Velocity Magnitude (Unrealistically High)

Using SimScale Fluid Flow / CFD
1

Hi,

I’m modelling the piston of a medical device compressing air inside a vented chamber and I’ve run into a puzzling result that I’d appreciate your thoughts on:

Intial Volume = 846.000 π‘šπ‘š^3
Final Volume = 182.400 π‘šπ‘š^3
Atmospheric Pressure (Pressure Outlet) = 101.325 π‘˜π‘ƒπ‘Ž
Compressed Pressure (Pressure Inlet) = 470.300 π‘˜π‘ƒπ‘Ž

I have performed an incompressible fluid simulation with these parameters. The simulation reports a peak velocity magnitude of roughly 850 m *s^‑1 (past supersonic), which strikes me as highly improbable.

Could this excessively high velocity magnitude be an artefact of using an incompressible‐flow model or is it more likely that something else in the setup is driving the error?

Thanks in advance for any guidance!

Here’s a link to my project.

2

Hi @tpinol, thanks for posting!

Quick pointers:

  1. I’m not sure what the real world application looks like, but the setup looks odd to me. Is this an internal or external flow application?
  2. The CAD could certainly benefit from some cleaning. I see some stamped manufacturer’s marks which won’t contribute to the fluid flow while at the same time make the meshing process harder (more info here)
  3. Pressure inlet + Outlet is not the best combination of boundary conditions (even if you have Total Pressure + Fixed value). I would advise changing this to Velocity inlet + Pressure outlet

Cheers
Igor