OpenFOAM/C2/Simulating-flow-in-a-Lid-Driven-Cavity/English

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Tutorial: Simulating Flow in a Lid Driven Cavity.


Script and Narration : Rahul Joshi


Keywords: Video tutorial,CFD,Lid Driven Cavity,Ghia et.al.


Visual cue Narration
Slide 1 Hello and welcome to the spoken tutorial on Simulating Flow in a Lid Driven Cavity using openfoam
Slide 2 : Learning Objectives 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.

Slide 3:

System Requirement

To record this tutorial


I am using Linux Operating system Ubuntu version 10.04 .


OpenFOAM version 2.1.0


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 4:

About Lid Driven Cavity flow

Lid driven cavity is the most widely used 2D test


case for validation of a CFD code

Slide 5 : Diagram 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

Path for lid driven cavity The path for the Lid Driven Cavity is the same as


discussed in the installation tutorial

Open a command terminal Now Open a command terminal and
Press ctrl +Alt+t keys simultaneously on keyboard To do this press Ctrl+Alt+t simultaneously on your keyboard
Path for lid driven cavity in terminal In the command terminal type the path for lid driven cavity
Type run and press enter type run and press enter
Type cd tutorials and press enter cd (space) tutorials and Press enter
Type cd incompressible and press enter cd (space) incompressible and Press enter
Type cd icoFoam and press enter cd (space) icoFoam (Note that F here is capital) and Press enter
Type cd cavity type cd (space) cavity and Press Enter
Type ls and press enter type ls and press enter
Three folders 0, constant and system In the file structure of cavity you will see 3 folders :

0 , constant , and system

Type cd constant Now type cd (space) constant and press enter
Type ls and press enter Now type ls and press enter
Constant >> polyMesh The constant folder contains another folder named polymesh


and a file describing the physical properties of fluid.

Cd polyMesh and press enter Now type cd (space) polymesh and Press Enter


Polymesh contains a file named blockMeshDict

Type ls Now type ls and press enter
You can see the blockMeshDict
Type gedit blockMeshDict and press enter 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

In blockMeshDict file This contains :


-cordinates for lid driven cavity

-blocking and meshing parameters

-and boundary patches.

No patches and arcs in the geometry Since there are arcs as well as no patches to be merged


edges and mergePatchPairs can be kept empty

Now close this
Terminal type cd .. and do this twice In the command terminal type : cd (space) .. (dot) (dot)
you will come back to the cavity folder
Cd system and press enter Now type cd (space) system and press enter,
Type ls and press enter Now type ls and press enter


this contains three files


controlDict, fvSchemes and fvSolutions

ControlDict


fvSolution


fvSchemes

controlDict contains control parameters for start/end time.


fvSolution contains discritization schemes used in run time.


fvSchemes contains equation for solver,


tolerance etc.

Type cd .. and press enter Now again type cd (space) (dot dot) . . and press enter
Cd 0 and press enter Now type cd ( space ) 0 (zero) and Press enter
Now type ls and press enter
Initial values for bounary This contains the initial values for boundary conditions like


Pressure ,Velocity,Temperature etc.

Type cd .. Type cd ( space ) (dot dot) . . to return to the cavity folder
Mesh the geometry Now we need to mesh the geometry


We are using a course mesh here.

Mesh the geometry by typing blockMesh in the terminal.
In terminal type blockMesh and press enter Now type blockMesh (Note that M and D here is capital)


and press enter

Meshing is done.
If there is some error in the blockMesh file


it will be shown in the terminal

Type paraFoam and press enter To view the geometry


Type paraFoam , Note that F here is capital


and press enter

This will open the paraview window
Click on apply button Now on the left hand side of the object inspector menu click on Apply.
You can see the lid driven cavity geometry


close this

Check the mesh Check the mesh by typing checkMesh in the terminal


Note that M here is capital


and press enter

After the checkMesh command 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.
Slide ; icoFoam The solver we are using here is icoFoam :
icoFoam is a Transient solver for incompressible flow of newtonian fluids
Let me switch back to the terminal
In terminal type icoFoam and press enter In the terminal type icoFoam


Note that F here is capital


and press enter

Iterations running will be seen in the terminal window.
Type paraFoam and press enter


Once the solving is done


type paraFoam in the terminal

to view the geometry and the results

Click on APPLY On the left hand side of object inspector menu


click on Apply

Scroll down in object inspector menu Now Scroll down the properties panel


of the objector inspector menu


for time step,regions and volume fields etc

Check or uncheck these boxes Check or uncheck these boxes in the mesh part


to view the different boundary regions of Lid driven cavity

Change from solid color to capital U


initial condition


I will select capital U

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

VCR control on top Now on top of the paraview window you can see the VCR control


Click on the play button

Final result of velocity in lid driven cavity Now this is the final result of velocity for lid driven cavity
Toggle on the color legend Toggle on the color legend by clicking on


top left of the active variable control menu

This is the color legend for U velocity
Validation of result We need to validate the results obtained


To do this let us plot the U and V velocity

We need to validate the result obtained


to do this let us plot the U and V velocity.

Menu > filters > data analysis > plot over line 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 and Y axis


Select the X 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
For non-dimensional analysis Since it is a non dimensional analysis


we need to plot the graph for u/U v/s y/L for Reynolds number =100

PLot data Line click Y axis and apply To do this in Plot Data click on the Y-axis


And click APPLY

Plot can be seen


Go to file save data

You can see the plot


In menu bar go to File > Save Data

Give and appropriate name to your file
Give a name to the file


save as .csv format

I will give this as cavity


The file will be saved as .csv file

Now click ok


Again click ok

Go to the cavity folder in icoFoam


cavity.csv file

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
Copy u0 and points 1 and save it another page of spreadsheet In the libreoffice spreadsheet copy


the U0 (u velocity) and to the right points1(Y-axis) columns


in another spreadsheet

U/U and y/L Now divide both these coloumns


that is u zero by capital U and points 1 by capital L

PLot the results using chart option

of spreadsheet

Plot the results in libreoffice charts option on top of the menu bar.
Now let me switch back to the slides
Slide 7 : Lid Driven Cavity (OpenFOAM) Results obtained will be similar to this figure
Slide 8: Ghia et al.(1982) & Fluent Validate the result obtained on Lid Driven Cavity by : Ghia et al. (1982) and


Results obtained from Fluent

Slide 9

Summary

In this tutorial we learnt how to install

File structure of Lid Driven cavity

Solved lid driven cavity.

Post-processing of results

Validation

Slide 10:

Assignment

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

Slide 11 :

About Spoken tutorials

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.

Slide 12:

About Spoken tutorials

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contact @spoken-tutorial.org

Slide : 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/

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We conduct free Workshops and provide solutions to CFD Problem Statements in OpenFOAM For more details visit this site: http://cfd.fossee.in/

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Slide 13:

Acknowledgement

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

Slide 14:

About the contributor

This is Rahul Joshi from IIT BOMBAY signing off.

Thanks for joining

Contributors and Content Editors

Chandrika, DeepaVedartham, Nancyvarkey, Rahuljoshi

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