Numerical simulation has been performed on the optical transmission enhancement properties of a one-dimensional Ag film single slit structure with grooves. The results show that the position,depth and number of the gr...Numerical simulation has been performed on the optical transmission enhancement properties of a one-dimensional Ag film single slit structure with grooves. The results show that the position,depth and number of the grooves have great influence on the optical transmission,and surface plasmon polariton and resonance mode are the primary factors. The maximal extinction ratio of 35.8 dB is achieved in the single slit structure by adjusting groove depth.展开更多
A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using L...A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using Lagrangian trajectory method. The flow Reynolds number is 180 based on the friction velocity and half-width of the channel. The particle is lycopodium with St=0.93 which may well follow the fluid phase. The mean and fluctuating velocities of both two phases are obtained, which are in good agreement with previous data. The strongest accumulations of particles in low-speed streak structures are observed at y~=l 1.3. Moreover, once particles are captured in low-speed streaks, most of them will reside there for a long period. Particles clustered in low-speed streaks obtain smaller instantaneous wall-normal and spanwise velocities than those out of there, which induce a larger particle flux into low-speed streaks than that out of there. The study is important for understanding particle dispersion mechanisms in gas-particle turbulent channel flows.展开更多
基金the Key Program of National Natural Science of China(Grant No.50734007)the Research Foundation from Ministry of Education of China (Grant No.208133)the Natural Science Foundation of Yunnan Province (Grant No.2007F005M)
文摘Numerical simulation has been performed on the optical transmission enhancement properties of a one-dimensional Ag film single slit structure with grooves. The results show that the position,depth and number of the grooves have great influence on the optical transmission,and surface plasmon polariton and resonance mode are the primary factors. The maximal extinction ratio of 35.8 dB is achieved in the single slit structure by adjusting groove depth.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.11132005)the National Natural Science Foundation of China(Grant No.50876053)Opening Fund of State of Key Laboratory of Nonlinear Mechanics
文摘A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using Lagrangian trajectory method. The flow Reynolds number is 180 based on the friction velocity and half-width of the channel. The particle is lycopodium with St=0.93 which may well follow the fluid phase. The mean and fluctuating velocities of both two phases are obtained, which are in good agreement with previous data. The strongest accumulations of particles in low-speed streak structures are observed at y~=l 1.3. Moreover, once particles are captured in low-speed streaks, most of them will reside there for a long period. Particles clustered in low-speed streaks obtain smaller instantaneous wall-normal and spanwise velocities than those out of there, which induce a larger particle flux into low-speed streaks than that out of there. The study is important for understanding particle dispersion mechanisms in gas-particle turbulent channel flows.
