Considering passenger trains'key role in remote regions,this study employed machine vision technology to monitor five posture parameters of the second car of a conventional passenger train,aiming to investigate th...Considering passenger trains'key role in remote regions,this study employed machine vision technology to monitor five posture parameters of the second car of a conventional passenger train,aiming to investigate the influence of windbreaks and crosswinds along railways on the operating postures of conventional passenger trains.The study found that when passing through the anti-wind tunnel with holes,the amplitudes of posture parameters were smaller than those of other windbreaks,demonstrating the superior performance of this windbreak in maintaining posture stability compared to others.In tunnel sections,larger amplitudes of these parameters were observed for the tail car than the head car,while the opposite occurred in non-tunnel sections.Notably,during tunnel transit,their amplitudes did not increase monotonically with speed but peaked at a specific speed that most adversely affected the operating posture.These conclusions have a great significance for improving operating safety under crosswinds.展开更多
The structural safety of high-speed trains is significantly endangered by increasing operating speeds.The objective of this research was to investigate the evolution of the flow field in trains passing through a tunne...The structural safety of high-speed trains is significantly endangered by increasing operating speeds.The objective of this research was to investigate the evolution of the flow field in trains passing through a tunnel while there is a strong crosswind at the tunnel entrance and exit.Moreover,the effect of aerodynamic pressure waves on structural strength was analyzed to evaluate the safety of the carbody.In this study,we selected the improved delayed detached-eddy simulation(IDDES)method as a turbulence model.The mechanism of interaction among the train,tunnel,and crosswind was evaluated through a complex computational fluid dynamics(CFD)model,simulating high-speed trains moving through tunnels at various crosswind speeds.Additionally,the dynamic stress response of the carbody was calculated using a sequential coupling approach,where integral aerodynamic forces were applied as substitutes for direct CFD pressure loads.We assessed the effect of aerodynamic loads on the dynamic stresses of the carbody at different crosswind velocities(0,10,15,and 20 m/s).The results indicate that crosswinds exert a substantial influence on the fluid structure surrounding the train.Consequently,the aerodynamic forces contribute significantly to potential damage to the carbody,posing increased safety risks for high-speed trains.展开更多
The dynamic performance of high-speed trains is significantly influenced by sudden changes in aerodynamic loads(ADLs)when exiting a tunnel in a windy environment.Focusing on a double-track tunnel under construction in...The dynamic performance of high-speed trains is significantly influenced by sudden changes in aerodynamic loads(ADLs)when exiting a tunnel in a windy environment.Focusing on a double-track tunnel under construction in a mountain railway,we established an aerodynamic model involving a train exiting the tunnel,and verified it in the Fluent environment.Overset mesh technology was adopted to characterize the train’s movement.The flow field involving the train,tunnel,and crosswinds was simulated using the Reynolds-averaged turbulence model.Then,we built a comprehensive train-track coupled dynamic model considering the influences of ADLs,to investigate the vehicles’dynamic responses.The aerodynamics and dynamic behaviors of the train when affected by crosswinds with different velocities and directions are analyzed and discussed.The results show that the near-wall side crosswind leads to sharper variations in ADLs than the far-wall side crosswind.The leading vehicle suffers from more severe ADLs than other vehicles,which worsens the wheel-rail interaction and causes low-frequency vibration of the car body.When the crosswind velocity exceeds 20 m/s,significant wheel-rail impacts occur,and the running safety of the train worsens rapidly.展开更多
Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China.Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodyna...Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China.Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodynamic assessment,this paper primarily reviews five meaningful progresses on the aerodynamics of the train-bridge system done by Wind Tunnel Laboratory of Central South University in the past several years.Firstly,the flow around the train and the uncertainty origin of the aerodynamic assessment are described from the fluid mechanism point of view.After a brief introduction of the current aerodynamic assessment methods with their strengths and weaknesses,a new-developed TRAIN-INFRASTRUCTURE rig with the maximum launch speed of 35 m/s is introduced.Then,several benchmark studies are presented,including the statistic results of the characterized geometry parameters of the currently utilized bridge-decks,the aerodynamics of the train,and the aerodynamics of the flat box/truss bridge-decks.Upon compared with the foregoing mentioned benchmarks,this paper highlights the aerodynamic interference of the train-bridge system associated with its physical natures.Finally,a porosity-and orientation-adjustable novel wind barrier with its effects on the aerodynamics of the train-bridge system is discussed.展开更多
In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measur...In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measurements of two typical sections, one train-head section and one train-body section, at the windward and leeward tracks were conducted under the smooth and turbulence flows with wind attack angles between-6° and 6°, and the corresponding aerodynamic force coefficients were also calculated using the integral method. The experimental results indicate that the track position affects the mean aerodynamic characteristics of the vehicle, especially for the train-body section. The fluctuating pressure coefficients at the leeward track are more significantly affected by the bridge interference compared to those at the windward track. The effect of turbulence on the train-head section is less than that on the train-body section. Additionally, the mean aerodynamic force coefficients are almost negatively correlated to wind attack angles, which is more prominent for vehicles at the leeward track. Moreover, the lateral force plays a critical role in determining the corresponding overturning moment, especially on the train-body section.展开更多
The irregularities on trains bodies are normally ignored or greatly simplified in studies concerned with aerodynamics.However,surface roughness is known to affect the flow characteristics in the boundary layer near th...The irregularities on trains bodies are normally ignored or greatly simplified in studies concerned with aerodynamics.However,surface roughness is known to affect the flow characteristics in the boundary layer near the wall,hence potentially influencing the aerodynamic performance of a train.This work investigates the effects of roughness on the overall aerodynamic characteristics of a high-speed train subjected to crosswinds.Both experimental work and numerical work have been conducted to simulate a typical high-speed train with a 90?yaw angle,with both a smooth and rough surface.Roughness is applied to the roof of the train surface in the form of longitudinal strips.Results reveal that the addition of roughness is able to reduce the surface pressure on the roof and leeside of the train.Numerical results agree well with experimental ones and confirm that an increase in the roughness relative size can effectively restrain flow separation and reduce surface pressure.Moreover,numerical simulation results show that side force coefficient and roll moment coefficient subjected to rough model significantly decreased compared with smooth model.The conclusions drawn in this study offer the chance to derive critical reference values for the optimization of the aerodynamic characteristics of high-speed trains.展开更多
The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(ID...The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.展开更多
Two trains passing each other is controlling factor for the wind-vehicle-bridge systems.To test the aerodynamic characteristics of moving vehicles under crosswinds when two trains are passing each other,a wind tunnel ...Two trains passing each other is controlling factor for the wind-vehicle-bridge systems.To test the aerodynamic characteristics of moving vehicles under crosswinds when two trains are passing each other,a wind tunnel test device,which has two moving tracks,was developed.The rationality of the test result was discussed,the effects of intersection mode,yaw angle and lane spacing on the aerodynamic coefficients of the leeward train were analyzed,and the difference of aerodynamic coefficients between the head vehicle and the tail vehicle was discussed.The results show that the proposed test device has good repeatability.The intersection modes have a certain effect on the aerodynamic force of the leeward train when two trains are passing each other,and the results should be more reasonable during the two trains dynamic passing each other.With the decrease of yaw angle,the sudden change of train aerodynamic coefficients is more obvious.The decrease of lane spacing will increase the sudden change of leeward vehicles.In the process of two trains passing each other,the aerodynamic coefficients of the head vehicle and tail vehicle are significantly different,so the coupling vibration analysis of wind-vehicle-bridge system should be considered separately.展开更多
Detached eddy simulation has been widely applied to simulate the flow around trains in recent years.The Reynolds-averaged Navier-Stokes(RANS)model for delayed detached eddy simulation(DDES)is an essential user input.T...Detached eddy simulation has been widely applied to simulate the flow around trains in recent years.The Reynolds-averaged Navier-Stokes(RANS)model for delayed detached eddy simulation(DDES)is an essential user input.The effect of the RANS model for DDES on the aerodynamic characteristics of a train in crosswinds is investigated in this study.Three different DDES models are used,based on the Spalart-Allmaras model(SA),the realizable k-εmodel(RKE),and the shear stress transport k-ωmodel(SST).Results show that all DDES models can give relatively accurate predictions of pressure coefficient on almost all surfaces.There are only some specific differences in the small vortices,while similar flow patterns around trains could be predicted.The SST based DDES model(SSTDDES)gives the most accurate numerical results among the three models for the surface pressure.The variations in pressure on the leeward face play a key role in the variation of the side force.展开更多
Understanding the aerodynamic and dynamic characteristics of unloaded freight trains in crosswinds is pivotal for ensuring their operational safety and reliability.The dynamic performance of unloaded gondola cars unde...Understanding the aerodynamic and dynamic characteristics of unloaded freight trains in crosswinds is pivotal for ensuring their operational safety and reliability.The dynamic performance of unloaded gondola cars under varying windbreak heights is therefore investigated in this study,revealing distinct differences in lateral stability and safety indicators,and enabling the determination of an optimal windbreak height.A 3D unsteady aerodynamic model was developed using the improved delayed detached eddy simulation(IDDES)method and an overset numerical mesh.Also leveraging a multi-body dynamics(MBD)model of a three-wagon freight car configuration,we investigate time-averaged aerodynamic forces,transient flow field distributions,and nonlinear dynamic responses.Parametric analyses reveal a non-monotonic relationship between the height of the windbreak and the stability of the train.A windbreak with a critical height of 2 m(0.74 relative to the car body height)results in 76%,64%,and 81%lower values of the derailment coefficient CD,wheel unloading ratio R,and overturning coefficient C_(O),respectively.Notably,when the height of the windbreak exceeds 2 m,vortices within the gondola induce an adverse pressure coefficient distribution(C_(p)=−2.17)on the leeward internal wall,intensifying the lateral force and overturning moment.Furthermore,frequency-domain analysis reveals that the lateral sway and overturning vibration mode are associated with low-frequency(1.61 Hz)lateral vibrations under crosswind conditions.This study provides a theoretical foundation for the design and optimization of railway windbreaks.展开更多
This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimi...This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimizing additional airflow resistance.Three novel windbreak designs,namely single-windbreak configuration with curved profile,double-windbreak configuration with curved profile,and double-windbreak configuration with inverted curved profile,are proposed accordingly and evaluated against conventional solutions.Three-dimensional numerical models of a 120 m high NDDCT equipped with these windbreaks,together with a conventional Y-shaped windbreak,are developed for systematic comparison.The results demonstrate that windbreak effectiveness strongly depends on crosswind intensity.At low crosswind speeds of 0-6 m/s,the Y-shaped windbreak provides the greatest enhancement,increasing the ventilation rate by 25.45%and the heat rejection rate by 21.37%at 6 m/s compared with the no-windbreak configuration.In contrast,under moderate to strong crosswinds of 6-18 m/s,the single-windbreak configuration with curved profile exhibits superior performance.At 18 m/s,it increases the ventilation rate by 148.88%and the heat rejection rate by 79.74%relative to the baseline case,outperforming the Y-shaped windbreak by 26.59%in ventilation rate and 17.01%in heat rejection capacity.Analysis of airflow structure,temperature fields,and velocity distributions confirms that the single-windbreak configuration with curved profile more effectively suppresses crosswind penetration and promotes stable upward airflow at higher wind speeds.Based on a comprehensive assessment of aerodynamic and thermal performance,the Y-shaped windbreak is recommended for regions where crosswind speeds remain below 6 m/s,whereas the single-windbreak configuration with curved profile is preferable for sites exposed to stronger crosswinds exceeding this threshold.展开更多
The share of freight transportation is increasing on Wyoming’s roads. These roads are characterized by challenging mountainous terrain and severe crosswinds. The stability of freight trucks in such conditions is of g...The share of freight transportation is increasing on Wyoming’s roads. These roads are characterized by challenging mountainous terrain and severe crosswinds. The stability of freight trucks in such conditions is of great concern to transportation agencies. Therefore, high-fidelity vehicle dynamics simulation modeling was implemented to investigate the rollover propensity of trucks navigating curves. Scenarios included various road geometric designs, truck characteristics and wind conditions. A multiple linear regression model was also developed to investigate the impact of key parameters on truck rollover propensity. The modeling results indicated that wind speed and direction were influential factors in terms of truck roll stability. Trucks had a 76% higher chance of rolling over when subjected to 40 mph winds relative to being subjected to 20 mph winds assuming all else was unchanged. This study also demonstrated that the most unfavorable wind direction was not perpendicular (90 degrees) to the truck since the truck would continuously change its orientation when traversing combined horizontal and vertical curves. Its speed would also constantly fluctuate. On the contrary, this study’s results indicated that the 120-degree wind direction was the most critical one. Also, under blowing lateral wind conditions, the gross weight of the truck was found to be a contributing factor to rollover risk. Its impact varied depending on the radius of the horizontal curve the truck was navigating. This critical interaction was ignored in the road safety literature. This study offered new insights about the impacts of truck rollover precursors and, hence, this would lead to the proposition of effective truck safety countermeasures.展开更多
The aerodynamic noise of high-speed trains increases significantly under crosswinds.Researches have typically focused on the characteristics of aerodynamic loads and the corresponding safety issues,with less attention...The aerodynamic noise of high-speed trains increases significantly under crosswinds.Researches have typically focused on the characteristics of aerodynamic loads and the corresponding safety issues,with less attention to flow-induced noise characteristics.In the present paper,the near-field unsteady flow behaviour around a pantograph was analysed using a large eddy simulation.The far-field aerodynamic noise from a pantograph was predicted using the Ffowcs Williams-Hawkings acoustic analogy.The results showed that asymmetric characteristics of the flow field could be observed using the turbulent kinetic energy and the instantaneous vortexes in crosswind conditions.Vortex shedding,flow separation and recombination around the pantograph were the key factors for aerodynamic noise generation.The directivity of the noise radiation was inclined towards the leeward side of the pantograph.The aerodynamic noise propagation pattern can be considered as a typical point source on spherical waves when the transverse distance from the pantograph geometrical centre is farther than 8 m.The sound pressure level grew approximately as the 6 th power of the pantograph speed.The peak frequency exhibited a linear relationship with the crosswind velocity.The numerical simulation results and wind tunnel experiments had high consistency in the full frequency domain,namely,the peak frequency distribution range,the main frequency amplitude and the spectral distribution shape.展开更多
The influence of train height on aerodynamic characteristics of high-speed train(HST)is significant in crosswind environments.This study employed the improved delayed detached eddy simulation(IDDES)turbulence model to...The influence of train height on aerodynamic characteristics of high-speed train(HST)is significant in crosswind environments.This study employed the improved delayed detached eddy simulation(IDDES)turbulence model to analyze the aerodynamic characteristics of trains with three different heights under a crosswind of 20 m/s.The numerical model was validated through comparison with wind tunnel experimental data.A comprehensive analysis was conducted on the characteristics of the flow field around trains,surface pressure distribution,and aerodynamic loads for trains with different heights.Results indicate that the side force coefficient increased by up to 61.54%with an increase in train height from 3.89 to 4.19 m.Compared with the 3.89 m case,the roll moment coefficient on the head,middle,and tail cars for 4.19 m cases increased by 18.11%,24.78%and 34.23%,respectively.The increase in train height widens the impact width of the leading car’s front vortex on the leeward side and intensifies the helical shedding and coupling interactions of two vortices in the wake,leading to an increase in the intensity and extent of wake flow in both vertical and longitudinal directions.Additionally,the increase in height shifted the flow separation point on the leeward side,moving vortices farther from the train,expanding the back-flow region,and intensifying Reynolds stress and turbulent fluctuations on the leeward side,which adversely impacted train stability and safety.The research findings can provide a reference for the design of train configurations and the assessment of dynamic performance in crosswind environments.展开更多
The aerodynamic performance of a high-speed train deteriorates sharply under crosswind,severely affecting its operational safety.This paper adopted a three-car high-speed train as the benchmark and established leeward...The aerodynamic performance of a high-speed train deteriorates sharply under crosswind,severely affecting its operational safety.This paper adopted a three-car high-speed train as the benchmark and established leeward side(LWS)airbag-train models.Based on the three-dimensional steady SST k-ωtwo-equation turbulence model,this study investigated the aerodynamic characteristics of trains under crosswind at three different airbag’s installation positions.The results show that the airbags installed on the LWS change the surface pressure distribution on the LWS of the train body,lowering the lateral force coefficient and overturning moment coefficient,and the aerodynamic performance of the train under crosswinds is enhanced.The airbag structure located at the top of the LWS(Model III)shows the most significant improvement in crosswind performance that the lateral force coefficient is reduced by 16.71%,and the lift coefficient is increased by 17.95%,which collectively led to a decrease in the train’s overturning moment coefficient by 23.65%.The research findings provide a reference for improving the anti-overturning performance of the next generation high-speed trains under crosswind.展开更多
The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to...The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to train safety,significantly lowering the critical wind velocity.Therefore,developing strategies to enhance crosswind stability is essential.This study focuses on the leeward region adjacent to the train body,where separated flows with large vortices generate significant negative surface pressure.Enhancing this negative pressure distribution is proposed as a potential method to improve a train’s resistance to overturning.To achieve this,winglets are installed on the leeward side as a flow control measure,and their effects at different deflection angles are evaluated.The influence of five deflection angles on the leeward-side flow field and aerodynamic loads is analyzed,considering the head,middle,and tail cars.Results indicate that a deflection angle of 90°optimally reduces the overall overturning moment by 27.6%compared to the baseline model in a three-car configuration.These findings highlight that optimizing the winglet deflection angle to approximately 90°can significantly enhance a train’s resistance to overturning,offering valuable insights for aerodynamic optimization in strong wind conditions.展开更多
Urban transportation systems are facing severe challenges due to the rapid growth of the urban population,especially in China.Suspended monorail system(SMS),as a sky rail transportation form,can effectively alleviate ...Urban transportation systems are facing severe challenges due to the rapid growth of the urban population,especially in China.Suspended monorail system(SMS),as a sky rail transportation form,can effectively alleviate urban traffic congestion due to its independent right-of-way and minimal ground footprint.However,the SMS possesses a special traveling system with unique vehicle structure and bridge configuration,which results in significant differences in both the mechanisms and dynamics problems associated with train–bridge interaction(TBI)when contrasted with those of traditional railway systems.Therefore,a thorough understanding of the SMS dynamics is essential for ensuring the operational safety of the system.This article presents a state-of-the-art review of the TBI modeling methodologies,critical dynamic features,field tests,and practice of the SMS in China.Firstly,the development history,technical features,and potential dynamics problems of the SMS are briefly described,followed by the mechanical characteristics and mechanisms of the train–bridge interactive systems.Then,the modeling methodology of the fundamental elements in the suspended monorail TBI is systematically reviewed,including the suspended train subsystem,bridge subsystem,train–bridge interaction relationships,system excitations,and solution method.Further,the typical dynamic features of the TBI under various operational scenarios are elaborated,including different train speeds,a variety of line sections,and a natural wind environment.Finally,the first new energy-based SMS test line in the world is systematically introduced,including the composition and functionality of the system,the details of the conducted field tests,and the measured results of the typical dynamic responses.At the end of the paper,both the guidance on further improvement of the SMS and future research topics are proposed.展开更多
Currently,the design of high-temperature superconducting(HTS)maglev trains adopts a U-shaped track operation mode,and the height of the side track significantly impacts the train’s aerodynamic characteristics.In this...Currently,the design of high-temperature superconducting(HTS)maglev trains adopts a U-shaped track operation mode,and the height of the side track significantly impacts the train’s aerodynamic characteristics.In this study,we used computational fluid dynamics(CFD)methods,based on the 3D Reynolds-averaged Navier-Stokes(RANS)method and shear stress transport(SST)k-ωturbulence model,to deeply investigate the effects of the presence or absence of a U-shaped track and different side track heights(800,880,and 960 mm)on the pressure distribution,velocity distribution,and flow field structure of HTS maglev trains at a speed of 400 km/h under crosswinds.The numerical methods were verified using a scaled ICE-2 model wind tunnel test.First,the aerodynamic characteristics of the train under different wind direction angles with and without side tracks were studied.We found that the aerodynamic performance of the train is the most adverse when the wind direction angle is 90°.The presence of a U-shaped track can effectively reduce the lateral force,lift,and yawing moment of the train.The aerodynamic performance of the first suspension bogie at the bottom,which is the worst,will also be effectively improved.Next,the aerodynamic effects of different side track heights on the HTS maglev train were studied.An increase in side track height will reduce the lift and lateral force of the train,while the increase in drag is relatively small.Under the premise of ensuring passengers can conveniently alight,we found that a U-shaped track with a side track height of 960 mm has the best aerodynamic performance.The research findings offer a valuable reference for the engineering application and design of the track structure of HTS maglev train systems.展开更多
Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetri...Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap,resulting in instability and deterioration of the train’s aerodynamic characteristics,significantly impacting its operational safety.In this study,we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results.We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds.We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties.The findings show that,without crosswinds,a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling,leading to the worst aerodynamic performance.Under crosswind conditions,a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train,resulting in the poorest aerodynamic performance.This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.展开更多
In view of the situation of multi-temperature,multi-medium and multi-discharge equipment on the integrated exhaust end platform of a natural gas distributed energy station,which is compact in layout,mutual influence,c...In view of the situation of multi-temperature,multi-medium and multi-discharge equipment on the integrated exhaust end platform of a natural gas distributed energy station,which is compact in layout,mutual influence,complex aerodynamic field and complex heat and mass transfer field,the temperature field and aerodynamic field of the platform were comprehensively studied through field experiments and numerical simulation.The research results show that the high temperature flue gas discharged from the chimney is hindered by the chimney cap and returns downward.The noise reduction walls around the chimney make the top of the platform pressurized under the crosswind,as a result,the inlet air temperature of each cooling equipment is generally higher than the ambient temperature,and the cooling efficiency is extremely low.According to the numerical simulation results,the effect of hot gas recirculation is intensified by the ambient crosswind.With the increase of the ambient crosswind,the flue gases coverage expands.The influence of ambient crosswind on inlet air temperature first increases and then decreases within the range of 1–8 m/s,showing a nearly normal distribution.Secondly,this study innovatively designed a new V-shaped chimney cap,compared with the A-shaped chimney cap,the new chimney cap effectively reduces its own obstruction to the smoke and changes the flow path of the smoke.After the smoke rises for a certain distance,the smoke returns downward,which effectively reduces the temperature of the smoke and thus reduces its impact on the air inlet of the cooling equipment.On-site measurement found that the cooling efficiency of various cooling equipment has increased by an average of 27.3%compared to before the renovation,and centrifuge’s refrigeration capacity increased by 0.78 GJ/h.展开更多
基金Projects(52302447,52388102)supported by the National Natural Science Foundation of China。
文摘Considering passenger trains'key role in remote regions,this study employed machine vision technology to monitor five posture parameters of the second car of a conventional passenger train,aiming to investigate the influence of windbreaks and crosswinds along railways on the operating postures of conventional passenger trains.The study found that when passing through the anti-wind tunnel with holes,the amplitudes of posture parameters were smaller than those of other windbreaks,demonstrating the superior performance of this windbreak in maintaining posture stability compared to others.In tunnel sections,larger amplitudes of these parameters were observed for the tail car than the head car,while the opposite occurred in non-tunnel sections.Notably,during tunnel transit,their amplitudes did not increase monotonically with speed but peaked at a specific speed that most adversely affected the operating posture.These conclusions have a great significance for improving operating safety under crosswinds.
基金supported by the National Natural Science Foundation of China(No.52375160)the Natural Science Foundation of Hebei Province(No.2024105064),China.
文摘The structural safety of high-speed trains is significantly endangered by increasing operating speeds.The objective of this research was to investigate the evolution of the flow field in trains passing through a tunnel while there is a strong crosswind at the tunnel entrance and exit.Moreover,the effect of aerodynamic pressure waves on structural strength was analyzed to evaluate the safety of the carbody.In this study,we selected the improved delayed detached-eddy simulation(IDDES)method as a turbulence model.The mechanism of interaction among the train,tunnel,and crosswind was evaluated through a complex computational fluid dynamics(CFD)model,simulating high-speed trains moving through tunnels at various crosswind speeds.Additionally,the dynamic stress response of the carbody was calculated using a sequential coupling approach,where integral aerodynamic forces were applied as substitutes for direct CFD pressure loads.We assessed the effect of aerodynamic loads on the dynamic stresses of the carbody at different crosswind velocities(0,10,15,and 20 m/s).The results indicate that crosswinds exert a substantial influence on the fluid structure surrounding the train.Consequently,the aerodynamic forces contribute significantly to potential damage to the carbody,posing increased safety risks for high-speed trains.
基金National Natural Science Foundation of China(No.52388102)New Cornerstone Science Foundation through the Xplorer Prize.
文摘The dynamic performance of high-speed trains is significantly influenced by sudden changes in aerodynamic loads(ADLs)when exiting a tunnel in a windy environment.Focusing on a double-track tunnel under construction in a mountain railway,we established an aerodynamic model involving a train exiting the tunnel,and verified it in the Fluent environment.Overset mesh technology was adopted to characterize the train’s movement.The flow field involving the train,tunnel,and crosswinds was simulated using the Reynolds-averaged turbulence model.Then,we built a comprehensive train-track coupled dynamic model considering the influences of ADLs,to investigate the vehicles’dynamic responses.The aerodynamics and dynamic behaviors of the train when affected by crosswinds with different velocities and directions are analyzed and discussed.The results show that the near-wall side crosswind leads to sharper variations in ADLs than the far-wall side crosswind.The leading vehicle suffers from more severe ADLs than other vehicles,which worsens the wheel-rail interaction and causes low-frequency vibration of the car body.When the crosswind velocity exceeds 20 m/s,significant wheel-rail impacts occur,and the running safety of the train worsens rapidly.
基金Project(2017YFB1201204)supported by National Key R&D Program of ChinaProjects(51925808,U1934209)supported by the National Natural Science Foundation of China。
文摘Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China.Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodynamic assessment,this paper primarily reviews five meaningful progresses on the aerodynamics of the train-bridge system done by Wind Tunnel Laboratory of Central South University in the past several years.Firstly,the flow around the train and the uncertainty origin of the aerodynamic assessment are described from the fluid mechanism point of view.After a brief introduction of the current aerodynamic assessment methods with their strengths and weaknesses,a new-developed TRAIN-INFRASTRUCTURE rig with the maximum launch speed of 35 m/s is introduced.Then,several benchmark studies are presented,including the statistic results of the characterized geometry parameters of the currently utilized bridge-decks,the aerodynamics of the train,and the aerodynamics of the flat box/truss bridge-decks.Upon compared with the foregoing mentioned benchmarks,this paper highlights the aerodynamic interference of the train-bridge system associated with its physical natures.Finally,a porosity-and orientation-adjustable novel wind barrier with its effects on the aerodynamics of the train-bridge system is discussed.
基金Projects(51808563,51925808)supported by the National Natural Science Foundation of ChinaProject(KLWRTBMC18-03)supported by the Open Research Fund of the Key Laboratory of Wind Resistance Technology of Bridges of ChinaProject(2017YFB1201204)supported by the National Key R&D Program of China。
文摘In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measurements of two typical sections, one train-head section and one train-body section, at the windward and leeward tracks were conducted under the smooth and turbulence flows with wind attack angles between-6° and 6°, and the corresponding aerodynamic force coefficients were also calculated using the integral method. The experimental results indicate that the track position affects the mean aerodynamic characteristics of the vehicle, especially for the train-body section. The fluctuating pressure coefficients at the leeward track are more significantly affected by the bridge interference compared to those at the windward track. The effect of turbulence on the train-head section is less than that on the train-body section. Additionally, the mean aerodynamic force coefficients are almost negatively correlated to wind attack angles, which is more prominent for vehicles at the leeward track. Moreover, the lateral force plays a critical role in determining the corresponding overturning moment, especially on the train-body section.
基金The work was financed by the program of China Scholarships Council,Youth Innovation Promotion Association CAS(2019020)a University of Birmingham(UK)funded scholarship and was supported by the EU H2O2O project LiftTRAIN(701693)。
文摘The irregularities on trains bodies are normally ignored or greatly simplified in studies concerned with aerodynamics.However,surface roughness is known to affect the flow characteristics in the boundary layer near the wall,hence potentially influencing the aerodynamic performance of a train.This work investigates the effects of roughness on the overall aerodynamic characteristics of a high-speed train subjected to crosswinds.Both experimental work and numerical work have been conducted to simulate a typical high-speed train with a 90?yaw angle,with both a smooth and rough surface.Roughness is applied to the roof of the train surface in the form of longitudinal strips.Results reveal that the addition of roughness is able to reduce the surface pressure on the roof and leeside of the train.Numerical results agree well with experimental ones and confirm that an increase in the roughness relative size can effectively restrain flow separation and reduce surface pressure.Moreover,numerical simulation results show that side force coefficient and roll moment coefficient subjected to rough model significantly decreased compared with smooth model.The conclusions drawn in this study offer the chance to derive critical reference values for the optimization of the aerodynamic characteristics of high-speed trains.
基金supported by Wuyi University Hong Kong and Macao Joint Research and Development Fund(GrantsNos.2021WGALH15,2019WGALH17,2019WGALH15)the National Natural Science Foundation of China-Guangdong Joint Fund(GrantsNo.2019A1515111052)+2 种基金the National Natural Science Foundation of China(Grant No.52202426)a grant from the Research Grants Council(RGC)of the Hong Kong Special Administrative Region(SAR),China(Grants No.15205723)a grant from the Hong Kong Polytechnic University(Grant No.P0045325).
文摘The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.
基金Projects(51778544,51978589,51908472) supported by the National Natural Science Foundation of ChinaProject(2682021CG014) supported by the Fundamental Research Funds for the Central Universities,China。
文摘Two trains passing each other is controlling factor for the wind-vehicle-bridge systems.To test the aerodynamic characteristics of moving vehicles under crosswinds when two trains are passing each other,a wind tunnel test device,which has two moving tracks,was developed.The rationality of the test result was discussed,the effects of intersection mode,yaw angle and lane spacing on the aerodynamic coefficients of the leeward train were analyzed,and the difference of aerodynamic coefficients between the head vehicle and the tail vehicle was discussed.The results show that the proposed test device has good repeatability.The intersection modes have a certain effect on the aerodynamic force of the leeward train when two trains are passing each other,and the results should be more reasonable during the two trains dynamic passing each other.With the decrease of yaw angle,the sudden change of train aerodynamic coefficients is more obvious.The decrease of lane spacing will increase the sudden change of leeward vehicles.In the process of two trains passing each other,the aerodynamic coefficients of the head vehicle and tail vehicle are significantly different,so the coupling vibration analysis of wind-vehicle-bridge system should be considered separately.
基金the National Natural Science Foundation of China(No.51605397)Sichuan Science and Technology Program(No.2019YJ0227)+1 种基金China Postdoctoral Science Foundation(No.2019M663550)Self-determined Project of State Key Laboratory of Traction Power(2019TPL_T02).
文摘Detached eddy simulation has been widely applied to simulate the flow around trains in recent years.The Reynolds-averaged Navier-Stokes(RANS)model for delayed detached eddy simulation(DDES)is an essential user input.The effect of the RANS model for DDES on the aerodynamic characteristics of a train in crosswinds is investigated in this study.Three different DDES models are used,based on the Spalart-Allmaras model(SA),the realizable k-εmodel(RKE),and the shear stress transport k-ωmodel(SST).Results show that all DDES models can give relatively accurate predictions of pressure coefficient on almost all surfaces.There are only some specific differences in the small vortices,while similar flow patterns around trains could be predicted.The SST based DDES model(SSTDDES)gives the most accurate numerical results among the three models for the surface pressure.The variations in pressure on the leeward face play a key role in the variation of the side force.
基金supported by the National Natural Science Foundation of China(No.52388102)the Science and Technology Research and Development Program of China State Railway Group Co.,Ltd.(No.N2024J039).
文摘Understanding the aerodynamic and dynamic characteristics of unloaded freight trains in crosswinds is pivotal for ensuring their operational safety and reliability.The dynamic performance of unloaded gondola cars under varying windbreak heights is therefore investigated in this study,revealing distinct differences in lateral stability and safety indicators,and enabling the determination of an optimal windbreak height.A 3D unsteady aerodynamic model was developed using the improved delayed detached eddy simulation(IDDES)method and an overset numerical mesh.Also leveraging a multi-body dynamics(MBD)model of a three-wagon freight car configuration,we investigate time-averaged aerodynamic forces,transient flow field distributions,and nonlinear dynamic responses.Parametric analyses reveal a non-monotonic relationship between the height of the windbreak and the stability of the train.A windbreak with a critical height of 2 m(0.74 relative to the car body height)results in 76%,64%,and 81%lower values of the derailment coefficient CD,wheel unloading ratio R,and overturning coefficient C_(O),respectively.Notably,when the height of the windbreak exceeds 2 m,vortices within the gondola induce an adverse pressure coefficient distribution(C_(p)=−2.17)on the leeward internal wall,intensifying the lateral force and overturning moment.Furthermore,frequency-domain analysis reveals that the lateral sway and overturning vibration mode are associated with low-frequency(1.61 Hz)lateral vibrations under crosswind conditions.This study provides a theoretical foundation for the design and optimization of railway windbreaks.
基金supported by the National Natural Science Foundation of China(Grant No.52476206)the Key R&D Program of Shandong Province,China(Grant No.2025CXGC010203)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515012123)the Shandong Natural Science Foundation(Grant No.ZR2022ME008).
文摘This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimizing additional airflow resistance.Three novel windbreak designs,namely single-windbreak configuration with curved profile,double-windbreak configuration with curved profile,and double-windbreak configuration with inverted curved profile,are proposed accordingly and evaluated against conventional solutions.Three-dimensional numerical models of a 120 m high NDDCT equipped with these windbreaks,together with a conventional Y-shaped windbreak,are developed for systematic comparison.The results demonstrate that windbreak effectiveness strongly depends on crosswind intensity.At low crosswind speeds of 0-6 m/s,the Y-shaped windbreak provides the greatest enhancement,increasing the ventilation rate by 25.45%and the heat rejection rate by 21.37%at 6 m/s compared with the no-windbreak configuration.In contrast,under moderate to strong crosswinds of 6-18 m/s,the single-windbreak configuration with curved profile exhibits superior performance.At 18 m/s,it increases the ventilation rate by 148.88%and the heat rejection rate by 79.74%relative to the baseline case,outperforming the Y-shaped windbreak by 26.59%in ventilation rate and 17.01%in heat rejection capacity.Analysis of airflow structure,temperature fields,and velocity distributions confirms that the single-windbreak configuration with curved profile more effectively suppresses crosswind penetration and promotes stable upward airflow at higher wind speeds.Based on a comprehensive assessment of aerodynamic and thermal performance,the Y-shaped windbreak is recommended for regions where crosswind speeds remain below 6 m/s,whereas the single-windbreak configuration with curved profile is preferable for sites exposed to stronger crosswinds exceeding this threshold.
文摘The share of freight transportation is increasing on Wyoming’s roads. These roads are characterized by challenging mountainous terrain and severe crosswinds. The stability of freight trucks in such conditions is of great concern to transportation agencies. Therefore, high-fidelity vehicle dynamics simulation modeling was implemented to investigate the rollover propensity of trucks navigating curves. Scenarios included various road geometric designs, truck characteristics and wind conditions. A multiple linear regression model was also developed to investigate the impact of key parameters on truck rollover propensity. The modeling results indicated that wind speed and direction were influential factors in terms of truck roll stability. Trucks had a 76% higher chance of rolling over when subjected to 40 mph winds relative to being subjected to 20 mph winds assuming all else was unchanged. This study also demonstrated that the most unfavorable wind direction was not perpendicular (90 degrees) to the truck since the truck would continuously change its orientation when traversing combined horizontal and vertical curves. Its speed would also constantly fluctuate. On the contrary, this study’s results indicated that the 120-degree wind direction was the most critical one. Also, under blowing lateral wind conditions, the gross weight of the truck was found to be a contributing factor to rollover risk. Its impact varied depending on the radius of the horizontal curve the truck was navigating. This critical interaction was ignored in the road safety literature. This study offered new insights about the impacts of truck rollover precursors and, hence, this would lead to the proposition of effective truck safety countermeasures.
基金supported by the National Key R&D Program of China(Grant No.2016YFE0205200)the High-Speed Railway Basic Research Fund Key Project of China(Grant No.U1234208)+1 种基金the National Natural Science Foundation of China(Grant Nos.11972179,51475394)the China Postdoctoral Science Foundation(Grant No.2019M662201)。
文摘The aerodynamic noise of high-speed trains increases significantly under crosswinds.Researches have typically focused on the characteristics of aerodynamic loads and the corresponding safety issues,with less attention to flow-induced noise characteristics.In the present paper,the near-field unsteady flow behaviour around a pantograph was analysed using a large eddy simulation.The far-field aerodynamic noise from a pantograph was predicted using the Ffowcs Williams-Hawkings acoustic analogy.The results showed that asymmetric characteristics of the flow field could be observed using the turbulent kinetic energy and the instantaneous vortexes in crosswind conditions.Vortex shedding,flow separation and recombination around the pantograph were the key factors for aerodynamic noise generation.The directivity of the noise radiation was inclined towards the leeward side of the pantograph.The aerodynamic noise propagation pattern can be considered as a typical point source on spherical waves when the transverse distance from the pantograph geometrical centre is farther than 8 m.The sound pressure level grew approximately as the 6 th power of the pantograph speed.The peak frequency exhibited a linear relationship with the crosswind velocity.The numerical simulation results and wind tunnel experiments had high consistency in the full frequency domain,namely,the peak frequency distribution range,the main frequency amplitude and the spectral distribution shape.
基金Project(2020YFA0710903)supported by the National Key R&D Program of ChinaProject(2024JK2037)supported by the Key Research and Development Program of Hunan Province,China+1 种基金Project(52402458)supported by the National Natural Science Foundation of ChinaProjects(2025ZZTS0703,2025ZZTS0209)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The influence of train height on aerodynamic characteristics of high-speed train(HST)is significant in crosswind environments.This study employed the improved delayed detached eddy simulation(IDDES)turbulence model to analyze the aerodynamic characteristics of trains with three different heights under a crosswind of 20 m/s.The numerical model was validated through comparison with wind tunnel experimental data.A comprehensive analysis was conducted on the characteristics of the flow field around trains,surface pressure distribution,and aerodynamic loads for trains with different heights.Results indicate that the side force coefficient increased by up to 61.54%with an increase in train height from 3.89 to 4.19 m.Compared with the 3.89 m case,the roll moment coefficient on the head,middle,and tail cars for 4.19 m cases increased by 18.11%,24.78%and 34.23%,respectively.The increase in train height widens the impact width of the leading car’s front vortex on the leeward side and intensifies the helical shedding and coupling interactions of two vortices in the wake,leading to an increase in the intensity and extent of wake flow in both vertical and longitudinal directions.Additionally,the increase in height shifted the flow separation point on the leeward side,moving vortices farther from the train,expanding the back-flow region,and intensifying Reynolds stress and turbulent fluctuations on the leeward side,which adversely impacted train stability and safety.The research findings can provide a reference for the design of train configurations and the assessment of dynamic performance in crosswind environments.
基金Project(2020YFA0710903)supported by the National Key Research and Development Program of ChinaProjects(52372370,52388102)supported by the National Natural Science Foundation of China。
文摘The aerodynamic performance of a high-speed train deteriorates sharply under crosswind,severely affecting its operational safety.This paper adopted a three-car high-speed train as the benchmark and established leeward side(LWS)airbag-train models.Based on the three-dimensional steady SST k-ωtwo-equation turbulence model,this study investigated the aerodynamic characteristics of trains under crosswind at three different airbag’s installation positions.The results show that the airbags installed on the LWS change the surface pressure distribution on the LWS of the train body,lowering the lateral force coefficient and overturning moment coefficient,and the aerodynamic performance of the train under crosswinds is enhanced.The airbag structure located at the top of the LWS(Model III)shows the most significant improvement in crosswind performance that the lateral force coefficient is reduced by 16.71%,and the lift coefficient is increased by 17.95%,which collectively led to a decrease in the train’s overturning moment coefficient by 23.65%.The research findings provide a reference for improving the anti-overturning performance of the next generation high-speed trains under crosswind.
基金Project(2020YFA0710903)supported by the National Key Research and Development Program of ChinaProject(2025ZZTS0623)supported by the Graduate Student Independent Innovation Project of Central South University,ChinaProject(202406370145)supported by the China Scholarship Council。
文摘The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to train safety,significantly lowering the critical wind velocity.Therefore,developing strategies to enhance crosswind stability is essential.This study focuses on the leeward region adjacent to the train body,where separated flows with large vortices generate significant negative surface pressure.Enhancing this negative pressure distribution is proposed as a potential method to improve a train’s resistance to overturning.To achieve this,winglets are installed on the leeward side as a flow control measure,and their effects at different deflection angles are evaluated.The influence of five deflection angles on the leeward-side flow field and aerodynamic loads is analyzed,considering the head,middle,and tail cars.Results indicate that a deflection angle of 90°optimally reduces the overall overturning moment by 27.6%compared to the baseline model in a three-car configuration.These findings highlight that optimizing the winglet deflection angle to approximately 90°can significantly enhance a train’s resistance to overturning,offering valuable insights for aerodynamic optimization in strong wind conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.52202483,52108476,and 52388102)。
文摘Urban transportation systems are facing severe challenges due to the rapid growth of the urban population,especially in China.Suspended monorail system(SMS),as a sky rail transportation form,can effectively alleviate urban traffic congestion due to its independent right-of-way and minimal ground footprint.However,the SMS possesses a special traveling system with unique vehicle structure and bridge configuration,which results in significant differences in both the mechanisms and dynamics problems associated with train–bridge interaction(TBI)when contrasted with those of traditional railway systems.Therefore,a thorough understanding of the SMS dynamics is essential for ensuring the operational safety of the system.This article presents a state-of-the-art review of the TBI modeling methodologies,critical dynamic features,field tests,and practice of the SMS in China.Firstly,the development history,technical features,and potential dynamics problems of the SMS are briefly described,followed by the mechanical characteristics and mechanisms of the train–bridge interactive systems.Then,the modeling methodology of the fundamental elements in the suspended monorail TBI is systematically reviewed,including the suspended train subsystem,bridge subsystem,train–bridge interaction relationships,system excitations,and solution method.Further,the typical dynamic features of the TBI under various operational scenarios are elaborated,including different train speeds,a variety of line sections,and a natural wind environment.Finally,the first new energy-based SMS test line in the world is systematically introduced,including the composition and functionality of the system,the details of the conducted field tests,and the measured results of the typical dynamic responses.At the end of the paper,both the guidance on further improvement of the SMS and future research topics are proposed.
基金supported by the National Natural Science Foundation of China(No.U23A20681)the S&T Program of Hebei Province,China(No.23567602H).
文摘Currently,the design of high-temperature superconducting(HTS)maglev trains adopts a U-shaped track operation mode,and the height of the side track significantly impacts the train’s aerodynamic characteristics.In this study,we used computational fluid dynamics(CFD)methods,based on the 3D Reynolds-averaged Navier-Stokes(RANS)method and shear stress transport(SST)k-ωturbulence model,to deeply investigate the effects of the presence or absence of a U-shaped track and different side track heights(800,880,and 960 mm)on the pressure distribution,velocity distribution,and flow field structure of HTS maglev trains at a speed of 400 km/h under crosswinds.The numerical methods were verified using a scaled ICE-2 model wind tunnel test.First,the aerodynamic characteristics of the train under different wind direction angles with and without side tracks were studied.We found that the aerodynamic performance of the train is the most adverse when the wind direction angle is 90°.The presence of a U-shaped track can effectively reduce the lateral force,lift,and yawing moment of the train.The aerodynamic performance of the first suspension bogie at the bottom,which is the worst,will also be effectively improved.Next,the aerodynamic effects of different side track heights on the HTS maglev train were studied.An increase in side track height will reduce the lift and lateral force of the train,while the increase in drag is relatively small.Under the premise of ensuring passengers can conveniently alight,we found that a U-shaped track with a side track height of 960 mm has the best aerodynamic performance.The research findings offer a valuable reference for the engineering application and design of the track structure of HTS maglev train systems.
基金Projects(52372369,52302447,52388102)supported by the National Natural Science Foundation of ChinaProjects(2022YFB4301201-02,2023YFB4302502-02)supported by the National Key R&D Program of China。
文摘Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap,resulting in instability and deterioration of the train’s aerodynamic characteristics,significantly impacting its operational safety.In this study,we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results.We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds.We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties.The findings show that,without crosswinds,a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling,leading to the worst aerodynamic performance.Under crosswind conditions,a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train,resulting in the poorest aerodynamic performance.This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.
基金support from the Shandong Provincial Science and Technology SMEs Innovation Capacity Improvement Project(2023TSGC0087)the Shandong Natural Science Foundation(Grant No.ZR2022ME008)China Postdoctoral Science Foundation(2023M732102).
文摘In view of the situation of multi-temperature,multi-medium and multi-discharge equipment on the integrated exhaust end platform of a natural gas distributed energy station,which is compact in layout,mutual influence,complex aerodynamic field and complex heat and mass transfer field,the temperature field and aerodynamic field of the platform were comprehensively studied through field experiments and numerical simulation.The research results show that the high temperature flue gas discharged from the chimney is hindered by the chimney cap and returns downward.The noise reduction walls around the chimney make the top of the platform pressurized under the crosswind,as a result,the inlet air temperature of each cooling equipment is generally higher than the ambient temperature,and the cooling efficiency is extremely low.According to the numerical simulation results,the effect of hot gas recirculation is intensified by the ambient crosswind.With the increase of the ambient crosswind,the flue gases coverage expands.The influence of ambient crosswind on inlet air temperature first increases and then decreases within the range of 1–8 m/s,showing a nearly normal distribution.Secondly,this study innovatively designed a new V-shaped chimney cap,compared with the A-shaped chimney cap,the new chimney cap effectively reduces its own obstruction to the smoke and changes the flow path of the smoke.After the smoke rises for a certain distance,the smoke returns downward,which effectively reduces the temperature of the smoke and thus reduces its impact on the air inlet of the cooling equipment.On-site measurement found that the cooling efficiency of various cooling equipment has increased by an average of 27.3%compared to before the renovation,and centrifuge’s refrigeration capacity increased by 0.78 GJ/h.
