Difference between revisions of "OpenFOAM/C3/Introduction-to-SnappyHexMesh/English-timed"

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| '''nRelaxIter''' option specifies the number of times the mesh should run a relaxing script, that removes bad '''mesh''' points.
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| In '''layers''' option, you can define the number of '''layers''' and the patch on which to attach the '''layers'''.It must be an'''Bold text''' STL patch in '''geomery''' sub-menu, and not a user defined region.
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| In '''layers''' option, you can define the number of '''layers''' and the '''patch''' on which to attach the '''layers'''. It must be an STL (Bold text)  patch in '''geomery''' sub-menu, and not a user defined region.
  
 
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| '''ExpansionRatio''' parameters sets the growth factor of the '''layers''' (that is ratio between two subsequent layers).
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| '''ExpansionRatio''' parameters set the growth factor of the '''layers''' (that is ratio between two subsequent layers).
  
 
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| '''finalLayerThickness''' parameter sets the thickness of the last layer.'''minThickness''' parameter sets the minimum allowable thickness of layer.
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| '''finalLayerThickness''' parameter sets the thickness of the last layer. '''minThickness''' parameter sets the minimum allowable thickness of layer.
  
 
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|"'''Advanced settings''' is the second group of parameters.It contains more specific controls that can help in layer creation.
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|'''Advanced settings''' is the second group of parameters. It contains more specific controls that can help in layer creation.
  
 
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| '''nRelaxIter''' option specifies the number of times the mesh will run a relaxing script.
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| '''nRelaxIter''' option specifies the number of times the '''mesh''' will '''run''' a relaxing script.
  
 
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| '''maxFaceThicknessRatio''' option specifiess the maximum allowable value of aspect ratio.
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| '''maxFaceThicknessRatio''' option specifiess the maximum allowable value of '''aspect ratio'''.
  
 
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| meshQualityControls parameter sets the minimum thresholds to generate '''mesh''' in '''snap''' and add-layers parts.
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| meshQualityControls parameter sets the minimum thresholds to generate '''mesh''' in '''snap''' and '''add-layers''' parts.
  
 
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|In 99% of the cases, it is better to leave the default values.But sometimes, you can deactivate one or more controls to force mesh generation.
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|In 99% of the cases, it is better to leave the default values. But sometimes, you can '''deactivate''' one or more controls to force mesh generation.
  
 
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| These are the different parameters in '''snappyHexMeshDict'''.These parameters are important to generate '''mesh''' using '''snappyHexMesh''' utility.
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| These are the different parameters in '''snappyHexMeshDict'''. These parameters are important to generate '''mesh''' using '''snappyHexMesh''' utility.
  
 
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| In this tutorial we learnt Different parameteres in '''snappyHexMesh '''to generate mesh in '''OpenFoam'''.
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| In this tutorial, we learnt different parameters in '''snappyHexMesh '''to generate mesh in '''OpenFoam'''.
  
 
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| Watch the video available at this URLhttp://spoken-tutorial.org/What_is_a_Spoken_Tutorial  
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| Watch the video available at this URL:
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It summarizes the Spoken Tutorial project. If you do not have good bandwidth, you can download and watch it.
+
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.
  
 
|-
 
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| 08:03
 
| 08:03
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| The Spoken Tutorial Project TeamConducts workshops using spoken tutorials
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| The Spoken Tutorial Project team:
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Gives certificates to those who pass an online test For more details, please write to  
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* Conducts workshops using spoken tutorials.
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contact@spoken-tutorial.org
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* Gives certificates to those who pass an online test.
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For more details, please write to:
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'''contact@spoken-tutorial.org'''
 
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| 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. More information on the same is available at following URL link http://spoken-tutorial.org/NMEICT-Intro
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| '''Spoken Tutorial'''s are 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 following URL:
 +
http://spoken-tutorial.org/NMEICT-Intro
  
 
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| 08:37
 
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| This is Chaitrali Ghodke from IIT BOMBAY signing off.Thanks for joining.
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| This is Chaitrali Ghodke from '''IIT Bombay''', signing off. Thanks for joining.
  
 
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Revision as of 17:15, 4 July 2016

Time Narration
00:00 Hello and welcome to the spoken tutorial on Introduction to snappyHexMesh in OpenFOAM.
00:07 In this tutorial, we will learn about

the parameters in snappyHexMesh to generate Mesh in OpenFOAM.

00:14 As a pre-requisite, the user requires:
  • Surface data files in STL format, located in constant/trisurface sub-directory of the case directory
  • A domain with hex mesh
  • snappyHexMeshDict dictionary located in the system sub-directory of case.
00:35 To record this tutorial, I am using:
  • Ubuntu Linux operating system 12.04
  • OpenFOAM version 2.2.2
  • ParaView version 3.12.0
00:50 Let us learn to create a Mesh with the snappyHexMesh utility.
00:55 The steps are as follows-

Step 1 : Create a base mesh by using blockMesh utility Step 2 : Refine base mesh Step 3 : Remove unused cells Step 4 : Snap mesh to surface Step 5 : Add layers.

01:18 We will open the terminal and enter the path for flange as shown.

Type: cd space OpenFOAM-2.2.2/tutorials/mesh/snappyHexMesh/flange and press Enter.

01:40 Now type "ls" and press Enter. There are two folders constant and system.
01:50 Type cd space system and press Enter.
01:55 Now type ls and press Enter. You can see snappyHexMeshDict file.
02:04 To view the contents of the file, type: -gedit space snappyHexMeshDict and press Enter.

(Note that H, M and D here are in capital letters.)

02:19 This will open up the snappyHexMeshDict file.
02:23 snappyHexMeshDict file contains all the instructions and the entire process revolves around this file.
02:32 With the first rows of snappyHexMeshDict, you can activate or skip sections of the process.
02:40 In the geometry section, all active regions that take part in snappy process can be defined.
02:50 The parameters that govern the process of cell splitting are described in castellatedMeshControls section.
02:58 The parameters that are listed below are well explained in snappyHexMeshDict file. nCellsBetweenLevels defines number of cells for each refinement level.
03:12 The higher it is, the more gradual the mesh will be.
03:17 In the Explicit feature edge refinement section, you can set specific refinement level for geometry’s feature edges. The ".eMesh" file can be obtained with the surfaceFeatureExtract utility.
03:34 In the surface-based refinement section, you can set the refinement levels of all surfaces defined in geometry file.
03:45 Mesh selection is a very important parameter. If the chosen point is inside the surface described in geometry file, then snappyHexMesh will create the internal mesh.
03:59 Otherwise the external part (i.e. inside the blockMesh) is meshed.
04:04 The next step involves moving cell vertex points onto the surface geometry.
04:12 The snapping process is carried out by four parameters:
  • nSmoothPatch
  • tolerance
  • nSolveIter
  • nRelaxIter.
04:23 These parameters control the number of iterations and tolerance between mesh and STL surface.
04:32 nSmoothPatch option specifies the number of times the exterior ( that is the boundary wall) should be iterated. The mesh will become smoother if the number of iterations are more.
04:46 Tolerance option specifies the distance the program should look for a point to snap. The distance will be the number that is in tolerance.
04:58 nSolveIter option specifies the number of times the snapping part of snappyHexMesh should be run.
05:07 nRelaxIter option specifies the number of times the mesh should run a relaxing script, that removes bad mesh points.
05:19 The process of mesh layer addition involves shrinking the existing mesh from the boundary and inserting layers of cells.
05:27 The first group of parameters define the dimensions for layers and surface, on which they will be attached.
05:36 RelativeSizes option ( that is true or false) changes the way to read the parameters given next.

true: next parameters define the layers' dimensions as parameters. false: next parameters define directly the layers' dimensions.

05:55 In layers option, you can define the number of layers and the patch on which to attach the layers. It must be an STL (Bold text) patch in geomery sub-menu, and not a user defined region.
06:10 ExpansionRatio parameters set the growth factor of the layers (that is ratio between two subsequent layers).
06:19 finalLayerThickness parameter sets the thickness of the last layer. minThickness parameter sets the minimum allowable thickness of layer.
06:34 Advanced settings is the second group of parameters. It contains more specific controls that can help in layer creation.
06:45 FeatureAngle is the angle above which the surface will not be extruded.
06:52 nRelaxIter option specifies the number of times the mesh will run a relaxing script.
07:00 maxFaceThicknessRatio option specifiess the maximum allowable value of aspect ratio.
07:10 meshQualityControls parameter sets the minimum thresholds to generate mesh in snap and add-layers parts.
07:18 In 99% of the cases, it is better to leave the default values. But sometimes, you can deactivate one or more controls to force mesh generation.
07:30 These are the different parameters in snappyHexMeshDict. These parameters are important to generate mesh using snappyHexMesh utility.
07:40 Let us summarize.
07:42 In this tutorial, we learnt different parameters in snappyHexMesh to generate mesh in OpenFoam.
07:50 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.

08:03 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

08:21 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.

More information on the same is available at following URL: http://spoken-tutorial.org/NMEICT-Intro

08:37 This is Chaitrali Ghodke from IIT Bombay, signing off. Thanks for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14

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