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

Tutorial: Turbulent flow in a lid driven cavity

Script : Chaitanya Talnikar, Shekhar Mishra , Rahul Joshi

Narration : Rahul Joshi

Keywords: Video tutorial ,CFD,Turbulent Flow in Lid driven cavity,OpenFOAM.

Visual Cue	Narration
Slide 1:	Hello and welcome to the spoken tutorial on modelling Turbulent flow in a Lid Driven Cavity using OpenFOAM
Slide 2: Learning Objectives	In this tutorial I will show you Solving turbulent case in OpenFOAM and Plotting streamlines in ParaView
Slide 3: System Requirement	To record this tutorial I am using Linux operating system Ubuntu version 12.04 OpenFoam version 2.1.1 and 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 5 : Prerequisites	To practice this tutorial you should have some basic knowledge of Turbulence modelling Knowledge of how to solve flow in a Lid driven cavity If not so please refer to the relevant tutorial on our website.
Demo: Set up working Directory	This problem is identical in geometry and boundary condition to the 'Lid Driven Cavity' problem discussed in the basic level tutorial. Please make a note this problem is already set up in pisoFoam solver in OpenFoam directory. The boundary conditions are the Lid velocity U is 1 m/s And we are solving this for a Reynolds number Re equal to 10000
Slide 6: Solver	We are using a Transient solver for incompressible turbulent flow of Newtonian fluids called as pisoFoam
Steps in setting up the problem	Now let us open the Terminal window by pressing Ctrl+Atl+T keys together
In the terminal window Type cd tutorials	In the terminal window type run and press Enter. Now type cd space tutorials and press Enter.
Type cd incompressible	Now type cd space incompressible and press Enter.
Type cd pisoFoam	Now type cd space pisoFoam (Note that F here is capital ) and press Enter
Type ls Two Folders les and ras Cavity folder inside RAS	Now type ls and press Enter. In this you will see two folders les and ras Our problem is setup inside ras folder which is called as reynolds averaged stress.
Type cd ras ls	Our folder name is cavity. Now type cd space ras and press Enter. Now type ls and press Enter.
Type cd cavity ls	You can see the cavity folder. Let me clear this off. Type cd space cavity and press Enter. Now type ls and press Enter.
Point to the 3 folders Boundary and Initial conditions 0 folder	You can see three folders 0, constant and system. The initial conditions are specified within the files in the '0' directory. Let us take a look at the files in the '0' directory.
Inside the 0 folder Type ls	To do this, in the command terminal type cd space 0 and press Enter. Now type ls and press Enter.
Point to the files as per narration	You can see files named as epsilon, k, nut, nutilda, p, R and U. 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 on Simulating flow in a channel using OpenFoam, to calculate these values.
Type cd..	Now type cd space dot dot and press Enter. Let me clear this off.
Type cd constant Type ls	Let us open the constant folder. To do this type cd space constant and press Enter. Now type ls and press Enter.
PolyMesh folder and fluid property files	In this you will see the polyMesh folder containing the geometry of the case inside blockMeshDict and the fluid properties.
Point to the two files as per narration	In this case you will see two more files other than transportProperties named as RASProperties and turbulenceProperties. Let us open these two files.
RASProperties	In the terminal type gedit (space) RASProperties and press Enter. Scroll down. RASProperties contain the Reynolds average stress model for this case, which is kept as kEpsilon Close this.
turbulentProperties	Now in the command terminal, type gedit space turbulentproperties and press Enter. Scroll down. The simulation type model for this case is kept as RASModel. Close this.
TransportModel Change the value of viscosity	Now let us open the transportProperties model. To do this, in the terminal type gedit space transportProperties and press Enter. The transportModel we are using here is Newtonian and the Viscosity is kept as 1 e raise to -4 Close this.
Do not change the blockMeshDict file The system folder is to be kept default	We are not changing the geometry in this case. So we need not go inside the polyMesh folder and look at the blockMeshDict file. It can be kept as it is.
Type cd..	In the terminal type cd space dot dot and press Enter. We will keep the system folder default as there are no changes inside it.
Meshing the geometry blockMesh Meshing is done	Now, we are done with the setup. We can mesh the geometry. To do this in the terminal window type blockMesh and press Enter. Meshing has been done.
Running the solver : pisoFoam	Now we can run the solver. To do this in the terminal type pisoFoam and press Enter. The iterations running can be seen in the terminal window. It may take some time for the iterations to stop.
Post-processing the results in paraview	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.
View the geometry Lid driven cavity geometry Change the drop down menu from solid color to U	On the left hand side in the Object Inspector menu click on Apply. You can see the lid driven cavity geometry. A common visualization is surface plots. Change the display to Surface in the column and from the drop down menu change from solid colour to U You can see the initial condition of velocity.
Click on the Play button on VCR control for animation Toggle on the color legend	Now on top of the ParaView window you can see the VCR control. Click on the Play button. You can see the motion of the fluid inside the cavity. You can also toggle on the colour legend on the left hand side top of ParaView active variable control menu. Click on it. You can see the colour legend.
Visualise the streamlines Filters > Common > Stream Tracers	Now to visualise the stream lines On top of the menu bar of ParaView Go to Filters > Common and Stream Tracers Click on it
Streamlines on top	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 centre of the lid driven cavity.
Streamlines view	You can also change the orientation in which the stream lines are viewed. To do this , scroll down. You can see the seed type.
Shift to right >> change point source to line source.	Let me shift this to the right and change from point source to line source.
Plot streamlines about X, Y and Z axis Click on the Y axis Click on the X axis Delete this.	You can see the X, Y and Z axes which are visible. Select any one of these axis in which you would like to view the stream lines. I will select the Y axis and click Apply. You can see the streamlines along the Y axis. Similarly you can select the X axis and plot the streamlines along the X axis. Now delete this.
Plot data over line Save as .csv format	You can also plot the velocity along X and Y axis using plot over line. To do this go to Filter > Data Analysis and Plot over line. Save the data as dot csv file from the file menu. Click on Save Data.
Plot the results Validate the results with Ghia et.al. For Re= 10000	You can plot this data in libre office spreadsheet or any other plotting software of your choice. Now let me switch back to the slides. The results obtained can be validated by using results of Ghia et.al for Reynolds Number , Re is equal to 10000
Slide 7: Summary	That's all we have in this tutorial. Let us summarise. Turbulent Flow in a Lid Driven Cavity and plotting stream lines in ParaView This brings us to the end of the tutorial.
Slide 8: Assignment	As an assignment Modify the grid size of the cavity Change it to (100 100 1) And visualise the results in ParaView using streamlines
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Slide 13: Acknowledgements	Spoken Tutorials project is a part of the Talk to a Teacher project. It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on the this mission is available at this URL http://spoken-tutorial.org/NMEICT-Intro
About the contributor	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, Nancyvarkey, Pravin1389, Rahuljoshi