Fluids

Fluids

Problem in meshing and simulation of implant impinged in the porous wall

    • BiomedModeller
      Subscriber

      This is a simplified version of a much complex case.


      I am struggling for a long time to mesh a case wherein some implants protrude into the wall. The implant is at the interface of fluid and porous zone and has a very low (almost tangent) angle of impingement. 



      I managed to mesh the case setting curvature proximity setting and defining thin cut in ICEM. It shows no error and only adds few faces (subset) in the areas where the device and interface are very close (almost tangent). 



      However when I simulate it, velocity goes very high (1000 m/s) in those areas.



      Anyone knows why this is happening?


      Thanks

    • BiomedModeller
      Subscriber

      The case runs if only inner cylinder is considered and it goes crazy as soon as the porous medium is considered and velocity goes very high exactly where the implant impinges with tangent angles.


    • BiomedModeller
      Subscriber

      Increasing the permeability considerably also fixes the problem and velocities are ok.



      The main problem is where the permeability is really low, and velocity keeps going insane only near those spots.

    • Rob
      Ansys Employee

      If the resistance is really high, where is the fluid trying to go? How do the velocity gradients look when resistance is moderate? 

    • BiomedModeller
      Subscriber

      Resistance is really high and we have typical parabolic flow profile with Vmax of 0.3 m/s in the inner cylinder and a radial flow of very low velocity (1e-8 m/s) exiting the outer wall.


      Without the implant I am able to capture it, but with it the velocity goes crazy near the impinging area. The question is why it is not going crazy in other places. That made me be suspicious about the mesh.


       

    • BiomedModeller
      Subscriber

      Although the flow problem is the main concern for this simple geometry, as this is the simplified version of a MUCH complex case, we also need to fix that mesh issue at impinging site. The software should be ICEM or Fluent meshing, as the geometry is in STL, and we could not manage to make the solid with Peter in Spaceclaim to use ansys meshing.

    • Rob
      Ansys Employee

      Have you adapted the mesh around the regions where the flow is hitting the porous media?

    • BiomedModeller
      Subscriber

      The mesh is well refined there. Is there an extra adaptation step I need to take there? Where should it be? in ICEM or CFX?

    • BiomedModeller
      Subscriber

      Any chance an ICEM expert can help me fix the mesh issue?


      This is the third time I am reaching out with the same problem with no success!
      Thanks

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