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Title: Breakup of the tail of a bubble in a non-Newtonian fluid - 2008 DFD Description: It is well known that the shape of an air bubble ascending in a non-Newtonian fluid is affected by the rheological properties of the fluid. In this work, a 1.5 wt. % aqueous solution of an associative polymer (hydrophobic alkali swellable emulsion) with 0.02 wt. % sodium salicylate was used. For different volumes, between 9.68 and 955 mm3, a high speed video recorded the bubble shape in motion. For the smallest volume tested, the bubble is spheroidal and behaves like a bubble in a Newtonian liquid. Increasing the bubble volume, a cusp and a tail, at the rear of the bubble, are observed. First, the tail is axisymmetric (155 mm^3); then for higher volumes, the tail becomes asymmetric and with a knife-edge shape (197 mm3). For a volume of 268 mm^3, the tail breaks into a “fish backbone” pattern. In the case of volumes higher than 268 mm^3 the tails break and split in several threads. At the moment, we do not yet have a full explanation of this breakup mechanism; its origin is certainly related to the structure and elasticity of the fluid. Credits: Enrique Soto, Roberto Zenit, and Octavio Manero References: Web Page: http://pof.aip.org/pof/gallery/2008-Manero.jsp#video Contributed By: |