A R, Premlata and Sahu, Kirti Chandra
(2018)
Dynamics of an air bubble rising in constant
and varying viscosity media.
PhD thesis, Indian Institute of Technology, Hyderabad.
Abstract
The dynamics of a gas bubble rising in a liquid is observed in many natural phenomena,
and also in industrial applications. Due to its practical relevance, this has been studied
from many centuries and it continues to be a problem of great interest even today. The main
objectives of the thesis are to investigate some novel problems on bubble rising in viscosity
varying systems. In several situations one could observed viscosity stratified media. Two
of them are considered in this work. (a) When viscosity stratification is inherently present in
the surrounding medium (say, viscosity of the outer fluid is increasing linearly with height).
(b) When the outer fluid is a non-Newtonian fluid, wherein the surrounding fluid viscosity
varies due to the shear caused by the motion of the bubble. Three-dimensional numerical
simulations and experiments are performed to study these flows. The flow dynamics
is governed by mass, momentum and energy conservation equations. A volume-of-fluid
(VoF) approach is used to track the interface separating the fluids. The computational and
experimental approaches used in this study are discussed in Chapter 2. The validations of
the present numerical solver are also performed in the same chapter. In order to compare
the bubble behaviour in a medium with varying viscosity with that observed in a constant
viscosity medium (standard system), the dynamics of a rising bubble in a standard air-water
system is also investigated.
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