[weicent]

Hi Foamers,

I am doing a simulation related to 3 incompressible fluids (ethanol, water and air), two of them are misible, from the Openfoam User Guide, I used interMixingFoam, my concentration is on the mixing process of water and ethanol. The physical process is firstly put the ethanol and water in a cup that have a inlet hole in the bottom, and then pump air into the cup from the bottom to help the mixing process (the geometry of the cup is shown in attatched pictures, the second picture shows that the ethanol is initially at the center of the water), the air is pumped into the cup within a specified time interval (which means the pressure at inlet is a time-dependent variable, and the inlet velocity should be calculated via this inlet pressure).

At the first time, I create the cup geometry by blockMeshDict and setup the varying pressure by uniformTotalPressure (I'm not familiar about this boundary condition, before this I have attempt timeVaryingTotalPressure, timeVaryingUniformFixedValue, timeVaryingMappedFixedValue and uniformFixedValue but all failed, the Openfoam returns an error indicate that there is no such a BC for the former two, I used Openfoam 2.3.1, for the latter two, I don't know how to use them since I didn't found a clear tutorial), after I start the simulation, it diverges at the begining and I don't know how to fix this problem.

After that, I tried to change the time-dependent boundary condition since I dont't familiar about it, I modified the inlet pressure to a fixed value and restart the simulation, but the diverge problem still exist. I have tried refine the mesh, decrease (or increase) the Courant number, decrease the deltaT value but all failed.

Then I have changed the geometry of the cup to a simple cylinder, and the simulation converges in the first 0.06s but diverges after that (under the fixed inlet pressure BC).

I have attatched the zip files of my simulation code (include varying pressure and fixed pressure) , could anyone help me to check my case file? I don't where is the problem, and if possible, could you help me to check if my time-dependent pressure BC is correct? Any suggestion will be appreaciated!

Best,

weicent