line 0.


Scroll up. line 0 upto convertTometers.

Copy this and paste it here.


Scroll down.

Now leave some space after convertTometers.

Type 1

Type ; >> Enter


Enter

Enter 1 as the geometry is in meters.

Insert a semi-colon and press Enter.


Again press Enter.

In the blockMeshDict file >>type vertices In the file, type vertices and press Enter.
Insert (

Enter >> Tab key

Insert the open bracket and press Enter.

Press the Tab key.

Start with point 0


Start with point 0.

Insert open close brackets.

Enter.

Type (0 0 0) >> Tab key>> Open close bracket >> move to positive x axis


enter (1 0 0) >> Enter

(0 space 0 space 0) and press Enter.

Again press Tab key.

Open close bracket.


Move towards point 1 in positive x-axis and enter (1 space 0 space 0) and press Enter.

Point 2 in the x-y plane Again press the Tab key. Open close bracket.

Move towards point 2 in the positive x-y plane and enter (1 space 1 space 0)

Press Enter.

Point 3 in y direction Again press the Tab key. Open close bracket.

Enter the 3rd point in positive y axis (0 space 1 space 0 )

Press Enter.

Point 4 in the front face

enter (0 0 0.1) >> Enter

Again press the Tab key.

Enter the 4th point on the front face.

Open close bracket. (0 space 0 space 0.1)

And press Enter.

Points 5,6,7 with unit cell thickness in z axis Similarly enter the other points with one unit value in the positive z -axis.
Inert ) and ; Close the bracket and insert a semicolon after it.

Press Enter.

Again press Enter.

Type blocks and insert (


Lid driven cavity is a single block

Below vertices are the blocks.

Type blocks and press Enter.


Insert an open bracket and press Enter.

Back to slides.


Let me switch back to the slides.

Note that Lid driven cavity is taken as a single block

Switch back to blockMeshDict.

Enter the vertices of block


hex (0 1 2 3 4 5 6 7 ) total 8 points

Let me switch back to blockMeshDict.


Enter the points for the blocks in the clockwise sense.


We are using here hexahedral blocks for meshing.


Now type hex H E X, leave some space, in brackets enter (0 space 1 space 2 space 3 space 4 space 5 space 6 space 7). Again leave some space.


Note that for multiple blocks the points will be more.

Enter grid points in x, y and z axis After this enter the grid points in the x,y and z directions.
Enter the mesh/grid size

enter ( 30 30 1)

In brackets enter open close bracket 30 space 30 space 1, leave some space.


You can modify the grid as when needed.

Grid point in z axis is kept as 1 Grid point in the z-axis can be taken as one.
Enter simpleGrading value ( 1 1 1 )


insert ) and ;

Now leave some space and type simple grading.

Leave some space and enter (1 space 1 space 1).

This is the grid spacing in the x,y and z direction.

Press Enter.


Insert close bracket. Insert a semicolon and press Enter.

Again press Enter.

Type edges Now type edges and press Enter.

As this is a simple geometry, edges can be kept empty.

Insert ( ); Insert open bracket press Enter.

Close the bracket, insert a semicolon and press Enter.

Boundary conditions Below edges are the boundary conditions.
Here you need to enter the boundary name for the faces.
Type boundary


insert (

Type boundary and press Enter.


Insert an open bracket and press Enter.


Let me switch back to slides.

Slide 7 : Geometry In the geometry the upper wall is moving and other three walls are fixed.
Front and back faces are named as empty The front and back faces are termed as empty as this is a 2D problem.
Open the current blockMeshDict file Open the new blockMeshDict file again.
Boundary patch as moving wall In boundary put the name of the patch as moving wall press Enter.
Insert { Insert an open curly bracket and press Enter.
Type of moving wall : wall


insert ;

Enter the type for the moving wall. Enter type space wall


Insert a semicolon and press Enter.

Type faces Now faces. Now press Enter.

Insert open bracket, and press Enter. Press the tab key.


Open close bracket. In this bracket, enter the points for faces.

Let me switch back to the slides.
Slide 8 : Geometry Note that the order of the points should be in such a way that the thumb should be normal to the face.
Clockwise curl of fingers And fingers make a curl as shown in the figure.

The curl can be clockwise or anticlockwise.

Points should be entered matching the points inserted in vertices Also note that the points should match with the points inserted in vertices.


Now let me switch back to new blockMeshDict file.

Enter (3 7 6 2)


insert } and ;

In the faces, enter (3 space 7 space 6 space 2).

Let me switch back to the slide.


These are the points for the moving wall (3 7 6 2).

Minimize this. Note that you can start from any point on that face.


Now press Enter. Close the bracket.

You need to enter the semicolon.


After you insert the points for the faces again press Enter.

Close the curly bracket.

Another note - now after the curly brackets, press Enter. Again press Enter.

Boundary patches for fixedWalls Similarly enter boundary condition and faces for the fixed walls.
For front and back face enter type as empty Being a 2D problem, the type of boundary for front and back faces can be kept as empty.


Refer to the figure in this slide for entering the points. Minimise this.


Insert the closed brackets and put a semicolon and press Enter. Again press Enter.

Insert mergePatchPairs Type mergePatchPairs and press Enter.

Since there are no patches to be merged, it can be kept empty.


Insert open close brackets and insert a semicolon. Again press Enter.

BlockMeshDict file is completed


We are done with creating the blockMeshDict file.

The complete blockMeshDict file is as shown here.

Close the original blockMeshDict file


The command terminal will not work till blockMeshDict is closed

Close both the original blockMeshDict files.


Note that the command terminal will not work until blockMeshDict file is closed.

Type cd .. twice Switch back to the terminal.


Now type cd space (dot) (dot) twice to return back to the cavity folder. Now mesh the geometry.

Meshing, type blockMesh To do this, in the terminal type blockMesh and press Enter.
Viewing the geometry type paraFoam View the geometry by typing in the command terminal- paraFoam and press Enter.


This will open the ParaView window.

In the object inspector menu click Apply On the left hand side, click Apply on object inspector menu. Now you can see the geometry.

Now let me switch back to the slides.

Slide 9: Summary In this tutorial we learnt:
  • Creating a simple geometry in OpenFOAM
  • Viewed the geometry in ParaView

This brings us to the end of the tutorial.

Slide 10 : Assignment Assignment
  • Change the dimensions of lid driven cavity.
  • Change the grid size to (50 50 1).
  • View the geometry in ParaView
Slide 11 : About spoken tutorials Watch the video available at this URL: http://spoken-tutorial.org/What_is_a_Spoken_Tutorial


It summarizes the Spoken Tutorial project.

If you do not have good bandwidth, you can download and watch it.

Slide 12 : spoken tutorials workshops The Spoken Tutorial Project Team

-Conducts workshops using spoken tutorials

-Gives certificates to those who pass an online test

-For more details, please write to us at contact@spoken-tutorial.org

Slide 13 : Forum to answer questions

Do you have questions on THIS Spoken Tutorial? Choose the minute and second where you have the question Explain your question briefly Someone from the FOSSEE team will answer them. Please visit http://forums.spoken-tutorial.org/

Slide 14 : Forum to answer questions

Questions not related to the Spoken Tutorial? Do you have general/technical questions on the Software? Please visit the FOSSEE forum http://forums.fossee.in/ Choose the Software and post your question

Slide 15 : Lab Migration project

We coordinate migration from commercial CFD software like ANSYS to OpenFOAM We conduct free Workshops and provide solutions to CFD Problem Statements in OpenFOAM For more details visit this site: http://cfd.fossee.in/

Slide 16 : Case Study project

We invite students to solve a feasible CFD problem statement of reasonable complexity using OpenFOAM We give honorarium and certificate to those who do this For more details visit this site: http://cfd.fossee.in/

Slide 17 : Acknowledgement Spoken Tutorials are part of Talk to a Teacher project,

It is supported by the National Mission on Education through ICT, MHRD, Government of India.

More information on the same is available at the following URL link http://spoken-tutorial.org/NMEICT-Intro

About the contributor This is Rahul Joshi from IIT BOMBAY signing off.

Thanks for joining.

Contributors and Content Editors

Chandrika, DeepaVedartham, Nancyvarkey, Rahuljoshi

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