Issues with modifying official LS-DYNA ex with S-ALE mesh

- July 11, 2025 at 10:14 pm
  
  HL
  Subscriber
  
  Hello, I would greatly appreciate some help with this. I am modifying an official LS-DYNA example, Underwater F (https://lsdyna.ansys.com/underwater-f/), to instead have a square field that is constructed with an S-ALE mesh. Everything else stays the same, so the resulting simulations should look identical for the first ~30 time steps, until the shock wave reaches the boundary of the cutout in the example. However, they look different and the shock wave is not propagating outward into the water and it looks like there is a boundary effect.
  I created an S-ALE mesh and a box region at the bottom left corner (the origin). I filled the entire region with water and then the box region with the explosive material. I detonated the material at the origin at time 0.
  1. There seems to be some kind of boundary effect at the box region. I don’t think I defined any boundaries and am wondering if there is a discontinuity or something between the two materials. However, I don’t know how to fix this, particularly with this S-ALE method.
  2. Originally, I kept the element sizes the same, 1 element = 1 cm. However, for my simulation, the velocity contour did not show the shock wave, which was very strange, so I refined the mesh to have each element be 0.16 cm. Now I can see the shock wave, but it is strange that this refinement was not necessary for the official example but was for mine. Would anyone know why this might be?
  Please, I would greatly appreciate some help, thank you very much in advance.
  
  Here is my code:
  *KEYWORD
  *NODE
  1 0.000000000E+00 0.000000000E+00 0.000000000E+00
  2 0.000000000E+00 0.000000000E+00 0.000000000E+00
  3 0.100000000E+00 0.000000000E+00 0.000000000E+00
  4 0.000000000E+00 0.100000000E+00 0.000000000E+00
  *ALE_STRUCTURED_MESH_CONTROL_POINTS
  1001
  1 0.0
  51 8.0
  201 32.0
  *ALE_STRUCTURED_MESH_CONTROL_POINTS
  1002
  1 0.0
  51 8.0
  201 32.0
  *ALE_STRUCTURED_MESH_CONTROL_POINTS
  1003
  1 0.0
  2 1.0
  *DEFINE_COORDINATE_NODES
  234 2 3 4
  *ALE_STRUCTURED_MESH
  7 5000 10000 10000
  1001 1002 1003 1 234
  *DEFINE_BOX
  9 0.0 8.0 0.0 8.0 0.0 1.0
  *PART
  
  1 1 1 1
  *PART
  
  2 2 2 2
  *MAT_NULL
  1 1.0
  *MAT_HIGH_EXPLOSIVE_BURN
  2 1.63 0.784 0.260 0.000E+00
  *EOS_GRUNEISEN
  1 1.5
  
  *EOS_JWL
  2 3.71 3.230E-02 4.15 0.950 0.300 4.300E-02 1.00
  *ALE_STRUCTURED_MULTI-MATERIAL_GROUP
  water 1 1
  expl 2 2
  *ALE_STRUCTURED_MESH_VOLUME_FILLING
  7 water
  ALL
  *ALE_STRUCTURED_MESH_VOLUME_FILLING
  7 expl
  BOXCOR 0 9
  *CONTROL_ALE
  0 1 2 -1.0
  
  *CONTROL_ENERGY
  2 1 2 2
  *INITIAL_DETONATION
  5000 0.000E+00 0.000E+00 0.000E+00 0.000E+00
  *CONTROL_TERMINATION
  100.0
  *DATABASE_BINARY_D3PLOT
  1.0
  *DATABASE_GLSTAT
  0.1
  *END
  
  And here are the screenshots of the pressure contours:
- July 14, 2025 at 9:25 am
  
  Rob
  Forum Moderator
  
  Duplicte https://innovationspace.ansys.com/forum/forums/topic/issues-with-modifying-official-ls-dyna-ex-with-s-ale-mesh/