• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.359-370
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• 2015

The present study aims to numerically investigate the behavior of liquid droplet driven by capillarity force imbalance on horizontal surfaces ranging from hydrophilic to hydrophobic, under various conditions. The droplet behavior has been simulated using an in-house solution code(PowerCFD), which employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The detailed droplet behavior was obtained under various conditions for droplets with different initial shapes, contact angles and surface tension forces(or Bond number). The mechanism of droplet transport was examined using the numerical results on the droplet shapes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.871-884
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• 2015

Fluid transport is a key issue in the development of microfluidic systems. Recently, Myong (2014) has proposed a new concept for droplet transport without external power sources, and numerically validated the results for a hypothetical 2D shape, initially having a hemicylindrical droplet shape. Myong and Kwon (2015) have also examined the transport mechanism for an actual water droplet, initially having a 3D hemispherical shape, on a horizontal hydrophilic/hydrophobic surface, based on the numerical results of the time evolution of the droplet shape, as well as the total kinetic, gravitational, pressure and surface free energies inside the droplet. In this study, a 3D numerical analysis of an initially spherical droplet is carried out to establish a new concept for droplet transport. Further, the transport mechanism of an actual water droplet is examined in detail from the viewpoint of the capillarity force imbalance through the numerical results of droplet shape and various energies inside the droplet.