| 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 Simulating 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
The Lid Driven Cavity file structure
Meshing the Geometry
Solving and post-processing results in Paraview
Plotting & validating results on a spreadsheet.
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| Slide 3:
System Requirement
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To record this tutorial
I am using Linux Operating system Ubuntu version 10.04 .
OpenFOAM version 2.1.0
ParaView version 3.12.0
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| Slide 4:
About Lid Driven Cavity flow
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Lid driven cavity is the most widely used 2D test
case for validation of a CFD code
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| Slide 5 : Diagram
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This is diagram of Lid Driven Cavity .
The boundary conditions remain the same.
A moving wall and three fixedwalls
We are solving this for Reynolds no (Re) = 100
The moving wall has a velocity of 1 meters per second
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| Demo.
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The path for the Lid Driven Cavity is the same as discussed in the installation tutorial.
Now Open a command terminal and
To do this press Ctrl+Alt+t simultaneously on your keyboard
In the command terminal type the path for lid driven cavity
type run and press enter
cd (space) tutorials and Press enter
cd (space) incompressible and Press enter
cd (space) icoFoam (Note that F here is capital) and Press enter
type cd (space) cavity and Press Enter
type ls and press enter
In the file structure of cavity you will see 3 folders :
0 , constant , and system.
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| Demo
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Now type cd (space) constant and press enter
Now type ls and press enter
The constant folder contains another folder named polymesh
and a file describing the physical properties of fluid.
Now type cd (space) polymesh and Press Enter
Polymesh contains a file named blockMeshDict
Now type ls and press enter
You can see the blockMeshDict
To view the file type gedit blockMeshDict
(Note that M and D here are capital)
Now press enter
This will Open up the blockMeshDict file
Let me drag this to the capture area
This contains :
-cordinates for lid driven cavity
-blocking and meshing parameters
-and boundary patches.
Since there are arcs as well as no patches to be merged
edges and mergePatchPairs can be kept empty.
Now close this
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| Demo
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In the command terminal type : cd (space) .. (dot) (dot)
do this twice
you will come back to the cavity folder
Now type cd (space) system and press enter,
Now type ls and press enter
this contains three files
controlDict, fvSchemes and fvSolutions
controlDict contains control parameters for start/end time.
fvSolution contains discritization schemes used in run time.
fvSchemes contains equation for solver,
tolerance etc.
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| Demo:
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Now again type cd (space) (dot dot) . . and press enter
Now type cd ( space ) 0 (zero) and Press enter
Now type ls and press enter
This contains the initial values for boundary conditions like
Pressure ,Velocity,Temperature etc.
Type cd ( space ) (dot dot) . . to return to the cavity folder.
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| Demo
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Now we need to mesh the geometry
We are using a course mesh here.
Mesh the geometry by typing blockMesh in the terminal.
Now type blockMesh (Note that M and D here is capital)
and press enter
The meshing is done.
If there is some error in the blockMesh file
it will be shown in the terminal.
To view the geometry
Type paraFoam , Note that F here is capital
and press enter
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| Demo:
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This will open the paraview window
Now on the left hand side of the object inspector menu click on Apply.
You can see the lid driven cavity geometry
close this
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| Demo:
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Check the mesh by typing checkMesh in the terminal
Note that M here is capital
and press enter
you can see the the number of cells ,
skewness and other parameters
which are associated with the mesh
let me switch back to the slides.
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| Slide 6 : icoFoam
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The solver we are using here is icoFoam :
icoFoam is a Transient solver for incompressible flow of newtonian fluids.
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| Demo :
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Let me switch back to the terminal
In the terminal type icoFoam
Note that F here is capital
and press enter
Iterations running will be seen in the terminal window.
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| Demo
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Once the solving is done
type paraFoam in the terminal
to view the geometry and the results
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| Demo
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On the left hand side of object inspector menu
click on Apply
Now Scroll down the properties panel
of the objector inspector menu
for time step,regions and volume fields etc
Check or uncheck these boxes in the mesh part
to view the different boundary regions of Lid driven cavity
Now after this on top of the active variable control
dropdown menu change from solid color to capital p or U
which are the initial conditions such as pressure or velocity
I will select capital U
Now this will show the initial condition of velocity
Now on top of the paraview window you can see the VCR control
Click on the play button
Now this is the final result of velocity for lid driven cavity
Toggle on the color legend by clicking on
top left of the active variable control menu
This is the color legend for U velocity
We need to validate the results obtained
To do this let us plot the U and V velocity
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| Demo
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We need to validate the result obtained to do this let us plot the U and V velocity.
For this Go to Filters Menu > Data Analysis > Plot Over line
Click on it
You can see the X , Y and Z axis
Select the X & Y axis turn by turn.
I will select the X axis and click Apply
You can see the Pressure and velocity plots being plotted.
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| Demo:
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Since it is a non dimensional analysis
we need to plot the graph for u/U v/s y/L for Reynolds number =100
To do this in Plot Data click on the Y-axis
And click APPLY
You can see the plot
In menu bar go to File > Save Data
Give and appropriate name to your file
I will give this as cavity
The file will be saved as .csv file
Now click ok
Again click ok
Now go to the cavity folder of openfoam directory.
Scroll down you can see the cavity.csv file
Open it in Open office or LibreOffice Spreadsheet
In the libreoffice spreadsheet copy
the U0 (u velocity) and to the right points1(Y-axis) columns
in another spreadsheet
Now divide both these coloumns
that is u zero by capital U and points 1 by capital L
Plot the results in libreoffice charts option on top of the menu bar.
Now let me switch back to the slides
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| Slide 7 : Lid Driven Cavity (OpenFOAM)
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Results obtained will be similar to this figure.
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| Slide 8: Ghia et al.(1982) & Fluent
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Validate the result obtained on Lid Driven Cavity by : Ghia et al. (1982) and
Results obtained from Fluent.
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| Slide 9
Summary
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In this tutorial we learnt how to install
File structure of Lid Driven cavity
Solved lid driven cavity.
Post-processing of results
Validation
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| Slide 10:
Assignment
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As as Assignment,
Change some parameters in the lid driven cavity
- Velocity Magnitude in the 0 folder
- Kinematic viscosity in transportPorpoerties in constant folder
Plot the results of u/U and y/L
This brings us to the end of the tutorial.
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| Slide 11 :
About Spoken tutorials
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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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| Slide 12:
About Spoken tutorials
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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
contact @spoken-tutorial.org
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| Slide 13:
Acknowledgement
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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.
More information on the same is available at the following URL link http://spoken-tutorial.org/NMEICT-Intro
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| Slide 14:
About the contributor
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This is Rahul Joshi from IIT BOMBAY signing off.
Thanks for joining.
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