Volume Fraction Decreasing with Mapped inlet - outlet (interFoam)
 

Hello,

I've been running into an issue with multiphase pipe flow simulations where over time the liquid volume fraction decreases. I use a mapped boundary from outlet to inlet for velocity and alpha.

The liquid loss does seems to vary from case to case, some cases appear to be completely draining the liquid phase if given enough time while others seem to stabilize. As such I have attempted to adjust my initial velocity fields with set fields after each iteration to see if it is related to that, but I am yet to resolve the issue, I have also refined the mesh significantly.

I've included below the U, p_rgh, alpha and boundary documents as attached files as well as an image to illustrate the liquid loss.Other perhaps relevant information is I haved used both LES and RANS (k-omega) turbulence models and I have tried different interface compression coefficients between 0.5 and 1.0 with seemingly no effect.

The pipes used vary, but the one shown in the image below is a 3m pipe with 800k elements, the outer diameter is 0.1m and the inner diameter of the annulus is 0.05m.

You may notice that my pipe is cut in half using a symmetryplane, the liquid draining does happen in a fully meshed pipe aswell.

I would be gratefull for any assistance my fellow foamers can provide, let me know if there is any more information you need to look at the problem.

- Christopher