| Summary: | Phenomenon of an air-water plug flow regime in horizontal pipes is simulated with
Computational Fluid Dynamics (CFD). Simulations performed with 3-dimensional
computational domain, transient, using commercial software FLUENT 6.3.26. Multiphase
model that used is Eulerian model. Eulerian model solved continuity and momentum
equations for each phase.
On plug flow regime simulations, before liquid slug has formed, it begins with wave
formation at the air-water interface. To be able to appearing Kelvin-Helmholtz instability
which is the begining of wave formation, it is necessary to make perturbation at the air-water
interface. In this research, perturbation at the velocity inlet boundary conditions is done by
two methods, with sinusoidal velocity at the velocity inlet boundary conditions, and a
sinusoidal arrangement of water level at the velcoity inlet boundary conditions.
The results from both methods were compared to determine the effect of the
superficial velocity of water and air against gas bubble length. Based on simulation results
and experimental data, the greater the difference between the water and the superficial
velocity of the air, then the length of the gas bubble is getting shorter. That is because when
the superficial velocity difference between the two phases increase, then the slip velocity at
the interface between the two phases is also getting bigger. The magnitude of the slip velocity
effect on the magnitude of the drag force which is the force of interaction between the two
phases. The greater the drag force, the force that drives the water - air interface to be lifted
to the top is getting bigger, so that the liquid slug is formed faster. This causes the length of
the gas bubble is getting shorter. The results of numerical simulations showed good
agreement when validated with experimental data.
|
|---|