8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P6.24Fri 911:10-14:00Differences in path instabilities between a bubble risingin water and in aqueous polymer solution in a Hele-Shawcell in the transient and steady statesMasami Kawaguchi 11 Mie University, 1577 Kurimamachiya, 514-8507, Tsu, Mie, JapanThe buoyancy-driven path instabilities of an air bubble rising in a Hele-Shaw cell filled with purewater are examined as a function of the E tv s number ( Eo ) in terms of changes in the shape,trajectory, and peripheral length ( L ) of the bubble in the transient and steady states. The pathinstabilities in an aqueous solution of hydroxypropyl methyl cellulose (HPMC) are also studiedas a function of the adsorption time of HPMC at a fixed Eo. The differences between the pathinstabilities in the transient state and those in the steady state are discussed. T he path instabilitiesof a bubble in water can be summarized as follows: (1) below Eo = 5, an oblate ellipse bubbleis accompanied by a vibrational trajectory with no changes in L in the steady state, while in thetransient state, the bubble shape changes from a more elongated oblate ellipse to a less elongatedone, and the bubble’s rise velocity in the latter state is greater than in the former one; (2) above Eo= 5, a comma-shaped bubble is accompanied by a vibrational motion of both the path and L in thesteady state, while in the transient state, an increase in the Eo produces a straight trajectory witha decrease in the amplitude of the vibration of L, and the rise velocity of a bubble in the transientstate is less than it is in the steady state. The adsorption of HPMC on the surface of a bubble causesa more rounded bubble, a suppression of changes in the bubble’s shape, and a decrease in its risevelocity.24