• Particle and aerosol research
• /
• v.10 no.1
• /
• pp.33-43
• /
• 2014

A differential mobility analyzer (DMA) has been widely used as a standard tool for classifying nanoparticles with a certain size. More recently, several new types of DMA have been tested in an attempt to produce size-monodisperse nanoparticles. It is a bit surprise to see how simple the working theory of the DMA is. Although the theory was demonstrated quite successful, no one can guarantee whether the theory still works in another geometry of the DMA. In this regard, we first investigated the validity of the theory under various working conditions and then moved to check the validity upon minor change in its design. For the valid test, we compared the results with those obtained from a computational fluid dynamics.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.4
• /
• pp.515-521
• /
• 1998

In this study the mixing process of two-phase flow which makes two jets existing vlocity difference are analyzed. The primary jet is jetted on the condition of the state mixed pulverized solid pariticle with air and the velocity in the secondary jet is changed into three kinds velocities(0.60, 75m/s) The velocity vector field concentration field and turbulent properties of solid particles are measured by using 3-Dimensional Particles Dynamics Analyzer. As the velocity of secondary jet increases the solid particle recirculation zone becomes larger. Also solid particle concentration gets dense due to velocity decrement of particles.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.2
• /
• pp.9-15
• /
• 2016

The dynamics of gas-particle flow from a supersonic abrasive blasting nozzle have been studied by 1-D analytical calculation, including wall friction effects inside the nozzle. The developed code in the present study shows a satisfactory agreement with the other study's results. By utilizing the code, the redesign and optimization of the inner contour of a commercial abrasive blasting nozzle were carried out, and it was found that the redesigned nozzle in the present study can produce faster particle velocities at the nozzle exit by up to 22% compared with the original commercial nozzle.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.119.2-119.2
• /
• 2012

Charged particle energization is an outstanding problem in space physics. This paper investigates the nonlinear dynamics of Alfve'n-cyclotron waves accompanying particle heating processes and the drift Alfv'en-cyclotron (or EMIC) instability associated with a current disruption event on 29 January 2008 observed with THEMIS satellite by means of a particle-in-cell simulation. The simulation shows that the drift Alfv'en-cyclotron instabilities are excited in two regimes, a relatively low frequency mode propagating in a quasi-perpendicular direction while the second high-frequency branch propagating in a predominantly parallel propagation direction, which is consistent with observation as well as earlier theories. It is shown that parametric decay processes lead to an inverse cascade of Alfv'en-cyclotron waves and the generation of ion-acoustic waves by decay instability. It is also shown that the nonlinear decay processes are accompanied by small perpendicular heating and parallel cooling of the protons, and a pronounced parallel heating of the electrons.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2002.10a
• /
• pp.45-50
• /
• 2002

This study presents a modeling method to predict fate of resuspended sediment in the development of deep-sea mineral resources. Resuspended deep-sea sediment during the development is considered a major environmental problem. In order to quantitatively analyze the resuspended sediment in the water column, particle size distribution (PSD) is considered an important factor. The model developed here includes PSD and coagulation process, as well as sedimentation process. Using the model, basic simulation was performed under representative environmental setting. The simulation showed the dynamics of change of particle size distribution for 50 m depth of water column up to 10 days of simulation time. Coagulation seemed an important factor in the fate of resuspended deep-sea sediment.

• Proceedings of the Korean Society of Rheology Conference
• /
• 2006.06a
• /
• pp.61-64
• /
• 2006

Soft materials, such as polymer solutions, gels and filamentous protein materials in cells, show complicated behavior due to their complex structures and dynamics with multiple characteristic time and length scales. Several complementary techniques have been developed to measure viscoelastic of soft materials. Especially, particle tracking microrheology, using the Brownian motion of particles in a medium to get rheological properties, has recently been improved both theoretically and experimentally. Compared to other conventional methods, video particle tracking microrheology has some advantages such as small sample volume, detecting spatial variation of local rheological properties, and less damage to sample materials. With these advantages, microrheology is more suitable to measure the properties of complex materials than other mechanical rheometries.

• Applied Chemistry for Engineering
• /
• v.30 no.4
• /
• pp.445-452
• /
• 2019

Shear thickening is an intriguing phenomenon in the fields of chemical engineering and rheology because it originates from complex situations with experimental and numerical measurements. This paper presents results from the numerical modeling of the particle-fluid dynamics of a two-dimensional mixture of colloidal particles immersed in a fluid. Our results reveal the characteristic particle behavior with an application of a shear force to the upper part of the fluid domain. By combining the lattice Boltzmann and discrete element methods with the calculation of the lubrication forces when particles approach or recede from each other, this study aims to reveal the behavior of the suspension, specifically shear thickening. The results show that the calculated suspension viscosity is in good agreement with the experimental results. Results describing the particle deviation, diffusivity, concentration, and contact numbers are also demonstrated.

• Particle and aerosol research
• /
• v.14 no.4
• /
• pp.181-189
• /
• 2018

In this study, the risk rates of different contamination sources of the contaminant in a minienvironment were analyzed through Computational Fluid Dynamics (CFD) simulation. The airflow pattern characteristics can only predict the qualitative variation of contaminant concentration, but cannot evaluate the quantitative variations in the risk rate of sources. From the results, the ambient contamination sources mainly affect wafers in the Front Opening Unified Pod (FOUP), whereas the internal contamination sources mainly affect wafers laid on the robot arm in the minienvironment. And the purging plenum system is very useful in protecting the wafers in the FOUP from contaminants transferred from the Fan Filter Unit (FFU). However, this system is unable to protect the wafers on the robot arm from internal contaminants and the wafers in the FOUP from sources of the interface between the FOUP and the minienvironment.

• Coupled systems mechanics
• /
• v.10 no.6
• /
• pp.491-507
• /
• 2021

The aim of this paper is to conduct a hydrodynamic analysis of fluid flow over different weir types using the analytical solution, the physical model taken from another article, and numericalsimulations through the Smoothed particle hydrodynamic method (SPH) using the compiled DualSPHysics source code. The paper covers the field of real fluid dynamics that includes a description of different proposed types of weirs in various flow regimes and the optimal solution for the most efficiency structure shape. A detailed presentation of the method, the structure and it's characteristics are included. Apart from the single stepped weir, two other weir types are proposed: a Divided type and a Downstream slopped type. All of them are modeled using the SPH method.

• Nuclear Engineering and Technology
• /
• v.50 no.5
• /
• pp.665-672
• /
• 2018

A venturi scrubber is an important element of Filtered Containment Venting System (FCVS) for the removal of aerosols in contaminated air. The present work involves computational fluid dynamics (CFD) study of dust particle removal efficiency of a venturi scrubber operating in self-priming mode using ANSYS CFX. Titanium oxide ($TiO_2$) particles having sizes of 1 micron have been taken as dust particles. CFD methodology to simulate the venturi scrubber has been first developed. The cascade atomization and breakup (CAB) model has been used to predict deformation of water droplets, whereas the Eulerian-Lagrangian approach has been used to handle multiphase flow involving air, dust, and water. The developed methodology has been applied to simulate venturi scrubber geometry taken from the literature. Dust particle removal efficiency has been calculated for forced feed operation of venturi scrubber and found to be in good agreement with the results available in the literature. In the second part, venturi scrubber along with a tank has been modeled in CFX, and transient simulations have been performed to study self-priming phenomenon. Self-priming has been observed by plotting the velocity vector fields of water. Suction of water in the venturi scrubber occurred due to the difference between static pressure in the venturi scrubber and the hydrostatic pressure of water inside the tank. Dust particle removal efficiency has been calculated for inlet air velocities of 1 m/s and 3 m/s. It has been observed that removal efficiency is higher in case of higher inlet air velocity.