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Revision as of 11:31, 30 July 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 case in OpenFOAM and
  • Plotting streamlines in ParaView
Slide 3:


System Requirement

To record this tutorial I am using
  • Linux operating system Ubuntu version 12.04
  • OpenFoam version 2.1.1 and
  • 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 condition 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 is 1 m/s


And we are solving this for a Reynolds number Re equal to 10000

Slide 6: Solver We are using a 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 Now type cd space incompressible and press Enter
Type cd pisoFoam Now 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 setup is 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


Now 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


Now 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 space 0 and press Enter


Now type ls and press Enter

Point to the files as per narration You can see the 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


The 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 space transportProperties and press Enter


The transportModel we are using here is Newtonian and the 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 as there are no changes inside it

Meshing the geometry


blockMesh


Meshing is done

Now, we are done with the setup


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 visualization is surface plots


Change the display to Surface in the column and from the drop down menu change from solid colour to capital 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 the top of the ParaView window you can see the VCR control


Click on the Play button


You can see the motion of the fluid inside the cavity


You can also toggle on the colour legend from 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


Now to visualise the stream lines
  • On top of the menu bar of ParaView
  • Go to Filters > Common and Stream Tracer
  • 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 centre 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 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 the streamlines along the X axis


Now delete this

Plot data over line


Save as .csv format

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

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

Save the data as dot csv file from the 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 using results of Ghia et.al for Reynolds Number , Re equal to 10000

Slide 7:

Summary

That's all we have in this tutorial

Let us summarise.

  • 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
  • And 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

contact at the rate spoken hyphen tutorial dot 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 project is a part of the Talk to a Teacher project

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

More information on the this mission is available at this URL 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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