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Revision as of 09:17, 29 June 2019

Tutorial: Turbulent flow in a lid driven cavity


Script : Chaitanya Talnikar, Shekhar Mishra , Rahul Joshi


Narration : Rahul Joshi


Keywords: Video tutorial ,CFD,Turbulent Flow in Lid driven cavity,OpenFOAM.


Visual Cue
Narration
Slide 1: Hello and welcome to the spoken tutorial on modelling Turbulent flow in a Lid Driven Cavity using OpenFOAM
Slide 2:


Learning Objectives

In this tutorial I will show you
  • Solving turbulent flow case in OpenFOAM
  • Plotting streamlines in ParaView
Slide 3:


System Requirement

To record this tutorial I am using
  • Linux operating system Ubuntu 12.04
  • OpenFoam version 2.1.1
  • 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
Slide 5 :


Prerequisites

To practice this tutorial you should have some basic knowledge of
  • Turbulence modelling
  • Knowledge of how to solve flow in a Lid driven cavity
  • If not so please refer to the relevant tutorial on our website.
Demo:

Set up working Directory


This problem is identical in geometry and boundary conditions to the 'Lid Driven Cavity' problem discussed in the basic level tutorial.


Please make a note - this problem is already set up in pisoFoam solver in OpenFoam directory.


The boundary conditions are the Lid velocity U =1 m/s


And we are solving this for a Reynolds number Re =10000

Slide 6: Solver We will be using the Transient solver for incompressible turbulent flow of Newtonian fluids called as pisoFoam
Steps in setting up the problem Now let us open the Terminal window by pressing Ctrl+Atl+T keys together.
In the terminal window

Type cd tutorials

In the terminal window type run and press Enter.


Now type cd space tutorials and press Enter.

Type cd incompressible Type cd space incompressible and press Enter.
Type cd pisoFoam Type cd space pisoFoam (Note that F here is capital ) and press Enter.
Type ls


Two Folders les and ras


Cavity folder inside RAS

Now type ls and press Enter.


In this you will see two folders les and ras


Our problem is setup inside ras folder which is called as reynolds averaged stress.

Type cd ras


ls

Our folder name is cavity.


Now type cd space ras and press Enter.


Now type ls and press Enter.

Type cd cavity

ls

You can see the cavity folder. Let me clear this off.


Type cd space cavity and press Enter.


Now type ls and press Enter.

Point to the 3 folders

Boundary and Initial conditions


0 folder

You can see three folders 0, constant and system.


The initial conditions are specified within the files in the '0' directory.


Let us take a look at the files in the '0' directory.

Inside the 0 folder


Type ls

To do this, in the command terminal type cd 0 and press Enter.


Now type ls and press Enter.

Point to the files as per narration You can see files named as epsilon, k, nut, nutilda, p, R and U.


These files are to be kept as default until the inlet parameters don't change.


If any changes are to be done please refer to the tutorial on Simulating flow in a channel using OpenFoam, to calculate these values.

Type cd.. Now type cd space dot dot and press Enter.


Let me clear this off.

Type cd constant

Type ls

Let us open the constant folder.


To do this type cd space constant and press Enter.


Now type ls and press Enter.

PolyMesh folder and fluid property files In this you will see the polyMesh folder containing
  • the geometry of the case inside blockMeshDict
  • and the fluid properties.
Point to the two files as per narration In this case you will see two more files other than transportProperties named as RASProperties and turbulenceProperties.


Let us open these two files.

RASProperties In the terminal type gedit (space) RASProperties and press Enter.


Scroll down.


RASProperties contain the Reynolds average stress model for this case, which is kept as kEpsilon


Close this.

turbulentProperties Now in the command terminal, type gedit space turbulentproperties and press Enter.


Scroll down.


Simulation type model for this case is kept as RASModel.


Close this.

TransportModel


Change the value of viscosity

Now let us open the transportProperties model.


To do this, in the terminal type gedit transportProperties and press Enter.


The transportModel we are using here is Newtonian and Viscosity is kept as 1 e raise to -4


Close this.

Do not change the blockMeshDict file


The system folder is to be kept default

We are not changing the geometry in this case.


So we need not go inside the polyMesh folder and look at the blockMeshDict file.


It can be kept as it is.

Type cd.. In the terminal type cd space dot dot and press Enter.


We will keep the system folder default ss there are no changes inside it.

Meshing the geometry


blockMesh


Meshing is done

Now, we are done with the setup.


Now we can mesh the geometry.


To do this in the terminal window type blockMesh and press Enter.


Meshing has been done.

Running the solver : pisoFoam Now we can run the solver.


To do this in the terminal type pisoFoam and press Enter.


The iterations running can be seen in the terminal window.


It may take some time for the iterations to stop.

Post-processing the results in paraview The iterations running will stop at the end of the time step.


To visualize the results let us open the ParaView window.


To do this in the terminal type paraFoam and press Enter.


This will open the ParaView window.

View the geometry


Lid driven cavity geometry


Change the drop down menu from solid color to U

On the left hand side in the Object Inspector menu click on Apply.


You can see the lid driven cavity geometry.


A common visualisation is surface plots.


Change the display to Surface in the column and from the drop down menu change from solid color to U


You can see the initial condition of velocity.

Click on the Play button on VCR control for animation


Toggle on the color legend

Now on top of the ParaView window you can see the VCR control.


Click the Play button.


You can see the motion of the fluid inside the cavity.


You can also toggle on the color legend on the left hand side top of ParaView active variable control menu.


Click on it. You can see the colour legend.

Visualise the streamlines


Filters > Common > Stream Tracers


To visualise the stream lines
  • On the top menu bar of ParaView
  • Go to Filters > Common > Stream Tracers
  • Click on it
Streamlines on top On the left hand side of the Object inspector menu you can see Apply. Click on it.


You can see the stream lines at the center of the lid driven cavity.

Streamlines view You can also change the orientation in which the stream lines are viewed.


To do this , scroll down.


You can see the seed type.

Shift to right >> change point source to line source. Let me shift this to the right and change from point source to line source.
Plot streamlines about X, Y and Z axis


Click on the Y axis

Click on the X axis

Delete this.

You can see the X, Y and Z axes which are visible.


Select any one of these axis in which you would like to view the stream lines.


I will select the Y axis and click Apply.


You can see the streamlines along the Y axis.


Similarly you can select the X axis and plot streamlines along the X axis.


Now delete this.

Plot data over line


Save as .csv format

You can also plot the velocity along the X and Y axis using plot over line.

To do this go to Filter > Data Analysis > Plot over line.

Save the data as .(dot) csv file from file menu.

Click on Save Data.

Plot the results


Validate the results with Ghia et.al.

For Re= 10000

You can plot this data in libre office spreadsheet or any other plotting software of your choice.

Now let me switch back to the slides.

The results obtained can be validated by results obtained by Ghia et.al for Reynolds No , Re= 10000

Slide 7:

Summary

That's all we have in this tutorial.

Let us summarise.

In this tutorial we learnt

  • Turbulent Flow in a Lid Driven Cavity
  • and plotting stream lines in ParaView

This brings us to the end of the tutorial.

Slide 8: Assignment As an assignment
  • Modify the grid size of the cavity
  • Change it to (100 100 1)
  • Visualise the results in ParaView using streamlines
  • 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.
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 9:

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 10:

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 11:

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 12:

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 13: Acknowledgements 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.

This project is coordinated by http://spoken-tutorial.org

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

About the contributor The script is contributed by Shekhar Mishra and Chaitanya talnikar

This is Rahul Joshi from IIT BOMBAY signing off.

Thanks for joining

Contributors and Content Editors

DeepaVedartham, Nancyvarkey, Pravin1389, Rahuljoshi

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