OpenFOAM/C2/2D-Laminar-Flow-in-a-channel/English-timed

Time	Narration
00:01	Hello and welcome to the spoken tutorial on Simulating 2D Laminar Flow in a Channel using OpenFoam.
00:09	In this tutorial, I will show you- 2D geometry of channel Meshing the Geometry Solving and Post Processing results in Paraview and Validation using analytic result.
00:25	To record this tutorial, I am using: Linux Operating system Ubuntu version 12.04. OpenFOAM version 2.1.1 ParaView version 3.12.0
00:39	Note that OpenFOAM version 2.1.1 is supported on ubuntu version 12.04.
00:45	Hence forth all the tutorials will be covered using OpenFOAM version 2.1.1 and ubuntu version 12.04.
00:56	As a prerequisite for this tutorial, you should know how to create geometry using OpenFOAM.
01:03	If not, please refer to the relevant tutorials on our website.
01:09	We simulate flow in a channel to determine flow development length along the downstream. Channel flow problem description.
01:19	The boundary names and the inlet conditions are shown as in this figure.
01:26	The flow develpoment length is given by the formula L= 0.05 * Re * D.
01:32	'Re' which is the Reynolds number and 'D' which is the channel height.
01:37	Using the formula, the length of the channel comes out to be 5 meters and height is kept as 1 meter.
01:45	The Inlet velocity is 1 meter per second. And, we are solving this for a Reynolds number ( Re ) equal to 100.
01:53	This is a steady state problem . Therefore we are using a steady state incompressible solver for this case.
02:01	This is the file structure of our case. The folder should be created in the solver type that we choose. I have already created a folder in simpleFoam folder of incompressible flow solvers.
02:18	The folder is named as channel. Now, let me switch to the folder.
02:25	Copy 0, Constant and System folders of any other case, in the simpleFoam directory.
02:34	I have copied the file structure of the case pitzDaily.
02:38	Paste it inside the channel folder and make the necessary changes in the geometry, boundary faces and boundary condition.
02:48	Now, let me open the command terminal.
02:51	To do this, press Ctrl+Alt +t keys simultaneously on your keyboard.
02:57	In the terminal, type "run" and press Enter.
03:01	Now type cd space tutorials and press Enter.
03:08	Now type cd space incompressible and press Enter.
03:15	Type cd space simpleFoam and press Enter.
03:20	Now type cd space channel and press Enter.
03:28	Now, type "ls" and press Enter.
03:33	You will see three folders 0, Constant and system.
03:37	Now type cd space constant and press Enter.
03:48	Now type "ls" and press Enter.
03:52	In this, you will see the files containing properties of fluid and a folder named polymesh.
03:59	RASProperties contains Reynolds-averaged stress model.
04:03	transportProperties contains the transport model and kinematic viscosity that is (nu), in this case is set at 0.01 m²/s.
04:17	Now in terminal, type cd space polyMesh and press Enter. Now, type "ls" and press Enter.
04:30	You will see the blockMeshDict file here.
04:33	To open up the blockMeshDict file, in the terminal, type "gedit space blockMeshDict" and press Enter. Scroll down.
04:48	The geometry is in meters. So, the convertTometers is set to 1. Next, we have defined the vertices of the channel.
04:59	We have used a 100 X 100 mesh size here and cell spacing is kept as ( 1 1 1 ).
05:07	Next, we have setup the boundary conditions and their types which are inlet, outlet, top and bottom.
05:19	As this is a 2D Geometry, front and Back are kept as empty.
05:27	Also, this being a simple geometry, mergePatchPair and edges are to be kept empty. Close the blockMeshDict file.
05:38	In the command terminal, type cd space ..(dot dot) and press Enter.
05:44	Again, type cd space .. (dot dot) and press Enter.
05:49	Now. in the terminal, type cd space 0 (Zero) and press Enter. Now, type "ls" and press Enter.
05:58	This contains the intial boundary conditions and wall functions for the channel case.
06:05	It should contain various files such as epsilon, k, nut, nuTilda which are the wall functionsand 'p' , 'R' and capital 'U' which are initial conditions of the flow.
06:20	Let me switch back to the slides.
06:24	Calculate 'k' which is the turbulent kinetic energy from the formula given in the slide
06:29	where Ux, Uy and Uz are the velocity components in the x, y and z directions and U' ( dash ) = 0.05 times u actual.
06:43	Calculate epsilon from the formula given where epsilon is the rate of dissipation of turbulent energy, C mu is a constant and its value is 0.09.
06:56	And 'l' is the length of the channel. Let me minimize this.
07:02	Change only the boundary names in each of the above files.
07:07	Note that the values of nut, nuTilda, R are kept to default.
07:13	Rest of the files should contain the initial value for each of the boundary faces.
07:21	Now, in the terminal, type cd (space) ..(dot dot) and press Enter.
07:27	There are no changes to be done in the system folder.
07:31	Now we need to mesh the geometry. To do this, in the command terminal, type "blockMesh" and press Enter.
07:40	The Meshing is done. Now let me switch back to the slide.
07:45	The type of solver we are using here is SimpleFoam. It is a Steady-state solver for in-compressible and turbulent flows.
07:55	Let me minimize this.
07:56	In the command terminal, type "simpleFoam" and press Enter.
08:03	Iterations running will be seen in the command terminal.
08:07	Iterations running may take some time.
08:11	The iterations will stop once the solution is converged or it reaches its end time value.
08:16	To view the results in paraView, in the terminal,
08:20	type "paraFoam" and press Enter. This will open up the paraView window.
08:28	On the left hand side of the paraView window, click Apply. The geometry can be seen here.
08:35	On top of the active variable control menu, change the drop down menu from solid color to capital U.
08:50	You can see the initial state of velocity magnitude at inlet.. On top of the paraView window, click on theplay button of the VCR control.
09:00	you can see the final value of the velocity magnitude.
09:07	Also toggle on the color legend from the left hand side top of active variable control menu, click APPLY again.
09:16	Now go to Display, scroll down. You can see Rescale, click on it.
09:24	We can see that once the flow has fully developed, it attains a maximum uniform velocity at the center. Now, let me switch back to the slides.
09:36	The results obtained can be validated with the analytical solution for laminar flow in achannel which is u(max)=1.5 Uavg.
09:46	Using openFoam, we obtain a result of u(max) = 1.48 meters per second which is a good match. This brings us to the end of the tutorial.
09:57	In this tutorial, we learnt the file structure of channel, obtained solution using steady state solver. Viewed the geometry in paraview and validation with analytic results.
10:08	As an assignment- solve the problem for Reynold's Number equal to 1500 and validate it with the analytical result.
10:17	Watch 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.
10:28	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: contact@spoken-tutorial.org
10:42	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.
10:52	More information on this mission is available at the following URL link: http://spoken-tutorial.org/NMEICT-Intro
10:57	This is Rahul Joshi from IIT Bombay, signing off. Thanks for joining.

Contributors and Content Editors

DeepaVedartham, PoojaMoolya, Pratik kamble, Sandhya.np14