To clarify the internal flow field characteristics of cavity vortex in the sediment transport pipe(STP)of the desilting channel with a swirling flow generator(DCSFG),this study adopted a method combining model test,nu...To clarify the internal flow field characteristics of cavity vortex in the sediment transport pipe(STP)of the desilting channel with a swirling flow generator(DCSFG),this study adopted a method combining model test,numerical simulation,and theoretical analysis to investigate flow field characteristics such as water flow regime,cavity morphology,pressure,flow velocity and vorticity,analyze the distribution of combined vortex indexes and radial pressure difference of cavity vortex,and discuss the motion feature differences between the combined vortex in the cavity vortex and the ideal combined vortex.The results show that large eddy simulation(LES)exhibits higher accuracy than the Realizable k-ε model,the distribution of combined vortex n values along typical cross-sections inside the STP ranges from -0.901 to 0.913 radially,indicating quasi-forced vortex motion on the inner side of the vortex area and quasi-free vortex motion on the outer side,the theoretical values of radial pressure difference align well with the simulation results,with a maximum relative error of 15%,confirming that the flow characteristics of the vortex are in accordance with the motion features of combined vortex,the distribution of radial pressure,tangential velocity,and vorticity in the cavity vortex conform to the distribution pattern of ideal combined vortex,whereas significant differences exist in terms of fluid force conditions,structural composition,and generation mechanism.The research findings may provide reference for further analyzing the sediment transport mechanism in the cavity vortex and for the practical engineering design and application of the DCSFG.展开更多
Multiplexing techniques have always been one of the important components of optical communication research.These techniques can transmit multiple signals in a shared information channel and can greatly increase the ma...Multiplexing techniques have always been one of the important components of optical communication research.These techniques can transmit multiple signals in a shared information channel and can greatly increase the maximum capacity of an information channel.The Dirac-vortex cavity is a type of photonic crystal surface emission system,and its characteristics of miniaturization and high stability make it very suitable for on-chip optical system.In this paper,we realized dual-channel emission of the Dirac-vortex cavity,which is achieved by modulating the size and phase of hexagonal holes in the hexagon lattice.The characteristics of dual-channel emission are investigated by numerical simulation,and the dual-channel emission rules are summarized.The double Diracvortex cavity model is not only explored for its multiplexing capability but also as an alternative scheme for the application of Dirac-vortex cavity in multiplex communication systems.展开更多
The Bypass Dual Throat Nozzle(BDTN)is a novel fluidic Thrust Vectoring(TV)nozzle,it switches to TV state by opening the valve in the bypass.To greatly manipulate the BDTN,the dynamic characteristics in the TV starting...The Bypass Dual Throat Nozzle(BDTN)is a novel fluidic Thrust Vectoring(TV)nozzle,it switches to TV state by opening the valve in the bypass.To greatly manipulate the BDTN,the dynamic characteristics in the TV starting process should be analyzed.This paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of BDTN and Dual Throat Nozzle(DTN).The dynamic responses of TV starting in typical DTN models are investigated at first.Then,the TV starting processes of BDTN in different Nozzle Pressure Ratio(NPR)conditions are simulated,and the valve opening durations(T)are also considered.Before the expected TV direction is achieved in the DTN,the jet is deflected to the opposite direction at the beginning of the dynamic process,which is called the reverse TV phenomenon.However,this phenomenon disappears in the BDTN.The larger injection width of DTN intensifies unsteady oscillations,and the reverse TV phenomenon is strengthened.In the BDTN,T determines the delay degree of performance variations compared to the static results,which is called hysteresis effect.At NPR=10,the hysteresis affects the final stable performance of BDTN.This study analyses the dynamic characteristics in DTN and BDTN,laying a foundation for further design of nozzles and control strategies.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52069011),the Youth Science and Technology Talent Innovation Project of Lanzhou(Grant No.2023-QN-33).
文摘To clarify the internal flow field characteristics of cavity vortex in the sediment transport pipe(STP)of the desilting channel with a swirling flow generator(DCSFG),this study adopted a method combining model test,numerical simulation,and theoretical analysis to investigate flow field characteristics such as water flow regime,cavity morphology,pressure,flow velocity and vorticity,analyze the distribution of combined vortex indexes and radial pressure difference of cavity vortex,and discuss the motion feature differences between the combined vortex in the cavity vortex and the ideal combined vortex.The results show that large eddy simulation(LES)exhibits higher accuracy than the Realizable k-ε model,the distribution of combined vortex n values along typical cross-sections inside the STP ranges from -0.901 to 0.913 radially,indicating quasi-forced vortex motion on the inner side of the vortex area and quasi-free vortex motion on the outer side,the theoretical values of radial pressure difference align well with the simulation results,with a maximum relative error of 15%,confirming that the flow characteristics of the vortex are in accordance with the motion features of combined vortex,the distribution of radial pressure,tangential velocity,and vorticity in the cavity vortex conform to the distribution pattern of ideal combined vortex,whereas significant differences exist in terms of fluid force conditions,structural composition,and generation mechanism.The research findings may provide reference for further analyzing the sediment transport mechanism in the cavity vortex and for the practical engineering design and application of the DCSFG.
基金National Natural Science Foundation of China(12404423,62375007,62405012)Natural Science Foundation of Beijing Municipality(1232024)Applied Basic Research Fund of School of Physics and Optoelectronic Engineering,Beijing University of Technology(ABRFSPOE03).
文摘Multiplexing techniques have always been one of the important components of optical communication research.These techniques can transmit multiple signals in a shared information channel and can greatly increase the maximum capacity of an information channel.The Dirac-vortex cavity is a type of photonic crystal surface emission system,and its characteristics of miniaturization and high stability make it very suitable for on-chip optical system.In this paper,we realized dual-channel emission of the Dirac-vortex cavity,which is achieved by modulating the size and phase of hexagonal holes in the hexagon lattice.The characteristics of dual-channel emission are investigated by numerical simulation,and the dual-channel emission rules are summarized.The double Diracvortex cavity model is not only explored for its multiplexing capability but also as an alternative scheme for the application of Dirac-vortex cavity in multiplex communication systems.
基金the continued support of Key Laboratory of Inlet and Exhaust system Technology (Nanjing University of Aeronautics and Astronautics), ChinaMinistry of Education, National Science and Technology Major Project of China (Nos. 2017-V-0004-0054, 2019-II-0007-0027, Y2022II-0005-0008)+6 种基金Defense Industrial Technology Development Program of China (No. JCKY2019605D001)Advanced Jet Propulsion Creativity Center of AEAC of China (No. HKCX2020-02-011)China Postdoctoral Science Foundation (No. 2022M721598)Jiangsu Funding Program for Excellent Postdoctoral Talent of China (No. 2022ZB214)the Youth Fund Project of Natural Science Foundation of Jiangsu Province of China (No. BK20230891)the National Natural Science Foundation of China (No. 12332018)Science Center for Gas Turbine Project, China (P2022-B-I-006-001) and some other related foundations
文摘The Bypass Dual Throat Nozzle(BDTN)is a novel fluidic Thrust Vectoring(TV)nozzle,it switches to TV state by opening the valve in the bypass.To greatly manipulate the BDTN,the dynamic characteristics in the TV starting process should be analyzed.This paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of BDTN and Dual Throat Nozzle(DTN).The dynamic responses of TV starting in typical DTN models are investigated at first.Then,the TV starting processes of BDTN in different Nozzle Pressure Ratio(NPR)conditions are simulated,and the valve opening durations(T)are also considered.Before the expected TV direction is achieved in the DTN,the jet is deflected to the opposite direction at the beginning of the dynamic process,which is called the reverse TV phenomenon.However,this phenomenon disappears in the BDTN.The larger injection width of DTN intensifies unsteady oscillations,and the reverse TV phenomenon is strengthened.In the BDTN,T determines the delay degree of performance variations compared to the static results,which is called hysteresis effect.At NPR=10,the hysteresis affects the final stable performance of BDTN.This study analyses the dynamic characteristics in DTN and BDTN,laying a foundation for further design of nozzles and control strategies.
