• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.578-586
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• 2006

Numerical simulations are carried out to investigate the thermal effects of the gravitational potential on the centrifugal instability of a Taylor-Couette flow, and to further study the detailed flow fields and flow bifurcations to spiral vortices. The effects of centrifugal potential on the centrifugal instability are also investigated in the current study. Spiral vortices have various types of mode depending on Grashof number and Reynolds number. The correlation of Richardson number with the spiral angle of the spiral vortices shows that the structure of the spiral vortices strongly depends on the Richardson number. The heat transfer rate of the inner cylinder increases with increasing Grashof number. It is also confirmed that the torque required to rotate the inner cylinder increases as Grashof number increases.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.52-55
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• 1997

여과가 진행됨에 따라 막의 표면에서 발생하여 여과선속을 저하시키는 케이크층의 형성은 막을 이용한 고-액 분리공정에서 발생하는 가장 큰 문제점의 하나로서 이는 막 분리공정의 경제성을 좌우하는 중요한 인자가 된다. 이러한 문제점을 극복하기 위하여 유체와 막 사이의 상대속도를 증가시켜 여과속도를 향상시키는 십자흐름 여과, 즉 CFF(crossflow filtration)에 대한 연구가 활발히 진행되어 왔다. 그러나 이러한 심자흐름 여과에서도 막과 유체 사이의 상대속도의 증가에 한계가 있고 또한, 막의 기공보다 작은 입자가 막의 기공 내에 침투하여 막을 오염시키는 현상을 예측하기 어렵기 때문에 여과기의 설계에 있어서 많은 문제점이 발생하고 있다. 이에 오염된 막을 재생시키기 위하여 기계적.화학적인 여러 가지 방법들이 개발되고 여과선속을 향상시키는 방법이 꾸준히 연구되어 분리막 기술의 경제성을 향상시켜 왔다. 본 연구에서는 매우 안정된 유동의 하나로서 막 표면의 전단력을 향상시키는 데에 효과가 있다고 알려진 Taylor와류를 응용한 회전막 여과기를 사용하여 여러 가지 크기의 입자에 대한 여과실험을 수행함으로써 이러한 유동이 케이크의 형성에 미치는 영향을 살펴보았다. 또한 여과선속에 영향을 미치는 여러 매개인자를 알아보고 실험결과를 간단한 모델식에 적용해 봄으로써 막의 저항을 예측할 수 있는 모델식으로의 개선 방향을 제시하고자 한다.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.67-73
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• 2015

Using a computational fluid dynamics technique, the flow characteristics and particle residence time in a Taylor reactor were studied. Since flow characteristics in a Taylor reactor are dependent on the operating conditions, effects of the inlet flow velocity and reactor rotational speed were investigated. In addition, the particle residence time of $LiNiMnCoO_2$ (NMC), which is a cathode material in lithium-ion battery, is estimated in the Taylor vortex flow (TVF) region. Without considering the complex chemical reaction at the inlet, the effect of Taylor flow was studied. The results show that the particle residence time increases as the rotating speed increased and the flow rate decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.630-637
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• 2006

The flow regimes for a Taylor-Couette flow with a stable, axial stratification in density are investigated using numerical simulation. The flow configuration identical to that in the experiment of Boubnov, et al. (1995) is considered in the present research. The main objectives of this investigation are to verify the experimental and numerical results carried out by Boubnov, et al. and Hua et al. (1997), respectively, and to further study the detailed flow fields and flow bifurcations. With increasing buoyancy frequency of the fluid (N), the stratification-dominated flow regime, called the S-regime, is observed. It is also confirmed that the important effect of an axial density stratification is to stabilize the flow field. The present numerical results are in good agreement with Boubnov, et al. and Hua et al.'s observations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1302-1310
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• 2002

A direct numerical simulation in turbulent curved channel flow is performed. The drifting Taylor-Gortler vortices are identified by applying a conditional averaging. A new algorithm is proposed based on the wavelet transform of the wall information. A continuous wavelet transform with Marr wavelets is employed to decompose the flow signals at a chosen length scale. An active cancellation is applied to attenuate the Taylor-Gortler vortices and to reduce the wall skin friction.

• Proceedings of the Membrane Society of Korea Conference
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• 1991.04a
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• pp.13-14
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• 1991

본 연구에서는 Tobler[1]가 십자흐름여과 (crossflow filtration)의 개선책으로 제안한 동역학적 여과기를 제작하여 그 특성을 실험적으로 고찰하였다. 이 여과기는 두 개의 동심원통 사이를 유체가 흐를 때 내부원통의 회전속도가 외부원통의 회전속도보다 매우 빠를 경우 발생하는 Taylor 와류를 응용한 것이다.

• Membrane Journal
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• v.13 no.2
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• pp.88-100
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• 2003

A change of filtrate flux in Taylor vortex flow filtration was investigated experimentally by rotating speed of inner cellulose ester membrane cylinder (average pore size: 1.2 ${\mu}m$), slurry concentration, and particle size. The filtrate flux was a direct proportion relation with TMP, but an inverse relation with resistances. A change of cake resistance with time was examined by rotating speed, slurry concentration, and particle size. Initial resistance increased dramatically as raising slurry concentration, and the pseudo-steady state was maintained at high resistance value. However, times to reach the pseudo-steady state did not depend on slurry concentration. The resistance was larger as smaller particle size, because possibility of pore blocking inside membrane could be higher and shear effect should be lower as smaller particle size. A model equation suggested in this study was composed of particle deposition and removal terms, and could confirm well experimental data using average values of experimental coefficients.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.97-102
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• 2003

An experimental study is conducted to investigate the effects of duct corrugation angle on heat/mass transfer characteristics in wavy ducts by using a naphthalene sublimation technique. The corrugation angles of the wavy ducts are $145^{\circ}$ , $130^{\circ}$ and $115^{\circ}$ . and the Reynolds numbers based on the duct hydraulic diameter vary from 300 to 3,000. At the low $Re(Re{\leq}1000)$, high heat/mass transfer regions are formed by the secondary vortex flows called Taylor-Gortler vortices on both pressure-side and suction-side walls. At the high $Re(Re{\geq}1000)$, the effects of these secondary flows are vanished. As corrugation angle decreases, the local peak Sh induced by Taylor-Gertler vortices are increased and average Sh also enhanced. More pumping power (pressure loss) is required with the smaller corrugation angle due to the stronger secondary vortex flows.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.13-24
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• 1993

The dispersion in the oscillatory flow generated by gravitational waves above the spatially periodic repples is studied. The steady parts of equations describing the orbit of the passive particle in a two dimensional field are assumed to be simply trigonometric functions. From the view point of nonlinear dynamics, the motion of the particle is chaotic under externally time-periodic perturbations which come from the wave motion. Two cases considered here are; (i) shallow water, and (ii) deep water approximation.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.120-122
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• 1997

1. 서론 : 본 연구에서는 매우 안정된 유동의 하나로 막 표면의 전단력을 향상시켜 여과가 진행됨에 따라 막의 표면에서 발생하여 여과선속을 저하시키는 케이크층의 형성을 억제하는 데에 효과가 있다고 알려진 Taylor와류를 응용한 회전막 여과기를 사용하여 여과실험을 수행함으로써 이러한 유동이 케이크층의 형성에 미치는 영향을 살펴보았다. 또한 여과선속에 영향을 미치는 여러 매개인자들을 포함하는 새로운 모델식을 제안하고 실험결과와 비교해봄으로써 그 타당성을 살펴보았다.