Fluids

Fluids

Separating touching walls in fluent

    • Gengyan Liu
      Subscriber

      Hi everyone, I am trying to run a simulation involving a pressurized capsule and a cap (imagine a trash can with a detachable lid). The goal is to find how much the cap’s motion in the air after it comes off the capsule affects the vortex ring formed by pressurized air escaping the capsule. (1) I used transient structural and fluent combined with system coupling to model the scenario. However, in the initial state of the cap resting on the capsule, Fluent considered that entire “wall” body as one single wall, so it does not let it to separate. We can only see the effect of pressure on the cap as attached below. (2) I do not know how to define the air body inside the capsule and the air body outside the capsule to be “interacting”. Since they are separate two bodies when the cap is closed, and are supposed to become one single body (or two bodies with boundary defined as interior) when the cap comes off. How do I make Fluent fill the gaps created by the movement of the cap? (3) I tried to get around that problem by making a hole at the back of the capsule, which resulted in a similar situation as (1). I also tried to go around the situation in (1) by making a small gap between the capsule and the cap, combined with a hinge to initiate the rotation. However, the cap would just oscillate in place and then crash with negative cell volume, so I suppose something is wrong with meshing settings. What should I do to fix?

      (1)

      What actually happens:



      (3)



      The interior is the cylindrical computational domain. The outlet is the boundary of the computational domain, and the wall is coupled with transient structural.


      Thank you! 

    • Gengyan Liu
      Subscriber

       

       

       

    • Rob
      Ansys Employee

      You need a gap as we can't change topology in the Fluent solver. You don't need Mechanical unless the lid deforms as the 6DOF solver will handle the motion. 

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