This paper aims to explore the influence of different noise barrier heights on the sound source generation mechanisms of higher-speed trains(400 km/h)using a combination of delayed detached eddy simulation(DDES)and Ff...This paper aims to explore the influence of different noise barrier heights on the sound source generation mechanisms of higher-speed trains(400 km/h)using a combination of delayed detached eddy simulation(DDES)and Ffowcs Williams-Hawkings(FW-H)equations.Four cases are investigated and compared,i.e.1)no barrier,2)2.3 m,3)3.3 m,and 4)4.3 m single-side barriers on a bridge.Numerical results show that the presence of noise barriers causes an increase in sound source intensity ranging from 2.1 to 2.8 dB(A).However,the relationship between the barrier height and the increase in sound source intensity varies across different parts of the train.Compared with the head and front middle cars,the boundary layer is thicker around the rear-middle and tail car areas.A thick boundary layer introduces the influence of the crash wall,causing asymmetry and increases in sound source intensity.This is due to the deceleration region formed between the crash wall and the rail surface,as well as the acceleration region formed by the contraction of the flow channel in the noise barrier,both of which influence the sound source's characteristics.In addition,higher barriers exacerbate asymmetry and increases in sound source intensity.展开更多
A train body's cross-sectional shape has a significant impact on aerodynamic drag and operational safety in high-speed trains(HSTs).This study extracts five design variables from a real-world HST body:height,width...A train body's cross-sectional shape has a significant impact on aerodynamic drag and operational safety in high-speed trains(HSTs).This study extracts five design variables from a real-world HST body:height,width,side arc radius,arc radius at the connection between the side and the roof,and arc radius at the connection between the side and the train's bottom.The cross-validated Kriging surrogate model and the genetic algorithm are used to perform two types of aerodynamic optimization,with the cross-sectional area as a constraint.Cross-sectional shapes are optimized in both windless and windy conditions.Numerical results indicate that in a windless environment,the aerodynamic drag coefficient of the whole train is reduced by 2.4%;in a windy condition,the aerodynamic drag coefficient of the entire vehicle is reduced by 2.4%,and the aerodynamic lateral force of the leading car is reduced by 37.8%.These suggest that a flat and wide shape helps to reduce not only overall aerodynamic drag in a windless environment but also aerodynamic load in a windy environment,which can be accomplished by reducing the area of the side wall and top region,lowering the train body's height,increasing its width,and lowering the radius of the side and top arcs.展开更多
Bogies are responsible for a significant amount of aerodynamic resistance and noise,both of which negatively affect high-speed train performance and passenger comfort.In the present study,the passive control method is...Bogies are responsible for a significant amount of aerodynamic resistance and noise,both of which negatively affect high-speed train performance and passenger comfort.In the present study,the passive control method is applied in designing the bogie cabins of a high-speed train to improve its aerodynamic characteristics.Two passive control measures are introduced,namely,adding a spoiler and creating diversion grooves near the bogie cabins.Furthermore,the aerodynamic and aeroacoustic characteristics of a high-speed train operating at 350 km/h under different control strategies are numerically investigated using the improved-delayed-detached-eddy simulation(IDDES)and the acoustic finite element method(FEM).The impacts of passive control devices on drag reduction,slipstream,and aerodynamic noise are presented and discussed.Numerical results reveal that the passive control devices have a major effect on the slipstream around the train.The amplitude of the fluctuating pressure is higher in the first half of the train than in the second half.The first bogie has the maximum amplitude of the acoustic pressure for both the train with and without passive devices.In the far field,the spoiler installation and placement of the diversion grooves in the front of the bogie cabin can significantly reduce aerodynamic drag and noise.Hence,as shown in this study,using passive control methods to improve the aerodynamic and aeroacoustic properties of high-speed trains can be a viable option.展开更多
Thermal parameters are important variables that have great influence on life time of turbine vanes.Therefore,accurate prediction of the thermal parameters is essential.In this study,a numerical approach for conjugate ...Thermal parameters are important variables that have great influence on life time of turbine vanes.Therefore,accurate prediction of the thermal parameters is essential.In this study,a numerical approach for conjugate heat transfer(CHT)and computational fluid dynamics(CFD)is used to investigate thermal sensitivity of a transonic guide vane which is fully film-cooled by 199 film holes.Thermal barrier coating(TBC),i.e.,the typical TBC and a new one as the candidate TBC,and turbulence intensity(Tu),i.e.,Tu=3.3%,10%and 20%,are two variables used for the present study.At first the external surface temperatures of the vane material are compared.Next,the TBC surface temperatures are considered.Results show the major role of the lower thermal conductivity of TBC which results in the lower and more uniform temperature on the external surface of the vane substrate.Finally,the thermal sensitivity is presented in terms of the percentage reduction of the external surface temperatures of the vane material and the structural temperatures of the vane material at midspan,including the variations of average and maximum vane temperatures.Results show that TBC and Tu have significant effects on the external surface and structural temperatures of the vane substrate.The lower thermal conductivity of TBC leads to the higher difference between the thermal conductivity of the vane substrate and TBC,the reduction of heat transfer and the more uniform temperature within the vane structure.The results also show more effective protection for the average vane temperature from the two TBCs at higher Tus.However,Tu does not significantly affect the reduction of the maximum vane temperature even though the new TBC,which has the very low thermal conductivity,is used.展开更多
基金Project(2022YFB2603400)supported by the National Key Research and Development Program,China。
文摘This paper aims to explore the influence of different noise barrier heights on the sound source generation mechanisms of higher-speed trains(400 km/h)using a combination of delayed detached eddy simulation(DDES)and Ffowcs Williams-Hawkings(FW-H)equations.Four cases are investigated and compared,i.e.1)no barrier,2)2.3 m,3)3.3 m,and 4)4.3 m single-side barriers on a bridge.Numerical results show that the presence of noise barriers causes an increase in sound source intensity ranging from 2.1 to 2.8 dB(A).However,the relationship between the barrier height and the increase in sound source intensity varies across different parts of the train.Compared with the head and front middle cars,the boundary layer is thicker around the rear-middle and tail car areas.A thick boundary layer introduces the influence of the crash wall,causing asymmetry and increases in sound source intensity.This is due to the deceleration region formed between the crash wall and the rail surface,as well as the acceleration region formed by the contraction of the flow channel in the noise barrier,both of which influence the sound source's characteristics.In addition,higher barriers exacerbate asymmetry and increases in sound source intensity.
基金Project(RE-KRIS/FF67/020)supported by the King Mongkut's Institute of Technology Ladkrabang(Fundamental Fund by National Science Research and Innovation Fund(NSRF)),Thailand。
文摘A train body's cross-sectional shape has a significant impact on aerodynamic drag and operational safety in high-speed trains(HSTs).This study extracts five design variables from a real-world HST body:height,width,side arc radius,arc radius at the connection between the side and the roof,and arc radius at the connection between the side and the train's bottom.The cross-validated Kriging surrogate model and the genetic algorithm are used to perform two types of aerodynamic optimization,with the cross-sectional area as a constraint.Cross-sectional shapes are optimized in both windless and windy conditions.Numerical results indicate that in a windless environment,the aerodynamic drag coefficient of the whole train is reduced by 2.4%;in a windy condition,the aerodynamic drag coefficient of the entire vehicle is reduced by 2.4%,and the aerodynamic lateral force of the leading car is reduced by 37.8%.These suggest that a flat and wide shape helps to reduce not only overall aerodynamic drag in a windless environment but also aerodynamic load in a windy environment,which can be accomplished by reducing the area of the side wall and top region,lowering the train body's height,increasing its width,and lowering the radius of the side and top arcs.
基金This work was supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No. 2019020)the Strategic Priority Research Program of the Chinese Academy of Sciences (Class B) (Grant No. XDB22020000)Informatization Plan of the Chinese Academy of Sciences (Grant No. XXH13506-204).
文摘Bogies are responsible for a significant amount of aerodynamic resistance and noise,both of which negatively affect high-speed train performance and passenger comfort.In the present study,the passive control method is applied in designing the bogie cabins of a high-speed train to improve its aerodynamic characteristics.Two passive control measures are introduced,namely,adding a spoiler and creating diversion grooves near the bogie cabins.Furthermore,the aerodynamic and aeroacoustic characteristics of a high-speed train operating at 350 km/h under different control strategies are numerically investigated using the improved-delayed-detached-eddy simulation(IDDES)and the acoustic finite element method(FEM).The impacts of passive control devices on drag reduction,slipstream,and aerodynamic noise are presented and discussed.Numerical results reveal that the passive control devices have a major effect on the slipstream around the train.The amplitude of the fluctuating pressure is higher in the first half of the train than in the second half.The first bogie has the maximum amplitude of the acoustic pressure for both the train with and without passive devices.In the far field,the spoiler installation and placement of the diversion grooves in the front of the bogie cabin can significantly reduce aerodynamic drag and noise.Hence,as shown in this study,using passive control methods to improve the aerodynamic and aeroacoustic properties of high-speed trains can be a viable option.
文摘Thermal parameters are important variables that have great influence on life time of turbine vanes.Therefore,accurate prediction of the thermal parameters is essential.In this study,a numerical approach for conjugate heat transfer(CHT)and computational fluid dynamics(CFD)is used to investigate thermal sensitivity of a transonic guide vane which is fully film-cooled by 199 film holes.Thermal barrier coating(TBC),i.e.,the typical TBC and a new one as the candidate TBC,and turbulence intensity(Tu),i.e.,Tu=3.3%,10%and 20%,are two variables used for the present study.At first the external surface temperatures of the vane material are compared.Next,the TBC surface temperatures are considered.Results show the major role of the lower thermal conductivity of TBC which results in the lower and more uniform temperature on the external surface of the vane substrate.Finally,the thermal sensitivity is presented in terms of the percentage reduction of the external surface temperatures of the vane material and the structural temperatures of the vane material at midspan,including the variations of average and maximum vane temperatures.Results show that TBC and Tu have significant effects on the external surface and structural temperatures of the vane substrate.The lower thermal conductivity of TBC leads to the higher difference between the thermal conductivity of the vane substrate and TBC,the reduction of heat transfer and the more uniform temperature within the vane structure.The results also show more effective protection for the average vane temperature from the two TBCs at higher Tus.However,Tu does not significantly affect the reduction of the maximum vane temperature even though the new TBC,which has the very low thermal conductivity,is used.
