*3.4. Liquid–Liquid Interface Distribution and Phase Entrainment*

Entrainment occurs when a bubble enters a new phase. Entrainment occurs via four main mechanisms, as shown in Figure 7:


**Figure 7.** Four mechanisms of liquid entrainment with an oil–oil viscosity of 50 cSt for (**a**) *Q* = 50 mL/min; (**b**) *Q* = 100 mL/min; (**c**) *Q* = 250 mL/min and (**d**) *Q* = 4000 mL/min.

In summary, entrainment in the oil phase was mainly produced via mechanisms (a) microscale entrainment, (b) mesoscale entrainment, (c) large-scale entrainment and (d) mixed entrainment with an increased gas flow rate.
