Sharaf M, Dilin
(2016)
Experimental Studies on Regime Mapping of a Rising Bubble.
Masters thesis, Indian Institute of Technology Hyderabad.
Abstract
An experimental study on shape variation of an initially spherical rising bubble in different liquids is presented, which validates the results from a paper by Tripathi et al.[2]. They had presented numerical simulation of an initially spherical gas bubble rising in a viscous fluid by Volume of Fluid method with a finite volume open source code, Gerris. They put forward the existence of a phase plot in Eotvos - Galilei plane having five different regimes of bubble behavior with well-defined boundaries. The regimes are characterized by differences in the shape of rising bubble (for example ellipsoidal, axisymmetric cap with a skirt and a doughnut like shape) as well as the path traversed by it (for example straight, zigzag and spiral path). The regime a bubble falls in depends on both its Eotvos and Galilei numbers. In the present study an experimental setup was developed to create an initial bubble of different sizes in a liquid and observe its rise behavior using a high-speed camera. This setup enabled us to get a 2D image of shape and path oscillation through high-speed video recordings. Aqueous glycerol solutions of different volume concentrations were used to obtain the range of Eotvos and Galilei numbers as presented by Tripathi et al [2]. The results indicate that at low Ga and Eo, the bubbles show similar path and shape behavior and show the demarcation of regime boundaries as the numerical simulation. But at high Ga and Eo, there is a mismatch in terms of the regime demarcation boundary indicating that initial condition of the bubble is a critical parameter.
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