Difference between revisions of "OpenFOAM/C3/Introduction-to-SnappyHexMesh/English-timed"
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(Created page with "{| border=1 | '''Time''' | '''Narration''' |- | 00:00 | Hello and welcome to the spoken tutorial on Introduction to '''snappyHexMesh''' in '''OpenFOAM'''. |- | 00:07 | In th...") |
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| 00:00 | | 00:00 | ||
| − | | Hello and welcome to the spoken tutorial on | + | | Hello and welcome to the '''spoken tutorial''' on '''Introduction to snappyHexMesh''' in '''OpenFOAM'''. |
|- | |- | ||
| 00:07 | | 00:07 | ||
| In this tutorial, we will learn about | | In this tutorial, we will learn about | ||
| − | + | the parameters in '''snappyHexMesh''' | |
| − | + | to generate '''Mesh''' in '''OpenFOAM'''. | |
|- | |- | ||
|00:14 | |00:14 | ||
| − | | As a pre-requisite, the user requires | + | | As a pre-requisite, the user requires: |
* Surface data files in '''STL''' format, located in '''constant/trisurface''' sub-directory of the '''case''' directory | * Surface data files in '''STL''' format, located in '''constant/trisurface''' sub-directory of the '''case''' directory | ||
* A domain with '''hex mesh''' | * A domain with '''hex mesh''' | ||
| − | * '''snappyHexMeshDict''' dictionary located in the '''system''' sub-directory of''' case''' | + | * '''snappyHexMeshDict''' dictionary located in the '''system''' sub-directory of''' case'''. |
|- | |- | ||
| 00:35 | | 00:35 | ||
| − | | To record this tutorial, I am using | + | | To record this tutorial, I am using: |
| − | * '''Ubuntu Linux''' | + | * '''Ubuntu Linux operating system''' 12.04 |
* '''OpenFOAM''' version 2.2.2 | * '''OpenFOAM''' version 2.2.2 | ||
* '''ParaView''' version 3.12.0 | * '''ParaView''' version 3.12.0 | ||
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| 00:50 | | 00:50 | ||
| − | | Let us learn to create a Mesh with the '''snappyHexMesh''' utility. | + | | Let us learn to create a '''Mesh''' with the '''snappyHexMesh''' utility. |
|- | |- | ||
| Line 38: | Line 38: | ||
Step 3 : Remove unused '''cells''' | Step 3 : Remove unused '''cells''' | ||
Step 4 : '''Snap mesh''' to surface | Step 4 : '''Snap mesh''' to surface | ||
| − | Step 5 : Add layers | + | Step 5 : Add '''layers'''. |
|- | |- | ||
| 01:18 | | 01:18 | ||
| − | | We will open the '''terminal '''and enter the path for '''flange '''as shown. | + | | We will open the '''terminal '''and enter the '''path''' for '''flange '''as shown. |
| − | Type '''cd OpenFOAM-2.2.2/tutorials/mesh/snappyHexMesh/flange''' and press '''Enter'''. | + | Type: '''cd space OpenFOAM-2.2.2/tutorials/mesh/snappyHexMesh/flange''' and press '''Enter'''. |
|- | |- | ||
| 01:40 | | 01:40 | ||
| − | | Now type | + | | Now type "ls" and press '''Enter.''' There are two folders '''constant '''and '''system'''. |
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| Line 55: | Line 55: | ||
|- | |- | ||
| 01:55 | | 01:55 | ||
| − | | Now type '''ls''' and press '''Enter.'''You can see '''snappyHexMeshDict '''file. | + | | Now type '''ls''' and press '''Enter.''' You can see '''snappyHexMeshDict '''file. |
|- | |- | ||
| 02:04 | | 02:04 | ||
| − | | To view the contents of the file type -'''gedit snappyHexMeshDict '''and press '''Enter.''' | + | | 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.) | (Note that H, M and D here are in capital letters.) | ||
| Line 80: | Line 80: | ||
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|02:50 | |02:50 | ||
| − | | The | + | | The '''parameter'''s that govern the process of cell splitting are described in '''castellatedMeshControls''' section. |
|- | |- | ||
| 02:58 | | 02:58 | ||
| − | | The parameters that are listed below are well explained in '''snappyHexMeshDict''' file.'''nCellsBetweenLevels''' defines number of cells for each refinement level. | + | | The parameters that are listed below are well explained in '''snappyHexMeshDict''' file. '''nCellsBetweenLevels''' defines number of cells for each refinement level. |
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| Line 92: | Line 92: | ||
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|03:17 | |03:17 | ||
| − | | In the '''Explicit feature edge refinement''' section, you can set specific refinement level for geometry’s feature edges.The | + | | 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. |
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| Line 100: | Line 100: | ||
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| 03:45 | | 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. | + | | '''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 | | 03:59 | ||
| − | |Otherwise the external part (inside the blockMesh) is meshed. | + | |Otherwise the external part (i.e. inside the blockMesh) is meshed. |
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| Line 116: | Line 116: | ||
* '''tolerance''' | * '''tolerance''' | ||
* '''nSolveIter''' | * '''nSolveIter''' | ||
| − | * '''nRelaxIter''' | + | * '''nRelaxIter'''. |
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| Line 124: | Line 124: | ||
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| 04:32 | | 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. | + | |'''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 | | 04:46 | ||
| − | |'''Tolerance''' option specifies the distance the program should look | + | |'''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 | | 04:58 | ||
| − | | '''nSolveIter '''option specifies the number of times the '''snapping''' part of '''snappyHexMesh '''should be run. | + | | '''nSolveIter '''option specifies the number of times the '''snapping''' part of '''snappyHexMesh '''should be '''run'''. |
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Revision as of 17:05, 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:
|
| 00:35 | To record this tutorial, I am using:
|
| 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:
|
| 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 anBold text STL patch in geomery sub-menu, and not a user defined region. |
| 06:10 | ExpansionRatio parameters sets 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 parameteres in snappyHexMesh to generate mesh in OpenFoam. |
| 07:50 | Watch the video available at this URLhttp://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 TeamConducts 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 link http://spoken-tutorial.org/NMEICT-Intro |
| 08:37 | This is Chaitrali Ghodke from IIT BOMBAY signing off.Thanks for joining. |
