Issue with Phase Segregation in Oil-Water Multiphase Simulation using interFoam
 

Hello everyone,

I am a newbie to CFD and Openfoam. I am currently working on a multiphase simulation in OpenFOAM using the `interFoam` solver to model the segregation of oil and water in a still atmospheric tank without any inlet/outlet flows. The tank dimensions are 4m x 2m with a height of 1m, and it is initially filled with an oil-water mixture where oil comprises 50% of the total volume. Despite setting up the simulation to observe the phases separating over time, I have not seen any segregation between oil and water, as the oil should float to the top due to its lower density.

Here are some details of my setup:
- Solver: interFoam
- Initial Condition: Uniform distribution of alpha.oil = 0.5 across the domain.
- Boundary Conditions: Walls are set to noSlip, and the top is a free-slip boundary at atmospheric pressure.
- Mesh: Structured mesh with 20 cells/m resolution.

I have tried to check the physical properties, boundary conditions, and numerical schemes, but the phases remain mixed without clear separation. Gravity is also applied in the constant/g file in negative Z direction.

I am looking for insights or suggestions that might help in diagnosing and resolving this issue. My next goal is to also add inlet/outlet nozzles and a weir plate also which I will model after I fix such a simple scheme:o

Could there be an issue with my solver settings, BCs or the way the initial conditions are applied?



I am attaching the complete case setup files along with the blockmesh dictionary.
Any advice on adjustments to the setup or further diagnostic steps would be greatly appreciated!

Hi,

Also a fairly new OpenFOAM/CFD user here, but I think I have a possible explanation.

I took your case and used setFieldsDict (look at e.g. multiphase/RAS/weirOverflow tutorial case) to set alpha.oil to 1 in the lower half of your domain and to 0 in the upper half. The subsequent behaviour seemed realistic. I think the lack of phase separation in your case might be due to a lack of gradients between cells.

Hope this helps :)