OpenFOAM/C3/Generating-Mesh-using-snappyHexMesh/English

Tutorial: Generating mesh using snappyHexMesh in OpenFOAM.

Script and Narration: Chaitrali Ghodke.

Keywords: Import STL file, background hex mesh, snappyHexMeshDict.

Visual Cue	Narration
Slide 1	Hello and welcome to the spoken tutorial on generating mesh using snappyHexMesh in OpenFOAM.
Slide 2 : Learning Objectives	In this tutorial we will learn to Generate mesh using snappyHexMesh utility Simulate temperature distribution of a flange.
Slide 3: Pre-requisite	As a pre-requisite, You should know parameters in snappyHexMeshDict to generate mesh. For more details, refer the tutorial on introduction to snappyHexMesh in OpenFOAM.
Slide 4: System Requirement	To record this tutorial, I am using Ubuntu Linux Operating system version 12.04. OpenFOAM version 2.2.2 ParaView version 3.12.0
Slide 5:	We are solving an existing case of flange from laplacianFoam in basic directory. laplacianFoam solver solves simple laplace equations.
Click on home >> OpenFoam-2.2.2	Now let us go to home folder and click on OpenFoam-2.2.2 folder.
Click on tutorials	You will see tutorials. Click on it.
Click on mesh	Then click on mesh folder.
Click on snappyHexMesh	You will see the snappyHexMesh folder. Click on it
Right click >> Create new folder >> flange_1	In this folder, create a new folder by name flange_1. Right click >> Create New Folder >> flange_1.
Go back to tutorials >> basic folder	Now let's go back two levels.
Double-click on basic folder	Open the basic folder.
Double-click on laplacianFoam	You will see laplacianFoam folder. Click on it.
Double-click on flange	You will see flange case. Click on it to open the folder.
Select 0, constant and system folders	Copy the three folders 0, constant and system.
Go back to mesh >> snappyHexMesh >> flange_1 folder	Now let us go three levels back.
Paste them there	Paste the copied folders inside the flange_1 folder.
Go back to snappyHexMesh >> flange folder	Now let us go one level back.
Double-click flange folder	Click on flange folder.
Double-click on system	You will see constant and system folders. Click on system folder.
Select snappyHexMeshDict and surfaceFeatureExtractDict	Copy snappyHexMeshDict and surfaceFeatureExtractDict from this folder.
Go back to snappyHexMesh >> flange_1 folder	Now let us go two levels back.
Paste them there	Paste these two files inside the system directory of flange_1 folder.
Right click >> Create new folder >> triSurface	Now let us go one level back. Click on constant folder. In this, create a folder by name triSurface.
Go back to tutorials >> resources >> geometry folder	Now let us go four levels back.
Double-click on resources	Open the resources folder.
Double-click on geometry	You will see geometry folder. Now, open the geometry folder.
Double-click flange.stl.gz file	In this, you will see flange.stl.gz file. Extract this file.
Go to tutorials >> mesh >> snappyHexMesh >> flange_1 >> constant >> triSurface	Give the path of triSurface folder in constant directory of flange_1 folder.
	Now close this.
Ctrl+Alt+t simultaneously cd OpenFOAM-2.2.2/tutorials/mesh/snappyHexMesh/flange_1	Open command terminal and enter the path for flange_1 as shown. Type cd OpenFOAM-2.2.2/tutorials/mesh/snappyHexMesh/flange_1
Type ls	Now type ls and press Enter.
Type cd constant	There are three folders 0, constant and system. Type cd space constant and press Enter.
Type ls	Now type ls and press Enter.
Type cd polymesh	You will see the polymesh and triSurface folders. Type cd space polymesh and press Enter.
Type ls	Now type ls and press Enter.
Type gedit blockMeshDict	You can see the blockMeshDict file. To view the contents of the file, type gedit blockMeshDict and press Enter.
	This will open up the blockMeshDict file. This file contains co-ordinates for hex mesh and boundary patches.
Close blockMeshDict Type cd .. Type cd ..	Now close this and in the command terminal type cd (space) .. (dot) (dot) and press Enter. Again type cd (space) .. (dot) (dot) and press Enter.
Type cd system	Now type cd space system and press Enter.
Type ls	Now type ls and press Enter. You can see the surfaceFeatureExtractDict file.
Type gedit surfaceFeatureExtractDict	To view the contents of the file, type gedit surfaceFeatureExtractDict and press Enter. (Note that F, E and D here are capital)
Open surfaceFeatureExtractDict	This will open up the surfaceFeatureExtractDict file. This file contains the information about geometry’s feature edges. The included angle is taken as 150.
Close surfaceFeatureExtractDict	Now close this.
Type gedit snappyHexMeshDict	In command terminal type gedit snappyHexMeshDict and press Enter. (Note that H, M and D here are capital)
Open snappyHexMeshDict	This will open up the snappyHexMeshDict file. This file contains all the instructions about snappyHexMesh.
Give the geometry name	In snappyHexMeshDict I have already made some changes. I have named flange.stl same as that of STL file, which is in the constant/trisurface directory.
Give the file name for explicit feature edge refinement.	For Explicit feature edge refinement in castellatedMeshControls, I have given the file name flange.eMesh. This file is obtained by surfaceFeatureExtract utility. The remaining details in the snappyHexMesh have changed as per requirements.
Type cd ..	Now close this and in command terminal, type cd (space) .. (dot) (dot) and press Enter.
Type cd 0	Type cd space 0 and press Enter.
Type ls	Type ls and press Enter. You can see the T file.
Type gedit T	Now type gedit space T and press Enter.
	This will open up the T file. You will see the initial conditions for every patch.
	Now, we have to give initial conditions for all patches of flange.
Copy the conditions	Copy the initial conditions for patch 1 and paste it after patch 4 in the same file T.
Type flange_	Now type flange_ before this patch 1.
Give initial conditions for all patches of flange. Save file T >> close	Similarly, we can do this for patch 2, 3 and 4. Save this T file and close it.
Type cd ..	And in the command terminal type cd (space) .. (dot) (dot) and press Enter.
On the terminal >> type blockMesh	Now, we need to mesh the geometry. For that in command terminal, type blockMesh and press Enter. Meshing is done.
Run surfaceFeatureExtract	Now type surfaceFeatureExtract and press Enter. (Note that F and E here are capital.) Surface feature extraction is done.
Type snappyHexMesh -overwrite	Now type snappyHexMesh -(dash) overwrite and press Enter.
	- (dash) overwrite command will prevent copying the files from the last time folders.
	If not, the resulting meshes will be inside the next time folders, possibly the folders 1, 2 and 3.
	Meshing will take some time. <<PAUSE>> Now meshing is completed.
	For simulating temperature distribution, we are using laplacianFoam solver.
Type laplacianFoam	In the command terminal type laplacianFoam and press Enter. (Note that F here is capital.) Iterations running will be seen in the terminal window.
Type paraFoam	Once solving is completed, type paraFoam and press Enter to view the geometry and the results. This will open up the Paraview window.
Click on Apply button	On the left hand side of Paraview window, click on Apply. The geometry can be seen here.
Check the box for T >> Click on Apply button	Scroll down the properties panel of the object inspector menu. Check the box for T in the volume fields and click on Apply.
In the drop down menu change from solid color to T	Now go to the top of Active variable control drop down menu. Change from solid color to capital T, which is the initial condition for the flange.
Click on the play button	Now on the top of the Paraview window, you can see the VCR controls. Click on the Play button. Now this is the final result for temperature distribution of a flange.
Toggle on the color legend	Toggle on the color legend by clicking on top left of the Active variable control menu. This is the colour legend for temperature T. <PAUSE> Now let me get back to the slides.
Slide 6 : Assignment	This brings us to the end of the tutorial. As an assignment, Change some parameters in the snappyHexMeshDict: Refinement parameters locationInMesh co-ordinates snapControls, etc. You can also change the temperature in the 0 folder and view the results in Paraview.
Slide 7 : Summary	In this tutorial we learnt : To generate mesh by snappyHexMesh utility in OpenFoam. Simulate temperature distribution of a flange.
Slide 8 : About Spoken tutorials	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.
Slide 9: 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 contact@spoken-tutorial.org
Slide 10: Acknowledgement	Spoken Tutorials are part of Talk to a Teacher project, It is supported by National Mission on Education through ICT, MHRD, Government of India. More information on the same is available at following URL link http://spoken-tutorial.org/NMEICT-Intro
About the contributor	This is Chaitrali Ghodke from IIT BOMBAY signing off. Thanks for joining.

Contributors and Content Editors

Chaitralighodke, Nancyvarkey