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, 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 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.
00:37 Lid driven cavity is the most widely used 2D test
00:41 case for validation of a CFD code.
00:44 This is the diagram of Lid Driven Cavity,
00:46 the boundary conditions remain the same.
00:49 A moving wall and three fixedwalls.
00:51 We are solving this for Reynolds no (Re) = 100.
00:56 The moving wall has a velocity of 1 meter per second.
01:01 The path for the Lid Driven Cavity is the same as discussed in the installation tutorial.
01:05 Now, open a command terminal.
01:07 To do this, press Ctrl+Alt+t keys simultaneously on your keyboard.
01:13 In the command terminal
01:17 and type "run" and press Enter.
01:20 cd (space) tutorials and press Enter.
01:25 cd (space) incompressible and press Enter.
01:31 cd (space) icoFoam (Note that F here is capital) and press Enter.
01:38 cd (space) cavity and press Enter.
01:43 Now, type "ls" and press Enter.
01:46 In the file structure of cavity, you will see 3 folders : 0 , constant , and system.
01:51 Now, type cd (space) constant and press Enter.
01:57 Now type "ls" and press Enter.
02:00 The constant folder contains another folder named polyMesh and a file describing the physical properties of fluid.
02:06 Now, type cd (space) polymesh and Press Enter.
02:13 PolyMesh contains a file named 'blockMeshDict'.
02:17 Now type "ls" and press Enter.
02:20 You can see the blockMeshDict
02:22 To open up the blockMeshDict file, type gedit space blockMeshDict.

(Note that M and D here are capital).Now press Enter.

02:35 This will Open up the blockMeshDict file.
02:37 Let me drag this to the capture area.
02:41 This contains: coordinates for the lid driven cavity,
02:46 blocking and meshing parameters
02:49 and boundary patches.
02:52 Since there are no arcs as well as no patches to be merged, edges and mergePatchPairs can be kept empty.
03:01 Now close this.
03:03 In the command terminal, type : cd (space) .. (dot) (dot) and press Enter.
03:09 Do this twice. You will come back to the cavity folder.
03:14 Now, type cd (space) system and press Enter.
03:20 Now type "ls", press Enter. This contains three files-
03:27 controlDict, fvSchemes and fvSolutions.
03:31 controlDict contains control parameters for start/end time.
03:35 fvSolution contains discritization schemes used in run time.
03:40 And, fvSchemes contains equation for solvers, tolerance etc.
03:45 Now, again type cd (space) (dot dot) .. and press Enter.
03:51 Now type cd ( space ) 0 (zero) and Press Enter.
03:58 Now type "ls" and press Enter.
04:02 This contains the initial values for boundary conditions like Pressure, Velocity, Temperature etc.
04:08 Now type cd ( space ) (dot dot) . . to return back to the cavity folder.
04:14 Now we need to mesh the geometry.
04:16 We are using a coarse mesh here.
04:19 Mesh the geometry by typing blockMesh in the terminal.
04:23 Now type blockMesh (Note that M here is capital) and press Enter.
04:30 The Meshing is done.
04:32 If there are some errors in the blockMesh file, it will be shown in the terminal.
04:36 To view the geometry,type paraFoam. Note that 'F' here is capital and press Enter.
04:45 This will open the paraview window.
04:49 Now on the left hand side of the object inspector menu, click on Apply.
04:54 You can see the lid driven cavity geometry. Now close this.
05:03 Check the mesh by typing "checkMesh" in the terminal.
05:09 Note that 'M' here is capital and press Enter.
05:13 you can see the number of cells, skewness and other parameters which are associated with the mesh.
05:20 Let me switch back to the slides.
05:22 The solver we are using here is icoFoam:
05:25 icoFoam is a Transient solver for incompressible flow of newtonian fluids.
05:31 Let me switch back to the terminal.
05:34 In the terminal, type "icoFoam".
05:38 Note that 'F' here is capital and press Enter.
05:42 The Iterations running will be seen in the terminal window.
05:45 After the solving is done, type paraFoam in the terminal to view the geometry and the results.
05:59 On the left hand side of object inspector menu
06:02 click on Apply.Now Scroll down the properties on object inspector menu.
06:07 you can see mesh parts, Volume Fields etc.
06:12 Check or uncheck these boxes in the mesh part, to view the different boundary regions of Lid driven cavity.
06:20 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.
06:36 I will select capital 'U'. Now this will show you the initial condition of velocity.
06:42 On top of the paraview window, you will see the VCR control.
06:49 Click on the play button.
06:52 Now this is the final result of velocity for the lid driven cavity.
06:57 Toggle on the color legend by clicking on the top left of the active variable control menu.
07:08 This is the color legend for U velocity.
07:12 We need to validate the results obtained.
07:14 To do this, let us plot the U and V velocity.
07:17 To do this, go to Filters scroll down > Data Analysis > Plot Over line.
07:26 Click on it.
07:30 You can see X , Y and Z axes.
07:33 Select the X & Y axis turn by turn.
07:39 I will select the X axis and click Apply.
07:45 You can see Pressure and velocity plots being plotted.
07:50 Since it is a non dimensional analysis, we need to plot the graph for u/U v/s y/L for Reynolds number =100
08:00 To do this, in Plot Data click on the Y-axis
08:06 and click APPLY.
08:09 You can see the plot.
08:11 Now in menu bar, go to File > Save Data.
08:15 Give appropriate name to your file.
08:19 I will give this as "cavity".
08:23 The file will be saved as ".csv" (dot csv) file.
08:27 Now click OK. Again click OK.
08:31 Now go to the cavity folder of openfoam directory.
08:37 Scroll down. you can see the cavity.csv file.
08:42 Open it in Open office or LibreOffice Spreadsheet.
08:47 In the LibreOffice spreadsheet, copy the U0 (u velocity) and to the right points 1(Y-axis) columns in another spreadsheet.
08:56 Now, divide both these columns, that is, u zero by capital U and points 1 by capital L
09:07 and plot the results in libreoffice charts option on top, in the menu bar.
09:16 Now let me switch back to the slides.
09:18 Results obtained will be similar to this figure.
09:24 Validate the results on a paper published on Lid Driven Cavity by : Ghia et al. (1982) and Results obtained from Fluent.
09:34 In this tutorial, we learnt:
09:36 File structure of Lid Driven cavity
09:38 Solved lid driven cavity.
09:40 Post-processing of solutions
09:42 And Validation.
09:44 As an assignment, Change some parameters in the lid driven cavity.
09:48 Velocity Magnitude in the 0 folder.
09:51 Kinematic viscosity in transport Properties in constant folder.
09:55 And, plot results of u/U and y/L.
10:00 Watch the video available at this URL: http://spoken-tutorial.org/What_is_a_Spoken_Tutorial
10:04 It summarizes the Spoken Tutorial project.
10:07 If you do not have good bandwidth, you can download and watch it.
10:10 The Spoken Tutorial project team:
10:12 Conducts workshops using spoken tutorials
10:15 Gives certificates to those who pass an online test.
10:19 For more details, please write to us at:contact@spoken-tutorial.org
10:40 Spoken Tutorials are part of Talk to a Teacher project.
10:43 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:48 More information on the same is available at the following URL: http://spoken-tutorial.org/NMEICT-Intro
10:52 This is Rahul Joshi from IIT Bombay, signing off.
10:55 Thanks for joining.

Contributors and Content Editors

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