[STEFGER]

Hello,

I have a problem which seems to be caused by the combination of cfMesh and interFoam. I used cfMesh several times with simpleFoam and got very good (and easy to achieve) results without any problems; but when using with multiphase solver interFoam, I sometimes run into a numerical problem (at least it looks to me like a numerical problem): At a certain time in simulation, the timesteps (deltaT) are getting smaller and smaller (down to 10E-90 or similar), until finally a Floating point exception happens. I have no idea how to look further in these cases, therefore I started from an existing (and running) tutorial and change it step by step to see when the problem arises.

Since I want to use the boubdary condition "variableHeightFlowRateInletVelocity", I started with the tutorial "weirOverflow" (located in multiphase/interFoam/ras/weirOverflow/), which has a blockMesh-generated 2D-geometry. I stretched the z-axis by factor 10, and still everything runs fine.

Then I rebuild the same geometry with salome and created a new mesh with cfMesh, and then I run into the well-known trouble: When the water reaches the end of the weir and start to flow down, the time steps decrease down to 4.37805e-86 and causes then a Floating point exception. To be near to the tutorial, I didn't use boundary layers; in fact, I only defined a maxCellSize (later I also tried with boundary layers but run into similar problems). The resulting mesh looks good to me (at least good enough for such a simple geometry). I'm pretty sure that the problem is caused by the mesh since everything runs fine if I exchange the constant/polyMesh - directory with the blockMesh-case.


I have no idea where to search for the reason, since the mesh looks good to me. Are there any special mesh requirements for multiphase simulation with interFoam?

EDIT: I've added clip images of the blockMesh / cfMesh