[HectorLee]

Hi, everyone,

I am trying to use interMixingFoam to simulation the interactions between immiscible and miscible fluids in a capillary tube. The simulation domain is a 12mm-long and 2mm-wide capillary tube and the initial condition in x-axis is: air occupies the space from 0mm to 1mm; 'other' fluid occupies the space from 1mm to 2mm and the left part of the tube is water. Then the constant velocity boundary is applied to the left side of the tube and the right side is zero gradient boundary.

In the first 4s, the distribution of 'other' fluid and water is fine as the first figure. However, after that, water starts to appear around the interface between air and 'other' as the second figure, which violates physics law apparently.
(Somehow, I can't upload the figures here, so there are the links for the figures shared in the dropbox:
At t = 4s: https://www.dropbox.com/s/zpao05jgef...%3D4s.png?dl=0
At t = 8s:
https://www.dropbox.com/s/eb8hmuzh02...%3D8s.png?dl=0
)

Is there anyone knowing what causes this strange phenomenon and reasons?

Thanks a lot!