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

{|border=1
| '''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''' 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.

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| 01:09
|we simulate flow in a channel to determine flow development length along the downstream '''Channel flow''' problem description.

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| 01:19
| The '''boundary names''' and the '''inlet conditions''' are shown in this figure.

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| 01:26
| The '''flow develpoment length''' is given by the formula '''L= 0.05 * Re * D'''.

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| 01:32
| 'Re' which is the '''Reynolds number''' and 'D' which is the '''channel height'''.

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| 01:37
| Using the formula, length of the '''channel''' comes out to be 5 meters and height is kept as 1 meter.

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| 01:45
|The '''Inlet velocity''' is 1 meters per second. And, we are solving this for a '''Reynolds number''' '''( Re ) equal 100'''.

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| 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'''.

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| 02:18
|The folder is named as ''' channel'''. Now, let me switch to the folder.

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| 02:25
| Copy '''0, Constant''' and '''System''' folders of any other case file in the '''simpleFoam''' directory.

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| 02:34
| I have copied the''' file structure''' of the case of''' pitzDaily'''.

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| 02:38
| Paste it inside the '''channel''' folder  and make the necessary changes in the '''geometry''','''boundary faces''' and '''boundary condition'''.

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| 02:48
| Now, let me open the command terminal.

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| 02:51
| To do this, press '''Ctrl+Alt +t''' keys simultaneously on your keyboard.

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| 02:57
| In the terminal, type '''run''' and press '''Enter'''.

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| 03:01
| Now type '''cd space tutorials''' and press '''Enter'''.

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| 03:08
| Now type '''cd space incompressible''' and press '''Enter'''.

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| 03:15
| Type '''cd space simpleFoam''' and press '''Enter'''.

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| 03:20
| Now type '''cd channel''' and press '''Enter'''.

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| 03:28
| Now, type "ls" and press '''Enter'''.

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| 03:33
| You will see three folders '''0, Constant''' and '''System'''.

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| 03:37
| Now type '''cd constant''' and press '''Enter'''.

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| 03:48
| Now type "ls" and press '''Enter'''.

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| 03:52
| In this, you will see files containing properties of fluid and a folder named '''polymesh'''.

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| 03:59
| '''RASProperties''' contains '''Reynolds-averaged stress '''model.

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|04:03
| '''transportProperties''' contains the '''transport model '''and '''kinematic viscosity''' that is (nu), in this case is set at 0.001 m²/s.

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| 04:17
| Now in terminal, type '''cd polyMesh''' and press '''Enter'''. Now, type "ls" and press '''Enter'''.

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| 04:30
|You will see the '''blockMeshDict''' file here.

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| 04:33
| To open up the '''blockMeshDict''' file, in the terminal, type "gedit blockMeshDict" and press '''Enter''', scroll down.

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| 04:48
| The geometry is in meters. So, the '''convertTometers''' is set to 1. Next, we have defined the vertices of the channel. 

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| 04:59
| We have used a '''100 X 100 mesh size''' here and '''cell spacing''' is kept as '''( 1 1 1 )'''.

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| 05:07
| Next, we have setup the '''boundary conditions''' and their types which are '''inlet, outlet, top and bottom '''.

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| 05:19
| As this is a 2D Geometry,  front and Back''' are  kept as '''empty'''.

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| 05:27
| Also, this being a simple geometry,  '''mergePatchPair''' and '''edges''' are to be kept '''empty'''. Close the '''blockMeshDict''' file. 

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| 05:38
| In the '''command terminal''', type '''cd space ..(dot dot) '''and press '''Enter'''. 

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| 05:44
| Again, type '''cd space .. (dot dot)''' and press '''Enter'''.

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| 05:49
| Now. in the terminal. type '''cd space 0 (Zero)''' and press '''Enter'''. Now, type "ls" and press '''Enter'''.

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| 05:58
| This contains the '''intial boundary conditions ''' and''' wall functions''' for the '''channel case'''.

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| 06:05
| It should contain various files such as '''epsilon, k, nut, nuTilda ''' which are the '''wall functions'''and  'p' , 'R' and capital 'U' which  are '''initial conditions''' of the '''flow'''.

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|06:20
|Let me switch back to the slides.

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| 06:24
| Calculate 'k' which is the '''turbulent kinetic energy''' from the formula given in the slide.

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| 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.

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| 06:43
| Calculate '''epsilon''' from the formula given where epsilon is the''' rate of dissipation turbulent  energy''', '''C mu''' is a '''constant''' and its value is 0.09.

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| 06:56
|And''' l''' is the length of the '''channel'''. Let me minimize this.

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| 07:02
| Change only the '''boundary names''' in each of the above '''folder'''.

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| 07:07
| Note that the values of '''nut, nuTilda and R ''' are to kept default.

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|07:13
| Rest of the files should contain initial value for each of the '''boundary faces'''.

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| 07:21
| Now, in the terminal, type '''cd (space) ..(dot dot)''' and press '''Enter'''.

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| 07:27
| There are no changes to be done in the '''system''' folder.

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| 07:31
|Now we need to '''mesh''' the geometry. To do this, in the command terminal, type "blockMesh" and press '''Enter'''.

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| 07:40
|'''Meshing''' is done. Now let me switch back to the '''slide'''.

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| 07:45
| The type of '''solver''' we are using here is '''SimpleFoam'''. It is a '''Steady-state''' solver for '''in-compressible, turbulent flow'''.

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| 07:55
|Let me minimize this. 

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| 07:56
| In the command terminal, type "simpleFoam" and press '''Enter'''.

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| 08:03
| '''Iterations''' running will be seen in the command terminal.

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| 08:07
| '''Iterations '''running may take some time.

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| 08:11
| The '''iterations''' will stop once the solution is converged or it reaches its '''end time value'''.

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| 08:16
| To view the results in '''paraView''', in the terminal, 

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| 08:20
|type "paraFoam" and press '''Enter'''. This will open up the '''paraview''' window.

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| 08:28
| On left hand side of the '''paraView''' window, click '''Apply'''. The geometry can be seen here.

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| 08:35
| On top of '''active variable control''' menu, change the drop down menu from '''solid color''' to capital '''U'''.

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| 08:50
| You can see the '''initial state''' of '''velocity magnitude''' at '''inlet.'''. On top of the '''paraView''' window, click on the'''play''' button of the '''VCR control'''.

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| 09:00
|you can see the final value of the '''velocity magnitude'''.

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| 09:07
| Also toggle on the '''color legend''' from the left hand side top of '''active variable control''' menu, click '''APPLY''' again.

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| 09:16
| Now go to '''Display''', scroll down. You can see '''Rescale''', click on it.

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| 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.

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| 09:36
| The results obtained can be validated with the analytical solution for '''laminar flow''', in a'''channel''' which is u(max)=1.5 Uavg.

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| 09:46
|Using '''openFoam''', we obtain a velocity of 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 ''''''Validation''' with '''analytic results'''

|-
| 10:08
| As an assignment- 
solve the problem for '''Reynold Number 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 the same 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.

|}