(440b) Bubble Rise Behavior in Cornstarch-Water Suspension

In this study, we investigate the rise behavior of a single bubble, and a single jet in dense cornstarch-water suspensions with varying packing fractions. Experimental results reveal that bubbles have a spherical cap shape at low packing fractions and their rise velocity has a damping oscillatory behavior. At 40 vol% packing fraction, the bubble has an oblate shape and the rise velocity of bubble increases as the bubble grows wider, followed by the bubble slowing down, and after this the cycle repeats itself. A gaseous jet of bubbles has a regular pattern of coalescence at 40 vol% and a particular flow rate, in which bubbles coalesce at the same points in space at a regular frequency. At other flow rates and packing fractions, bubbles coalesce at more random points in space and time. We attribute these behaviors to the unique rheological behavior involving discontinuous shear-thickening in this suspension.