View source for OpenFOAM/C2/Simulating-flow-in-a-Lid-Driven-Cavity/English-timed

{| border=1
|| '''Time'''
|| '''Narration'''

|-
|  00:01
|  Hello and welcome to the '''spoken tutorial''' on '''Simulating Flow in a Lid Driven Cavity''' using '''openFoam'''.

|-
|  00:07
|   In this tutorial, I will show you: 

|-
|  00:09
|*   The''' Lid Driven Cavity''' file structure

|-
|  00:12
|*   '''Meshing '''the Geometry 

|-
|  00:14
|*   Solving and post-processing results in '''Paraview'''

|-
|  00:17
|*   Plotting & validating results on a spreadsheet. 

|-
|  00:21
|  To record this tutorial, 

|-
|  00:22
|   I am using: '''Linux Operating system Ubuntu''' version 10.04 

|-
|  00:27
|   '''OpenFOAM''' version 2.1.0 and  '''ParaView''' version 3.12.0. 

|-
|  00:32
|   '''Lid driven cavity''' is the most widely used 2D test 

|-
|  00:36
|   case for validation of a '''CFD code'''.

|-
|  00:39
| This is the diagram of '''Lid Driven Cavity''',

|-
| 00:41
| the '''boundary conditions''' remain the same.

|-
| 00:44
| A '''moving wall''' and '''three fixedwalls'''.

|-
|  00:46
|  We are solving this for '''Reynolds no (Re) = 100'''.

|-
| 00:50
| The '''moving wall''' has a velocity of 1 meter per second.

|-
|  00:54
|   The '''path''' for the '''Lid Driven Cavity''' is the same as discussed in the installation tutorial.

|-
|01:00
|  Now, open a '''command terminal'''.  

|-
|  01:02
|  To do this, press '''Ctrl+Alt+t ''' keys simultaneously on your keyboard.

|-
|  01:08
|  In the command terminal, type the '''path''' for the '''lid driven cavity'''

|-
| 01:12
|and type "run" and press '''Enter'''.

|-
|01:15
|  '''cd (space) tutorials''' and press '''Enter'''.

|-
| 01:20
| '''cd '''(space)''' incompressible''' and press '''Enter'''.

|-
| 01:26 
|'''cd '''(space)''' icoFoam '''(Note that F here is capital) and press '''Enter'''.

|-
| 01:33
|  '''cd '''(space) '''cavity''' and press '''Enter'''.

|-
| 01:38
|Now, type "ls" and press '''Enter'''.

|-
| 01:41
|In the file structure of '''cavity''', you will see 3 folders : '''0 , constant , and system'''.

|-
|01:46
|  Now, type '''cd''' (space) '''constant''' and press '''Enter'''.

|-
| 01:52
| Now type "ls" and press '''Enter'''.

|-
|01:55
|  The '''constant''' folder contains another folder named '''polyMesh''' and a file describing the physical properties of fluid.

|-
| 02:01
| Now, type '''cd (space) polymesh''' and Press '''Enter'''.

|-
| 02:08
| '''PolyMesh''' contains a file named 'blockMeshDict'.

|-
| 02:12
|  Now type "ls" and press '''Enter'''.

|-
| 02:15
|  You can see the '''blockMeshDict'''

|-
|  02:17
| To open up the  '''blockMeshDict''' file,  type '''gedit space blockMeshDict'''.

(Note that M and D  here are capital)

Now press '''Enter'''.

|-
| 02:30
|  This will Open up the '''blockMeshDict''' file.

|-
| 02:32
| Let me drag this to the capture area.

|-
|  02:36
|  This contains: coordinates for the '''lid driven cavity''',

|-
|  02:41
|'''blocking''' and '''meshing parameters'''

|-
|  02:44
|and '''boundary patches.'''

|-
|  02:47
| Since there are  no '''arcs''' as well as no '''patches''' to be merged, '''edges''' and '''mergePatchPairs''' can be kept empty.

|-
| 02:56
| Now close this.

|-
|  02:58
|  In the command terminal, type : '''cd (space) .. (dot) (dot)'''  and press '''Enter.'''

|-
| 03:04
| Do  this twice. You will come back to the''' cavity''' folder.

|-
| 03:09
|  Now, type '''cd''' (space) '''system''' and press '''Enter'''.

|-
|03:15
|  Now type "ls", press '''Enter'''.  This contains three files-

|-
|  03:22
|'''controlDict, fvSchemes''' and '''fvSolutions'''.

|-
|  03:26
| '''controlDict''' contains '''control parameters''' for start/end time.


|-
|  03:30
|'''fvSolution''' contains '''discritization schemes''' used in '''run time'''.

|-
|  03:35
|And, '''fvSchemes''' contains equation for '''solvers''', '''tolerance''' etc. 

|-
| 03:40
| Now, again type '''cd (space) (dot dot) .. '''and press '''Enter'''.

|-
| 03:46
|  Now type '''cd ( space )''' 0 (zero) and Press '''Enter'''.

|-
|03:53
| Now type "ls" and press '''Enter'''.

|-
| 03:57
|  This contains the initial values for '''boundary conditions''' like '''Pressure, Velocity, Temperature''' etc. 

|-
|  04:03
| Now type''' cd ( space ) (dot dot) . .''' to return back to the '''cavity''' folder.

|-
| 04:09
|  Now we need to '''mesh '''the geometry.

|-
|  04:11
|We are using a coarse mesh here.

|-
|  04:14
|  '''Mesh''' the geometry by typing '''blockMesh''' in the '''terminal'''.

|-
|04:18 
| Now type '''blockMesh '''(Note that M  here is capital) and press '''Enter'''.

|-
| 04:25
|  The '''Meshing''' is done.

|-
| 04:27
| If there are some '''errors''' in the '''blockMesh''' file, it will be shown in the '''terminal'''.

|-
|  04:31
|  To view the geometry, 

|-
|  04:32
|type '''paraFoam'''. Note that 'F' here is capital and press '''Enter'''.

|-
|  04:40
|  This will open the '''paraview window'''.

|-
|  04:44
|  Now on the left hand side of the '''object inspector''' menu, click on '''Apply.'''

|-
| 04:49
| You can see the '''lid driven cavity''' geometry. Now close this.

|-
|04:58
|  Check the mesh by typing "checkMesh" in the terminal.

|-
|  05:04
|Note that 'M' here is capital and press '''Enter'''.

|-
|05:08
| you can see  the number of cells, '''skewness''' and other parameters which are associated with the '''mesh'''.

|-
|05:15
|  Let me switch back to the '''slides'''.

|-
|  05:17
|  The solver we are using here is '''icoFoam''':

|-
|  05:20
|   '''icoFoam''' is a '''Transient solver''' for '''incompressible flow''' of '''newtonian fluids'''.

|-
|  05:26
|  Let me switch back to the terminal.

|-
|  05:29
|   In the terminal, type "icoFoam". 

|-
|  05:33
|Note that 'F' here is capital and press '''Enter'''.

|-
|  05:37
| The  '''Iterations '''running will be seen in the terminal window.

|-
| 05:40
| After the solving is done, type '''paraFoam''' in the terminal to view the geometry and the results.

|-
| 05:54
|  On the left hand side of '''object inspector''' menu

|-
|  05:57
|click on '''Apply'''.

|-
|  05:58
|  Now '''Scroll''' down the properties on '''object inspector''' menu. 

|-
|  06:02
|you can see '''mesh parts, Volume Fields''' etc.

|-
| 06:07
|   Check or uncheck these '''boxes''' in the '''mesh''' part, to view the different boundary regions of '''Lid driven cavity'''.

|-
|   06:15 
|  Now, after this, on top of the left-hand side on  '''active variable control ''' drop-down menu, change this from '''solid color''' to '''p''' or capital '''U''' which are the '''initial conditions''' such as '''pressure, velocity'''.

|-
|  06:31
|I will select capital 'U'. Now this will show you the initial condition of velocity. 

|-
|  06:37
|  On top of the''' paraview''' window, you will see the''' VCR control'''.

|-
|  06:44
|Click on the '''play''' button.

|-
|  06:47
|  Now this is the final result of '''velocity''' for the '''lid driven cavity'''.

|-
| 06:52
| Toggle on the '''color legend''' by clicking on  the top left of the '''active variable control''' menu.

|-
|  07:03
| This is the''' color legend''' for '''U velocity'''.

|-
| 07:07
| We need to validate the results obtained.


|-
|  07:09
|To do this, let us plot the '''U''' and '''V velocity'''.
 
|-
|  07:12
| To do this, go to '''Filters''' scroll down > '''Data Analysis''' > '''Plot Over line'''.

|-
|  07:21
| Click on it.

|-
| 07:23
|  You can see  X , Y and Z axes.

|-
| 07:25
|   Select the '''X & Y axis''' turn by turn.

|-
|  07:31
|I will select the '''X axis''' and click '''Apply'''.

|-
| 07:37
|  You can see '''Pressure''' and '''velocity''' '''plots''' being plotted.

|-
| 07:42
|  Since it is a non dimensional analysis, we need to plot the graph for '''u/U v/s y/L''' for '''Reynolds number =100'''

|-
| 07:52
|  To do this, in '''Plot Data''' click on the '''Y-axis'''

|-
|  07:58 
|and click '''APPLY'''.

|-
| 08:01
|  You can see the''' plot'''.

|-
|  08:03
|Now in menu bar, go to '''File > Save Data'''.

|-
| 08:09
| Give   appropriate name to your file.

|-
|  08:11
|  I will give this as "cavity".

|-
|  08:15
|The file will be saved as ".csv" (dot csv) file.

|-
|  08:19
| Now click OK. Again click OK.

|-
| 08:23
|  Now go to the '''cavity''' folder of '''openfoam directory'''.

|-
|  08:29
|Scroll down. you can see the '''cavity.csv''' file.

|-
| 08:34
| Open it in '''Open office''' or '''LibreOffice Spreadsheet'''.

|-
|   08:39
| In the LibreOffice spreadsheet, copy the U0 (u velocity) and to the right points 1(Y-axis) columns
in another spreadsheet. 

|-
|  08:48
|  Now, divide both these columns, that is, '''u zero''' by capital U and '''points 1''' by capital L

|-
|  08:59
| and plot the results in '''libreoffice''' charts option on top, in the menu bar.

|-
|  09:08
| Now let me switch back to the slides.

|-
|  09:10
| Results obtained will be similar to this figure.

|-
| 09:16
| '''Validate''' the results on a  paper published on '''Lid Driven Cavity by : Ghia et al. (1982''') and 
Results obtained from Fluent.

|-
|09:24  
|  In this tutorial, we learnt:   

|-
|  09:26
|* File structure of '''Lid Driven cavity'''

|-
|  09:28
|* '''Solved lid driven cavity'''.

|-
|  09:30
|* '''Post-processing of solutions'''

|-
|   09:32
|And '''Validation'''.

|-
| 09:34
|   As an assignment, 

|-
|  09:35
|Change some parameters in the '''lid driven cavity'''.

|-
|  09:38
|* '''Velocity Magnitude''' in the '''0 folder'''.
|-
|  09:41
|* '''Kinematic viscosity'''  in '''transport Properties''' in '''constant''' folder.

|-
|  09:45
|And, plot results of '''u/U and y/L'''.

|-
| 09:50
| Watch the  video available at this URL: 
http://spoken-tutorial.org/What_is_a_Spoken_Tutorial 

|-
|  09:54
|It summarizes the '''Spoken Tutorial''' project. 

|-
|  09:57
|If you do not have good bandwidth, you can download and watch it.

|-
|  10:00
|   The Spoken Tutorial project team:

|-
|  10:02
|* Conducts workshops using spoken tutorials

|-
|  10:05
|* Gives certificates to those who pass an online test.

|-
|  10:09
|For more details, please write to us at:
contact@spoken-tutorial.org

|-
| 10:15
| '''Spoken Tutorials''' are part of '''Talk to a Teacher''' project. 

|-
|  10:18
|It is supported by the National Mission on Education through ICT, MHRD, Government of India. 

|-
|  10:23
|More information on the same is available at the following URL:  http://spoken-tutorial.org/NMEICT-Intro

|-
| 10:27
|  This is Rahul Joshi from IIT Bombay, signing off.

|-
|  10:30
|Thanks for joining.

|}