• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.125-128
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• 2004

Chemical Mechanical Polishing(CMP) in semiconductor production is characterized its output property by Removal Rate(RR) and Non-Uniformity(NU). Some Previous works shows that RR is determined by production of pressure and velocity and NC is also largely affected by velocity of flow-field during CMP. This study is about the direct measurement of velocity of slurry during CMP and reconstruction whole flow-field by Particle Image Velocimetry(PIV) Techniques. Typical PIV system is tuned adequately for inspecting CMP and Slurry Flow-field is measured by changing both Pad RPM and Carrier RPM. The results show that velocity is majorly determined not by Carrier RPM, but by Pad RPM.

• 대한기계학회논문집B
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• 제29권1호
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• pp.123-130
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• 2005

A digital in-line holographic particle image velocimetry (HPIV) which can be applied to measure three-dimensional velocity fields of turbulent flows was developed. There are three different implementation methods of HPIV: traditional film-based HPIV, intermediate HPIV and digital HPIV. The traditional film-based HPIV and intermediate HPIV method is rather troublesome to do experiments and takes long calculation time, compared with the digital HPIV, Configuration of the digital in-line HPIV is simple and the data processing routine is similar to conventional 2D PIV methods. The digital HPIV velocity field measurement consists of four steps: recording, numerical reconstruction, particle extraction and velocity extraction. In the velocity extraction process, we improved PTV algorithm to extract the displacement of particle each placed in 3D space. The developed digital in-line HPIV system was applied to a vertical jet flow. The 3D velocity vectors measured by the digital HPIV method in the near field are in a good agreement with 2D PIV results.

• Interaction and multiscale mechanics
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• 제6권2호
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• pp.157-172
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• 2013

This paper presented an investigation of macromolecular suspension in a grooved channel by using the dissipative particle dynamics (DPD) with finitely extensible non-linear elastic (FENE) bead spring chains model. Before studying the movement and evolution of macromolecules, the DPD method was first validated by modeling the simple fluid flow in the grooved channel. For both simple fluid flow and macromolecular suspension, the flow fields were analyzed in detail. It is found that the structure of the grooved channel with sudden contraction and expansion strongly affects the velocity distribution. As the width of the channel reduces, the horizontal velocity increases simultaneously. Vortices can also be found at the top and bottom corners behind the contraction section. For macromolecular suspension, the macromolecular chains influence velocity and density distribution rather than the temperature and pressure. Macromolecules tend to drag simple fluid particles, reducing the velocity with density and velocity fluctuations. Particle trajectories and evolution of macromolecular conformation were investigated. The structure of the grooved channel with sudden contraction and expansion significantly influence the evolution of macromolecular conformation, while macromolecules display adaptivity to adjust their own conformation and angle to suit the structure so as to pass the channel smoothly.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.368-378
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• 2018

Understanding of turbulent flow in the reactor coolant pump (RCP) is a premise of the optimal design of the RCP. Flow structures in the RCP, in view of the specially devised spherical casing, are more complicated than those associated with conventional pumps. Hitherto, knowledge of the flow characteristics of the RCP has been far from sufficient. Research into the nonintrusive measurement of the internal flow of the RCP has rarely been reported. In the present study, flow measurement using particle image velocimetry is implemented to reveal flow features of the RCP model. Velocity and vorticity distributions in the diffuser and spherical casing are obtained. The results illuminate the complexity of the flows in the RCP. Near the lower end of the discharge nozzle, three-dimensional swirling flows and flow separation are evident. In the diffuser, the imparity of the velocity profile with respect to different axial cross sections is verified, and the velocity increases gradually from the shroud to the hub. In the casing, velocity distribution is nonuniform over the circumferential direction. Vortices shed consistently from the diffuser blade trailing edge. The experimental results lend sound support for the optimal design of the RCP and provide validation of relevant numerical algorithms.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.567-570
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• 2008

내경 0.109 m의 유동층에서 다입자경 모래에 대한 압력요동의 표준편차와 유속간의 선형회귀분석을 이용한 최소유동화속도 측정법의 적용성을 조사하였다. 다입자경 모래를 평균입자크기가 같은 Gaussian 분포에서 입자분포의 표준편차에 따른 최소유동화속도를 측정하고, 측정치를 타 연구자들의 식과 비교 검토하였다. 압력요동의 표준편차 값 선형회귀분석법과 층내 압력강하로부터 구한 최소유동화속도를 구하였다. 최소유동화속도 결정에서 유속 범위는 혼합도가 낮은 유속범위와 free bubbling 영역 이상을 제외한 범위값 이어야 하며, 이 유속범위에서 측정위치는 혼합이 양호한 층 중앙이 가장 적절하다.

• 한국군사과학기술학회지
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• 제11권6호
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• pp.164-171
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• 2008

A modified generalized particle algorithm, MGPA, was suggested to improve the computational efficiency of standard SPH method in numerical analysis of high speed impact behavior. This method uses a numerical failure mechanism than material failure models to describe the target penetration. MGPA algorithm was more effective to describe the impact phenomena and new boundaries produced during the calculation process were well recognized and treated in the target penetration problem of a bullet. When bullet perforation problems were analyzed by this method, MGPA algorithm calculation gives the stable numerical solution and stress oscillation or particle penetration phenomena were not shown. The error range in ballistic velocity limit is less than $2{\sim}13%$ for various target thickness.

• 한국해양공학회지
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• 제17권1호
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• pp.55-60
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• 2003

The effect of size and volume fraction of ceramic particles, with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by the pressureless infiltration process. The metal matrix composites exhibited about 5.5 - 6 times the wear resistance compared with AC8A alloy at high sliding velocity, and by increasing the particle size and decreasing the volume fraction, the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity, linearly : whereas, metal matrix composites indicated more wear loss than AC8A alloy at the slow velocity region. However, a transition point of wear loss was found at the middle velocity region, which shows the minimum wear loss. Further, wear loss at the high velocity region exhibited nearly the same value as the slow velocity region. In terms of wear mechanism, the metal matrix composites generally exhibited abrasive wear at slow to high sliding velocity； however, AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.379-384
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• 2002

The effect of size and volume fraction of ceramic particles with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by pressureless infiltration process. The particulate metal matrix composites exhibited about 5.5 - 6 times of excellent wear resistance compared with AC8A alloy at high sliding velocity, and as increasing the particle size and decreasing the volume fraction the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity linearly. whereas metal matrix composites indicated more wear loss than AC8A alloy at slow velocity region, however a transition point of wear loss was found at middle velocity region which show the minimum wear loss, and wear loss at high velocity region exhibited nearly same value with slow velocity region. In terms of wear mechanism, the metal matrix composites exhibited the abrasive wear at slow to high sliding velocity generally, however AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

• 한국분무공학회지
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• 제16권2호
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• pp.69-75
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• 2011

This article presents computational fluid dynamics (CFD) simulations of sub-micron particle movements and flow characteristics in laboratory-scale electrostatic precipitator (ESP) without corona discharge, and for simulation, it uses the commercial CFD program (CFD-ACE) including electrostatic theory and Lagrangian-based equation for sub-micron particle movement. For validation of CFD results, a simple cylindrical type of ESP is simulated and numerical prediction shows fairly good agreement with the analytical solution. In particular, the present study investigates the effect of particle diameter, inlet flow rate, and applied electric potential on particle collection efficiency and compares the numerical prediction with the experimental data, showing good agreement. It is found that the particle collection efficiency decreases with increasing inlet flow rate because the particle detention time becomes shorter, whereas it decreases with the increase in sub-micron particle diameter and with the decrease of applied electric voltage resulting from smaller terminal electrostatic velocity.

• 한국가스학회지
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• 제19권3호
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• pp.25-31
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• 2015

본 연구에서는 부유 Mg분진의 최소발화온도(MIT)에 있어서 입자 체류시간이 어떠한 영향을 주는지를 실험자료와 입자속도의 계산결과를 사용하여 조사하였다. 평균입경이 증가하면 Mg분진의 MIT는 증가하는 반면에 입자 체류시간(Residence time)은 지수함수적으로 감소하여 분진의 발화 가능성이 저하되는 요인이 될 수 있음을 계산을 통해 확인할 수 있었다. 또한 온도증가에 의한 입자속도에의 영향은 평균입경이 클수록 미세하지만 증가하는 결과가 얻어졌다.