Motion of gas bubbles in non-Newtonian liquids

The available theoretical knowledge of the motion of gas bubbles in Newtonian liquids is reviewed, and the possibility of extension to non-Newtonian liquids, both purely viscous and viscoelastic, is studied. Experimental data on the rising velocities of gas bubbles in a variety of non-Newtonian liquids are presented and interpreted on the basis of theoretical knowledge. Peculiarities that have been observed in highly elastic liquids are discussed, and a tentative interpretation is offered.