Abstract: Visual experiments are conducted for studying the characteristics of bubble growth at the permeable sidewall in rectangular liquid flow channel and water invasion in reticulate structure with uniform small channels. The results show that water invasion process can be observed when the bubble is at the rapid growth stage. Under the smaller air flow rate conditions, single bubble departure volume increases with the increasing of air flow rate, but the largest invasion height of water decreases with the increasing of air flow rate. Under the larger air flow rate conditions, single bubble departure volume reduces with the increasing of air flow rate, and the phenomenon of air bubbled from more than one pore usually occurrs at the permeable sidewall, which along with small bubbles rapidly shrink and disappear. With the increasing of water flow rate, single bubble departure volume reduces, however, the largest invasion height of water increases in reticulate structure.

Key words: Bubble, Invasion, Permeable sidewall, Two-phase flow, Visualization study