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Salome "Merge Nodes" feature

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16 years 4 months ago #2170 by JMB
Hello,

I am trying to use the Merge Nodes dialog and found little or no help from the Help text. Can somebody elaborate how one is supposed to use this window please?

After clicking on the "Detect" button, several nodes are displayed ( "7, 17484, 17485, 17486, 17487, 17488, 17489, 17490" ) in the "Coincident Nodes" sub-panel. The questions I have are:

"Co-Incident nodes" Sub-Panel:
1. Does this mean that nodes "7, 17484, 17485, 17486, 17487, 17488, 17489, 17490" all happen to be co-incident? Or are they each coincident with some other node that is not shown?
2. Do I delete all nodes except node "7"?
3. Do I delete all nodes including "7"?
4. What do the "Add" and "Remove" buttons do?

"Edit Group" Sub-panel:
4. What does the "Select All" check box do?
5. What is the purpose of the "Edit Selected group" of this sub-panel.
6. What do the "X" and "+" buttons beside this sub-panel do?
7. What is the function of the "|<<" button of this sub-panel?

Some detailed explanations would help me immensely and perhaps other users too. Thank you.

Regards,
JMB
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16 years 2 months ago #2288 by kwou
Hoi JMB

I have been playing with the 'Merge Nodes' tools (Modification --> Transformation --> Merge Nodes in the Mesh module), just to learn how it works. Using a block of 1*2*4 and setting tolerances to 0.4 I have 4 lines with 'coinciding' nodes (within tolerance of 0.4 I guess). Each line consist of a group of coinciding nodes, see also attached image.

In the 'edit selected group' you can add one row (one coinciding group of nodes) or repeat this for several rows. Then, if you select 'apply' or 'okee' the attached elements to the nodes disappear in my mesh. How this is controlled I am not know at the moment.

Hope this helps, although a lot of questions remain.
Kind regards - kees<br /><br />Post edited by: Kees Wouters, at: 2008/10/05 15:01

Interest: structural mechanics, solar energy (picture at 'my location' shows too little pv panels)

--
kind regards - kees
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16 years 2 months ago #2290 by kwou
Hoi JMB

sorry the picture was too big, so I hope this smaller one is going well:<br /><br />Post edited by: Kees Wouters, at: 2008/10/05 14:59

Interest: structural mechanics, solar energy (picture at 'my location' shows too little pv panels)

--
kind regards - kees
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16 years 2 months ago #2291 by kwou

Interest: structural mechanics, solar energy (picture at 'my location' shows too little pv panels)

--
kind regards - kees
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16 years 2 months ago #2292 by JMB
Hello Kees Wouters,

I am glad to hear a reply from you about this feature. What I do not know is if one of the nodes of each group is kept intact. If one among them is not deleted then which one is it? Is it the lowest numbered node? It is details like this that are completely un-documented in Salome. I have posted in the Salome forums as well, but developers don't seem to be responding!

Thank you again for your response. Hopefully as we experiment with it adequately to document it here in these forums.

Regards,
JMB
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16 years 2 months ago #2300 by kwou
hi JMB

Trying to find out how the Merge Node functions, I made a small mesh on a block (1*2*4) with a chamfered edge. After moving node 14 from (x;y;z): (1.0; 0.5; 3.8) --&gt; (1.0; 0.2; 3.8) the distance to node 1: (1.0; 0.0; 3.8) is 0.2. Only the y positions of both nodes are different. See images below.

Then merging nodes 1 and 14 twice, yields two different end situations:
- first one has same boundary is orginal mesh and node 14 removed and corresponding elements.
- seconde situation is as given in the image: node 1 removed and the element at the border of the mesh has been removed.

So there seams to be no real logic how to decide which node will be removed. But then, in case the tolerance is small, it should not matter which node and corresponding elements will be removed since the change in geometry will not be significant.
kind regards - kees



Here the modified node 14 is displayed.

This image shows merged nodes 1 and 14: node 1 removed and the element at the edge removed.

This image shows merged nodes 1 and 14: node 14 removed and the element(s) at the inner side removed. The overall geometry remains the same.<br /><br />Post edited by: Kees Wouters, at: 2008/12/17 13:19

Interest: structural mechanics, solar energy (picture at 'my location' shows too little pv panels)

--
kind regards - kees
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