Deformation and breakup of drops and filaments

Balasubramanian Ambravaneswaran, Purdue University

Abstract

Drops and filaments are prominent in inkjet printing, surface and bulk property measurement, atomization, genomic analysis and drug discovery. Accurate prediction of their dynamics is the major objective of this thesis. Predicting the formation of drops from a capillary and analysis of the effects of surfactants and heat on the deformation and/or breakup of liquid filaments are central goals of this thesis. These situations are studied by one of two approaches: one-dimensional (1-d) analysis based on the slender-jet approximation which, when appropriate to use, results in two to three orders of magnitude reduction in computational time and exact two-dimensional (2-d) analysis using Galerkin/finite element method. Algorithms are developed for analyzing (i) the formation of hundreds of consecutive drops from capillaries, (ii) the effects of surfactants on the nonlinear deformation and/or breakup of stretching and oscillating liquid bridges and (iii) the deflection of planar jets emerging out of 2-d channels when asymmetric heating or wetting is imposed at the slot exit. Key to the success of the 2-d algorithms is the generation of meshes that can follow the deformation of the free surface(s). For this purpose, algebraic and elliptic mesh generation techniques are employed. In drop formation from a capillary at constant flow rate, the 1-d algorithm developed in this thesis is demonstrated to be within 1–2% of established rigorous 2-d algorithms at low flow rates. However, the 1-d predictions can err by 10–15% at high flow rates and be in total disagreement with the 2-d predictions in analyses of (i) drop formation when the flow rate is oscillatory or (ii) contraction of free liquid filaments, which are models of satellites. Analyses of surfactant-laden bridges reveal that convection-diffusion of an insoluble surfactant along an interface can result in complex interplay with the bulk flow and significantly alter the breakup of stretching liquid bridges and the frequency response of oscillating liquid bridges. Studies on the effects of differential wetting and heating on the deflection of planar jets yield windows of operation in the space of governing parameters that are favorable to significant deflection. Channel geometry is shown to contribute nontrivially to the angular momentum of the jet. The methods reported here are not only of scientific interest but should prove indispensable in future studies of microelectromechanical systems (MEMS).

Degree

Ph.D.

Advisors

Basaran, Purdue University.

Subject Area

Chemical engineering

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