S-ALE and mapping ?
Vincent Denefeld
James M. Kennedy
Dear Vincent,
A 2D Multi-Material Arbitrary Lagrange Euler (MM-ALE) code was implemented in LS-DYNA. Like the 3D MM-ALE, already available, each 2D computational cycle is divided into two steps. First a multi-material version of the two-dimensional shell formulations solves the physical problem on quadrangle meshes during the Lagrangian step. The 2D shell formulations are plane strain and are-weighted axisymmetric. An advection cycle adapted to the 2D shell approaches follows to control the mesh motion. 2D ALE data of the last cycle can be mapped on 3D ALE mesh:
Aquelet, N., and Souli, M., "2D to 3D ALE Mapping", 10th International LS-DYNA User's Conference, Dearborn, Michigan, June, 2008.
http://www.dynalook.com/international-conf-2008/FluidStructure-3.pdf
A new 2D ALE method with an associated Mapping became available with LS-DYNA v971 r4. Mapping enables the decomposition of a calculation in several steps; at the end of a 2D ALE calculation, data from the last cycle can be mapped into another 2D or 3D mesh. Several finite element studies of Air Blast were modeled to evaluate efficiency and potential of this LS-DYNA feature:
Lapoujade, V., Van Dorsselaer, N., Kevorkian, S., and Cheval, K., "A Study of Mapping Technique for Air Blast Modeling", 11th International LS-DYNA User's Conference, Dearborn, Michigan, June, 2010.
http://www.dynalook.com/international-conf-2010/BlastImpact-1-3.pdf
A solution had to be found in order to protect buildings neighboring an industrial site from the blast effects of possible accidental explosions on the site. A possible answer was to build a blast-mitigating wall between the buildings and possible blasts. The MM-ALE features of LS-DYNA provided a way to evaluate the effects of the wall on the pressure waves around the building. As the amount of explosive was rather small when compared to the distances involved, the new 2D to 3D and 3D to 3D re-mapping methods came in handy to avoid the use of an impractically large numerical model:
Lacambre, J., and Delmas, L., "Using LS-DYNA MM-ALE Capabilities to Help Design a Wall Mitigating Accidental Blast Effects", 8th European LS-DYNA Users Conference, Strasbourg, France, May, 2011.
http://www.dynalook.com/8th-european-ls-dyna-conference/session-15/Session15_Paper2.pdf
This study used LS-DYNA 2D ALE model and 2D ALE mapping model, and numerical results were compared with U. S. Army Technical Manual TM5-1300:
Cheng, D.-S., Hung, C.-W., and Pi, S.-J., "Numerical Simulation of Near-Field Explosion", Journal of Applied Science and Engineering, Vol. 16, No. 1, pp. 61-67, March, 2013.
http://www2.tku.edu.tw/~tkjse/16-1/09-889.pdf
Kalra, A., Zhu, F., Yang, K.H., and King, A.I., "Key Parameters in Blast Loading Using 2D to 3D ALE Mapping Technique", 13th International LS-DYNA Users Conference, Dearborn, Michigan, June, 2014.
In this work, the effects of ALE mapping technique were investigated for buried charge simulations. Before mapping studies, a mesh sensitivity study was performed for the pure ALE simulations to investigate the effect of 3D mesh size on the impulse. The ALE mapping was performed from a 2D axisymmetric model to full 3D model:
Kurtoglu, I., "An Assessment of ALE Mapping Technique for Buried Charge Simulations", 10th European LS-DYNA Users Conference, Wurzburg, Germany, May, 2015.
When simulating structures subjected to the effects of blast loading, one might resort to three different methods of simulation. These methods are the empirical blast method, also known as *LOAD_BLAST_ENHANCED (LBE), the Arbitrary Lagrangian Eulerian (ALE) method, and a coupling method that allows the application of empirical blast loads (LBE) on air domain simulated with the ALE formulation. Furthermore, for the ALE method, both a mapping technique, that allows the mapping of data from 2D ALE simulations to 2D and 3D ALE meshes, and a complete 3D ALE simulation could be performed. In order to verify and compare the efficiency and accuracy of these air blast methods, an air blast loading on a reinforced concrete slab was modelled. Additionally, mesh convergence studies of 2D and 3D ALE simulations were performed:
Rebelo, H.B., and Cismasiu, C., "A Comparison between Three Air Blast Simulation Techniques in LS-DYNA", 11th European LS-DYNA Users Conference, Salzburg, Austria, May, 2017.
input deck:
ftp://ftp.lstc.com/outgoing/aquelet/ale2d/underwaterexplo.bounmapping.tar.gz
KEYWORD descriptions (most of the mapping applications only require the first 2 entries):
ftp://ftp.lstc.com/outgoing/aquelet/ale2d/SECTION_ALE2D.doc
ftp://ftp.lstc.com/outgoing/aquelet/ale2d/INITIAL_ALE_MAPPING.doc
ftp://ftp.lstc.com/outgoing/aquelet/ale2d/BOUNDARY_ALE_MAPPING.doc
examples of ALE1D modeling
Here are some input decks applying the 1D to 3D (or 2D) mapping and the keyword description:
ftp://ftp.lstc.com/outgoing/aquelet/ale1d/ale1dqa3.underwaterexplo.zip
ftp://ftp.lstc.com/outgoing/aquelet/ale1d/SECTION_ALE1D.doc
Sincerely,
James M. Kennedy
KBS2 Inc.
August 26, 2022
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James M. Kennedy
Dear Vincent,
From LS-DYNA User’s Manual:
https://ftp.lstc.com/anonymous/outgoing/jday/manuals/DRAFT_Vol_I.pdf
*ALE_STRUCTURED_MESH
4. ALE to S-ALE Converter. For existing ALE models with rectilinear meshes,
*ALE_STRUCTURED_MESH can invoke the conversion of the ALE mesh into
an S-ALE mesh. To use this feature, add a *ALE_STRUCTURED_MESH card
in the model input with CPIDX = -1 or 0 leaving all other fields blank. LS-DYNA
will then convert all ALE keywords to the S-ALE format and write the
modified input to a file named saleconvrt.inc. The solver used to perform the
analysis depends on the value of CPIDX. If -1, the S-ALE solver is used; if 0,
the ALE solver is used.
Sincerely,
James M. Kennedy
KBS2 Inc.
August 26, 2022
Hello everybody,
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