OpenFOAM/C2/Creating-simple-geometry-in-OpenFOAM/English-timed

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Time Narration
00:01 Hello and welcome to the spoken tutorial on creating simple geometry in OpenFOAM.
00:06 In this tutorial, I will show you:
00:08 * How to create simple geometry
00:11 * How to view the geometry in paraview.
00:15 To record this tutorial,
00:16 I am using:
  • Linux Operating system Ubuntu version 10.04
  • OpenFOAM version 2.1.0
  • ParaView version 3.12.0
00:27 In CFD the Pre-processing part consists of creating geometry and meshing it.
00:33 Let us take the Lid driven cavity case of the previous tutorial as an example.
00:38 Recall the path for the earlier tutorial,
00:40 I have already opened the command terminal and entered the path for lid driven cavity.
00:48 There are three folders '0, constant' and 'system'. 'Geometry' is inside the 'polymesh' folder of 'constant'.
00:55 In the command terminal, type: cd space constant and press Enter.
01:03 Now, type "ls" and press Enter.
01:06 In this, there is another folder called as 'polymesh'.
01:10 Now type: cd space polymesh and press Enter.
01:18 Now type "ls" and press Enter.
01:22 This contains the 'geometry' file called as 'blockMeshDict'.
01:26 Open the 'blockMeshDict' file with any editor of your choice.
01:30 In the terminal, type: gedit space blockMeshDict( Note that M and D are capital) and press Enter.
01:45 Let me drag this to the capture area.
01:49 Now minimize this.
01:53 Let me switch back to the slides.
01:55 In openfoam, the entire geometry is broken into blocks .
01:59 The blocks are numbered starting from 0 as shown in the figure.,
02:08 Note that in OpenFOAM, for creating a 2D geometry you need to give an unit cell thickness value in the z-axis.
02:19 lid driven cavity is of length 1 and height 1. Minimize the slide.
02:29 On your desktop, create an empty file by right click > create document > Empty file. Name this as 'blockMeshDict.' (Note that M and D here are capital).
02:48 Open this. Now Copy the data from the original lid driven cavity 'blockMeshDict' file to the new 'blockMeshDict' file from line 0.
02:59 Scroll up line 0 upto 'convertTometers'. Copy this and paste it here.
03:15 Scroll down. Now leave some space after 'converttometers'.
03:21 Enter 1 as the geometry is in meters. Insert a semicolon and press Enter.
03:30 Again press Enter. In the file, type "vertices" and press Enter.
03:39 Insert the open bracket and press Enter.
03:43 Press the tab key. Start with point 0, insert open, close brackets, Enter.
03:52 0 space 0 space 0 and press Enter. Again, press tab key, open close bracket .
04:02 Move towards point 1 in positive x-axis and enter 1 space 0 space 0 and press Enter.
04:12 Again press tab key, open close bracket. Move towards point 2 in positive x-y plane and enter 1 space 1 space 0 and press Enter.
04:26 Again press tab key, open close bracket. Enter the 3rd point in positive y-axis 0 space 1 space 0 , press Enter.
04:39 Again press tab key. Enter the 4th point on the front face, open close bracket 0 space 0 space 0.1 and press Enter.
04:51 Similarly, enter the other points with one unit value in the positive z- axis.
04:56 close the bracket and insert a semicolon after it. Press Enter, again press Enter.
05:03 Below vertices are the blocks. Type blocks and press Enter. Insert a Open bracket and press Enter.
05:16 Let me switch back to the slides.
05:19 Note that Lid driven cavity is taken as a single block.
05:24 Let me switch back to 'blockmeshdict'.
05:27 Enter the points for the blocks in the clockwise sense.
05:31 We are using here hexa hedal blocks for meshing.
05:34 Now, type "hex". Leave some space. In brackets, enter 0 space 1 2 3 4 5 6 7 , again leave some space.
05:53 Note that for multiple blocks, the points will be more.
05:58 After this, enter the grid points in the x, y and z directions.
06:02 In brackets open close brakets enter 30 space 30 space 1 leave some space , you can modify the grid as an when needed
06:16 Grid point in z-axis can be taken as one
06:22 Now leave some space and type simple grading leave some space open close bracket enter 1 space 1 space 1
06:36 This is the grid spacing in the x y and z direction. Press Enter
06:43 Insert close bracket, insert a semicolon and press Enter
06:48 Again press Enter. Now type edges, and press Enter
06:55 As this is a simple geometry edges can be kept empty
07:00 Insert open bracket press Enter, close the bracket ,insert a semicolon and press Enter
07:07 Again press Enter. Below edges are the boundary conditions.
07:11 Here you need to enter the boundary name for the faces
07:15 Type boundary and press Enter .
07:19 insert a open bracket and press Enter
07:23 Now let me switch back to the slides
07:26 In the geometry the upper wall is moving and other three walls are fixed.
07:31 The front and back faces are named as empty as this is a 2D problem
07:39 Open the new blockMeshDict file again
07:42 In boundary put the name of the patch as moving wall . Press Enter
07:51 Now Insert a open curly bracket and press Enter
07:56 Now enter the type for the moving wall , enter type space wall
08:06 insert a semicolon and press Enter
08:09 Now insert open bracket, and press Enter. Press the tab key. Open close bracket.
08:20 In this bracket enter the pointfor for faces
08:24 Let me switch to the slide
08:27 Note that order of the points should be in such a way that the thumb should be normal to the face
08:34 And fingers making a curl as shown in the figure .
08:39 The curl can be clockwise or anti- clockwise
08:43 Also note that the points should match with the points inserted in vertices
08:48 Now let me switch back to the new blockmeshdict file .
08:52 Now in the faces enter 3 space 7 space 6 space 2.
09:01 Let me switch back to the slide. These are the point for the moving wall 3,7,6,2.
09:09 Minimise this. Note that you can start from any point on that face. Now press Enter
09:17 Close the bracket again press Enter. Close the curly bracket.
09:22 Another note we need to enter a semi- colon, after you insert the points, a faces now after the curly brackets, press Enter again press Enter
09:35 Now similarly enter boundary condition and faces for the fixed wall
09:40 Being a 2D problem the type of boundary for front and back face can be kept as empty.
09:46 Refer to the figure in the slide. For entering the points. Minimise this
09:52 Insert the closed brackets, put a semicolon and press Enter, again press Enter
09:59 Now type mergePatchPairs and press Enter
10:04 Since their are no patches to merge it can be kept empty
10:08 Insert open close bracket. Insert a semi-colon and press Enter
10:14 We are done with creating the blockmeshdict file. Save this
10:18 The complete blockMeshDict file is as shown here.
10:26 Close both the blockMeshDict files
10:29 Note that the command terminal will not work until blockMeshDict file is closed
10:35 Switch back to the terminal. Now type cd (dot) (dot) twice to return back to the cavity folder. Now Mesh the geometry
10:45 To do this in a terminal type: blockMesh and press Enter
10:53 Now View the geometry by typing in the command terminal paraFoam and press Enter
10:59 This will open the ParaView window
11:03 Now On the left hand side click Apply on object inspector menu thus you can see the geometry.
11:13 Now let me switch back to the slides
11:16 In this tutorial we learnt:
11:18 Creating a simple geometry in OpenFOAM
11:22 Viewing the geometry in Paraview
11:25 This brings us to the end of the tutorial
11:29 As an Assignment
11:31 Change the direction of lid driven cavity ,Change the grid size to 50 50 1and View the geometry in paraview
11:41 Watch the video available at this URL: http://spoken-tutorial.org/What_is_a_Spoken_Tutorial
11:44 It summarizes the Spoken Tutorial project.
11:46 If you do not have good bandwidth, you can download and watch it.
11:51 The Spoken Tutorial Project Team
11:53 -Conducts workshops using spoken tutorials
11:55 -Gives certificates to those who pass an online test
11:59 -For more details, please write to contact@spoken-tutorial.org
12:05 Spoken Tutorial project is part of Talk to a Teacher project,
12:09 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
12:15 More information on the same is available at the following URL link http://spoken-tutorial.org/NMEICT-Intro
12:19 This is Rahul Joshi from IIT BOMBAY signing off.Thanks for joining.

Contributors and Content Editors

DeepaVedartham, Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14, Sneha