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Chun, Byoungjin,Chun, Myung-Suk IOP 2019 Journal of Physics. D, Applied Physics Vol.52 No.22
<P>The model framework of hydrodynamic filtration was examined for the rational design of particle sorting, by considering the complete analysis of 3D laminar flow for flow fraction and complicated networks of main and multiple branch channels. As the objective parameters for tuning of the design, both the number of branch channels and each length of individual branches were decided for different aspect ratios (i.e. <I>H</I>/<I>W</I> = 0.5–2.5) of rectangular channel. In order to validate our model framework, we compared the results estimated by analytical model with those computed by numerical simulations. The number of branches and the their individual lengths decrease distinctly with increasing channel aspect ratio, so that a channel with deep geometry enables compact design of microfluidic-chip being operated by lower pressure drop under the same throughput condition. Pursuing the justification of this behavior, pressure drop, average fluid velocity, and the ratio of flow fraction at each branch point were quantified with variations of aspect ratios.</P>
Lattice Boltzmann modeling and analysis of ceramic filtration with different pore structures
이기욱,Byoungjin Chun,정현욱 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.6
The pressure drop in the ceramic filter system of the after-treatment device has a great effect on automobile engine performance. To predict the pressure drop under various operating conditions, it is necessary to analyze how the structural properties of porous media affect the permeability. The commonly used Kozeny-Carman model correlating permeability and porosity is useful for porous media composed of spherical grains, but exhibits considerable deviations in the actual ceramic filter system with low porosity. In this study, the permeability of overlapped-random structured porous media with low porosity was numerically solved by mesoscopic lattice Boltzmann (LB) method in Darcy flow regime. Based on LB simulation results, a new capillary model modified from Kozeny-Carman model is proposed for practically predicting the permeability of complex porous filter systems, using key structural variables such as porosity, tortuosity, and effective pore-throat radius.
Practical operations for intermittent dual-layer slot coating processes
Jin Seok Park,Sanghun Jee,Byoungjin Chun,정현욱 한국유변학회 2022 Korea-Australia rheology journal Vol.34 No.3
Transient behaviors of dual-layered patches for Newtonian liquids were numerically investigated in dual-layer slot coating processes for the first time using step-changed inlet flows. To further tune the leading and trailing edges in a patch cycle, startup and end lag times between the top and bottom layers were proposed, considering the fl ow state of a bottom-layer liquid in a coating bead region. Carefully chosen lag times significantly reduced the defects in the leading and trailing edges of a dual-layered patch. It was also found that a greater coating layer viscosity results in a greater amount of residue left on the die lips, which affects the next patch cycle.
Effect of solution pH on the microstructural and rheological properties in boehmite suspensions
이기욱,Kim Seong Hwan,이다영,Lee Kwan-Young,Byoungjin Chun,정현욱 한국유변학회 2023 Korea-Australia rheology journal Vol.35 No.1
The relationship between microstructure changes and rheological properties in suspensions containing boehmite particles, which are well applied in various industrial wash-coating processes, was investigated by changing pH condition. The boehmite particles in suspensions were either well dispersed or aggregated depending on the pH, owing to the relative contributions of repulsive interaction between particles as well as hydrolysis and condensation reactions. Four groups of boehmite suspensions were classifi ed as very low, intermediate, almost zero charge, and high pH regimes based on their colloidal behaviors, and their microstructural diff erences were investigated using transmission electron microscopy (TEM) and multi-speckle diff using wave spectroscopy (MSDWS). For gel-like suspensions of three groups, various rheological properties such as shear viscosity, viscoelastic modulus, yield stress, and recovery behavior were extensively compared, and the results clearly demonstrated that a suspension with high yield stress was not fully recovered into the original state when disturbed at high shear rates.
Lattice Boltzmann simulations for wall-flow dynamics in porous ceramic diesel particulate filters
Lee, Da Young,Lee, Gi Wook,Yoon, Kyu,Chun, Byoungjin,Jung, Hyun Wook Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.429 No.-
<P><B>Abstract</B></P> <P>Flows through porous filter walls of wall-flow diesel particulate filter are investigated using the lattice Boltzmann method (LBM). The microscopic model of the realistic filter wall is represented by randomly overlapped arrays of solid spheres. The LB simulation results are first validated by comparison to those from previous hydrodynamic theories and constitutive models for flows in porous media with simple regular and random solid-wall configurations. We demonstrate that the newly designed randomly overlapped array structures of porous walls allow reliable and accurate simulations for the porous wall-flow dynamics in a wide range of solid volume fractions from 0.01 to about 0.8, which is beyond the maximum random packing limit of 0.625. The permeable performance of porous media is scrutinized by changing the solid volume fraction and particle Reynolds number using Darcy’s law and Forchheimer’s extension in the laminar flow region.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flows through porous walls were investigated using lattice Boltzmann method. </LI> <LI> Overlapped-random pore configuration was newly designed for actual porous filter. </LI> <LI> Permeability of porous filters with complex pore walls was reliably interpreted. </LI> <LI> Permeation rate of porous filters was evaluated in Darcy-Forchheimer flows. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Sharkskin-mimetic desalination membranes with ultralow biofouling
Choi, Wansuk,Lee, Changhoon,Lee, Dahye,Won, Young June,Lee, Gi Wook,Shin, Min Gyu,Chun, Byoungjin,Kim, Taek-Seung,Park, Hee-Deung,Jung, Hyun Wook,Lee, Jong Suk,Lee, Jung-Hyun The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.45
<P>Biofouling is a pervasive problem for any materials that are exposed to aquatic environments. Especially, it is a dire problem for the desalination membranes used to sustainably supply clean water, necessitating development of the methods to mitigate membrane biofouling. We present a topological modification approach to achieve ultralow fouling of water desalination membranes by realizing the sharkskin-mimetic (Sharklet) surface patterns and identify their unique antifouling mechanism based on computational fluid dynamics simulation. Our approach relies on a newly developed layered interfacial polymerization that can produce a conformal selective layer on patterned porous supports prepared by phase separation micromolding. The Sharklet-patterned membrane exhibited remarkably low biofouling compared to the conventional membranes with irregular roughness and topologically modulated membranes with simple patterns. Its superior biofouling resistance is attributed to the unique Sharklet geometry that can significantly inhibit biofilm growth. Furthermore, under dynamic flow conditions, the intricate Sharklet geometry induces a complex surface flow by symmetrically generating a secondary flow perpendicular to the primary flow, forming a periodic inflow and outflow along the pattern. The reinforced primary and secondary flows of the Sharklet pattern may further contribute to its excellent biofouling resistance.</P>