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EMMS drag model for simulating a gas-solid fluidized bed of geldart B particles: Effect of bed model parameters and polydisperity

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Particuology 2020年第4期18卷 142-154页

作者： Krishnadash SKshetrimayum seongho park Chonghun Han Chul-Jin Lee School of Chemical Engineering and Materials Science Chung-Ang University06974 SeoulSouth Korea School of Chemical and Biological Engineering Seoul National UniversitySan 56-1Shillim-dongKwanak-guSeoul151-742South Korea

The energy minimization multi-scale(EMMS)is a heterogeneous drag model widely used to simulate gas-solid fluidized *** this work,we conducted computational fluid dynamics simulations of a gas-solid fluidized bed for Geldart B particles to compare the EMMS with the homogeneous Gidaspow drag *** results from both the homogeneous and heterogeneous drag models were compared with literature experimental data on pressure drop and bed *** was no noticeable difference in predicted bed characteristics in the slugging ***,in the turbulent regime,the EMMS model predicted slightly lower bed expansion than did the Gidaspow *** evaluated the effects of solid-solid and solid-wall interaction parameters by varying the restitution and specularity *** expansion increases by a factor of 1.05-1.08 when the restitution coefficient increases from 0.9 to *** models predict a higher solid volume fraction and higher solid downflow velocity near the wall for a low specularity coefficient of 0.01 or *** we considered solid phases of different sizes to model polydisperity,the simulation predicted vertical segregation of 300,350,and 400μm in the fluidized region due to ***,the drag models made similar predictions in bad characteristics from cold model simulation ofa polysilicon fluidized-bed reactor,although there was very little vertical segregation of solid particles for this case.

关键词： CFD simulation Energy minimization multi-scale drag Gas-solid fluidized bed Polydisperity Fluidized-bed reactor

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Strain-tunable optical microlens arrays with deformable wrinkles for spatially coordinated image projection on a security substrate

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Microsystems & Nanoengineering 2022年第5期8卷 225-237页

作者： In Sik Choi seongho park Sangheon Jeon Young Woo Kwon Rowoon park Robert A.Taylor Kwangseuk Kyhm Suck Won Hong Department of Cogno-Mechatronics Engineering Department of Optics and Mechatronics EngineeringPusan National UniversityBusan 46241Republic of Korea Research Center for Dielectric and Advanced Matter Physics Pusan National UniversityBusan 46241Republic of Korea Department of Physics University of OxfordOxford OX13PUUK Department of Nano-Fusion Technology Pusan National UniversityBusan 46241Republic of Korea

As a new concept in materials design,a variety of strategies have been developed to fabricate optical microlens arrays(MLAs)that enable the miniaturization of optical systems on the micro/nanoscale to improve their characteristic performance with unique optical *** this paper,we introduce a cost-effective and facile fabrication process on a large scale up to~15 inches via sequential lithographic methods to produce thin and deformable hexagonally arranged MLAs consisting of polydimethylsiloxane(PDMS).Simple employment of oxygen plasma treatment on the prestrained MLAs effectively harnessed the spontaneous formation of highly uniform nanowrinkled structures all over the surface of the elastomeric *** strain-controlled tunability,unexpected optical diffraction patterns were characterized by the interference combination effect of the microlens and deformable ***,the hierarchically structured MLAs presented here have the potential to produce desirable spatial arrangements,which may provide easily accessible opportunities to realize microlens-based technology by tunable focal lengths for more advanced micro-optical devices and imaging projection elements on unconventional security substrates.

关键词： projection arrays spatially

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