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  • Authors: Vinh T. Nguyen; Truong V. Vu; Phan H. Nguyen; Nang X. Ho; Binh D. Pham; Hoe D. Nguyen; Hung V. Vu;  Advisor: -;  Co-Author: - (2021)

    Compound and simple droplets have been studied and appeared in many life applications, e.g., drug processing and microfluidic systems. Many studies have been conducted on the thermocapillary effects on simple droplets, but similar studies on compound droplets are quite rare. Filling this missing gap, this paper presents the front-tracking-based simulation results of the thermocapillary effects on compound droplets in a certain limited domain. The compound droplet consists of a single inner core that is initially concentric with the outer one. Various dimensionless parameters including Reynolds number from 1 to 50, Marangoni number from 1 to 100, droplet radius ratio from 0.3 to 0.8, and viscosity ratios from 0.1 to 6.4 are varied to reveal their influences on the migration of a comp...

  • Authors: Vinh T. Nguyen; Truong V. Vu; Phan H. Nguyen; Hoe D. Nguyen; Binh D. Pham; Hung V. Vu;  Advisor: -;  Co-Author: - (2022)

    In this paper, we numerically investigate the dynamics of a compound droplet driven by surface tension variation induced by a thermal gradient in a sinusoidal constriction tube. Initially, the compound droplet with a concentric inner core is spherical and placed in the constriction's upstream region at a low temperature. As time progresses, it migrates downstream with a high temperature. Due to the constriction, the droplet is slowed down in the upstream region and accelerated again right after passing the constriction. This acceleration maximizes the eccentricity. However, the constriction results in an increase in the maximum eccentricity when increasing its depth to a value corresponding to the size of the tube neck, which is greater than or equal to the droplet size. Effects of ...

  • Authors: Truong V. Vu;  Advisor: -;  Co-Author: - (2021)

    A compound droplet solidifying on a cold curved surface in a gaseous environment is numerically studied by an axisymmetric three-phase front tracking method. The compound droplet containing an inner core of gas is initially assumed to be part of a sphere, and the curved surface is maintained at temperature below the solidification point of the shell liquid. The effects of the radius of the cold surface, volume change (in terms of the solid-to-liquid density ratio ρsl), supercooling degree (in terms of the Stefan number St), growth angle ϕgr and shell liquid thickness on the solidified droplet shape, the solidification rate and the solidification times are under consideration. Volume expansion (ρsl < 1.0) induces an apex, and volume shrinkage (ρsl > 1.0) results in a cavity on top of...

  • Authors: Nguyen, Cuong T.;  Advisor: Vu, Hung V.; Vu, Truong V.; Truong, Thuan V.; Ho, Nang X.; Pham, Binh D.; Nguyen, Vinh T.; Nguyen, Hoe D.;  Co-Author: - (2021)

    Compound droplets with different sizes are increasingly used in industrial production and academic research. This study aims to improve understanding of the dynamical behaviors of the compound droplet moving in microchannels. The compound droplet consisting of one inner core is initially concentric and placed at the entrance of a circular channel with a cone at the downstream region. Following this primary channel is a secondary channel that is circular and straight. Manipulation of the droplet is assisted by a flow introduced via the gap between two channels. The numerical results show that when passing through these confined channels, the droplet experiences a finite deformation or breakup mode. In each mode, the deformation or breakup of the compound droplet is also different whe...