| Visual Cue
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Narration
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| Slide 1:
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Hello and welcome to the spoken tutorial on modelling turbulent flow in a Lid Driven Cavity using OpenFOAM
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| Slide 2:
Learning Objectives
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In this tutorial I will show you
Solving turbulent flow case in OpenFOAM
Plotting streamlines in Paraview
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| Slide 3:
System Requirement
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To record this tutorial I am using Linux operating system Ubuntu 12.04
OpenFoam version 2.1.1
Paraview version 3.12.0
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| Slide 4 :
Prerequisites
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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
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| Demo:
Set up working Directory
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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
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| Slide 5: Solver
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We will be using the Transient solver for incompressible,
turbulent flow of Newtonian fluids.
It is called pisoFoam
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| Steps in setting up the problem
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Now let me open the terminal window
To do this press Ctrl+Atl+t keys simultaneously on your keyboard.
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| In the terminal window
Go to the pisoFoam folder
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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
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| Two Folders les and ras
Cavity folder inside RAS
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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
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| Cavity folder
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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
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| Boundary and Initial conditions
0 folder
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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.
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| 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
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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.
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| Let us view the constant folder
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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
Now type ls and press enter
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| PolyMesh folder and fluid property files
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In this you will see the polyMesh folder containing the geometry
of the case inside blockMeshDict
And the fluid properties.
In this case you will see two more files
other than transportProperties named as
RASProperties and turbulenceProperties
Let us open these two files
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| RASProperties
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In the terminal type gedit (space) RASProperties and press enter.
Let me drag this to the capture area
Scroll Down
RASProperties contain the Reynolds average stress model for this case.
Which is kept as kepsilon
close this
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| turbulentProperties
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Now in the command terminal now type
gedit (space) turbulentproperties and press enter
turbulentProperties contain the turbulent model ,
Simulation type model for this case is kept as RASModel
Close this
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| TransportModel
Change the value of viscosity
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Now let us open the transportProperties file
In the terminal window type transportProperties and press enter.
The transportModel we are using here is Newtonian and
Viscosity is kept as 1 e raise to -4
close this
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| Do ot change the blockMeshDict file
The system folder is to be kept default
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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
In the terminal type cd .. and press enter
We will keep the system folder default
As there are no changes inside it
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| Meshing the geometry
blockMesh
Meshing is done
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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
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| Running the solver : pisoFoam
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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.
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| Post-processing the results in paraview
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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
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| View the geometry
Lid driven cavity geometry
Change the drop down menu from solid color to U
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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
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| Click on the Play button on VCR control for animation
Toggle on the color legend
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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
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| Visualise the streamlines
Filters > Common > Stream Tracers
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To visualise the stream lines
On the top menu bar of paraview
Go to Filters > Common > Stream Tracers
Click on it
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| Streamlines on top of the
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On the left hand side of the Object inspector menu click on Apply.
You can see the stream lines at the center of the lid driven cavity.
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
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| Plot streamlines about X, Y and Z axis
Click on the Y axis
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You can see the X, Y and Z axis 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
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| Plot data over line
Save as .csv format
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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
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| Plot the results
Validate the results with Ghia et.al.
For Re= 10000
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You can plot this data in libreoffice 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
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| Slide :
Summary
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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
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| Slide : Assignment
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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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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.
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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
contacts@spoken-tutorial.org
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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
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| About the contributor
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The script is contributed by Shekhar Mishra and Chaitanya talnikar
This is Rahul Joshi from IIT BOMBAY signing off.
Thanks for joining
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