Ansys Free Student Software

Ansys Free Student Software

LBE coupling to the MM-ALE

    • Vratislav Košek
      Subscriber

      Hello everyone,

      I would like to ask for advice. I have problem simulating an explosion using the LBE coupling to the MM-ALE method. I can t get the shock wave to pass throught the ambient layer to the ALE domain (air). I have no idea what the problem could be. I would appreciate any advice  or link to working keyword deck for this method.

      Thank you

    • Jim Day
      Ansys Employee
      I ran a similar test case and the pressure in the ambient ale elements does transmit to the rest of the ALE domain. Below are some guidelines. It appears you've correctly followed nos. 1 and 2. Check nos. 3 and 4. If that doesn't help, tell me which version of LS-DYNA you're running. 1) A one element thick layer of the ALE air domain which faces the blast source is given a new part ID. This new part is assigned material properties identical to those used in the rest of the air domain. In the *SECTION_SOLID definition of this new part the ambient type is set as AET=5. 2) The segments of the part described above which face the blast source are treated with *LOAD_BLAST_SEGMENT(_SET) and in that keyword IALEPID is set equal to that part ID number. 3) Currently the feature works only for air modeled using the ideal gas law with *EOS_LINEAR_POLYNOMIAL. The equation of state should be set up so that its initial pressure is equal to atmospheric pressure. 4) PREF in *CONTROL_ALE should be set to atmospheric pressure.
      • Vratislav Košek
        Subscriber

        Hello,

        thank you for your reply. I am using the version ANSYS 2020R2 LS-DYNA Student 12.0.0 As for your advice. I think everything is fine. I am attaching images of all keywords used in the model. Maybe I´m just overlooking a basic thing... I can send the whole k-file if it helps.

        Thank you

    • Jim Day
      Ansys Employee
      Your simulation runs to Normal Termination? To confirm whether pressure transmits into the non-ambient air, overlay a pressure time history of a blue, ambient element with a pressure time history of a nearby red, non-ambient air element. Post that image.
      • Vratislav Košek
        Subscriber

        Yes, the simulation ends with the normal termination. Here is a comparsion.

        Thank you.

    • Jim Day
      Ansys Employee
      So you're concerned about the difference between the pressure loading on the surface of the ambient layer and the pressure seen in the ambient element. As an experiment, remove the *LOAD_BLAST commands and apply the pressure from blstfor directly using *LOAD_SEGMENT_SET. Do you get the same response?
    • Jim Day
      Ansys Employee
      I think what you've plotted from blstfor is "P=(Pi,Pr,theta)". Note that blstfor also includes "Pi" or "incident pressure". I think that incident pressure is what is applied to the ambient air elements in the coupled ALE approach. A number of papers on the subject of *LOAD_BLAST_ENHANCED may be found through dynalook.com or simply by Googling "*LOAD_BLAST_ENHANCED".
Viewing 4 reply threads
  • You must be logged in to reply to this topic.