General Mechanical

General Mechanical

Inhibit pressure wave reflections in transient analysis (PML gives error)

    • a_l_o
      Subscriber

      Hi folks,

      I use Ansys Mechanical 2022 R2 to investigate pressure wave propagation in a Coupled Field Transient Analysis. As I want to simulate infinite behavior at the outer surfaces of my structure, i.e. no reflections, I used the condition "perfectly matched layers" (PML) for the outer "slice" of my structure (physics region set to "structural", geometry set to PML with APDL snippet "keyopt,matid,15,1"). Now I got an error and truncation:

      If I am not allowed to use PML in a transient analysis: How do I inhibit pressure wave reflections at the outer surface of my solid structure? E.g., at one end of a pipe structure?

      Thank you very much in advance!

    • Bill Bulat
      Ansys Employee

      I'm afraid that PML is only available for harmonic response analyses:

      You can truncate structural media in transient analyses with a non-reflective boundary using INFIN257 which are created with the MAPDL EINFIN command:

      Note however, that INFIN257 may only be used to trucate pure structural elements, not coupled field ones (SOLID226): I have a MAPDL example that works but am so far unable to get EINFIN to create INFIN257 elements with a command object in Mechanical. If I get that working I'll share images of the project with you (company policy forbides me uploading files to the Forum).

      Best,

      Bill

    • a_l_o
      Subscriber

      Hi Bill,

      Your answer is really perfect, thank you very much! I am stilling looking into this matter at the side, so if you had any success in Mechanical, I'ld be glad if you share it here. I will also have look into INFIN257 elements!

      Best regards,

      alo

    • Ushnish Basu
      Ansys Employee

      Please note that transient elastic and acoustic PML is available in LS-DYNA:

      https://lsdyna.ansys.com/pml/

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