The dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model.Typical characters of the superhydrophobic phenomenon are well observed from our...The dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model.Typical characters of the superhydrophobic phenomenon are well observed from our simulations,including air trapped in the surface microstructures,high contact angles,low contact angle hysteresis,and reduced friction to fluid motions.Increasing the roughness of a hydrophobic surface can produce a large flow rate through the channel due to the trapped air,implying less friction or large apparent slip.The apparent slip length appears to be independent to the channel width and could be considered as a surface property.For a moving droplet,its behavior is affected by the surface roughness from two aspects:the contact angle difference between its two ends and the surface-liquid interfacial friction.As a consequence,the resulting droplet velocity changes with the surface roughness as firstly decreasing and then increasing.Simulation results are also compared with experimental observations and better agreement has been obtained than that from other numerical method.The information from this study could be valuable for microfluidic systems.展开更多
A concave two-dimensional （2D） photonic crystal waveguide （PCW） with corrugated surface is theoret- ically used as a focusing structure. To design this structure, a genetic algorithm is combined with the finite-di...A concave two-dimensional （2D） photonic crystal waveguide （PCW） with corrugated surface is theoret- ically used as a focusing structure. To design this structure, a genetic algorithm is combined with the finite-difference time-domain method. For PCWs with different degrees of concaveness, the power reaches about 80% at different focusing points when the morphology of the concave surface is optimized. More importantly, the focusing location is easily controlled by changing the location of the detector placed in the outout field.展开更多
基金This work was supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)and the Laurentian University Research Fund to JZ.
文摘The dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model.Typical characters of the superhydrophobic phenomenon are well observed from our simulations,including air trapped in the surface microstructures,high contact angles,low contact angle hysteresis,and reduced friction to fluid motions.Increasing the roughness of a hydrophobic surface can produce a large flow rate through the channel due to the trapped air,implying less friction or large apparent slip.The apparent slip length appears to be independent to the channel width and could be considered as a surface property.For a moving droplet,its behavior is affected by the surface roughness from two aspects:the contact angle difference between its two ends and the surface-liquid interfacial friction.As a consequence,the resulting droplet velocity changes with the surface roughness as firstly decreasing and then increasing.Simulation results are also compared with experimental observations and better agreement has been obtained than that from other numerical method.The information from this study could be valuable for microfluidic systems.
基金supported by research funding fromthe Nanjing University of Science and Technology (Nos.2010ZYTS059 and AE88030)the Natural Science Foundation of Jiangsu Province (No.BK2010483)
文摘A concave two-dimensional （2D） photonic crystal waveguide （PCW） with corrugated surface is theoret- ically used as a focusing structure. To design this structure, a genetic algorithm is combined with the finite-difference time-domain method. For PCWs with different degrees of concaveness, the power reaches about 80% at different focusing points when the morphology of the concave surface is optimized. More importantly, the focusing location is easily controlled by changing the location of the detector placed in the outout field.
