Hi!

I am just looking for some explanations about "plug flow". Anyone who could help me?

BR

Franck

what do you want to know I can help

What is a Plug Flow? Equations? Where does a Plug Flow appear? Thanks for helping!

I recommend a book for two phase flow on this item. But to make it short.

Plug flow is a two phase flow pattern(liquid and gas) in a pipe. Large bubbles with arbitrary shape occur.

Assuming a liquid/gas cocurrent flow in a horizontal pipe with constant liquid flow rate you will observe the following when increasing the gas mass flow:

very low flow rates: small bubbles are transported by the liquid. The bubble shape is spherical.

low flow rates: stratified flow with a smooth or wavy interface between liquid and gas can be observed.

increasing flow rates: the wave amplitude increases until the waves reach the top wall of the pipe. Now you have plug flow. The bubbles are concentrated along the top side of the pipe and have arbitrary shape.

even larger flow rates: The bubbles connect to each other until you have a gaseous core and the liquid flows along the pipe wall. The gas entrains liquid droplets into the gas core.

You observe plug flow in inclined or vertical pipes too.

To determine what kind of flow you have in a pipe, a lot of flow pattern maps exist, where the flow pattern is marked according to dimensionless mass flow rates of liquid and gas.