LS Dyna

LS Dyna

Looking for ways on how to decrease model run time when using an ALE mesh

    • Caleb Wood

      Does anyone know of any methods to decrease model run time when using an ALE mesh? I am modelling a fluid-structure interaction problem and am facing very high run times for a relatively simple model. The model consists of a rigid wave maker, water composed of ALE NULL material, air composed of ALE VACUUM material, and a steel column modeled with shell elements and a PLASTIC_KINEMATIC material.

      If I have the column set as a rigid material, the total model run time is 10 minutes, however as soon as I change it to a plastic_kinematic material the run time increases to 13.5 hours using just 800 shell elements to model the column.

    • ido
      Ansys Employee

      Hello Calleb,

      So there is only 1 single change you made, i.e. MAT_RIGID to MAT_PLASTIC_KINEMATIC ==> and dt drops?

      Can you check to see which elm type control dt? LAG or ALE? I think SW2 may give that info.

      Are you using ALE or SALE approach?

      Did you verify the mat data accuracy?

      Same rho and bulk modulus used for both mat types?

      Did you see any leakage in either model? If there are any, you must first correct that, by defining and tuning PFAC load curve.

      dt_max ~ dl_min/C

      dl_min = min elm width

      C = sound speed of that medium

      Note: modeling environmental air space as vacuum may make it easier for the coupling to leak. Using air provide a back P of 1 atm may help stabilize the coupling sometimes.

      Those are the things you can check.

      Good luck!

      Ian Do 

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