View source for OpenFOAM-version-7/C2/Setting-up-a-Test-Case-in-OpenFOAM/English

'''Title of the script''': Setting-up a test case in OpenFOAM

'''Author''': Ashley Melvin

'''Keywords''': OpenFOAM, ParaView, lid driven cavity, pre-processing, blockMesh, controlDict, post-processing, video tutorial



{| border = "1"
|- 
|| '''Visual Cue'''
|| '''Narration'''
|- 
|| Slide: Opening Slide
|| Hello and welcome to this tutorial on '''Setting up a test case in OpenFOAM'''.
|- 
|| Slide: Learning Objective
|| In this tutorial, we will learn to:
* Set up a '''case''' in '''OpenFOAM'''
* Access the '''case files''' using '''terminal'''
* '''Pre-process''' a '''case'''
* '''Run''' a '''case''', and
* '''Post-process''' a '''case'''
|- 
|| Slide: System Specifications
|| This tutorial is recorded using,
* '''Ubuntu Linux''' OS version 18.04
* '''OpenFOAM''' version 7
* '''ParaView''' version 5.6.0, and
* '''gedit Text editor'''

You may use any other '''text editor''' of your choice.
|- 
|| Slide: Prerequisites



|| As a prerequisite:
* You should be familiar with basic '''Linux commands'''.
* If not, please go through the prerequisite '''Linux '''tutorials on this website.
|- 
|| Slide: Lid Driven Cavity
|| In this tutorial, we will learn to set up the '''lid driven cavity case'''.

'''Lid driven cavity''' is one of the most widely used '''2D test cases''' for the validation of a '''CFD '''code.
|- 
|| Slide: Diagram
|| This is the diagram of '''Lid Driven Cavity Flow'''.

It consists of 3 fixed walls and a moving top wall.
|-
|| Highlight '''Terminal''' on the machine
|| Open a '''terminal''' by pressing the '''Ctrl, Alt '''and''' T''' keys together.
|-
|| Only Narration
|| Here onwards please remember to press the '''Enter''' key after typing each '''command'''.
|-
|| [Terminal] Type:
'''mkdir -p $FOAM_RUN'''
|| Now, let’s create a '''RUN directory'''.

To do so, type the '''command''' as shown.
|- 
|| [Terminal] Highlight

'''FOAM_RUN'''
|| '''Tutorial cases''' will later be copied into the '''RUN directory'''.
|- 
|| [Terminal] Type:

'''cd $FOAM_RUN'''
|| Go to the '''RUN directory''' using the '''cd command'''.

Now our present working directory is the '''RUN directory'''.
|- 
|| Only Narration
|| '''OpenFOAM''' installation comes with a set of '''test cases'''.

The '''TUTORIALS directory''' contains these '''test cases'''. 

The '''Lid driven cavity case''' already exists inside the '''TUTORIALS directory'''.
|- 
|| [Terminal] Type:

'''cp -r $FOAM_TUTORIALS/incompressible/icoFoam/cavity/cavity .'''
|| We’ll now copy the '''Lid driven cavity case''' from the '''TUTORIALS directory''' into the '''RUN directory'''.

To do so, type the following '''command'''.
|- 
|| Slide: blockMesh
|| 
* The '''mesh generator''' for '''OpenFOAM''' is a utility called '''blockMesh'''.
* The '''input dictionary''' for '''blockMesh''' utility is '''blockMeshDict'''.
|- 
|| [Terminal] Type:

'''gedit cavity/system/blockMeshDict'''
|| The '''blockMeshDict''' file is located in the '''system''' folder.

Open the '''blockMeshDict''' file in a '''text editor'''.
|- 
|| [gedit - '''blockMeshDict'''] Highlight

vertices, blocks, edges and boundary
|| Now let’s look at the contents of the file.

The '''blockMeshDict''' contains details of the geometry like vertices, blocks, edges and boundaries.
|- 
|| [gedit - '''blockMeshDict'''] Close the window
|| Close the '''blockMeshDict''' file.
|- 
|| [Terminal] Type:

'''cd cavity/0'''
|| The '''0''' folder contains the '''initial''' and '''boundary conditions''' for the '''simulation'''.

Type the following '''command''' to move into the '''0''' folder inside the '''cavity case directory'''.
|- 
|| [Terminal] Type: 

'''ls'''
|| Type '''ls''' and press '''Enter''' to view the files in the '''0''' folder.
|- 
|| [Terminal] Highlight 

'''p''' and '''U''' 
|| The '''0''' folder contains the '''kinematic pressure file p''' and the '''velocity file U'''.
|- 
|| [Terminal] Type:

'''gedit p'''
|| Open the '''kinematic pressure file p''' in a '''text editor'''.
|- 
|| Only Narration
|| The '''p''' file contains the '''initial''' and '''boundary conditions''' of '''kinematic pressure'''.
|- 
|| [gedit - '''p'''] Highlight

'''dimensions [0 2 -2 0 0 0 0] '''
|| The '''dimensions''' of '''kinematic pressure''' is meter squared per second squared. 
|- 
|| [gedit - '''p'''] Highlight

'''internalField '''
|| The '''internalField''' defines the values in the interior of the domain.
|- 
|| [gedit - '''p'''] Highlight

'''uniform 0'''
|| The initial field is set as '''0 kinematic pressure'''.

This field is '''uniform''' across the domain.
|- 
|| [gedit - '''p'''] Highlight

Both the '''zeroGradient'''
|| You can see that all walls are imposed with a '''zero gradient pressure boundary condition'''.
|- 
|| [gedit - '''p'''] Close the window
|| Let us close the '''p''' file.
|- 
|| [Terminal] Type:

'''gedit U'''
|| Now open the '''velocity file U''' in a '''text editor'''.
|- 
|| Only Narration
|| The '''U file''' contains the '''initial''' and '''boundary conditions''' of '''velocity'''.
|- 
|| [gedit - '''U'''] Highlight

'''uniform (1 0 0);'''
|| You can see that the moving wall is imposed with a '''velocity''' of '''1 m/s''' in the x direction.
|- 
|| [gedit - '''U'''] Highlight

'''noSlip '''
|| Also notice that the '''no-slip condition''' is imposed on the three fixed walls.
|- 
|| [gedit - '''U'''] Close the window
|| Now let us close the '''U''' file.
|- 
|| [Terminal] Type:

'''cd ..'''
|| We’ll go back to the '''cavity''' folder.

Type '''cd (space)(dot)(dot)'''
|- 
|| [Terminal] Type:

'''gedit constant/transportProperties'''
|| Next, we will view the '''transport properties file '''which is in the '''constant '''folder.
|- 
|| [gedit - '''transportProperties'''] Highlight 

'''nu '''
|| The '''transportProperties''' file contains the details of '''kinematic viscosity'''.
|- 
|| [gedit - '''transportProperties'''] 

Highlight '''[0 2 -1 0 0 0 0] '''
|| The dimensions of '''kinematic viscosity''' is meter squared per second.
|- 
|| Slide: Kinematic Viscosity
|| 
The '''kinematic viscosity''' is defined by:
'''''nu'' equals magnitude of ''U'' times ''d'' by ''Re'''''

where 
*'''velocity''' is '''1 m per second'''
*characteristic length is '''0.1 meters'''


The '''Reynolds number (Re)''' for the '''flow''' is taken as '''10'''.


The '''kinematic viscosity''' is therefore '''0.01 meter squared per second'''
|- 
|| Narration Only
|| Now let me switch back to '''transportProperties''' file.
|- 
|| [gedit - '''transportProperties'''] 

Highlight '''0.01'''
|| The value of '''kinematic viscosity''' is indicated in the '''transportProperties''' file.
|- 
|| [gedit - '''transportProperties'''] Close the window
|| Close the '''transportProperties''' file.
|- 
|| [Terminal] Type:

'''cd system'''
|| To move into the '''system''' folder, type the following '''command'''.
|- 
|| [Terminal] Type:

'''ls'''
|| Type '''ls''' to view the contents of the '''system''' folder.
|- 
|| [Terminal] Highlight 


'''blockMeshDict controlDict fvSchemes fvSolution''' 
|| The '''system''' folder contains the following files:

'''blockMeshDict, controlDict, fvSchemes''' and '''fvSolution'''.
|- 
|| [Terminal] Highlight 

'''fvSchemes'''
|| The '''fvSchemes dictionary''' contains the '''finite volume discretisation schemes'''.
|- 
|| [Terminal] Highlight 

'''fvSolution'''
|| The '''fvSolution dictionary''' contains the '''linear equation solvers''' and '''tolerances'''.

It contains other '''algorithm controls''' as well.
|- 
|| [Terminal] Highlight 

'''controlDict'''
|| The '''controlDict dictionary''' contains the '''simulation control parameters'''. 

The '''dictionary''' input includes the '''control''' of '''time''' and '''reading''' and '''writing''' of the '''solution data'''.
|- 
|| [Terminal] Type: 

'''gedit controlDict'''
|| Let’s open the '''controlDict''' file in a '''text editor'''.
|- 
|| [Terminal] Highlight 

'''startFrom '''and '''startTime'''
|| The '''start '''and''' stop times''' and the '''time step''' for the '''run''' must be set.
|- 
|| [gedit - '''controlDict'''] Highlight 

'''startTime''' '''0;'''
|| The '''start time''' is set at '''0''' seconds.
|- 
|| [gedit - '''controlDict'''] Highlight 

'''stopAt''' '''endTime;'''
|| The time at which the '''simulation''' stops, is specified using the '''keyword stopAt'''.

Here, '''stopAt''' is specified using the keyword '''endTime'''.
|- 
|| [gedit - '''controlDict'''] Highlight

'''endTime''' '''0.5;'''
|| The '''endTime''' is set at '''0.5 seconds'''.

This means that '''simulation''' stops after '''0.5 seconds'''.
|- 
|| [gedit - '''controlDict'''] Highlight

'''deltaT 0.005;'''
|| The value of the '''keyword deltaT''' defines the '''time step''' for the '''simulation'''.

The '''time step''' for the current '''simulation''' is set as '''0.005 seconds'''.

'''Temporal accuracy''' and '''numerical stability''' is essential while running the '''simulation'''.

To achieve this, a''' Courant number''' of less than 1 is required.

Keeping this in mind, the '''time step''' is set to '''0.005 seconds'''.

Please refer to the '''additional reading material''' on this tutorial page for details.

It mentions the steps used to calculate the '''time-step'''. 
|-
|-
|- 
|| [gedit - '''controlDict'''] Highlight

'''application''' '''icoFoam'''<nowiki>;</nowiki>
|| '''icoFoam''' is the '''OpenFOAM solver''' used to '''simulate''' the '''lid driven cavity flow'''.
|- 
|| [gedit - '''controlDict'''] Close the window
|| Close the '''controlDict''' file.
|- 
|| [Terminal] Type:

'''cd ..'''
|| Go back to the '''cavity''' folder using '''cd command'''.
|- 
|| [Terminal] Type:

'''blockMesh''' >> '''Enter'''
|| Type the '''command blockMesh''' and press '''Enter''' to '''mesh''' the geometry.

The '''command''' takes input from the '''blockMeshDict dictionary''' and creates the geometry and '''meshes''' it.
|- 
|| [Terminal] Highlight '''End'''
|| The '''meshing''' is now complete.
|- 
|| [Terminal] Type:

'''icoFoam'''
|| The '''lid driven cavity flow''' is an '''incompressible flow'''.

It is solved using the''' OpenFOAM solver icoFoam.'''

To start the '''simulation''', type '''icoFoam''' in the '''terminal.''' 
|- 
|| [Terminal] Highlight '''End'''
|| The iterations are now complete.
|- 
|| [Terminal] Type:

'''paraFoam'''
|| Let us view the '''simulated''' results in '''ParaView'''.


So, type '''paraFoam''' in the '''terminal.'''
|- 
|| [ParaView] '''Properties''' Tab

Click on '''Apply'''
|| In the '''ParaView''' window, go to the '''Properties''' tab on the left.

Then click on the green coloured '''Apply '''button.
|- 
|| [ParaView]

Click on '''vtkBlockColors''' >> Click on '''U'''
|| Go to the '''Active Variable Controls '''at the top. 

Click on the '''vtkBlockColors''' dropdown and select '''U'''.

Ensure that you click on the '''U''' option with a '''point icon''' and not the '''box icon''', in the dropdown.

The '''box icon''' would display '''contours''' without any grading.
|- 
|| [ParaView] 

Velocity Contours in the Layout
|| The '''velocity contour''' at the start of the '''simulation''' is now displayed in the''' layout'''.
|- 
|| [ParaView]

Go to '''VCR Controls''' and click on the '''Play''' Button
|| Let us see how the '''velocity contours''' develop through the '''simulation'''.

To do so, go to the '''VCR Controls''' and click on the '''Play''' button.
|- 
|| [ParaView] 

Final Velocity Contours in the Layout
|| The '''velocity contour''' at the end of the '''simulation''' is now displayed in the''' layout'''.
|- 
|| [ParaView] Close the Window
|| Close the '''ParaView''' window.
|- 
|| Only Narration
|| With this we have come to the end of the tutorial.

|- 
|| Slide: Summary
|| To summarise, in this tutorial we have learnt to:
* Set up a''' case''' in '''OpenFOAM'''
* Access the '''case files''' using '''terminal'''
* '''Pre-process''' a '''case'''
* '''Run''' a '''case''', and
* '''Post-process''' a '''case'''
|-
|| Slide: About the Spoken Tutorial Project
|| The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.
|-
|| Slide: Spoken Tutorial Workshops
|| We conduct workshops using Spoken Tutorials and give certificates.

Please contact us.
|-
|| Slide: Spoken Tutorial Forum
|| Please post your timed queries in this forum.
|-
|| Slide: FOSSEE Forum
|| 
* Do you have any general/technical questions?
* Please visit the forum given in this link.
|-
|| Slide: FOSSEE Case Study Project
|| 
* The FOSSEE team coordinates solving feasible '''CFD''' problems of reasonable complexity using '''OpenFOAM'''.
* We give honorarium and certificates to those who do this.
* For more details, please visit these sites.
|- 
|| Slide: Spoken Tutorial 
|| The Spoken Tutorial project is supported by MHRD, Govt. of India.

The script for this tutorial is contributed by Ashley Melvin.

And this is Swetha Sridhar from IIT Bombay signing off.

Thank you for joining.
|-
|}