OpenFOAM/C3/Turbulent-Flow-in-a-Lid-driven-Cavity/English

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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 :


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 revelent 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 Lid velocity , U =1m/s


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

Slide 5: Solver We will be using the Transient solver for incompressible,


turbulent flow of Newtonian fluids.


It is called pisoFoam



Steps in setting up the problem Now let me open the terminal window


To do this press Ctrl+Atl+t keys simultaneously on your keyboard.



In the terminal window


Go to the pisoFoam folder

In the terminal window type run and press enter


Now type cd tutorials and press enter


type cd incompressible and press enter


type cd pisoFoam (Note that F here is capital ) and press enter

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



Cavity folder Our folder name is cavity.


Now type cd ras and press enter


Now type ls and press enter


You can see the cavity folder


type cd cavity and press enter


Now type ls and press enter

Boundary and Initial conditions


0 folder

In this you will 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


ls to view the files inside this folder


Do not edit the files unitil inlet parameters don't change


Refer to the earlier tutorial on channel flow for calculating these values


Type the following command

cd 0 and press enter


Now type ls and press enter


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.



Let us view the constant folder Now type cd .. and press enter


Let me clear this off


Let us open the constant folder.


To do this type cd constant 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.


In this you will see two more files named RASProperties and turbulenceProperties


Let us open these two files

RASProperties In the terminal type gedit RASProperties and press enter.


RASProperties contain the Reynolds average stress model for the case.


Which is kept as kepsilon


close this

turbulentProperties in the terminal now type gedit turbulentproperties and press enter


Scroll down


turbulentProperties contain the turbulent model ,


Simulation type for this case is kept as RASModel

TransportModel


Change the value of viscosity

In the terminal window type cd ..

and press enter.


The transportModel we are using here is Newtonian


Viscosity is kept as 1 e raise to -4


close this file

Do ot 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


and look at the blockMeshDict file


It can be kept as it is


In the terminal type cd .. and press enter


We will keep the system folder default


As there are no changes inside it

Meshing the geometry


blockMesh


Meshing is done

We are done with the setup


Now we can mesh the geometry


To do this in the teminal 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 till the iterations stop.

Post-processing the results in paraview Iterations 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

Click on the Play button on VCR control for animation


Toggle on the color legend

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.


Also toggle on the color legend on the left hand side top


of paraview active variable control menu.


Click on it

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


You can see the stream lines near the top surface of moving wall.


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


To do this scroll down


You can see the seed type


Let me shift this to the right


and change the seed type from point source to line source

Plot streamlines about X, Y and Z axis


Click on the Y axis


X, Y and Z axis are visible select any one of these axis


in which you would like to view the stream lines.


Click on the Y axis


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 libreoffice spreadsheet or any other plotting software of your choice

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 :

Summary

Thats all we have in this tutorial

Let us summarise

In this tutorial we learnt Turbulent Flow in a Lid Driven Cavity

And plotting streamlines in paraView

This brings us to the end of the tutorial

Slide : Assignment As an assignment

Modify the grid size of the cavity

Change it to (100 100 1)

Visualise the results in paraview using streamlines

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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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