Steady-state, multiphase gas-liquid flow in a pipe is typically classified into one of several regimes such as bubbly, plug, churn, or annular flow. In this effort, numerical simulations are performed to simulate a transient, air-water multiphase flow as it transitions between several of these flow regimes. The setup consists of a slug of water, initially at rest inside a horizontal pipe, and suspended by thin partitions on each side. Pressurized air in the range of 1-50 MPa is applied to one side of the slug, which breaks the partitions and pushes the slug through the pipe. As the slug deforms and the air-water interface evolves, the flow regime transitions from pure slug flow into a mix of annular, dispersed, and plug flow.
The results show that the timing of transitions between flow regimes is largely dependent on the driving pressure.
Interestingly, however, the rate of penetration of the driver gas through the slug is very linear with respect to distance traveled through the tube.Video presentation