• Progress in Superconductivity and Cryogenics
• /
• v.18 no.1
• /
• pp.10-13
• /
• 2016

In this study, we developed a new volume reduction technique for cesium contaminated soil by magnetic separation. Cs in soil is mainly adsorbed on clay which is the smallest particle constituent in the soil, especially on paramagnetic 2:1 type clay minerals which strongly adsorb and fix Cs. Thus selective separation of 2:1 type clay with a superconducting magnet could enable to reduce the volume of Cs contaminated soil. The 2:1 type clay particles exist in various particle sizes in the soil, which leads that magnetic force and Cs adsorption quantity depend on their particle size. Accordingly, we examined magnetic separation conditions for efficient separation of 2:1 type clay considering their particle size distribution. First, the separation rate of 2:1 type clay for each particle size was calculated by particle trajectory simulation, because magnetic separation rate largely depends on the objective size. According to the calculation, 73 and 89 % of 2:1 type clay could be separated at 2 and 7 T, respectively. Moreover we calculated dose reduction rate on the basis of the result of particle trajectory simulation. It was indicated that 17 and 51 % of dose reduction would be possible at 2 and 7 T, respectively. The difference of dose reduction rate at 2 T and 7 T was found to be separated a fine particle. It was shown that magnetic separation considering particle size distribution would contribute to the volume reduction of contaminated soil.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.252-261
• /
• 1991

A particle trajectory model to simulate two-phase particle-laden crossjets into two-dimensional horizontal free stream has been developed to study the variations of the jet trajectories and velocity variations of the gaseous and the particulate phases. The following conclusions may be drawn from the predicted results, which are in agreement with experimental observations. The penetration of the two-phase jet in a crossflow is greater than that of the single-phase jet. The penetration of particles into the free stream increases with increasing particle size, solids-gas loading ratio and carrier gas to free stream velocity ratio at the jet exit. When the particle size is large, the solid particles separate from the carrier gas , while the particles are completely suspended in the carrier gas for the case of small size particles. As the particle to carrier gas velocity ratio at the jet exit is less than unity, the particles in the vicinity of the jet exit are accelerated by the carrier gas. As the injection angle is increased, the difference of the particle trajectory from that of the pure gas becomes larger. Therefore, it can be concluded that the velocities and trajectories of the particle-laden jets in a crossflow change depending on the solids-gas loading ratio, particle size, carrier gas to free stream velocity ratio and particle to gas velocity ratio at the jet exit.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.5
• /
• pp.18-23
• /
• 2011

A CFD analysis method is developed and applied for investigating the gas flow and the byproduct particle trajectory in Roots type vacuum pump. The internal fluid flow and thermal fields between the rotors and the housing of vacuum pump are analyzed by using the dynamic mesh, the numerical methods for unsteady 2-D Navier-Stokes equation and the standard k-$\varepsilon$ turbulence model of the Fluent code. Coupled with the flow simulation results, the particle trajectory of the byproduct flowing into the pump with gas stream is analyzed by using discrete phase modeling technique. The CFD analysis results show the pressure, the velocity and the temperature distributions in pump change abruptly due to the rotation of rotors, and back flows are produced due to the strong reverse pressure gradients at rotor/rotor and rotor/housing clearances. The predicted byproduct particle trajectory results also show the particles impinge on the clearance surfaces between the housing and the rotor of pump and then may form the deposit layer causing the failure of pump.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.241-251
• /
• 1991

The present simulation model relies on a new approach of the heavy particle motion in a turbulent flow considering the time and space correlation to the Lagrangian point of view. The turbulent field is, here, assumed that its characteristic scales are random and follow a Poisson's distribution. Using this model, we have computed the trajectory of each particle, that is, its velocity and position at each time in order to study the dispersion of particles in a grid turbulent flow. The computed results have been compared to the corresponding experimental data. Due to the complex mechanism of turbulence and the theoretically and experimentally lacking information, we had to make some assumptions for simplifying the situation, but we have found the good agreement between simulated and measured results. In particular, the application of the present method on the Lagrangian correlation of particle provides an interesting alternative to the usual computational methods.

• Journal of the Semiconductor & Display Technology
• /
• v.21 no.2
• /
• pp.1-6
• /
• 2022

This computational investigation of micro-sized particle dispersion concerns the fume particle contamination over target surface in high-precision laser line machining process of semiconductor and display device materials. Employing the random sampling based on probabilistic fume particle generation distributions, the effects of sphericity for nonspherical fume particles are analyzed for the fume particle dispersion and contamination near the laser machining line. The drag coefficient correlation for nonspherical particles in a low Reynolds number regime is selected and utilized for particle trajectory simulations after drag model validation. When compared to the corresponding results by the assumption of spherical fume particles, the sphericity of nonspherical fume particles show much less dispersion and contamination characteristics and it also significantly affects the particle removal rate in a suction air flow patterns.

• Journal of Mechanical Science and Technology
• /
• v.19 no.12
• /
• pp.2312-2320
• /
• 2005

The aerodynamic effects of leading-edge accretion can raise important safety concerns since the formulation of ice causes severe degradation in aerodynamic performance as compared with the clean airfoil. The objective of this study is to develop a numerical simulation strategy for predicting the particle trajectory around an MS-0317 airfoil in the test section of the NASA Glenn Icing Research Tunnel and to investigate the impingement characteristics of droplets on the airfoil surface. In particular, predictions of the mean velocity and turbulence diffusion using turbulent flow solver and Continuous Random Walk method were desired throughout this flow domain in order to investigate droplet dispersion. The collection efficiency distributions over the airfoil surface in simulations with different numbers of droplets, various integration time-steps and particle sizes were compared with experimental data. The large droplet impingement data indicated the trends in impingement characteristics with respect to particle size ; the maximum collection efficiency located at the upper surface near the leading edge, and the maximum value and total collection efficiency were increased as the particle size was increased. The extent of the area impinged on by particles also increased with the increment of the particle size, which is similar as compared with experimental data.

• Journal of the Semiconductor & Display Technology
• /
• v.19 no.4
• /
• pp.51-58
• /
• 2020

Many types of optical plastic films are essential in optoelectronics display unit fabrication and it is important to develop high precision laser cutting methods of optical films with extremely low level of film surface contamination by fume particles. This study investigates the effects of suction and blowing air motions with air flow misalignment in removing fume particles from laser cut line by employing random particle trajectory simulation and probabilistic particle generation model. The computational results show fume particle dispersion behaviors on optical film under suction and blowing air flow conditions. It is found that suction air flow motion is more advantageous to blowing air motion in reducing film surface contamination outside designated target margin from laser cut line. While air flow misalignment adversely affects particle dispersion in blowing air flows, its effects become much more complicated in suction air flows by showing different particle dispersion patterns around laser cut line. It is required to have more careful air flow alignment in fume particle removal under suction air flow conditions.

• Particle and aerosol research
• /
• v.5 no.3
• /
• pp.123-131
• /
• 2009

This paper presents simulation results of particle transport in low-pressure, low-temperature plasma environment. The size dependent transport of particles in the plasma is investigated with a two-dimensional simulation tool developed in-house for plasma chamber analysis and design. The plasma model consists of the first two and three moments of the Boltzmann equation for ion and electron fluids respectively, coupled to Poisson's equation for the self-consistent electric field. The particle transport model takes into account all important factors, such as gravitational, electrostatic, ion drag, neutral drag and Brownian forces, affecting the motion of particles in the plasma environment. The particle transport model coupled with both neutral fluid and plasma models is simulated through a Lagrangian approach tracking the individual trajectory of each particle by taking a force balance on the particle. The size dependant trap locations of particles ranging from a few nm to a few ${\mu}m$ are identified in both electropositive and electronegative plasmas. The simulation results show that particles are trapped at locations where the forces acting on them balance. While fine particles tend to be trapped in the bulk, large particles accumulate near bottom sheath boundaries and around material interfaces, such as wafer and electrode edges where a sudden change in electric field occurs. Overall, small particles form a "dome" shape around the center of the plasma reactor and are also trapped in a "ring" near the radial sheath boundaries, while larger particles accumulate only in the "ring". These simulation results are qualitatively in good agreement with experimental observation.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.19 no.1
• /
• pp.95-104
• /
• 2016

To make a firing table of artillery with trajectory simulation, a precise trajectory model which corresponds with real firing test is required. Recent 4-DOF modified point mass trajectory model is considered accurate as a theoretical model, but fitting coefficients are used in calculation to match with real firing test results. In this paper, modified point mass trajectory model is presented and method of setting ballistic coefficient is introduced by applying optimization algorithms. After comparing two different algorithms, Particle Swarm Optimization and Covariance Matrix Adaptation - Evolutionary Strategy, we found that using CMA-ES algorithm gives fine optimization result. This fitting coefficient setting method can be used to make trajectory simulation which is required for development of new projectiles in the future.

• Journal of Drive and Control
• /
• v.15 no.3
• /
• pp.1-7
• /
• 2018

Humanoid robots have fascinated many researchers since they appeared decades ago. For the requirement of both accurate tracking control and the safety of physical human-robot interaction, torque control is basically desirable for humanoid robots. Humanoid robots are highly nonlinear, coupled, complex systems, accordingly the calculation of robot model is difficult and even impossible if precise model of the humanoid robots are unknown. Therefore, it is difficult to control using traditional model-based techniques. To realize model-free torque control, time-delay control (TDC) for humanoid robot was proposed with time-delay estimation technique. Using optimal walking trajectory obtained by particle swarm optimization, TDC with proposed scheme is implemented on whole body of a humanoid, not on biped legs even though it is performed by a virtual humanoid robot. The simulation results show the validity of the proposed TDC for humanoid robots.