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-   -   [ICEM] Blocking technique. Issues of the day. (http://www.cfd-online.com/Forums/ansys-meshing/114348-blocking-technique-issues-day.html)

Zeppo March 9, 2013 14:59

Blocking technique. Issues of the day.
 
I have some questions concerning ANSYS ICEM CFD 14.0 Windows 64-bit

1) Having changed something in Blocking structure (moved vertices, for example) and selected checkbox Model -> Blocking -> Pre-Mesh in the Display Control Tree to make ICEM show pre-mesh the following message window pops up
http://s17.postimage.org/4vyjd3gov/image001.png
Iíd like pre-mesh to be recomputed and showed in visualisation window right after I have selected the checkbox Model -> Blocking -> Pre-Mesh without asking me if I really want it to be recomputed or not.



2) Suppose I want to blank out a lot of blocks from the screen with only few blocks left shown. I go to Model -> Blocking -> Blank Blocks and select which blocks to blank. Is there any reverse-selection-option so that I could select only those blocks which I want to be left shown with all the rest of blocks being hidden?



3) What is the option Pre-Mesh Params -> Match Edges for?
http://s1.postimage.org/9gvlqrjpb/image003.png
I want Edge_01 and Edge_02 to have identical node distribution parameters: the same number of nodes, the same node spacing, and the same mesh law. So changing of any node distribution parameter of one edge is bound to result in changing conformable node distribution parameter of another edge. I set Edge_01 as a Reference Edge and Edge_02 as a Target Edge, select Link spacing checkbox. Than changing number of nodes distributed along Edge_01 I see nothing happen to nodes along Edge_02, they donít change at all. How on earth does that Edge Matching work?
http://s13.postimage.org/sfp4bogfr/image006.png



4) I have a mapped block, connected to some other mapped blocks. I want to convert its type from mapped to swept. To do so I go to Edit Block -> Convert Block Type and set top face of the block to be a Swept Face. Top face seems to have disappeared after converting and no mesh is generated inside the block. Output error message is ďA serious internal error has occurred. Continuing to work may be dangerous. Please save your work as soon as possible and use a previous copy of your work. If you cannot proceed without getting this message please contact technical support. The following message was designed to aid developers fix the problem: error constructing superblock 303251Ē.
http://s9.postimage.org/gvwytzl1b/image007.png



5) I have a block with a face split into 3 parts. Thereíre no adjacent blocks to share this face with (with the exception of those in VORFN). I want 3 parts of the face to be merged into single part. Edit Block -> Merge Faces.
http://s24.postimage.org/xr52ld8kl/image008.png
After I select the corner vertices of the 3-part face and click "apply" an error arises:"node's don't form a facemerge face failed" (the same as at the end of my question #7). I had some relevant pictures, but they were lost somehow.



6) I want to split a block face into 2 parts (Split block -> Split Face). I select specific face to split and select the edge where the split will take place.
http://s8.postimage.org/p1mf1frut/image009.png
What I get is the whole block split into 2 blocks with the split direction determined in according to the edge I have selected.
http://s3.postimage.org/tb7rse2hf/image010.png

Zeppo March 9, 2013 15:02

[ICEM] Blocking technique. Issues of the day.
 
7) I want to merge 2 blocks into single block (Edit Block -> Merge Blocks)
http://s15.postimage.org/4073v0l3v/image011.png
Merging of the blocks results in a single block which has 6 faces, 4 of them being split into 2 parts each.
http://s8.postimage.org/bku1wb6x1/image012.png
I try merging 2 parts of the face into single face by means of Edit Block -> Merge Faces tool.
http://s24.postimage.org/lp0yj41id/image013.png
It says I have to select the corners of the face to merge. So I do, I select 2 corner vertices and get nothing but an error message box. Why doesnít Merge Face work as expected?
http://s11.postimage.org/6ngccto4j/image014.png
http://s10.postimage.org/rj22t7tp5/image015.png



8) Aproach recommended (in according to Documentation for ANSYS ICEM CFD 14.0) for mesh generation by means of blocking is a top-down approach. That means I have to create one large global block to encapsulate geometry and than I have to split this global block into several small blocks to capture all the geometry features. This strategy implies I shouldnít extensively apply such block creation techniques as Extrude Face or From Vertices/Faces (a bottom-up approach). If I donít follow this recommendation I can incur trouble easily. Creation of blocks in a random manner results in a chaotic, disorderly pale of blocks which are very difficult to handle. All the blocks which are supposed to have been deleted actually have been put into VORF part. You can see in the pictures below what this leads to.
http://s18.postimage.org/hsoqhz4dl/image016.png
http://s23.postimage.org/um63ta6jf/image020.png
The problem seems to be due to structured block index system which ICEM have to maintain whatever real block arrangment is. Why Canít ICEM give up that structured block index system and apply unstructured block index system? It could resolve the issue. Iíd like to have the opportunity to create blocks in the unconditioned, arbitrary way. Having a very comlex geometry I canít imagine beforehand what the block structure will look like. Iíd like to have the opportunity to create a block from scratch (for example, from vertices or by extruding a face of any existing block) and than move it to the right place and merge it to the existing blocks. ICEM has such means but they are not considered be be your preferable choice because of imposing a top-down approach on you.
http://s13.postimage.org/5xiocbeif/image022.png



9) Suppose I have a block and I want to move its vertex (Blocking -> Move Vertices) in a plane which is parallel to the ďscreen planeĒ and passes through this vertex.
http://s22.postimage.org/3wpi5gwwh/image023.png
As I drag the vertex with a mouse cursor it moves along the specific edge as if I have fixed movement direction. But I haven't, as you can see, put any movement constraints in the options for Move Vertices tool. I could resolve the issue if I created local coordinate system with axes oriented in the appropriate directions. Than I could move vertices in that local coordinate system. Is there any way I can rid of such superfluous, troublesome operations?
http://s18.postimage.org/r78g6zoq1/image025.png

Zeppo March 9, 2013 15:03

[ICEM] Blocking technique. Issues of the day.
 
10) How can I measure such block quantities as the distance between 2 vertices, the length of an edge, the surface area of a face, the volume of a block etc.



11) Some operations on blocks require you to select location. The following window pops up to control selection of the points. What I canít realize is how some buttons in this window work.
http://s23.postimage.org/98tpzar2z/image026.png
http://s14.postimage.org/qs7c1p3y5/image027.png Toggle allow any plane selection (If toggled ON, a location on any plane can be selected). What does it mean? How can I specify this ďanyĒ plane? What if I wanted to select location at the point of a block face?



12) What if I wanted to create 2D blocks and 3D blocks simultaneously? In the picture below I have a green surface and a blue solid. I want to create 2D blocks for surface and 3D blocks for solid so that 2D mesh is connected to 3D mesh on the node by node base.
http://s23.postimage.org/6j384g4uz/image028.png
First I create 3D block around the solid
http://s23.postimage.org/pklupfst7/image030.png
Then I go to Create Block -> From Vertices -> 2D and try creating 2D block around the surface. ICEM refuses to do this because the current blocking is 3D.
http://s17.postimage.org/6h0jcjs8v/image032.png
http://s21.postimage.org/8ozbgwrk7/image033.png



13) I want to create 4 new blocks by means of extruding 4 faces (marked with blue color) of an existing block in the directions normal to each face at once. I.e. each block should be created by extruding in the direction normal to the face it is extruded from. But ICEM can only extrude in one directions determined by the normal to the face selected first.
http://s10.postimage.org/rznqz0ye1/image034.png
http://s16.postimage.org/jjfzkvvhx/image035.png

BrolY March 11, 2013 05:31

1) I don’t think so, but that could be a nice feature.
2) I don’t think so, but that could be a nice feature.
3) Edge_01 and Edge_02 must have the same number of nodes. But the nodes distribution can be different (mesh law) if you don’t select ę copy parameters Ľ (Edge Params). If you want more info about Match Edges, have a look at the help guide.
4) No idea what’s going on here.
5) 6) 7) I have already asked this question on this forum, and nobody answered. That’s one of the biggest mystery of ICEM !
8) This is a question for an ANSYS employee. Simon ? ;)
9) i don’t get it. Why don’t you use the tools such as Fix direction or others ? It can be a superfluous operation to you, but when you have to move vertices which are not in the global coordinate system and also vertices which are in the global coordinate system, ICEM can’t ę understand Ľ what you want to do. It’s a computer, you have to work a little bit ! Try the other options of Blocking -> Move Vertices, some are very useful !
10) Look for the tool Measure Distance (you can apply it on mesh too). For the surface area : Info -> Surface Area. For the volume, right click on a part and then Info.
11) I have never used that tool.
12) Not the right way. First idea, create a 2D block on the block, split the edge and extrude face. Second idea, create a 3D block, and delete the extra blocks.
13) You are right.

Far March 11, 2013 19:44

Quote:

Originally Posted by zeppo (Post 412780)
7) i want to merge 2 blocks into single block (edit block -> merge blocks)
http://s15.postimage.org/4073v0l3v/image011.png
merging of the blocks results in a single block which has 6 faces, 4 of them being split into 2 parts each.
http://s8.postimage.org/bku1wb6x1/image012.png
i try merging 2 parts of the face into single face by means of edit block -> merge faces tool.
http://s24.postimage.org/lp0yj41id/image013.png
it says i have to select the corners of the face to merge. So i do, i select 2 corner vertices and get nothing but an error message box. Why doesnít merge face work as expected?
http://s11.postimage.org/6ngccto4j/image014.png
http://s10.postimage.org/rj22t7tp5/image015.png



[/img]


I can not fid any problem. Tried on similar case and every thing is fine...

Far March 11, 2013 19:53

Quote:

Originally Posted by zeppo (Post 412779)

6) i want to split a block face into 2 parts (split block -> split face). I select specific face to split and select the edge where the split will take place.
http://s8.postimage.org/p1mf1frut/image009.png
what i get is the whole block split into 2 blocks with the split direction determined in according to the edge i have selected.
http://s3.postimage.org/tb7rse2hf/image010.png

play with block index control and display only required face and apply operation. you will get the required face split. But why you want to do it?

Far March 11, 2013 19:55

Quote:

5) I have a block with a face split into 3 parts. There’re no adjacent blocks to share this face with (with the exception of those in VORFN). I want 3 parts of the face to be merged into single part. Edit Block -> Merge Faces.
do you get any problem ? I dont see any problem in applying this function.


Q # 8 . Delete blocks permanently

Zeppo March 15, 2013 14:16

Quote:

Originally Posted by Far (Post 413258)
do you get any problem ? I dont see any problem in applying this function.

I do. After I select the corner vertices of the 3-part face and click "apply" an error arises:"node's don't form a facemerge face failed" (the same as at the end of my question #7). I had some relevant pictures, but they were lost somehow.

Quote:

Originally Posted by Far (Post 413258)
Q # 8 . Delete blocks permanently

I tried to delete all the blocks from part VORFN. They wouldn't. No dice! They all "survived". If you have to delete a block do you usually delete it permanently?

Far March 15, 2013 14:40

Actually I tried on two face block and it worked ok.


What happens if you turn off VORFN? Blocks are deleted permentally for two reasons:

1. To break the mesh connectivity.

2. To reconstruct VORFN

Zeppo March 15, 2013 15:34

Quote:

Originally Posted by Far (Post 413255)
I can not fid any problem. Tried on similar case and every thing is fine...

Quote:

Originally Posted by Far (Post 413257)
play with block index control and display only required face and apply operation. you will get the required face split. But why you want to do it?

Please look at my question #8 one more time.
Quote:

Originally Posted by Zeppo (Post 412780)
Having a very comlex geometry I canít imagine beforehand what the block structure will look like. Iíd like to have the opportunity to create a block from scratch (for example, from vertices or by extruding a face of any existing block) and than move it to the right place and merge it to the existing blocks.

Most of threads on cfd-online, as far as I can see, have a deal with rather "toy" geometry, not a "complex" one by any means. Moreover, I couldn't designate the geometry in my question #8 as complex too. But for all that, this simple geometry took 750 blocks to capture only a part of it. I didn't manage to finish my meshing right. I just gave up trying to overcome those ICEM bugs. As the number of blocks increases, ICEM bug probability increases more and more, with a saturation point coming sooner or later. Unfortunately I'm not allowed to show a real complex geometry I and my colleagues deal with from time to time. If I tried to use ICEM to mesh it with block technique I would failed by all means.
I'd like to repeat again what I said before:
Quote:

Originally Posted by Zeppo (Post 412780)
The problem seems to be due to structured block index system which ICEM have to maintain whatever real block arrangment is. Why Canít ICEM give up that structured block index system and apply unstructured block index system? It could resolve the issue

.

Zeppo March 31, 2013 09:19

Quote:

Originally Posted by BrolY (Post 413046)
9) i donít get it. Why donít you use the tools such as Fix direction or others ? It can be a superfluous operation to you, but when you have to move vertices which are not in the global coordinate system and also vertices which are in the global coordinate system, ICEM canít ę understand Ľ what you want to do. Itís a computer, you have to work a little bit ! Try the other options of Blocking -> Move Vertices, some are very useful !

What If I haven't got the edge to use it as the move direction? I would be happy if I could specify the move direction right on the spot, the way similar to that realized in SpaceClaim, a CAD direct modeler. I'd like ICEM to have the user interface of a modern style to some extent, to be more user-friendly.
Quote:

Originally Posted by BrolY (Post 413046)
10) Look for the tool Measure Distance (you can apply it on mesh too). For the surface area : Info -> Surface Area. For the volume, right click on a part and then Info.

I'd like to measure block-related things not geometry. The Measure Distance tool is only applied to measure the distance between 2 geometry points. How can I measure the distance between 2 vertices of a block?


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