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

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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 result 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 as Assignment,
09:35 Change some parameters in the lid driven cavity
09:38 * Velocity Magnitude in the 0 folder
09:41 * Kinematic viscosity in transportPorpoerties 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 link http://spoken-tutorial.org/NMEICT-Intro
10:27 This is Rahul Joshi from IIT BOMBAY signing off.
10:30 Thanks for joining

Contributors and Content Editors

DeepaVedartham, Gaurav, Nancyvarkey, PoojaMoolya, Sandhya.np14, Sneha