• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1289-1297
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• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Serpentine Laminating Micromixer (SLM) in the present study, Part 1. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other term, lamination) mechanism is obtained by the successive arrangement of 'F'-shape mixing units in two layers. The chaotic advection is induced by the overall three-dimensional serpentine path of the microchannel. Chaotic mixing performance of the SLM was fully characterized numerically. To compare the mixing performance, a T-type micromixer which has the same width, height and length of the SLM was also designed. The three-dimensional numerical mixing simulations show the superiority of the SLM over the T-type micromixer. From the cross-sectional simulation results of mixing patterns, the chaotic advection effect from the serpentine channel path design acts favorably to realize the ideal lamination of fluid flow as Re increases. Chaotic mixing mechanism, proposed in this study, could be easily integrated in Micro-Total-Analysis-System, Lab-on-a-Chip and so on.

• Journal of The Korean Astronomical Society
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• v.32 no.2
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• pp.119-126
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• 1999

The standard stellar models for $\alpha$ Cen A and B have been constructed without resorting to the arbitrary constraint of the Solar mixing length ratio. Assuming that the chemical compositions and the ages of the two stars are the same, series of models have been constructed. Using the observational constraints, [Z/X], we were able to constrain the number of the 'possible' models. We find that utilizing the observational constraints of [Z/X] the best models for $\alpha$ Cen system are with the initial Z = 0.03, X = 0.66$\~$0.67. In particular, the primary and the secondary stars may have the same mixing length ratio 1.6$\~$1.7, which is the same as that of the calibrated Solar model. And, the age of the system is about 5.4 Gyr. Finally, the large spacing of the p-modes is predicted to be 104 $\pm$ 4$\mu$Hz for $\alpha$ Cen A.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.4
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• pp.331-340
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• 1982

Numerical analysis is made on the turbulent heat transfer with suspension of solid particles in circular tube with constant heat flux. The mean motion of suspending particles in mixture is treated as the secondary gas flow with virtual density and viscosity. Our modeling of turbulent transport phenomena of suspension flow is based on this assumption and conventional mixing length theory. This paper gives the evidence that the mixing length models can be extended to close the governing equations for two phase turbulent flow with solid boundary at a first order level. Results on Nusselt numbers obtained by analytical treatments are compared with available experimental data and discussed. They suggest that the most important parameters of two phase turbulent heat transfer phenomena are relative particle diameter to pipe diameter, gas-solid loading ratio, and specific heat of suspending material.

• Journal of computational fluids engineering
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• v.12 no.2
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• pp.46-52
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• 2007

An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present study was 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 33 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.166-170
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• 2007

An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present studywas 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 34 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.

• Elastomers and Composites
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• v.27 no.4
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• pp.262-266
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• 1992

A number of tin-containing elastomers are produced commercially by Korea Kumho Petrochemical Co., Ltd. (KKPC) under the Kosyn Sol tradename. The effect of mastication of commercial and laboratory polymerized S-SBR has, been investigated using chemical mixer(ML-500), NMR, GPC and Mooney viscometer. Mastication of polymers containings coupling bonds is affected by the amount of stearic acid, the temperature of mixing and the time length of mixing.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.201-201
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• 2011

• Journal of the Korean Statistical Society
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• v.12 no.2
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• pp.95-99
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• 1983

Limiting law for maximum queue length in G/M/1 queue system is derived. Furthermore, a simple approach using mixing sequence is also discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.68-76
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• 2016

This research is carried out for the performance evaluation of the injector that is one of the critical components of bipropellant-rocket-engine. Spray characteristics are investigated in detail according to the recess length and injection pressure on the swirl-coaxial-injector using gaseous methane and liquid oxygen as propellants. A visualization is conducted by the Schlieren photography that is composed of a light source, concave mirrors, knife, and high-speed-camera. A hollow-cone-shape is identified in the liquid spray that is spread only by inner injector and the spray angle is decreased due to the diminution of swirl strength in accordance with the increase of the length of injector orifice. When the injector sprays the liquid through the inner injector with the aid of gas through the outer injector, the spray angle in external mixing region tends to increase with rise of the recess length, while in internal mixing region, it is decreased. It is also confirmed that the same tendency of the spray angle with recess length appears irrespective of the injection pressure of liquid spray.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.363-370
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• 2017

This paper is concerned with the evaluation of mixing performance of a particle mixer, which consists of a vertical cylindrical vessel and a rotating impeller with several blades. We consider four design variables for the mixer blades, such as the angle, length, and number of blades, and the gap between the blades and the vessel bottom. The particle mixing process due to the impeller rotation is simulated using the discrete element method, and the mixing performance is quantitatively evaluated by introducing a mixing index. Analyzing the main effects and interactions of the four design variables through the design-of-experiments approach, it is concluded that the blade angle has the most dominant influence on the mixing performance whereas the gap has no significant influence. In addition, we determine the best combination of design parameters to maximize the mixing performance.