[kjh9537]

Hello everyone,
I'm doing project to simulate slug flow in the pipe.

The flow is 2-phase consisting of oil and gas. To achieve slug frequency, I set fluctuating time-dependent oil volume fraction from 0 to 1 using UDF.
*****I attached my code.********

I wanted to observe flow regime. however my calculation shows gradation for the volume fraction... like below




In my understanding, 2 phase flow forms clear interface between each phase, but my result shows gradation of volume fraction as if oil/gas I set has same phase.

I quadruply cheked my setting or UDF in the simulation and then tried to find the reason in everyway, but couldn't find any clue.


May I ask your opinion that if it can still show the gradation for phase volume fraction in 2 phase flow though it is properly set?
If it doesn't, could you share any clue came up with?




Below is summary of my setting :


Phase 1 : air (default material in Fluent)
Phase 2 : oil (modified density and viscosity from diesel liquid which is default material in Fluent)

Inlet velocity of mixture : 8m/s
Inlet Phase 1 volume fraction : N/A
Inlet Phase 2 volume fraction : UDF (code is attached in this thread)

Phase 2 volume fraction changes between 0 and 1 every 0.1 seconds.