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

Tutorial: Simulating Flow in a Lid Driven Cavity.

Script and Narration : Rahul Joshi

Keywords: Video tutorial,CFD,Lid Driven Cavity,Ghia et.al.

Visual cue	Narration
Slide 1	Hello and welcome to the spoken tutorial on Simulating Flow in a Lid Driven Cavity using openfoam
Slide 2 : Learning Objectives	In this tutorial I will show you The Lid Driven Cavity file structure Meshing the geometry Solving and post-processing results in Paraview Plotting and validating results on a spreadsheet.
Slide 3: System Requirement	To record this tutorial I am using Linux Operating system Ubuntu version 10.04. OpenFOAM version 2.1.0 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 4: About Lid Driven Cavity flow	Lid driven cavity is the most widely used 2D test case for validation of a CFD code.
Slide 5 : Diagram	This is diagram of Lid Driven Cavity.
Slide 6: Boundary Conditions	The boundary conditions remain the same. A moving wall and three fixed walls.
	We are solving this for Reynolds no (Re) = 100 The moving wall has a velocity of 1 meter per second
Path for lid driven cavity	The path for the Lid Driven Cavity is the same as discussed in the installation tutorial.
Open a command terminal	Now open a command terminal.
Press ctrl +Alt+t keys simultaneously on keyboard	To do this, press Ctrl+Alt+t keys simultaneously on your keyboard.
Path for lid driven cavity in terminal	In the command terminal.
Type run and press enter	Now type run and press Enter.
Type cd tutorials and press enter	cd (space) tutorials and press Enter.
Type cd incompressible and press enter	cd (space) incompressible and press Enter.
Type cd icoFoam and press enter	cd (space) icoFoam (Note that F here is capital) and press Enter.
Type cd cavity	cd (space) cavity and press Enter.
Type ls and press enter	Now type lsand press Enter.
Three folders 0, constant and system	In the file structure of cavity you will see 3 folders : 0 , constant, and system.
Type cd constant	Now type cd (space) constant and press Enter.
Type ls and press enter	Now type ls and press Enter.
Constant >> polyMesh	The constant folder contains another folder named polymesh. And the file describing the physical properties of fluid.
Cd polyMesh and press enter	Now type cd (space) polymesh and press Enter. Polymesh contains a file named blockMeshDict.
Type ls	Now type ls and press Enter.
	You can see the blockMeshDict.
Type gedit blockMeshDict and press enter	To open the blockMeshDict file, type gedit blockMeshDict. (Note that M and D here are capital). Now press Enter.
	This will open up the blockMeshDict file. Let me drag this to the capture area.
In blockMeshDict file	This contains : coordinates for lid driven cavity blocking and meshing parameters and boundary patches.
No patches and arcs in the geometry	Since there are arcs as well as no patches to be merged, edges and mergePatchPairs can be kept empty.
	Now close this.
Terminal type cd .. and do this twice	In the command terminal type : cd (space) (dot) (dot)
	You will come back to the cavity folder.
Cd system and press enter	Now type cd (space) system and press Enter.
Type ls and press enter	Now type ls and press Enter. This contains three files - controlDict, fvSchemes and fvSolutions.
ControlDict fvSolution fvSchemes	controlDict contains control parameters for start/end time. fvSolution contains discritization schemes used in run time. fvSchemes contains equation for solvers, tolerance, etc.
Type cd .. and press enter	Now again type cd (space) (dot dot) and press Enter.
Cd 0 and press enter	Now type cd ( space ) 0 (zero) and press Enter.
	Now type ls and press Enter.
Initial values for bounary	This contains the initial values for boundary conditions like Pressure ,Velocity, Temperature, etc.
Type cd ..	Type cd ( space ) (dot dot) to return to the cavity folder.
Mesh the geometry	Now we need to mesh the geometry. We are using a course mesh here.
	Mesh the geometry by typing blockMesh in the terminal.
In terminal type blockMesh and press enter	Now type blockMesh (Note that M here is capital). And press Enter.
	Meshing is done.
	If there is some error in the blockMesh file, it will be shown in the terminal.
Type paraFoam and press enter	To view the geometry, type paraFoam. Note that F here is capital. And press Enter.
	This will open the ParaView window.
Click on apply button	Now on the left hand side of the object inspector menu click on Apply.
	You can see the lid driven cavity geometry. Now close this.
Check the mesh	Check the mesh by typing checkMesh in the terminal. Note that M here is capital. And press Enter.
After the checkMesh command	You can see the the number of cells, skewness and other parameters which are associated with the mesh.
	Let me switch back to the slides.
Slide 6: icoFoam	The solver we are using here is icoFoam.
	icoFoam is a Transient solver for incompressible flow of Newtonian fluids.
	Let me switch back to the terminal.
In terminal type icoFoam and press enter	In the terminal type icoFoam. Note that F here is capital. And press Enter.
	Iterations running will be seen in the terminal window.
Type paraFoam and press enter	After the solving is done, type paraFoam in the terminal to view the geometry and the results.
Click on APPLY	On the left hand side of object inspector menu, click on Apply.
Scroll down in object inspector menu	Now scroll down the properties of objector inspector menu. You can see mesh parts, volume fields etc.
Check or uncheck these boxes	Check or uncheck these boxes in the mesh part to view the different boundary regions of Lid driven cavity.
Change from solid color to capital U initial condition I will select capital U	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 or velocity. I will select capital U. Now this will show you the initial condition of velocity.
VCR control on top	Now on top of the ParaView window, you can see the VCR control. Click on the Play button.
Final result of velocity in lid driven cavity	Now this is the final result of velocity for lid driven cavity.
Toggle on the color legend	Toggle on the color legend by clicking on the top left of the active variable control menu.
	This is the color legend for U velocity.
Validation of result	We need to validate the results obtained. To do this, let us plot the U and V velocity.
Menu > filters > data analysis > plot over line	For this go to Filters > Data Analysis > Plot Over line
	Click on it.
	You can see the X , Y and Z axis
Select the X and Y axis Select the X axis	Select the X & Y axis turn by turn. I will select the X axis and click Apply.
	You can see the Pressure and Velocity plots being plotted.
For non-dimensional analysis	Since it is a non dimensional analysis, we need to plot the graph for u/U v/s y/L for Reynolds number =100.
PLot data Line click Y axis and apply	To do this in Plot Data, click on the Y-axis. And click Apply
Plot can be seen Go to file save data	You can see the plot. In menu bar go to File > Save Data
	Give an appropriate name to your file.
Give a name to the file save as .csv format	I will give this as cavity. The file will be saved as dot csv file.
	Now click Ok. Again click Ok.
Go to the cavity folder in icoFoam cavity.csv file	Now go to the cavity folder of openfoam directory. Scroll down, you can see the cavity.csv file
	Open it in OpenOffice or LibreOffice spreadsheet.
Copy u0 and points 1 and save it another page of spreadsheet	In the LibreOffice spreadsheet copy the U0 (u velocity) and to the right point1 column in another spreadsheet.
U/U and y/L	Now divide both these columns. That is u zero by capital U and points 1 by capital L.
PLot the results using chart option of spreadsheet	Plot the results in LibreOffice Charts option on top of the menu bar.
	Now let me switch back to the slides.
Slide 7 : Lid Driven Cavity (OpenFOAM)	Results obtained will be similar to this figure.
Slide 8: Ghia et al.(1982) & Fluent	Validate the result obtained on Lid Driven Cavity by : Ghia et al. (1982) and results obtained from Fluent.
Slide 9: Summary	In this tutorial we learnt File structure of Lid Driven cavity Solved lid driven cavity Post-processing of results Validation
Slide 10: Assignment	As as assignment, Change some parameters in the lid driven cavity Velocity magnitude in the 0 folder Kinematic viscosity in transportPorpoerties in constant folder Plot the results of u/U and y/L
Slide 11 : 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 12: 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 contact @spoken-tutorial.org
Slide 13: Forum to answer questions Do you have questions on THIS Spoken Tutorial? Choose the minute and second where you have the question Explain your question briefly Someone from the FOSSEE team will answer them. Please visit http://forums.spoken-tutorial.org/
Slide 14: Forum to answer questions Questions not related to the Spoken Tutorial? Do you have general/technical questions on the Software? Please visit the FOSSEE forum http://forums.fossee.in/ Choose the Software and post your question
Slide 15: Lab Migration project We coordinate migration from commercial CFD software like ANSYS to OpenFOAM We conduct free Workshops and provide solutions to CFD Problem Statements in OpenFOAM For more details visit this site: http://cfd.fossee.in/
Slide 16: Case Study project We invite students to solve a feasible CFD problem statement of reasonable complexity using OpenFOAM We give honorarium and certificate to those who do this For more details visit this site: http://cfd.fossee.in/
Slide 17: Acknowledgement	Spoken Tutorial 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. More information on the same is available at the following URL link http://spoken-tutorial.org/NMEICT-Intro
Slide 18: About the contributor	This is Rahul Joshi from IIT BOMBAY signing off. Thanks for joining

Contributors and Content Editors

Chandrika, DeepaVedartham, Nancyvarkey, Rahuljoshi