Influence of Viscosity Gradient on Bubble Formation at a Submerged Orifice PDF Download

Author: Leily Majidi
Publisher:
ISBN:
Category : Bubbles
Languages : en
Pages : 89

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Book Description
The objective of the present work was to experimentally investigate bubble formation in different viscosities of Silicone oil. The purpose of these experiments was to try to understand how the shape of the bubbles, formed from a small lower orifice, is affected by aspects of viscosity. The two major directions of investigation involved bubble formation in (i) single and finite liquid layers of varying viscosity and (ii) multiple layers of varying viscosities, to create a viscosity gradient. The experiments were inspired by recent observations of Focused Ion Beam FIB movies of thermal sprayed obsidian splats, in which different elongated 'frozen' bubbles exist. It was hypothesized that the rapidly cooling obsidian would therefore have bubbles growing in a thermal gradient, leading to a viscosity gradient from bottom to top. The results indicated that the process of bubble formation and detachment from the orifice is strongly affected by the viscosity gradient. Elongation in bubble shape, changes in the geometry of bubble, growth dynamics and growth time were the parameters that proved the effect of viscosity gradient compared to the case of finite layer of single viscosity. The resulted bubbles were also very close in shape to those observed in FIB movies. These findings lead to a better understanding of the process of bubble formation occurring in splats and provide a potential to control the shape and formation of bubbles in thermal spray process.