• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2460-2464
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• 2008

The present paper suggests new method to know the effects of molecular diffusion and the helicity of microchannel flows on mixing in passive micromixers, which are essential components of a microfluidic chip. In this study, 'Helix Index' is newly defined as the magnitude of chaotic advection. Relationship between Helix Index and Mixing Index is analyzed numerically such as the wide range of Peclet and Reynolds numbers in three dimensional serpentine microchannel when using soluble solutions (water/glycerol). As a result, a simple algebraic equation is derived by this relationship based on a regression analysis. The algebraic equation is found to be able to accurately predict the mixing performance without solving the coupled, complex momentum and mass transfer equations.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.101-106
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• 2003

In this work, mixing phenomena in the mixing chamber of a ultrasonic micromixer are analyzed through an analytical approach. A simplified 2-dimensional model for the ultrasonic micromixer is presented. Analytical solutions for fluid flow induced by ultrasonic waves are obtained through successive approximations method. From simulation results on thermal diffusion in the mixing chamber, effects of relative location, size, and vibration frequency of a piezoelectric material and aspect ratio of the mixing chamber on mixing performance of the ultrasonic micromixer are investigated. Finally, design guidelines for the ultrasonic micromixer are suggested based on the parametric study.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.275-281
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• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method was employed to simulate mixing performance of Passive mixer in a micro-channel. It physically analyzed stream line and Pressure drop for passive mixer in a micro-channel. The flow characteristics in a micro-channel was a function of Peclet number. The results indicated that the size of static element was more effect on the mixing than the number of static element and the distance of static elements.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4357-4366
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• 2023

MARS-KS, a domestic regulatory confirmatory code of Republic of Korea, had been developed by integrating RELAP5/MOD2 and COBRA-TF. The integration of COBRA-TF allowed to extend the capability of MARS-KS, limited to one-dimensional analysis, to multi-dimensional analysis. The use of COBRA-TF was mainly focused on subchannel analyses for simulating multi-dimensional behavior within the reactor core. However, this feature has been remained as a legacy without ongoing maintenance. Meanwhile, MARS-KS also includes its own multidimensional component, namely MULTID, which is also feasible to simulate three-dimensional convection and diffusion. The MULTID is capable of modeling the turbulent diffusion using simple mixing length model. The implementation of the turbulent mixing is of importance for analyzing the reactor core where a disturbing cross-sectional structure of rod bundle makes the flow perturbation and corresponding mixing stronger. In addition, the presence of this turbulent behavior allows the secondary transports with net mass exchange between subchannels. However, a series of assessments performed in previous studies revealed that the turbulence model of the MULTID could not simulate the aforementioned effective mixing occurred in the subchannel-scale problems. This is obvious consequence since the physical models of the MULTID neglect the effect of mass transport and thereby, it cannot model the void drift effect and resulting phasic distribution within a bundle. Thus, in this study, the turbulence mixing model of the MULTID has been improved by means of the inter-channel mixing model, widely utilized in subchannel analysis, in order to extend the application of the MULTID to small-scale problems. A series of assessments has been performed against rod bundle experiments, namely GE 3X3 and PSBT, to evaluate the performance of the introduced mixing model. The assessment results revealed that the application of the inter-channel mixing model allowed to enhance the prediction of the MULTID in subchannel scale problems. In addition, it was indicated that the code could not predict appropriate phasic distribution in the rod bundle without the model. Considering that the proper prediction of the phasic distribution is important when considering pin-based and/or assembly-based expressions of the reactor core, the results of this study clearly indicate that the inter-channel mixing model is required for analyzing the rod bundle, appropriately.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.111-118
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• 2014

In drilling process of oil wells, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. In this paper, a commercial CFD package(ANSYS Fluent 15.0) was used to solve the hydrodynamic force and evaluate mud mixing time in the mud mixing tank on offshore drilling platforms. Prediction of power consumption in co-rotating and counter-rotating models has been compared with results of Nagata's correlation equation. This research shows the hydrodynamic effect inside the two phase mud mixing tank according to rotating directions(co-rotating and counter-rotating). These results, we can conclude that the co-rotating direction of the two shafts with mixing blade in the mud mixing tank can be a preferable in power consumption and mixing time reduction.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.1-8
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• 1999

Mixing efficiency of the unlike Impinging split triplet injector(FOOF type) were measured to investigate the effect of the momentum ratio variation. $H_2$O/kerosene were used as a propellant simulant. The maximum mixing efficiency occured at the momentum ratio 1.5 (total mixture ratio 1.89). Calculated mixing efficiency of real propellant LOX/Kerosene showed similar trend but maximum efficiency of characteristic velocity occurs at the momentum ratio 2.0(total mixture ratio 2.17). Although there exist a little discrepancy between calculated mixing efficiency based on simulant cold test and hot fire test results, this calculated mixing efficiency can be used to predict hot fire mixing efficiency.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1642-1648
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• 2006

This paper describes enhancement of the mixing efficiency of a multilamination micro mixer by adding a number of recirculation zones downstream of the mixing zone. Numerical simulation was employed to estimate the mixing efficiency and the pressure drop under various conditions. Numerical results indicated that recirculation micro mixer brought about not only the increase of the mixing efficiency but also the decrease of the pressure drop. Micro mixers were fabricated using photosensitive glass by anisotropic wet etching technique. The width and height of the micro channel were $150{\mu}m$ and $500{\mu}m$, respectively. The performance of micro mixer was measured using color intensity variation of the fluid. Except for extremely low Re below 40, the recirculation micro mixer of the present study showed improved mixing. And the enhancement of the mixing increased as Re rose. When Re increased beyond 400, more than 90% of the mixing was observed in the experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.377-380
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• 2006

HPFRCCs(High performance fiber reinforced cementitious composites) is a class of FRCCs(Fiber reinforced cementitious composites) exhibit multiple crack. Multiple crack lead to improvement in ductility, toughness, and deformation capacity under compressive and tensile stress. These properties of HPFRCCs are affected by type of fiber, water cement ratio, type of admixture and rate of substitution. Furthermore these influence dispersion of fiber, mixing performance and fluidity of mixture. In this paper, HPFRCCs made of steel cord and carbon fiber were tested with water cement ratio, type of admixture and rate of substitution to evaluate characteristics of mixing and flexural strength.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.233-236
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• 2003

The micro-stereolithography technology made it possible to fabricate a freeform 3D micro-structure. Using this technology, two kind of applications were fabricated and tested: micro-lens and micro-mixers. The focal length and f-number of the micro-lens were 5 mm and 2.5, respectively. The focusing ability of the micro-lens was verified by defocusing the He-Ne laser beam after passing the lens. Two mixers are Kenics micro-mixer and BEKM. BEKM is a modified Kenics micro-mixer by introducing barriers on the pipe walt periodically to enhance the mixing via the chaotic mechanism in the helical flow of Kenics micro-mixer. Experimental result shows good mixing performance of developed mixers. Especially, the BEKM shows better mixing performance then Kenics micro-mixer.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1016-1020
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• 2003

In this paper, we present a technology of producing anew chaotic micromixer, named Micromixer with Arranged Blocks(MAB), and the experimental result of the mixing performance. Chaotic mixing was successfully achieved by introducing periodic perturbation in the field of the channel flow by means of slanted blocks. The MAB was made by an RP(Rapid Prototyping) technology. We performed flow visualization experiments for the quantification of the mixing performance with the MAB. Lyapunov exponent was measured to be 0.3557 and 0.1305 for the block height 0.8 and 0.2 times the channel width.