The increase in aerodynamic drag brings high energy consumption,which is a critical issue in the development of high-speed trains.Inspired by the excellent hydrodynamic characteristics of fish movement in nature,a two...The increase in aerodynamic drag brings high energy consumption,which is a critical issue in the development of high-speed trains.Inspired by the excellent hydrodynamic characteristics of fish movement in nature,a two-dimensional numerical simulation method based on spring-smoothing model and adaptive mesh technology was utilized to explore the effects of different fishtail structures and two flexible motion modes(Eel mode and Lunate-tail mode)on the wake of high-speed trains,and to assess their potential for aerodynamic drag reduction.Results indicate that the biomimetic fishtail successfully suppresses the alternating shedding of vortices in the wake,and induces the aerodynamic drag fluctuation period to align with the fishtail oscillation period.The fishtail length,oscillation mode,and frequency have a significant impact on the wake flow and aerodynamic drag of the train.Among these,a 1850 mm Eel fishtail with parameters ofλ=1 and T=8 s achieves the optimal drag reduction effect,with drag reduction rates of 39.12%and 26.00%for the tail car and the entire train,respectively.These findings provide a theoretical basis for the design of new low-resistance railway trains,promoting the sustainable development of rail transit towards goals of high-speed and energy-efficient.展开更多
Flow field around a two-bladed horizontal-axis wind turbine(HAWT)is simulated at various tip speed ratios to investigate its wake characteristics by analyzing the tip and root vortex trajectories in the nearwake,as we...Flow field around a two-bladed horizontal-axis wind turbine(HAWT)is simulated at various tip speed ratios to investigate its wake characteristics by analyzing the tip and root vortex trajectories in the nearwake,as well as the vertical profiles of the axial velocity.Results show that the pitch of the tip vortex varies inversely with the tip speed ratio.Radial expansion of the tip vortices becomes more obvious as the tip speed ratio increases.Tip vortices shed not exactly from the blade tip but from the blade span of 96.5%—99%radius of the rotor.The axial velocity profiles are transformed into V-shape from W-shape at the distance downstream of eight rotor diameters due to the momentum recovery.展开更多
A numerical investigation on the effectiveness of the actuator disc method in producing the interactions of multiple tidal stream devices via the 3D-RANS finite element model Telemac3D is explored. The methodology for...A numerical investigation on the effectiveness of the actuator disc method in producing the interactions of multiple tidal stream devices via the 3D-RANS finite element model Telemac3D is explored. The methodology for the implementation of the source term to represent an array of 20 m rotor diameter turbines deployed in an idealized channel is reviewed and discussed in detail. Flow interactions between multiple turbines are investigated for a single row arrangement with only two turbines and a two row arrangement containing three turbines. The results demonstrate that the non-hydrostatic solver shows better agreement when validated against published experimental data. Notably,the mesh density at the device location can strongly influence the simulated thrust from the disc. Although the actuator disc model can generally replicate the wake interactions well, the results indicate that it cannot accurately characterize the flow for regions with high turbulences. While a model setup with the largest lateral spacing(1.5D) demonstrates excellent agreement with the experimental data, the 0.5D model(smallest gap) deviates by up to 25%. These findings demonstrate the effectiveness of the applied source term in reproducing the wake profile, which is comparable with the published data, and highlight the inherent nature of the RANS and actuator disc models.展开更多
基金Project(2025A1515011803)supported by the Guangdong Basic and Applied Basic Research Foundation,ChinaProject(2023JC01020)supported by the Jiangmen Basic and Theoretical Science Research Plan,China。
文摘The increase in aerodynamic drag brings high energy consumption,which is a critical issue in the development of high-speed trains.Inspired by the excellent hydrodynamic characteristics of fish movement in nature,a two-dimensional numerical simulation method based on spring-smoothing model and adaptive mesh technology was utilized to explore the effects of different fishtail structures and two flexible motion modes(Eel mode and Lunate-tail mode)on the wake of high-speed trains,and to assess their potential for aerodynamic drag reduction.Results indicate that the biomimetic fishtail successfully suppresses the alternating shedding of vortices in the wake,and induces the aerodynamic drag fluctuation period to align with the fishtail oscillation period.The fishtail length,oscillation mode,and frequency have a significant impact on the wake flow and aerodynamic drag of the train.Among these,a 1850 mm Eel fishtail with parameters ofλ=1 and T=8 s achieves the optimal drag reduction effect,with drag reduction rates of 39.12%and 26.00%for the tail car and the entire train,respectively.These findings provide a theoretical basis for the design of new low-resistance railway trains,promoting the sustainable development of rail transit towards goals of high-speed and energy-efficient.
基金supported partly by the National Basic Research Program of China(″973″Program)(No.2014CB046201)the National Natural Science Foundation of China(No.51166009)+5 种基金the National High Technology Research and Development Program of China(No2012AA052900)the Natural Science Foundation of Gansu ProvinceChina(No.1308RJZA283145RJZA059)the Gansu Province University Scientific Research ProjectChina(No.2013A-026)
文摘Flow field around a two-bladed horizontal-axis wind turbine(HAWT)is simulated at various tip speed ratios to investigate its wake characteristics by analyzing the tip and root vortex trajectories in the nearwake,as well as the vertical profiles of the axial velocity.Results show that the pitch of the tip vortex varies inversely with the tip speed ratio.Radial expansion of the tip vortices becomes more obvious as the tip speed ratio increases.Tip vortices shed not exactly from the blade tip but from the blade span of 96.5%—99%radius of the rotor.The axial velocity profiles are transformed into V-shape from W-shape at the distance downstream of eight rotor diameters due to the momentum recovery.
基金supported by the Inner Mongolia Autonomous Region Open Major Basic Research Project(Grant No.20120905)the National Natural Science Foundation of China(Grant No.51666014)
文摘Wind tunnel experiments of the wake characteristics of a two-blade wind turbine, in the downstream region of 0
文摘A numerical investigation on the effectiveness of the actuator disc method in producing the interactions of multiple tidal stream devices via the 3D-RANS finite element model Telemac3D is explored. The methodology for the implementation of the source term to represent an array of 20 m rotor diameter turbines deployed in an idealized channel is reviewed and discussed in detail. Flow interactions between multiple turbines are investigated for a single row arrangement with only two turbines and a two row arrangement containing three turbines. The results demonstrate that the non-hydrostatic solver shows better agreement when validated against published experimental data. Notably,the mesh density at the device location can strongly influence the simulated thrust from the disc. Although the actuator disc model can generally replicate the wake interactions well, the results indicate that it cannot accurately characterize the flow for regions with high turbulences. While a model setup with the largest lateral spacing(1.5D) demonstrates excellent agreement with the experimental data, the 0.5D model(smallest gap) deviates by up to 25%. These findings demonstrate the effectiveness of the applied source term in reproducing the wake profile, which is comparable with the published data, and highlight the inherent nature of the RANS and actuator disc models.
