t A series of inline pico hydropower systems,which could be used in confined space,especially for water distribution networks(WDNs),was designed and investigated.The turbine with an eye-shaped vertical water baffle wa...t A series of inline pico hydropower systems,which could be used in confined space,especially for water distribution networks(WDNs),was designed and investigated.The turbine with an eye-shaped vertical water baffle was developed to evaluate the hydraulic performance.A three-dimensional dynamic mesh was employed and the inlet velocity was considered as the inlet boundary condition,whereas the outlet boundary was set as the outflow.Then,numerical simulations were conducted and the standard k-εturbulence model was found to be the best capable of predicting flow features through the comparison with the experimental results.The effects of the opening diameter of the water baffle and installation angle of the rotor on the flow field in the turbine were investigated.The results suggested that the water baffle opening at d=30 mm and the rotor at a 52°angle could achieve the highest efficiency of 5.93%.The proper eye-shaped baffle not only accelerates the fluid flow and generates positive hydrodynamic torque,but also eliminates the flow separation.The scheme proposed in this paper can be exploited for practical applications in the water pipelines at various conditions and power requirements.展开更多
Slow light with high group index and wideband is achieved in photonic crystal coupled-resonator optical waveguides （PC-CROWs）. According to the eye-shaped scatterers and various microcavities, saddle- like curves be...Slow light with high group index and wideband is achieved in photonic crystal coupled-resonator optical waveguides （PC-CROWs）. According to the eye-shaped scatterers and various microcavities, saddle- like curves between the normalized frequency f and wave number k can be obtained by adjusting the parameters of the scatterers, parameters of the coupling microcavities, and positions of the scatterers. Slow light with decent flat band and group index can then be achieved by optimizing the parameters. Simulations prove that the maximal value of the group index is 〉 104, and the normalized delay bandwidth product within a new varying range of ng 〉 102 or ng 〉 103 can be a new and effective criterion of evaluation for the slow light in PC-CROWs.展开更多
文摘t A series of inline pico hydropower systems,which could be used in confined space,especially for water distribution networks(WDNs),was designed and investigated.The turbine with an eye-shaped vertical water baffle was developed to evaluate the hydraulic performance.A three-dimensional dynamic mesh was employed and the inlet velocity was considered as the inlet boundary condition,whereas the outlet boundary was set as the outflow.Then,numerical simulations were conducted and the standard k-εturbulence model was found to be the best capable of predicting flow features through the comparison with the experimental results.The effects of the opening diameter of the water baffle and installation angle of the rotor on the flow field in the turbine were investigated.The results suggested that the water baffle opening at d=30 mm and the rotor at a 52°angle could achieve the highest efficiency of 5.93%.The proper eye-shaped baffle not only accelerates the fluid flow and generates positive hydrodynamic torque,but also eliminates the flow separation.The scheme proposed in this paper can be exploited for practical applications in the water pipelines at various conditions and power requirements.
基金This work was supported by the National Natural Science Foundation of China （Grant No. 11144007） and the Natural Science Foundation of Shandong Province （Grant No. ZR2016AM27）.
文摘Slow light with high group index and wideband is achieved in photonic crystal coupled-resonator optical waveguides （PC-CROWs）. According to the eye-shaped scatterers and various microcavities, saddle- like curves between the normalized frequency f and wave number k can be obtained by adjusting the parameters of the scatterers, parameters of the coupling microcavities, and positions of the scatterers. Slow light with decent flat band and group index can then be achieved by optimizing the parameters. Simulations prove that the maximal value of the group index is 〉 104, and the normalized delay bandwidth product within a new varying range of ng 〉 102 or ng 〉 103 can be a new and effective criterion of evaluation for the slow light in PC-CROWs.
