Multi resolution in SPH

pohan
pohan Altair Community Member
edited May 31 in Community Q&A

Hello,

I am trying to reduce the computation time of SPH simulation by multi resolution in which there are two regions fine and coarse ones.

The diameter of SPH particle in the coarse region (r1) is double than the diameter of the fine one (r2). And the distance between the two regions is r1+r2

As far as I know, in Radioss the contact between the two SPH regions is automatic. However, in my model the connect between them is not smooth.

If anyone has any ideal about this problem?

Thank you in advance.

 

Answers

  • Polyvios Romanidis
    Polyvios Romanidis New Altair Community Member
    edited May 28

    Hi pohan,

    What you propose is not an effective way to use SPH approach, because of the issues appear like the one you referred to.  So, generally do not use different particle diameters in SPH.

    There is a situation were smoother change in particle diameter could work, but by changing the diameter by a factor of 2 causes problems.

    In order to run your simulation faster I can propose you to use the SOL2SPH methodology.  In this methodology the solid elements turn to SPH particles when and where is necessary only.

    You can find some exhibition of this method and the way to set up a problem like this in the Knowledge Base article contained in the following link.

    https://community.altair.com/community/en/5-56x45-ss109-impact-on-an-armox-500t-plate?sys_kb_id=bd0e9a3adb6e3554cfd5f6a4e296194d&id=kb_article_view&sysparm_rank=1&sysparm_tsqueryId=c611e4041b6eced8c4dfdbd9dc4bcbcb

    Polyvios

  • pohan
    pohan Altair Community Member
    edited May 28

    Hi pohan,

    What you propose is not an effective way to use SPH approach, because of the issues appear like the one you referred to.  So, generally do not use different particle diameters in SPH.

    There is a situation were smoother change in particle diameter could work, but by changing the diameter by a factor of 2 causes problems.

    In order to run your simulation faster I can propose you to use the SOL2SPH methodology.  In this methodology the solid elements turn to SPH particles when and where is necessary only.

    You can find some exhibition of this method and the way to set up a problem like this in the Knowledge Base article contained in the following link.

    https://community.altair.com/community/en/5-56x45-ss109-impact-on-an-armox-500t-plate?sys_kb_id=bd0e9a3adb6e3554cfd5f6a4e296194d&id=kb_article_view&sysparm_rank=1&sysparm_tsqueryId=c611e4041b6eced8c4dfdbd9dc4bcbcb

    Polyvios

    Hello. Thank you for your answer. I will try the Sol2solid later. You has mentioned that There is a situation were smoother change in particle diameter could work, but by changing the diameter by a factor of 2 causes problems.

    Could you please give me more details about this situation?

    Best regards

  • Polyvios Romanidis
    Polyvios Romanidis New Altair Community Member
    edited May 29
    pohan said:

    Hello. Thank you for your answer. I will try the Sol2solid later. You has mentioned that There is a situation were smoother change in particle diameter could work, but by changing the diameter by a factor of 2 causes problems.

    Could you please give me more details about this situation?

    Best regards

    Hi pohan,

    Maybe if you try to reduce the diameter very smoothly you can make this model work.  But to do that you should probably use command line orders to create a model with very smooth decrease.  After all I am not sure if indeed this model will work.  What I am saying is that potentially can.

    From my point of view it is preferable to start with SOL2SPH and if the simulation time is still that big to attempt change the diameter smoothly with command orders.  I am saying that because it can be very challenging and time-consuming to create a model like that in pre-processors.

    Polyvios

  • pohan
    pohan Altair Community Member
    edited May 29

    Hi pohan,

    Maybe if you try to reduce the diameter very smoothly you can make this model work.  But to do that you should probably use command line orders to create a model with very smooth decrease.  After all I am not sure if indeed this model will work.  What I am saying is that potentially can.

    From my point of view it is preferable to start with SOL2SPH and if the simulation time is still that big to attempt change the diameter smoothly with command orders.  I am saying that because it can be very challenging and time-consuming to create a model like that in pre-processors.

    Polyvios

    Hello,

    In my opinion Sol2SPH is a good solution in the case of solid simulation. However, in my case, I want to model water, so it is not easy because of failure criterial of water.

    Best regards 

  • Polyvios Romanidis
    Polyvios Romanidis New Altair Community Member
    edited May 29
    pohan said:

    Hello,

    In my opinion Sol2SPH is a good solution in the case of solid simulation. However, in my case, I want to model water, so it is not easy because of failure criterial of water.

    Best regards 

    Hi pohan,

    In this case you can use the attached files.

    In order to create the smooth diameter increase you should first create an increasing size mesh.  Then you can use any of the following macro .tcl I include in this message.

    The one file creates particles in the same coordinates that nodes exist in solid mesh and the other at the center of the solid elements.  The only difference between them is the definition of connections or BCS with solid elements, where particles placement can be important.

    Hope this helps.

    Polyvios

  • pohan
    pohan Altair Community Member
    edited May 31

    Hi pohan,

    In this case you can use the attached files.

    In order to create the smooth diameter increase you should first create an increasing size mesh.  Then you can use any of the following macro .tcl I include in this message.

    The one file creates particles in the same coordinates that nodes exist in solid mesh and the other at the center of the solid elements.  The only difference between them is the definition of connections or BCS with solid elements, where particles placement can be important.

    Hope this helps.

    Polyvios

    Thank you very much, I will try and fed back soon!