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Summer Research Fellowship Programme of India's Science Academies

Prediction of shape of compound bubble

Nidhi Menon

Amrita Vishwa Vidyapeetham, Ettimadai, Coimbatore, 641112

Prof. Gaurav Tomar

Indian Institute of Science, Bangalore, 560012

Abstract

Dichloromethane (DCM) is denser and more volatile than water and is also immiscible. DCM is an organic compound found naturally in oceans, wetlands and volcanoes and its effect on the ecology and local currents. It is commonly used as a solvent in wood varnishes, paints, strippers, cements, vapor degreasing of metal parts. A small amount of DCM below a water pool when heated from below would start boiling and would release bubbles into much cooler water. As the bubbles rise, a portion of DCM condenses in the rising bubbles and leads to formation of interesting compound droplets. With sufficient condensation of DCM the compound bubble becomes heavier and settles down back to the heated surface. Consider one such compound bubble. The top part of the bubble interacts with the cooler water causing it to condense partially. The condensed part of the fluid being relatively heavier settle at the base of the droplet. This bubble, being heavy on the base will have an interesting shape. The goal of the project is to predict the shape of the compound bubble considering all the three phases. This is done by deriving equations for the curve based on force balance, considering all the forces acting on the bubble. These equations are simultaneously solved numerically to obtain the shape of the curve

Keywords: immiscible, compound bubble.

The shape of an interface of different phase is dependent on the forces acting upon it. These forces are surface tension, gravitational force, pressure difference. In the absence of gravity the profile is a part of a sphere. However, in the presence of gravity, the curvature varies at every point. The relation of the curve can be found using the Laplace equation. Considering the number of variables in this case, it is difficult to solve it analytically, hence it is verified numerically.

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