Learning Forum

[Amrith Mariappan]

Hi everyone,

I’m working on a 2D axisymmetric hypervelocity impact simulation in LS-DYNA and am trying to apply non-reflecting boundary conditions to the outer edges of the target domain (bottom and right boundaries).

When I select all nodes along those boundaries and assign:

*BOUNDARY_NON_REFLECTING_2D

I receive the following error:

*** Error 21385 (STR+1385)
The node set of *BOUNDARY_NON_REFLECTING_2D 1 has
2 non-consecutive nodes: 94606 94884

However, if I apply the boundary card to only a single node on each boundary, the error disappears — but that clearly isn’t physically correct for wave absorption.

My understanding is that node numbering along the boundary must be sequential for NRBC to work correctly, but I’m not sure of the best practice to enforce this in a 2D axisymmetric mesh (e.g., whether to define separate segments, sort nodes, or restructure the mesh).

Could anyone please advise on the correct way to define non-reflecting boundaries for a 2D axisymmetric ALE/Lagrangian model? I’ve attached my keyword files at the link provided for reference.

Any guidance would be greatly appreciated!

Thanks,
Amrith

Keyword File

[ErKo]

 

 

 

 

Hi

We are not allowed to download any files – perhaps other users can provide more feedback –

 

in general it is a bit diff./hard to apply this in 2D analysis (as you say the nodes need to come in certain order- see keyword manual for more on that – see figure 5-2 in the keyword. manual I).

So nodes should go as manual, and say we start with nr 1, and the next one on top of it on the that boundary is 5 (right edge starts from bottom to top counter clock.), then use a node set list that goes like 1,5, etc. (see below), called say 997 and use that in the BC (make sure nodes are after each other on that edge/side):

*SET_NODE_LIST
997
1,5,6,7,8,9,10,11,
12,13,14,15,16,17,18,19,
20,21,22,23,24,25,26,27,
28,29,30,31,32,33,34,35,
36,37,38,39,40,41,42,43,
44,45,46,47,48,49,50,51,
52,53,54,55,56,57,58,59,
60,61,62,63,64,65,66,67,
68,69,70,71,72,73,74,75,
76,77,78,79,80,81,82,83,
84,85,86,87,88,89,90,91,
92,93,94,95,96,97,98,99,
100,101,102,103,2,
*BOUNDARY_NON_REFLECTING_2D
       997         0         0

All the best

Erik

 

 

 

 

[Amrith Mariappan]

Thank you for your response. I will try that.

Amrith