Wrong boundary behaviour by interFoam
Performing simulations with interFoam, with an outlet for both phases, if the whole simulation domain is in the positive or negative quarter of coordinate system, then the simulation is correct and correct behavior of both fluids at the outlet is predicted. But as soon a part of the geometry is in the negative and the other part is in positive quarters of the coordinate system, then the outlet misbehaves and based on the used boundary conditions blocks or repels the fluid! This issue has been discussed in the very old forums of the cfd-online.com but no reason or solution was presented: https://www.cfd-online.com/Forums/openfoam/79714-not-outflow-outlet-interfoam.html
Steps to reproduce
Using the original damBreak example of interFoam the mentioned behavior can be reproduced by changing the gravity direction from -y to -x and moving the geometry partially to the negative quarters (e.g. transformPoints -translate '(-0.3 -0.3 -0.007)' ).
Please find the sample simulation with the original coordinates (original) and the sample with translated coordinates (translated) in the attachment. Note: in both cases the gravity direction has been changed from -y to -x (that the water phase exits the atmosphere outlet)
What is the current bug behavior?
The outlet boundary (in this case "atmosphere") behaves as a wall and repels the flow or causes non-physical behavior!
What is the expected correct behavior?
The water should flow outside the geometry. In general it is not expected that the behaviour of the simulation changes just by changing the coordinate system!!!
Relevant logs and/or images
Pic1: the original simulation Pic2: translated simulation
OpenFOAM version : v2006 (but as it can be seen from the forum link provided it is also happening in the older versions) Operating system : ubuntu 20.04.1 LTS Hardware info : - Compiler : gcc