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Numerical Study on Mixing Performance of Straight Groove Micromixers
Hossain, Shakhawat,Kim, Kwang-Yong Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.3
Numerical analyses have been performed to investigate the effects of geometric parameters of a straight groove micromixer on mixing performance and pressure drop. Three-dimensional Navier-Stokes equations with two working fluids, water and ethanol have been used to calculate mixing index and pressure drop. A parametric study has been carried out to find the effects of the number of grooves per cycle, arrangement of patterned walls, and additional grooves in triangular dead zones between half cycles of grooves. The three arrangements of patterned walls in a micromixer, i.e., single wall patterned, both walls patterned symmetrically, and both walls patterned asymmetrically, have been tested. The results indicate that as the number of grooves per cycle increases the mixing index increases and the pressure drop decreases. The microchannel with both walls patterned asymmetrically shows the best mixing performance among the three different arrangements of patterned walls. Additional grooves confirm the better mixing performance and lower pressure drop.
Impact of the Isolation Source on the Biofilm Formation Characteristics of Bacillus cereus
( Mohammad Shakhawat Hussain ),( Deog-hwan Oh ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.1
The human pathogen and food spoiler Bacillus cereus can form biofilms that act as a persistent source of contamination, which is of public health concern. This study aimed to understand how the source of isolation might affect the behavior of biofilm formation. Biofilm formation abilities of 56 strains of B. cereus isolated from different environments, including human food poisoning, farm, and food, were determined. Crystal violet assay results revealed significant (p < 0.05) differences in biofilm formation abilities among the strains isolated from different sources only at an early stage of incubation. However, strain origin showed no impact on later stage of biofilm formation. Next, correlation of the group of isolates on the basis of their biofilm-forming abilities with the number of sessile cells, sporulation, and extracellular polymeric substance (EPS) formation was determined. The number of sessile cells and spores in biofilms was greatly influenced by the groups of isolates that formed dense, moderate, and weak biofilms. The contribution of extracellular DNA and/or proteins to EPS formation was also positively correlated with biofilm formation abilities. Our results that the source of isolation had significant impact on biofilm formation might provide important information to develop strategies to control B. cereus biofilm formation.
Hossain, Shakhawat,Lee, Insu,Kim, Sun Min,Kim, Kwang-Yong Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.327 No.-
<P><B>Abstract</B></P> <P>A novel design is presented for a chaotic micromixer using two-layer serpentine crossing microchannels. The performance of the micromixer was analyzed both numerically and experimentally. The numerical analysis was performed using three-dimensional Navier-Stokes equations with a convection–diffusion model for the species concentration in a Reynolds number range of 0.2–120. An experimental model of the micromixer was fabricated by soft lithography with polydimethylsiloxane (PDMS). Two working fluids, water and dye-water mixture were used for numerical analysis except for the experimental validation of numerical results. Both the numerical and experimental analyses confirm that the micromixer achieves a high level of mixing over a wide range of Reynolds numbers through splitting, enlarging, recombination, and folding mechanisms. The micromixer showed over 95% mixing throughout the tested range of Reynolds number. Especially, about 99% mixing was achieved at Reynolds numbers less than ten. Thus, the proposed micromixer can be used in microfluidic systems which require fast mixing at low Reynolds numbers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Experimental and numerical analyses of a novel micromixer with two-layer crossing channels were performed. </LI> <LI> The micromixer showed at least 96% mixing throughout a Reynolds number range (0.2–120). </LI> <LI> At low Reynolds numbers (0.2–10), the micromixer showed about 99% mixing at the exit. </LI> <LI> The proposed micromixer showed lower pressure drop than TLCCM for Re larger than 10. </LI> </UL> </P>