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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

ENHANCED MODELLING AND INVESTIGATION OF MICRO-DROPLET FORMATION IN IMMISCIBLE FLUIDS AT A T-JUNCTION

DOI: 10.1615/TFESC1.mnp.012955
pages 1553-1560

Tilak T. Chandratilleke
Department of Mechanical Engineering, Curtin University of Technology, GPO Box U1987, Perth WA6845, Western Australia

Nima Nadim
Department of Mechanical Engineering, Curtin University, GPO Box U1987, Perth, Western Australia A 6845, Australia


KEY WORDS: Microfluidics, Immiscible fluid intercations, Droplet formation

Abstract

Fluid mechanisms within micro/nano-scale passages are commonly deployed for flow control and droplet generation in modern technologies from Micro-Electro-Mechanical Systems (MEMS) and microfabrication to enzymatic and DNA analysis in molecular biology and pharmaceutical product manufacture. Such microfluidic behaviour is uniquely different to macro-scale fluid flow, for its characteristics are essentially governed by molecular diffusion-biased momentum transport with profound influence from surface tension and fluid viscous dissipation. This paper presents a numerical study supported by experimental validation to examine the micro-mixing behaviour of two immiscible fluids at an intersecting T-junction of flow passages for a range of flow rate combinations and fluid property variations. The computational fluid dynamics analysis is developed as a 3-dimensional flow model for predicting the nature of fluid interactions and pressure fluctuations leading to (any) droplet formation, droplet generation frequency, droplet interfacial area and volume distribution characteristics within the fluid mixture. The analysis also investigates the transverse and axial pressure variations exhibited by the mixing process, inferring key features to describe various phases of droplet generation and detachment. The results identify that the droplet formation is primarily regulated by the volumetric flow rate ratio between the primary and secondary fluids. At low flow rate ratio both fluids flow as a mixture without breaking up while beyond a certain ratio, droplets are produced at regular time intervals. The droplet size, interfacial area and frequency are strong functions of the flow rate ratio exhibiting a mechanistic relationship with the fluid pressure profiles.

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