Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session E24: Microscale Flows: Applications |
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Chair: Harris Wong, Louisiana State University Room: Georgia World Congress Center B312 |
Sunday, November 18, 2018 5:10PM - 5:23PM |
E24.00001: Abstract Withdrawn
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Sunday, November 18, 2018 5:23PM - 5:36PM |
E24.00002: Enhancing mixing in curved membrane micro reactor channels K Farzin, Akash Choudhary, S Pushpavanam We study the effect of mass transport of reacting species through curved membrane micro-channels. The direct synthesis of Hydrogen Peroxide from Hydrogen and Oxygen is studied. Inside the channel, the solvent flows with the catalyst suspended in it. The gaseous reactants enter the channel by diffusion from the micro-membrane walls. The momentum and species transport pertinent equations are solved numerically. It is observed that the conversion is determined by diffusion in straight channels. In the curved channel, the Poiseuille flow is disturbed by centrifugal forces which results in the formation of counter-rotating vortices and skews axial velocity profile. The vortices formed increase the mixing in the transverse direction. This results in higher conversion for curved micro-channel compared to the straight channel. The reactor geometry is further optimized. Keywords: Curved Micro-channel, reactive mixing |
Sunday, November 18, 2018 5:36PM - 5:49PM |
E24.00003: Experimental study in optimizing enzyme-based polymeric membrane bioreactors Mohammad Shafquatul Islam, Cindy Kathleen Harnett Enzyme-coated polymeric membranes are versatile catalysts for biofuel production and other chemical production from feedstocks like plant biomass. Such bioreactors are more energy efficient than high-temperature methods because enzymes catalyze chemical reactions near room temperature. A major challenge in processing plant biomass is the presence of lignin, a complex aromatic polymer that resists chemical breakdown. Therefore, membranes coated with enzymes such as laccase that can degrade lignin are sought for energy extraction systems. We present an experimental study on optimizing an enzyme-based membrane bioreactor by modelling the tradeoff between high flow rate and short dwell time in the active region. Zero flow rate voltammetry experiments measure the electrochemical activity for a specific enzyme and coverage density, both for screening enzyme variants and providing inputs to the reactor model. Membrane pore size and density are verified with electron microscopy. Our flow-through spectroscopy device with laccase-coated membranes and a colorimetric laccase activity indicator is designed to measure reaction rate and percent conversion as a function of flow rate and membrane microstructure. |
Sunday, November 18, 2018 5:49PM - 6:02PM |
E24.00004: Selective separation of lithium using brown algae-inspired alginate hydrogel incorporated with phosphonate metal organic framework Sung Ho Park, Kiwoong Kim, Sang Joon Lee The separation of Li+ from brine with a high Mg/Li ratio is of great importance. In this study, we fabricated a new phosphonate metal organic framework (pMOF)-incorporated alginate hydrogel inspired by the Li+ adsorption mechanism of brown algae. Firstly, the Li+ adsorption by brown algae was investigated. Based on the result, fabricated biomimetic pMOF-incorporated alginate hydrogel was used to separate Li+. The pMOF incorporated Cu2+-based alginate hydrogel increased Li+ adsorption, while decreasing Mg2+ adsorption. The effect of size confinement by Cu2+-pMOF was utilized to selectively adsorb Li+. By contrast, the pMOF incorporated Al3+-based alginate hydrogel greatly increased Mg2+ adsorption, whereas Li+ adsorption was decreased. This reverse adsorption behavior might be attributed to partial dehydration, depending on the dehydration energy. The fabricated alginate hydrogels could be reused by washing them with ethanol/DI water due to weak electrostatic force. The present study would help selective separation of Li+. |
(Author Not Attending)
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E24.00005: Double-network self-healing hydrogels with ultra-stretchability and 3D printability Gang Qu, Yaming Liu, Zhou Liu, Tiantian Kong Double network hydrogels that can bear enormous mechanical loads enable advances in fields such as electronic skin, tissue engineering and soft robotics. The high toughness of these hydrogels are endowed by intertwined networks, a brittle network and a reversible network that dissipates energy under deformation. Despite improved mechanical properties, the double network hydrogels suffer from the loss of mechanical strength upon loading, poor recovery from rupture and complicated preparation steps. Achieving simultaneously high toughness, self-healing property, and printability in hydrogels remain a challenge. Here, by using a microfluidic printer-head, we achieve continuous printing of double network hydrogels with both covalent and physical crosslinks with self-healing property. The self-healing of the hydrogels is achieved simply by spraying water, and accelerated by increasing pH. The resultant hydrogels demonstrate a stretch up to 24 times of their original length, and up to 21 times after cutting and self-healing. The presented results provide new strategy that enable the development of tough, self-healing hydrogels for practical applications. |
Sunday, November 18, 2018 6:15PM - 6:28PM |
E24.00006: Adjoint-based shape optimisation for viscothermal acoustic flow in inkjet printheads Petr Kungurtsev, Matthew P Juniper
A drop-on-demand inkjet printhead is a narrow channel containing a piezo-electric actuator and a small orifice. Ink is pumped continuously through the channel. When the actuator pulses, it pushes a droplet out of the orifice. After each pulse, acoustic reverberations remain in the channel until they decay due to viscous and thermal dissipation, or propagate out of the channel. If the next droplet is demanded before the reverberations have sufficiently died away, it can differ from previous droplets, reducing print quality. We formally split the compressible Navier-Stokes equations into (i) an incompressible steady flow and (ii) a viscothermal acoustic flow. We useA drop-on-demand inkjet printhead is a narrow channel containing a piezo-electric actuator and a small orifice. Ink is pumped continuously through the channel. When the actuator pulses, it pushes a droplet out of the orifice. After each pulse, acoustic reverberations remain in the channel until they decay due to viscous and thermal dissipation, or propagate out of the channel. If the next droplet is demanded before the reverberations have sufficiently died away, it can differ from previous droplets, reducing print quality. We formally split the compressible Navier-Stokes equations into (i) an incompressible steady flow and (ii) a viscothermal acoustic flow. We use adjoint method to derive the shape sensitivity of (i) the incompressible flow pressure drop and (ii) the acoustic decay rate in Hadamard form, and combine the sensitivities with the CAD representation of the channel's geometry. We use the method of moving asymptotes for shape optimization of a generic geometry and increase the decay rate by 50% while keeping the pressure drop constant. |
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