Constant speed in MMALE material

[R. D.]

Dear All,

I want to apply a constant speed on a MMALE material. The material is filled inside the mesh using *INITIAL_VOLUME_FRACTION_GEOMETRY card. 

I cannot used the initial velocity option in the aforementioned keyword since it is only an initial velocity and not a constant one throughout the simulation.

One may suggest the use of an overlapping mesh and use the *CONSTRAINED_LAGRANGE_IN_SOLID keyword but due to some considerations this option is not applicable.

I do not know if it is even possible to apply a velocity only on one MMALE material considering the MMALE formulation.

One approach that came to my mind is to use the *BOUNDARY_PRESCRIBED_MOTION_SET_BOX where the box moves with the same speed as the  material but I could not find a keyword to make a moving box.

Sincerely,
Reza Daryaei

[James M. Kennedy]

Dear Reza,

 

See if these examples are of some help:

 

https://www.dynaexamples.com/ale/bird

 

---------------------

 

Some other considerations:

 

*ALE_PRESCRIBED_MOTION

 

Purpose: Define an imposed nodal motion on a set of multi-material ALE groups for a

given time span (if this time frame is short enough, velocity initialization by group can

be considered).

 

*ALE_REFERENCE_SYSTEM_CURVE

 

Purpose: This command defines a motion and/or a deformation prescribed for a

geometric entity, where a geometric entity may be any part, part set, node set, or

segment set. The motion or deformation is completely defined by the 12 parameters

shown in the equation below. These 12 parameters are defined in terms of 12 load

curves. This command is required only when PRTYPE = 3 in the *ALE_REFERENCE_-

SYSTEM_GROUP command.

 

*ALE_REFERENCE_SYSTEM_GROUP

 

Purpose: Associate a geometric entity to a reference system type. A geometric entity

may be any part, part set, node set, or segment set of a model (or a collection of

meshes). A reference system type refers to the possible transformation allowed for a

geometric entity (or mesh). This command defines the type of reference system or

transformation that a geometric entity undergoes. In other words, it prescribes how a

specified mesh can translate, rotate, expand, contract, be fixed in space, etc.

 

*ALE_REFERENCE_SYSTEM_NODE

 

Purpose: Define a group of nodes that control the motion of an ALE mesh. This

keyword is used only when PRTYPE = 5 or 7 in a corresponding *ALE_REFERENCE_-

SYSTEM_GROUP card.

 

Sincerely,

James M. Kennedy

KBS2 Inc.

April 29, 2021

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[l...@schwer.net]

Have a look at the keyword *ALE_REFERENCE_SYSTEM_GROUP

I think this can do what you want, but I do not think it can be used with an MMALE mesh defined by *INITIAL_VOLUME_FRACTION_GEOMETRY, so you will need to mesh that part directly.               --len

 

From: ls-d...@googlegroups.com <ls-d...@googlegroups.com> On Behalf Of R. D.
Sent: Wednesday, April 28, 2021 4:37 AM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] Constant speed in MMALE material

 

Dear All,

--

[R. D.]

Dear All, 

Thanks for all the comments and sorry for the late reply, since I was working the solutions thoroughly and I concluded the following:

*ALE_REFERENCE_SYSTEM keywords is not applicable with my model settings since the whole mesh would be moved and not the MMALE material model.

 *ALE_PRESCRIBED_MOTION is only available after the release of R11 version. 
There are three methods to initiate the velocity on Material as I understood the manual:

1. when an element is partially filled by one of MMALE materials, the motion of all its nodes will be prescribed. 

2. Only nodes connected to at least one element fully filled by a group in MMSID.

3. Nodes connected to only fully filled elements are considered.

However, as I made a simple model and applied the velocity and plotted the initialized nodes, yet they are not as exactly as I expected. Attached you can see the pictures. (the numbers correspond to the INSIDE keyword)

Have I understood the keyword description wrong?

Thanks in advance for the help.

Regards,
Reza Daryaei

[James M. Kennedy]

Dear Reza,

 

Perhaps this tutorial may be of some help (a bit old?):

 

Olovsson, L., Souli, M., and Do, I., "LS-DYNA – ALE Capabilities (Arbitrary-Lagrangian-Eulerian)

Fluid-Structure Interaction Modeling", Livermore Software Technology Corporation, Livermore,

California, (draft) January, 2003.

 

https://ftp.lstc.com/anonymous/outgoing/jday/aletutorial-278p.pdf

 

Sincerely,

James M. Kennedy

KBS2 Inc.

June 11, 2021

To view this discussion on the web visit https://groups.google.com/d/msgid/ls-dyna2/3475e1c0-c155-42f4-aa43-9b989c7fdeaan%40googlegroups.com.

[James M. Kennedy]

Dear Reza,

 

This paper presented a validation study of the LS-DYNA MMALE approach with existing

experimental studies of blast wave clearing and blast in an urban environment, as well as numerical

results from the finite volume method software Air3d. The overpressure histories, peak overpressures

and impulses were compared:

 

Huang, Y., Willford, M.R., and Schwer, L., "Validation of LS-DYNA MMALE with Blast

Experiments", 12th International LS-DYNA Users Conference, Dearborn, Michigan, June, 2012.

 

http://www.dynalook.com/international-conf-2012/blast-impact20-c.pdf

 

In this manuscript the ignition and growth of the reaction in high explosives equation-of-state was

introduced along with model parameters for COMP-B. Some comments were included concerning

alternative versions of these model parameters that are available in the literature. The manuscript

focused on the experimental data of Almond and Murray [2006], their simulations results, the

imulation results of Urtiew et al. [2006] and the present results which make use of the relatively

new LS-DYNA Multi-Material Arbitrary Eulerian Lagrange (MMALE) capability which thus serve

as a post-test form of model validation:

 

Schwer, L.E., "Impact and Detonation of COMP-B - An Example Using the LS-DYNA EOS:

Ignition and Growth of Reaction in High Explosives", 12th International LS-DYNA Users

Conference, Dearborn, Michigan, June, 2012.

 

http://www.dynalook.com/international-conf-2012/blast-impact13-d.pdf

 

Carlsson, D., “Arbitrary Lagrangian-Eulerian Simulations of a Pressure Pulse inside a Flexible

Porous Fabric Bag”.

 

https://publications.lib.chalmers.se/records/fulltext/199953/199953.pdf

 

Sincerely,

James M. Kennedy

KBS2 Inc.

June 14, 2021

 

From: R. D. [mailto:doome...@gmail.com]
Sent: Monday, June 14, 2021 4:40 AM
To: James M. Kennedy <j...@kbs2.com>
Subject: Re: [LS-DYNA2] Constant speed in MMALE material

 

Dear Dr. Kennedy,

Thanks for the tutorial file. There were several interesting points in the slides such as averaging the history variables. I am interested to see if the draft had become a paper.

Do you know if there is a paper where the implemented MMALE method of LS-DYNA is described in more detail including the theory, equations etc.? I mostly obtained the theories from the paper of 

 

  "Benson, D. 1992. Computational methods in Lagrangian and Eulerian hydrocodes. Computer Methods in Applied Mechanics and Engineering (99), pp. 235–394."

 

where the advection methods, and special treatment of velocity advaction (using the momentum to advect the velocity) are described. Yet I was hoping if there is a paper where the interface reconstruction is also described.

 

Thanks you again for the help.

Best regards,
Reza Daryaei

[James M. Kennedy]

During the recent years, several promising finite element solutions have been presented for finding

the response of structures subjected to blast loading. This thesis gives as a comparative study on 3

major solution strategies, and their implication on the response on constrained plates of varying

standoff distances. The strategies chosen are the Lagrangian method using load blast function in

LS-DYNA, in which the plate nodes are subjected directly to forces attained from empirical

CONWEP data. The Arbitrary Lagrangian Eulerian (ALE) method in LS-DYNA, where an initial

charge is detonated within an air medium and impulse transferred through contact algorithms. Finally

a particle method, where air and soil are treated as discrete particles. This novel approach gives faster

calculations than the ALE method and possible more reliable results than the Lagrangian method:

 

Kaurin, C.M., and Varslot, M.O., "Blast Loading on Square Steel Plates; A Comparative Study of

Numerical Methods", Master's Thesis, Department of Structural Engineering, Norwegian University

of Science and Technology, Trondheim, Norway, June, 2010.

 

http://www.diva-portal.org/smash/get/diva2:380860/FULLTEXT01.pdf

Sincerely,

James M. Kennedy

KBS2 Inc.

June 14, 2021

 

From: R. D. [mailto:doome...@gmail.com]

Sent: Monday, June 14, 2021 4:40 AM
To: James M. Kennedy <j...@kbs2.com>

Subject: Re: [LS-DYNA2] Constant speed in MMALE material

 

Dear Dr. Kennedy,

Thanks for the tutorial file. There were several interesting points in the slides such as averaging the history variables. I am interested to see if the draft had become a paper.

Do you know if there is a paper where the implemented MMALE method of LS-DYNA is described in more detail including the theory, equations etc.? I mostly obtained the theories from the paper of 

 

  "Benson, D. 1992. Computational methods in Lagrangian and Eulerian hydrocodes. Computer Methods in Applied Mechanics and Engineering (99), pp. 235–394."

 

where the advection methods, and special treatment of velocity advaction (using the momentum to advect the velocity) are described. Yet I was hoping if there is a paper where the interface reconstruction is also described.

 

Thanks you again for the help.

Best regards,
Reza Daryaei

On Fri, Jun 11, 2021 at 5:13 PM James M. Kennedy <j...@kbs2.com> wrote: