|
[Sponsors] |
[snappyHexMesh] How to draw a 3D-Drawing for Meshing |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
May 29, 2021, 01:58 |
How to draw a 3D-Drawing for Meshing
|
#1 |
Member
Join Date: Feb 2018
Posts: 58
Rep Power: 8 |
Hello,
i have a problem with a 3D-Geometry with an interior, SHM generates Patches on surfaces who allready have a patch... First Question: How you draw your OpenFoam Geometrys with or without a wallthickness ? Due to the fact that i need the interior i cant do it without a wallthickness*. I draw it on onshape, everything is fine until it comes to the meshingpart. I downloaded it as an obj Format and execute the following commands before meshing. "surfaceAutoPatch bla.obj bla.obj 90" and "surfacePointMerge bla.obj bla.obj 0" At a first look i get nice GroupIDs (Picture GroupIDs) to generate my custome patch names and do surface refinements and thinks like that, but at the second its a little bit messed up. You can see it on GroupIDs_2. Why is this like this ? The green Patch vertical for example ? I proceed, and on GroupIDs_3 you can see the IDs, for the Manhole, the pipe from the right and the pipe from the bottom. For testing i define this GroupIDs in the region section: Code:
{ patch1 {name Manhole;} patch15 {name Pipe_right;} patch24 {name Pipe_bottom;} } This is my second question. Why i cant assign patch15 ? When i delete patch15 and pipe_right SHM will mesh the geometry. But then its get worse and worse. If i show it in vtkBlockColors, even the pipes get two patches, on the top side. In OnShape its possbile to delete all outside surfaces, i did this. I execute the two commands above and try to mesh it. But then OpenFoam shows this message: "Shell CAD does not support testing for inside Probably it is not closed." So this is also a dead end. Do i need to draw a new geometry, or is it savable ? Best reagrds Kai |
|
May 30, 2021, 14:09 |
|
#2 |
Senior Member
M
Join Date: Dec 2017
Posts: 703
Rep Power: 13 |
Its a bit hard to follow what you are actually doing, at least for me.
Regarding question one: why would you build it with a wall thickness, if you are only interested in what happens inside? Instead of building the actual pipes (like, the solid part of it), build the volume it encloses. That's all you need (I assume.) I think what you are experiencing is, that you gave some kind of small wall thickness. When it comes to meshing, some of these small gaps might be meshed, some might collapse while snappy is running and then it probably creates that mess of regions you see there. Doesn't look like you have to rebuild the geometry, if build in a good way, you should be able to make some boolean operations on the bodies you have and extract the relevant volume in no time. Just carefully rethink what parts of the volume you really need. |
|
June 3, 2021, 03:20 |
|
#3 | |
Senior Member
Franco
Join Date: Nov 2019
Location: Compiègne, France
Posts: 129
Rep Power: 7 |
Quote:
well here you have another onshape user (i recognize the last screen shot) as they mentioned before if you need to simulate for example the liquid inside a pipe you dont need the geometry of the pipe, you need to create the thing INSIDE the pipe, so a commun cylinder. the workflow that you should take is the following: 1. create your geometry in onshape 2. export it in STEP 3. import it in salome-platform , geometry module (salome-platform.org) 4. generate faces groups for each different patch you want 5. go to the mesh module (inside salome) and mesh it in a 2D mesh geometry, and export each group you created SEPARATLY in different .stls 6. you combine them in one cat *.stl >> model.stl 7. you use a stl region setup in snappy hex mesh (snappyHexMesh does not remove internal cells) some documentation about this to lear further than my simplified scheme that I just explained: tobias holzmann video tutorial: https://www.youtube.com/watch?v=CeuFdBqPebc ppt explenation of Wolfdynamics: http://www.wolfdynamics.com/wiki/meshing_OF_SHM.pdf all credits to them for their great work. edit: PS you can also export each surface directly from onshape in different stls (you create an offset surface (it is a feature of onshape) of each patch you want and then export the surface as stl in onshape) but i do not recommend to do this as it will have highly long triangles that can bring problems in the snappying phase (see Creating waterproof STL using snappyHexMesh or salome). best regards. |
||
June 3, 2021, 05:55 |
|
#4 |
Member
Join Date: Feb 2018
Posts: 58
Rep Power: 8 |
Hello,
thank you for your replies and your detailed Salome Manuel . I draw a new geometry only with "solid" interior. Of course i can do it like this, i was wrong . At the next time, i will try it with salome, its also an interesting way. Here are two screenshots. Best regards Kai |
|
June 15, 2021, 13:16 |
|
#5 |
Member
Join Date: Feb 2018
Posts: 58
Rep Power: 8 |
Hello,
i encountered a problem, with my patches . Im tried to assign three inletpatches and one outletpatch. First of all, the outlet patch is generated flawlessly, with the groupid0 maybe the number 0 is related to it and made it work. In Pic_1 you can see the geometryfile loaded in Paraview, the groupids of the inlets are shown in the tabel an the left side. This is the Code i used for that: Code:
patch83 {name inlet;} patch84 {name inlet1;} patch82 {name inlet2;} patch0 {name outlet;} Code:
Adding patches for surface regions ---------------------------------- Patch Type Region ----- ---- ------ CAD: 1 patch outlet 2 wall CAD_patch1 3 wall CAD_patch2 4 wall CAD_patch3 5 wall CAD_patch4 6 wall CAD_patch5 7 wall CAD_patch6 8 wall CAD_patch7 9 wall CAD_patch8 10 wall CAD_patch9 11 wall CAD_patch10 12 wall CAD_patch11 13 wall CAD_patch12 14 wall CAD_patch13 15 wall CAD_patch14 16 wall CAD_patch15 17 wall CAD_patch16 18 wall CAD_patch17 19 wall CAD_patch18 20 wall CAD_patch19 21 wall CAD_patch20 22 wall CAD_patch21 23 wall CAD_patch22 24 wall CAD_patch24 25 wall CAD_patch25 26 wall CAD_patch26 27 wall CAD_patch27 28 wall CAD_patch28 29 wall CAD_patch30 30 wall CAD_patch31 31 wall CAD_patch32 32 wall CAD_patch34 33 wall CAD_patch35 34 wall CAD_patch37 35 wall CAD_patch38 36 wall CAD_patch39 37 wall CAD_patch40 38 wall CAD_patch41 39 wall CAD_patch42 40 wall CAD_patch43 41 wall CAD_patch44 42 wall CAD_patch45 43 wall CAD_patch46 44 wall CAD_patch47 45 wall CAD_patch48 46 wall CAD_patch49 47 wall CAD_patch50 48 wall CAD_patch51 49 wall CAD_patch52 50 wall CAD_patch53 51 wall CAD_patch54 52 wall CAD_patch55 53 wall CAD_patch57 54 wall CAD_patch58 55 wall CAD_patch60 56 wall CAD_patch61 57 wall CAD_patch62 58 wall CAD_patch63 59 wall CAD_patch64 60 wall CAD_patch65 61 wall CAD_patch66 62 wall CAD_patch67 63 wall CAD_patch68 64 wall CAD_patch69 65 wall CAD_patch70 66 wall CAD_patch71 67 wall CAD_patch72 68 wall CAD_patch73 69 wall CAD_patch74 70 wall CAD_patch75 71 wall CAD_patch76 72 wall CAD_patch77 73 wall CAD_patch78 74 wall CAD_patch79 75 wall CAD_patch80 76 wall CAD_patch81 77 patch inlet2 78 patch inlet 79 patch inlet1 80 wall CAD_patch85 81 wall CAD_patch86 82 wall CAD_patch87 83 wall CAD_patch88 84 wall CAD_patch89 85 wall CAD_patch90 Added patches in = 0.04 s So my questions are: Why is SHM messing up my groupid system delivered from the obj file ? Can i stop SHM doing that and assign the right faces with custom names ? For now, i change the names afterwards the meshing process in the boundary file and nSurfaceLayerDict. Best regards Kai |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
[General] Drawing a cylindrical object for viewing in Paraview | jeosol | ParaView | 1 | May 23, 2017 04:08 |
Hi everyone, My draw is duct with wall thickness . when i draw wall thickness in geo | reslan | FLUENT | 0 | March 6, 2016 09:09 |
heat exchanger drawing in Ansys Geometry | flyEmirates | ANSYS Meshing & Geometry | 1 | June 7, 2011 09:01 |
What a Strange Drawing in GAMBIT... | teguhtf | ANSYS Meshing & Geometry | 3 | October 5, 2009 12:17 |
drawing of contour plots | chinthakindi | Main CFD Forum | 1 | April 27, 2004 05:33 |