Study on breakup of bubble rising in viscoelastic surrounding medium

A study of bubble breakup during its rise in a viscoelastic surrounding fluid enclosed in a vertical pipe is presented. When the favorable conditions are met, the bubble breaks into a large toroidal and a small spherical bubble parts. The present study finds a breakup mode in which the bubble deforms into a disk shape and then breaks when its thickness at the center becomes sufficiently thin. The bubble breakup is studied for various combinations of Galilei number (Ga), Eötvös number (Eo), Weissenberg number (Wi), bubble to surrounding fluid viscosity ratio (μr), and the ratio of solvent to total viscosity (β) of viscoelastic fluid and pipe diameter (Dp) values. Regimes of various bubble behaviors on the Ga−Eo plane are found, including the regime of bubble breakup. The regimes of bubble breakup on Wi−β, μr−Ga, μr−Eo, and Wi−Dp parametric planes are obtained. The results show that the breakup of bubble, through the mode examined in the present study, takes place in a narrow range of Eötvös numbers. The bubble breakup takes place only in certain ranges of parameter values. The viscoelastic surroundings provide breakup promoting environment compared to Newtonian surroundings. Increasing polymeric concentration of surrounding viscoelastic fluid promotes the bubble breakup. Confinement effect due to the presence of pipe wall shows inhibitive effect on breakup. Many of the behaviors of the bubble rising in unbounded medium are also exhibited by the bubble rising in a vertical pipe.