Youngho Suh

Numerical Simulation of Droplet Deposition and Self-Alignment on a Microstructured Surface

Numerical simulation is performed for droplet impact and deposition on a microstructured surface. The droplet deformation is calculated by a sharp-interface level-set method which is extended to treat the immersed solid structure and the contact angle at the liquid–gas–solid interline. The computations are further carried out to investigate the droplet self-alignment behavior derived by the interfacial characteristics between the liquid-gas-solid phases, which can be used to overcome a droplet placement error and to improve the accuracy in film formation. The effects of contact angle, surface tension, and microstructure configuration on the droplet deposition are quantified.

A numerical method for the calculation of drag and lift of a deformable droplet in shear flow

We present a new numerical method for the calculation of drag and lift acting on a deformable droplet in linear shear flow. The droplet interface is captured by the level-set (LS) method. In order to determine the acting force on a droplet in shear flow field, we adopt the feedback forces which can maintain the particle position while efficiently handling deformation. The stability analysis of the feedback forcing function is performed to provide the precise stability boundaries in the forcing parameter space for the time-advancing scheme used in our study. The present method is applied to simulations of spherical, deformed, and oscillating droplets in uniform flow for validations. The present method is further applied to an investigation of the effects of deformation of a droplet in shear flow. We observed that drag and lift forces acting on a droplet depend strongly on the deformation characteristics.

Numerical Study of Droplet Impact on Solid Surfaces Using a Coupled Level Set and Volume-of-Fluid Method

A level set method is combined with the volume-of-fluid method so that the coupled method can not only calculate an interfacial curvature accurately but also can achieve mass conservation well. The coupled level set and volume-of-fluid(CLSVOF) method is efficiently implemented by employing an interface reconstruction algorithm which is based on the explicit relationship between the interface configuration and the fluid volume function. The CLSVOF method is applied for numerical simulation of droplet impact on solid surfaces with variable contact angles. The numerical results are found to preserve mass conservation and to be in good agreement with the data reported in the literature. Also, the present method proved to be applicable to the complex phenomena such as breakup and rebound of a droplet.

Numerical Study on Deformation Behavior of a Fluid Particle Under Shear Flow

In this work, we studied the deformation behavior of a droplet under the various flow conditions. The droplet deformation is calculated by a level-set method. In order to determine the acting force on a particle in shear flow field, we propose the feedback forces which can maintain particle position with efficient handling of deformation. Computations were carried out to investigate the deformation behavior of a droplet caused by the surrounding gaseous flow and the effect of the deformation on the droplet characteristics with various dimensionless parameters. Based on the numerical results, we observed that drag and lift forces acting on a droplet depend strongly on the deformation. Also, the present method is proven to be applicable to a three-dimensional deformation of droplet in shear flow, which cannot be properly analyzed by the previous studies. The drag and lift forces obtained from the present numerical method are favorably compared with the data reported in the literature.Copyright

A Numerical Study on Droplet Deposition in a Micro-Groove

Microdroplet deposition in a micro-groove is studied numerically. The droplet shape is determined by a level-set method which is improved by incorporating a sharp-interface modeling technique for accurately enforcing the matching conditions at the liquid-gas interface and the no-slip and contact angle conditions at an immersed solid surface. The computations are carried out to investigate the droplet behavior derived by the interfacial characteristics between the liquid-gas-solid phases. The effects of contact angle, impact velocity and groove geometry on droplet deposition in a micro-groove are quantified.