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

Tutorial: Turbulence flow in a lid driven cavity

Script : Chaitanya Talnikar, Shekhar Mishra

Narration : Rahul Joshi

Keywords: Video tutorial ,CFD.

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 flow case in OpenFOAM Plotting streamlines in Paraview.
Slide 3: System Requirement	To record this tutorial i am using Linux operating system Ubuntu 12.04 OpenFoam version 2.1.1 Paraview version 3.12.0
Slide 4 Prerequisites	To practice this tutorial you should have some basic knowledge of Turbulence modelling Also watch the spoken-tutorial on “Simulating flow in a Lid Driven Cavity”.
Demo: Set up working Directory	This problem is identical in geometry and boundary conditions 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.
Slide 5: Solver	We will be using the Transient solver for incompressible, turbulent flow of Newtonian fluids. It is called pisoFoam
Slide: Steps in setting up the problem	Now let me open the terminal window To do this press Ctrl+Atl+t keys simultaneously on your keyboard.
Demo: Meshing	In the terminal window type run and press enter Now type cd tutorials and press enter type cd incompressible and press enter type cd pisoFoam and press enter Now type ls and press enter In this you will see two folders les and ras Our problem is setup inside ras which is called as reynolds averaged stress by the name cavity. Now type cd ras and press enter type cd cavity and press enter
Demo: Boundary and Initial Conditions	In this you will 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. Type the following command cd 0 and press enter We can see files named as p, U, epsilon, k, nut, nutilda. These files are to be kept as default until the inlet parameters don't change. If any changes do occur refer to the tutorial on Simulating flow in a channel using OpenFoam to calculate these values.
Transport Properties	Now type cd.. and press enter Let us open the constant folder. In this you will see the polyMesh folder containing the geometry of the case inside blockMeshDict And the fluid properties. You will see two more files named RASProperties and turbulenceProperties, we will open these two files. In the terminal type gedit RASProperties and press enter. RASProperties contain the Reynolds average stress model for the case. close this and in the terminal now type gedit turbulentproperties and press enter turbulentProperties contain the turbulent model ,here we use a very common turbulent model named k epsilon. The transport properties the model is kept newtonain. In the terminal window type cd .. and press enter. We will keep the system folder default.
Demo: Time Step	Now we are done with the setup, run the solver This can be done by typing 'pisoFoam' in the terminal. And press enter the iterations running will be seen in the terminal window. It may take some time till the iterations stop.
Demo: Post processing	Iterations will stop at the end of the time step. To visualize the results open the paraview window. To do this in the terminal type paraFoam and press enter. Now click on Apply in the column on the left of the screen under object inspector menu. You can see the lid driven cavity geometry. A common visualisation is surface plots. Change the display to Surface in the column and from the drop down menu change from solid color to U. Click the play button of the VCR control menu on top of paraview window. You can see the motion of the fluid inside the cavity. Also toggle on the color legend on the left hand side top of paraview active variable control menu.
Demo: Streamlines	To visualise the stream lines On the top menu bar of paraview Go to Filters > Common > Stream Tracers On the left hand side in Object inspector menu click on Apply. You can see the stream lines near the top surface of moving wall. You can also change the orientation in which the stream lines are viewed. To do this scroll down and change the seed type from point source to line source. X, Y and Z axis are visible select any one of these axis in which you would like to view the stream lines.
Slide 11:	You can also plot the velocity along the x and y axis using plot over line. Save the data as. csv file from file option in paraview menu bar. You can plot this data in libreoffice spreadsheet or any other plotting software of your choice. The results obtained can be validated by results obtained by Ghia et.al at Re= 10000. Let me switch back to the slides.
Slide 12: Summary	In this tutorial we learnt how to setup OpenFOAM to solve the lid driven cavity problem with turbulence. Visualised the streamlines in paraview This brings us to the end of the tutorial
Slide 13: Assignment	As an assignment modify the grid size and change it to (100 100 1) Visualise the flow using streamlines in paraview
Slide 14: About Spoken tutorials	The video available at this URL: http://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.
Slide 15: About spoken tutorials	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 contacts@spoken-tutorial.org
Slide 16: Acknowledgement	Spoken Tutorials are part of Talk to a Teacher project, It is supported by the National Mission on Education through ICT, MHRD, Government of India. This project is coordinated by http://spoken-tutorial.org More information on the same is available at the following URL link 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