OpenFOAM/C3/Turbulent-Flow-in-a-Lid-driven-Cavity/English-timed

Time	Narration
00:01	Hello and welcome to the spoken tutorial on modelling Turbulent flow in a Lid Driven Cavity using OpenFOAM.
00:09	In this tutorial, I will show you: Solving turbulent case in OpenFOAM Plotting streamlines in Paraview.
00:20	To record this tutorial, I am using: Linux operating system Ubuntu version 12.04 OpenFoam version 2.1.1 Paraview version 3.12.0
00:33	To practice this tutorial, you should have some basic knowledge of Turbulence modelling, knowledge of how to solve flow in a Lid driven cavity.
00:43	If not so, please refer to the relevant tutorial on our website.
00:50	This problem is identical in geometry and boundary conditions to the 'Lid Driven Cavity' problem discussed in the basic level tutorial.
00:59	Please make a note this problem is already set up in'pisoFoam' solver in OpenFoam directory.
01:07	The boundary conditions are the Lid velocity U =1 m/s. We are solving this for a Reynolds number Re =10000.
01:20	We are using a transient solver for in-compressible, turbulent flow of Newtonian fluids called as pisoFoam.
01:29	Now, let us open the terminal window by pressing Ctrl+Atl+t keys together.
01:37	In the terminal window, type "run" and press Enter. Now type cd space tutorials and press Enter. Now type cd incompressible and press Enter.
01:59	Now, type cd pisoFoam (Note that F here is capital ) and press Enter.
02:10	Now type "ls" and press Enter. In this, you will see two folders les and ras. Our problem setup is inside ras folder which is called as reynolds averaged stress.
02:26	Our folder name is cavity. Now type cd ras and press Enter. Now type ls and press Enter.
02:39	You can see the cavity folder. Let me clear this off. Now type cd cavity and press Enter. Now type "ls" and press Enter.
02:57	You can see three folders 0, constant and system. The initial conditions are specified within the files in the '0' directory.
03:08	Let us take a look at the files in the '0' directory.
03:12	To do this, in the command terminal, type cd 0 and press Enter. Now type "ls" and press Enter.
03:22	You can see files named as epsilon, k, nut, nutilda, p, R and U.
03:30	These files are to be kept as default until the inlet parameters don't change. If any changes are to be done please refer to the tutorial
03:41	on Simulating flow in a channel using OpenFoam to calculate these values.
03:47	Now type cd .. and press Enter. Let me clear this off. Let us open the constant folder. To do this, type cd constant and press Enter. Now type "ls" and press Enter.
04:08	In this, you will see the polyMesh folder containing the geometry of the case inside blockMeshDict and the fluid properties.
04:19	In this case, you will see two more files other than transportProperties named as RASProperties and turbulenceProperties.
04:29	Let us open these two files.
04:32	In the terminal, type gedit (space) RASProperties and press Enter. Let me drag this to the capture area.
04:49	Scroll down. RASProperties contains the Reynolds average stress model for this case which is kept as kepsilon close this.
05:03	Now in the command terminal, now type gedit (space) turbulentproperties and press Enter.
05:15	Scroll down. Simulation type model for this case is kept as RASModelClose this.
05:25	Now let us open the transportProperties model. to this In the terminal window, type gedit transportProperties and press Enter.
05:36	The transportModel we are using here is Newtonian and Viscosity is kept as 1 e raise to -4close this
05:46	We are not changing the geometry in this case So we need not go inside the polyMesh folder and look at the blockMeshDict file
05:54	It can be kept as it is In the terminal type cd .. and press enter We will keep the system folder default As there are no changes inside it.
06:08	Now we are done with the setup we can mesh the geometryTo do this in the teminal window type blockMesh and press Enter Meshing has been done
06:22	Now we can run the solverTo do this in the terminal type pisoFoam and press enterthe iterations running can be seen in the terminal window.
06:34	It may take some time for the iterations to stop.
06:40	The Iterations running will stop at the end of the time step.To visualize the results let us open the paraview window.To do this in the terminal type paraFoam and press enter.This will open the paraview window
06:57	On the left hand side in the Object Inspector menu click on ApplyYou can see the lid driven cavity geometry.A common visualisation is surface plots.
07:09	Change the display to Surface in the column and from the drop down menu change from solid color to UYou can see the initial condition of velocity
07:22	Now on top of the paraview window you can see the VCR controlClick on the play button You can see the motion of the fluid inside the cavity.
07:34	You can also toggle on the color legend from the left hand side top of paraview active variable control menu.Click on it. you can see colour legend
07:46	Now to visualise the stream linesOn the top menu bar of paraviewGo to Filters > Common > Stream Tracers Click on it
07:58	On the left hand side of the Object inspector menu you can see apply click on it.You can see the stream lines at the center of the lid driven cavity.
08:10	You can also change the orientation in which the stream lines are viewed.To do this , scroll down You can see the seed type
08:21	Let me shift this to the right change from point source to line source
08:27	You can see the X, Y and Z axis which are visible select any one of these axis in which you would like to view the stream lines.
08:36	I will select the Y axis and click ApplyYou can see the streamlines along the Y axis.
08:44	Similarly you can select the X axis and plot the streamlines along the X axisNow delete this.
08:53	You can also plot the velocity along the x and y axis using plot over line To do this go to Filter > Data Analysis > Plot over line
09:06	Save the data as .(dot) csv file from file menu Click on save data
09:13	You can plot this data in libreoffice spreadsheet or any other plotting software of your choice.Now let me switch back to the slides
09:23	The results obtained can be validated by using results of Ghia et.al for Reynolds No , Re= 10000
09:32	Thats all we have in this tutorial Let us summarise
09:34	Turbulent Flow in a Lid Driven Cavity And plotting streamlines in paraViewThis brings us to the end of the tutorial
09:44	As an assignment Modify the grid size of the cavity Change it to (100 100 1) and Visualise the results in paraview using streamlines
09:55	Watch the video available at this URLhttp://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.
10:05	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
10:20	Spoken Tutorials project is a part of Talk to a Teacher project, It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:30	More information on the same is available at the following URL link http://spoken-tutorial.org/NMEICT-Intro
10:34	The script is contributed by Shekhar Mishra and Chaitanya talnikar.This is Rahul Joshi from IIT BOMBAY signing off.Thanks for joining

Contributors and Content Editors

DeepaVedartham, PoojaMoolya, Pratik kamble, Sandhya.np14