The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In th...The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In this study,computational fluid dynamics(CFD)based on three-dimensional steady incompressible Reynolds-average Naiver-Stokes(RANS)equations and Realizable k-εturbulence model were utilized for numerical simulations.Inspired by the concept of streamlined design and the idea of bottom flow field control,this study iteratively designed the bogies in a streamlined shape and combined them with the bottom deflectors to investigate the joint drag reduction mechanism.Three models,i.e.,single-bogie model,simplified train model,and eight-car high-speed train model,were created and their aerodynamic characteristics were analyzed.The results show that the single-bogie model with streamlined design shows a noticeable drag reduction,whose power bogie and trailer bogie experience 13.92%and 7.63%drag reduction,respectively.The range of positive pressure area on the bogie is reduced.The aerodynamic drag can be further reduced to 15.01%by installing both the streamlined bogie and the deflector on the simplified train model.When the streamlined bogies and deflectors are used on the eight-car model together,the total drag reduction rate reaches 2.90%.Therefore,the proposed aerodynamic kit for the high-speed train bottom is capable to improve the flow structure around the bogie regions,reduce the bottom flow velocity,and narrow the scope of the train’s influence on the surrounding environment,achieving the appreciable reduction of aerodynamic drag.This paper can provide a new idea for the drag reduction of high-speed trains.展开更多
The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed trains.An appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces...The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed trains.An appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind circumstances.In this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence model.The different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 m.In order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the literature.Numerical simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on results.The impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure distributions.In comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic resistance.Additionally,the lift forces on the head and tail cars increased by 35.7%and 75.5%,respectively.On the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic drag.Furthermore,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,respectively.The aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.展开更多
The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train.For this reason,evacuated tube trains(ETT)are being considered as valid alternatives to be imple...The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train.For this reason,evacuated tube trains(ETT)are being considered as valid alternatives to be implemented in the future.The atmosphere in the tube,the so-called blocking ratio and the length of the streamlined nose are the key factors affecting the aerodynamic performances of these trains.In the present work,we investigate evacuated tube trains with different lengths of the streamline nose on the basis of computational fluid dynamics(CFD).The three-dimensional steady compressible Navier-Stokes equations are solved.The running speed of the ETT is 800 km/h and the blocking ratio is 0.2.Results show that with the increase of the streamlined nose length,the aerodynamic drag and lift forces of the head car decrease gradually,and the drag and lift forces of the middle car change slightly.For the tail car,the drag force decreases,whereas the absolute value of the lift force increases.At a speed of 800 km/h,a slight shock wave appears at the rear of the tail car,which affects the aerodynamic forces acting on the train.展开更多
With continuous changes to energy-saving requirements,the task of train aerodynamic optimization becomes important.Traditional aerodynamic optimization of a high-speed train is carried out assuming the same shape of t...With continuous changes to energy-saving requirements,the task of train aerodynamic optimization becomes important.Traditional aerodynamic optimization of a high-speed train is carried out assuming the same shape of the head and tail cars,which ignores the combined effect of the two cars on aerodynamic forces.The streamlined structure of the train has different effects on the aerodynamics of the head and tail cars.In-depth study of these effects will help engineers improve their shape design capabilities.Based on the surrogate model method,this paper studies the influence of five shape parameters of the streamlined area on the resistance of the head and tail cars and the lift force of the tail car of CRH380A,and compares the aerodynamic performance of the two optimization schemes.The research results show that the optimization direction for reducing drag of the head car is opposite to that for reducing the drag and lift of the tail car,while the optimization directions for reducing both drag and lift for the tail car alone,are roughly the same.Therefore,the same shaped head and tail cars are problematic for improving aerodynamic performance.After optimization,the head car’s resistance,the tail car’s resistance,and the tail car’s lift of the train with the same shape of head and tail cars are reduced by 1.7%,0.5%,and 3.5%,respectively.The train with different shapes had values decreased by 5.6%,1.4%,and 7.5%,respectively.The optimization effect of the latter is more than twice that of the former.展开更多
Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis dur...Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis during blood delivery.In this paper,a new valveless piezoelectric(PZT)pump with streamlined flow tubes(streamlined pump)is proposed.The design method and the working principle of the pump are analyzed.The velocity streamlines are simulated,and the results demonstrate that there are no obvious vortexes in the flow tube of the streamlined pump.Five prototype pumps(two cone pumps and three streamlined pumps)are designed and fabricated to perform flow rate and flow resistance experiments.The experimental results illustrate that the maximum flow rate of the streamlined pump is 142 mL/min,which is 179%higher than that of the cone piezoelectric pump,demonstrating that the streamlined pump has a large flow rate performance.This research provides an inspiration for future research on simple structure,low vortex and large flow rate volume-type pumps,and also provides a useful solution for thrombosis preventing.展开更多
In foundries a lot of effort is done to minimize energy consumption in the production to reduce costs and hence increase the competitiveness. At the same time the foundries must live up to the increased demands for hi...In foundries a lot of effort is done to minimize energy consumption in the production to reduce costs and hence increase the competitiveness. At the same time the foundries must live up to the increased demands for high quality castings. Traditional gating systems are known for a straight tapered down runner, a well base and 90° bends in the runner system. Previous work has shown that the traditional way of designing gating systems creates high inconsistency in flow patterns during filling. In the streamlined gating systems there are no sharp changes in direction and a large effort is done to confine and control the flow of the molten metal during mould filling. The main objective in the work presented here is to use the principles of the streamlined gating systems to reduce the weight of the gating system relative to the traditional layouts. By reducing the weight of gating system and thereby improving yield, the amount of molten iron needed is also reduced, hence reducing the energy consumption for melting. Experiments in real production lines have proven that it is possible to achieve a reduction in the poured weight by using the streamlined gating systems. In a layout for casting of three valve housings in a vertically parted mould the weight of the gating system was reduced by 1.1 kg changing from the traditional layouts to the streamlined gating systems. This weight reduction corresponds in this case to a 20% weight reduction for the gating system. Using streamlined gating systems with fan gates to give a beneficial heat distribution in the castings may be an efficient tool to eliminate the need for heat treatment. In the experiments the change in gating system from the traditional layout to the streamlined layout removed the need for heat treatment. This obviously means a huge energy saving in the foundry. The energy consumption for heat treatment of iron has been found to be 0.489 kWh/ kg. The valve housing in the experiments weighs 3 kg so when the need for heat treatment is removed, around 1.5 kWh is saved per casting. Along with the reduction in energy used the foundry also save the cost of handling the castings for the heat treatment and the production times is reduced considerably When the moulds for the vertical layout is produced on a DISAMATIC that produces 350 moulds an hour the total energy saved per hour for both melting and heat treatment becomes 2,000 kWh and per eight hour work day 16,000 kWh. Seen in this perspective the potential for saving energy in the foundries is substantial. Furthermore the experiments where ductile iron valve housings was cast also proved that it is possible to lower the pouring temperature from 1,400℃ to 1,300℃ without the risk of cold runs. This is possible due to a high flow rate during mould filling in combination with low velocities due to the use of fan gates. All of this has also been investigated in experiments using glass plate fronted moulds.展开更多
WANG Xianlong didn＇t expect it would take only five working days to register his business, an outdoor products company based in Yiwu, a city in east China＇s Zhejiang Province. ＂Previously, getting administrative ap...WANG Xianlong didn＇t expect it would take only five working days to register his business, an outdoor products company based in Yiwu, a city in east China＇s Zhejiang Province. ＂Previously, getting administrative approval used to take at least three weeks.＂ Wang said. ＂1 would have to go back and forth between several government departments. But now, the Yiwu Administration Service Center offers a onestop service for enterprises. It＇s much faster.＂展开更多
Bathed in the golden light of September,Beijing’s Shougang Park hosted the 2025 China International Fair for Trade in Services(CIFTIS).At the heart of the event,a dynamic spirit of renewal was evident,as emerging pat...Bathed in the golden light of September,Beijing’s Shougang Park hosted the 2025 China International Fair for Trade in Services(CIFTIS).At the heart of the event,a dynamic spirit of renewal was evident,as emerging patterns in cultural,tourism,and sports consumption unfolded throughout the fair.From the creative integration of the centuries-old Peking Opera with innovative business models,to immersive sports experiences and the rollout of streamlined tax refund procedures for international visitors,the fair showcased a nuanced yet significant shift in consumption practices.展开更多
Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider...Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider bridge decks and larger aspect ratios(B/D).To obtain more effective and aerodynamic design shapes for streamlined box girders,it is essential to investigate the impact of B/D on their aerodynamic performance.Accordingly,in this study we investigate the buffeting responses of large-span suspension bridges using girders of varying aspect ratios(B/D of 7.5,9.3,and 12.7).First,the aerodynamic coefficients of these girders are estimated using computational fluid dynamics(CFD)simulations.Subsequently,spatial finite element(FE)models of three long-span suspension bridges with different girders(B/D of 7.5,9.3,and 12.7)are established in Ansys software,and the dynamic characteristics of these bridges are obtained.Then,the time-domain buffeting analysis is performed by simulating the fluctuating wind fields acting on the bridge through the spectral representation method.Ultimately,the buffeting responses are computed using Ansys software,and the impact of B/D on these responses is assessed.The results reveal that the root mean square(RMS)values of the main girder’s buffeting displacement are highest at the midspan position and are lowest at the ends of the bridge.A decrease in B/D of the main girder leads to a more severe buffeting response because both the range and the effective value of the displacement increase with the decreasing B/D.Comparing the buffeting displacements in three directions,B/D plays a significant role in the vertical buffeting displacement,moderately impacts the torsional displacement,and has the least effect on the lateral displacement.The findings of this study may help wind resistance analysis and design optimization for bridges.展开更多
The unsteady magnetohydrodynamical(MHD)free convection flow of an incompressible,electrically conducting hybrid nanofluid within a vertical cylindrical geometry is investigated,incorporating the effects of thermal rad...The unsteady magnetohydrodynamical(MHD)free convection flow of an incompressible,electrically conducting hybrid nanofluid within a vertical cylindrical geometry is investigated,incorporating the effects of thermal radiation,viscous dissipation,and internal heat generation.The system is subjected to a time-periodic boundary temperature condition.The Laplace and finite Hankel transforms are used to derive the exact solutions for the velocity and temperature distributions.The effects of various key physical parameters,including the Richardson number,the Eckert number,the radiation parameter,the heat source parameter,and the nanoparticle volume fraction,are considered.The numerical results reveal that increasing the volume fraction significantly enhances the thermal conductivity and temperature,while the magnetic field intensity and viscous dissipation strongly influence the fluid motion and heat transport.Additionally,the pulsating boundary conditions produce distinct oscillatory behaviors in both the velocity and temperature fields.These findings provide important insights into optimizing the heat transfer performance in cylindrical systems such as electronic cooling modules and energy storage devices operating under dynamic thermal conditions.展开更多
AIM:To evaluate the one-year clinical outcomes of a novel canaloplasty device used in combination with cataract extraction(CE)in patients with mild to severe open angle glaucoma(OAG).METHODS:This study reviewed patien...AIM:To evaluate the one-year clinical outcomes of a novel canaloplasty device used in combination with cataract extraction(CE)in patients with mild to severe open angle glaucoma(OAG).METHODS:This study reviewed patients diagnosed with mild to severe OAG,who underwent canaloplasty with the STREAMLINE®Surgical System combined with CE.The primary outcome was surgical success,defined as achieving≥20%intraocular pressure(IOP)reduction and/or a reduction of≥1 glaucoma medication compared to baseline.Secondary outcomes included mean IOP,average number of glaucoma medications,and best-corrected distance visual acuity(BCDVA).Data was collected preoperatively and at multiple postoperative time points up to one year.RESULTS:A total of 68 eyes of 47 patients were included with mean age was 73.1±7.0y and 60%were females.Surgical success at one year was achieved in 68.8%of eyes,with 67.6%success in mild,80.0%in moderate,and 66.7%in severe OAG cases.IOP was significantly reduced from a baseline of 16.1±0.5 to 14.7±0.4 mm Hg at one year(P=0.0004).The number of medications decreased significantly in all eyes from a baseline of 1.2±0.1 to 0.6±0.1 at one year(P<0.0001).When stratified by glaucoma severity,only the mild group experienced a statistically significant decrease from a baseline of 1.1±0.1 to 0.4±0.1(P<0.0001).BCDVA improved significantly from baseline to one year.No sight-threatening complications were reported.CONCLUSION:Canaloplasty using the STREAMLINE®surgical system combined with CE effectively reduces IOP at one year in mild to severe OAG with minimal complications.IOP lowering efficacy,reduction in IOP lowering medications,and safety in moderate to severe OAG require further study.展开更多
Using the satellite altimeter data from 1993 to 2021,this study investigates the seasonal and interannual variations of Kuroshio surface water intrusion into the East China Sea(ECS)with an emphasis on transports acros...Using the satellite altimeter data from 1993 to 2021,this study investigates the seasonal and interannual variations of Kuroshio surface water intrusion into the East China Sea(ECS)with an emphasis on transports across different isobaths.The results reveal that the intrusion variability differs among the isobaths used to identify the intrusion.On the seasonal scale,the transport volume and proportion of intrusion into the outer shelf(across 200 m isobath)are greatest in spring compared to other seasons possibly because of the relief of northerly monsoon and the increase of Kuroshio transport.However,in the inner shelf regions(across 100 m isobath),the strongest intrusion occurs in summer,with a much longer residence period and broader spatial range,though the Kuroshio moves farthest away from the coast.This implies that the Kuroshio may have the highest exchange efficiency with the ECS shelf water during summer.On the interannual scale,increased upstream transport from the Kuroshio and shoreward movement of the current almost equally contribute to the enhancement of surface water intrusion into the outer shelf regions.In contrast to the seasonal characteristics,the interannual intrusion into the shallower shelf regions(across the 120 m and 100 m isobaths)is primarily correlated to the position of the Kuroshio axis,i.e.,the closer to the coast the Kuroshio is,the more water can enter the inner continental shelf.This result highlights that the importance of factors that control the intrusion variabilities may also change between seasonal and interannual time scales when different isobaths are used.展开更多
Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing ex...Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing excellent petrophysical properties,such as high porosity and permeability,these reservoirs typically exhibit a notably low recovery factor,sometimes falling below 10%.Previous research has indicated that various enhanced oil recovery(EOR)methods,such as water alternating gas(WAG),can substantially augment the recovery factor in pre-salt reservoirs,resulting in improvements of up to 20%.Nevertheless,the fluid flow mechanism within Brazilian carbonate reservoirs,characterized by complex pore geometry,remains unclear.Our study examines the behavior of fluid flow in a similar heterogeneous porous material,utilizing a plug sample obtained from a vugular segment of a Brazilian stromatolite outcrop,known to share analogies with certain pre-salt reservoirs.We conducted single-phase and multi-phase core flooding experiments,complemented by medical-CT scanning,to generate flow streamlines and evaluate the efficiency of water flooding.Subsequently,micro-CT scanning of the core sample was performed,and two cross-sections from horizontal and vertical plates were constructed.These cross-sections were then employed as geometries in a numerical simulator,enabling us to investigate the impact of pore geometry on fluid flow.Analysis of the pore-scale modeling and experimental data unveiled that the presence of dead-end pores and vugs results in a significant portion of the fluid remaining stagnant within these regions.Consequently,the injected fluid exhibits channeling-like behavior,leading to rapid breakthrough and low areal swept efficiency.Additionally,the numerical simulation results demonstrated that,irrespective of the size of the dead-end regions,the pressure variation within the dead-end vugs and pores is negligible.Despite the stromatolite's favorable petrophysical properties,including relatively high porosity and permeability,as well as the presence of interconnected large vugs,the recovery factor during water flooding remained low due to early breakthrough.These findings align with field data obtained from pre-salt reservoirs,providing an explanation for the observed low recovery factor during water flooding in such reservoirs.展开更多
Purpose – The volume of passenger traffic at metro transfer stations serves as a pivotal metric for theorchestration of crowd flow management. Given the intricacies of crowd dynamics within these stations andthe recu...Purpose – The volume of passenger traffic at metro transfer stations serves as a pivotal metric for theorchestration of crowd flow management. Given the intricacies of crowd dynamics within these stations andthe recurrent instances of substantial passenger influxes, a methodology predicated on stochastic processesand the principle of user equilibrium is introduced to facilitate real-time traffic flow estimation within transferstation streamlines.Design/methodology/approach – The synthesis of stochastic process theory with streamline analysisengenders a probabilistic model of intra-station pedestrian traffic dynamics. Leveraging real-time passengerflow data procured from monitoring systems within the transfer station, a gradient descent optimizationtechnique is employed to minimize the cost function, thereby deducing the dynamic distribution of categorizedpassenger flows. Subsequently, adhering to the tenets of user equilibrium, the Frank–Wolfe algorithm isimplemented to allocate the intra-station categorized passenger flows across various streamlines, ascertainingthe traffic volume for each.Findings – Utilizing the Xiaozhai Station of the Xi’an Metro as a case study, the Anylogic simulation softwareis engaged to emulate the intra-station crowd dynamics, thereby substantiating the efficacy of the proposedpassenger flow estimation model. The derived solutions are instrumental in formulating a crowd controlstrategy for Xiaozhai Station during the peak interval from 17:30 to 18:00 on a designated day, yielding crowdmanagement interventions that offer insights for the orchestration of passenger flow and operationalgovernance within metro stations.Originality/value – The construction of an estimation methodology for the real-time streamline traffic flowaugments the model’s dataset, supplanting estimated values derived from surveys or historical datasets withreal-time computed traffic data, thereby enhancing the precision and immediacy of crowd flow managementwithin metro stations.展开更多
This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re ...This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re = 900. Three-dimensional streamlines and limiting streamlines on wall surface are used to analyze the three-dimensional flow characteristics. Topological theory is applied to limiting streamlines on inner walls of the channel and two-dimensional streamlines at several cross sections. It is also shown that the flow impinges on the end wall of turn and the secondary flow is induced by the curvature in the sharp turn.展开更多
R-phycoerythrin, a light-harvesting protein in some marine algae, and can be widely used in medicine, was isolated and purified from a red alga, Palmaria palmata (Lannaeus) Kuntze, using the streamline column (expande...R-phycoerythrin, a light-harvesting protein in some marine algae, and can be widely used in medicine, was isolated and purified from a red alga, Palmaria palmata (Lannaeus) Kuntze, using the streamline column (expanded bed adsorption) combined with ion-exchange chromatography. Because the crude extract was applied to the column upwardly, the column would not be blocked by polysaccharides usually very abundant in the extract of marine alga, this kind of blockage could hardly lie overcome in ordinary chromatographic column. After applying the crude extract containing 0.5 mol/L (NH4)(2)SO4, (NH4)(2)SO4 solution of different concentrations (0.2 mol/L, 0.1 mol/L and 0.05 mol/L) was used to elute the column downwardly and the eluates were collected and desalted. The desalted eluates were then applied onto all ion-exchange chromatographic column loaded with Q-sepharose for further purification of the R-phycoerythrin. Through these two steps, the purity (OD565/OD280) of the R-phycoerythrin from P. palmata was up to 3.5, more than 3.2, the commonly accepted criterion for purity, and the yield of the purified R-phycoerythrin could reach 0.122 mg/g of frozen P. palmata, much higher than that of phycobiliproteins purified with the previous methods. The result indicated that the cost of R-phycoerythrin will drop down with the method reported in this article.展开更多
Gyrnnarchus niloticus swims by undulations of a long-based dorsal fin, while its body axis is in many cases held straight during swimming. This paper provides a brief relevant introduction to Gyrnnarchus niloticus, wh...Gyrnnarchus niloticus swims by undulations of a long-based dorsal fin, while its body axis is in many cases held straight during swimming. This paper provides a brief relevant introduction to Gyrnnarchus niloticus, which belongs to the African freshwater electric eels but can inspire our bionic interests in propulsion besides its abilities in electric sensing. A special larva of Gyrnnarchus niloticus was morphologically measured by photographing it with a piece of scale-calibrated paper as the background. Then we analyzed the data by a CFD-aided approach. Detailed flow patterns around the larva and a NACA0012 hydrofoil were respectively calculated and visualized at the Reynolds number of 7350 or so. The results show that the profile of Gyrnnarchus niloticus is well streamlined.展开更多
基金Project(2020YFA0710901)supported by the National Key Research and Development Program of ChinaProject(2023JJ30643)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(12372204)supported by the National Natural Science Foundation of ChinaProject(2022ZZTS0725)supported by the Self-exploration and Innovation Project for Postgraduates of Central South University,China。
文摘The complex structure of the bottom of a high-speed train is an important source of train aerodynamic drag.Thus,improving the bottom structure is of great significance to reduce the aerodynamic drag of the train.In this study,computational fluid dynamics(CFD)based on three-dimensional steady incompressible Reynolds-average Naiver-Stokes(RANS)equations and Realizable k-εturbulence model were utilized for numerical simulations.Inspired by the concept of streamlined design and the idea of bottom flow field control,this study iteratively designed the bogies in a streamlined shape and combined them with the bottom deflectors to investigate the joint drag reduction mechanism.Three models,i.e.,single-bogie model,simplified train model,and eight-car high-speed train model,were created and their aerodynamic characteristics were analyzed.The results show that the single-bogie model with streamlined design shows a noticeable drag reduction,whose power bogie and trailer bogie experience 13.92%and 7.63%drag reduction,respectively.The range of positive pressure area on the bogie is reduced.The aerodynamic drag can be further reduced to 15.01%by installing both the streamlined bogie and the deflector on the simplified train model.When the streamlined bogies and deflectors are used on the eight-car model together,the total drag reduction rate reaches 2.90%.Therefore,the proposed aerodynamic kit for the high-speed train bottom is capable to improve the flow structure around the bogie regions,reduce the bottom flow velocity,and narrow the scope of the train’s influence on the surrounding environment,achieving the appreciable reduction of aerodynamic drag.This paper can provide a new idea for the drag reduction of high-speed trains.
基金supported by the National Natural Science Foundation of China(No.12372049)the Sichuan Science and Technology Program(No.2023JDRC0062)+1 种基金the Independent Project of State Key Laboratory of Rail Transit Vehicle System(No.2023TPL-T06)the Fundamental Research Funds for the Central Universities,China(No.2682023ZTPY036).
文摘The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed trains.An appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind circumstances.In this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence model.The different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 m.In order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the literature.Numerical simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on results.The impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure distributions.In comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic resistance.Additionally,the lift forces on the head and tail cars increased by 35.7%and 75.5%,respectively.On the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic drag.Furthermore,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,respectively.The aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.
基金supported by Sichuan Science and Technology Program(No.2019YJ0227)China Postdoctoral Science Foundation(No.2019M663550)+1 种基金National Natural Science Foundation of China(No.51605397)Science and Technolgoy program of China Railway Group Limited(No.2018-S-02).
文摘The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train.For this reason,evacuated tube trains(ETT)are being considered as valid alternatives to be implemented in the future.The atmosphere in the tube,the so-called blocking ratio and the length of the streamlined nose are the key factors affecting the aerodynamic performances of these trains.In the present work,we investigate evacuated tube trains with different lengths of the streamline nose on the basis of computational fluid dynamics(CFD).The three-dimensional steady compressible Navier-Stokes equations are solved.The running speed of the ETT is 800 km/h and the blocking ratio is 0.2.Results show that with the increase of the streamlined nose length,the aerodynamic drag and lift forces of the head car decrease gradually,and the drag and lift forces of the middle car change slightly.For the tail car,the drag force decreases,whereas the absolute value of the lift force increases.At a speed of 800 km/h,a slight shock wave appears at the rear of the tail car,which affects the aerodynamic forces acting on the train.
基金supported by the National Key R&D Program of China(Nos.2020YFA0710902 and 2018YFB1201603-12)the National Natural Science Foundation of China(No.12172308)+1 种基金the Sichuan Provincial Science and Technology Program of China(No.2019YJ0227)the Foundation of the State Key Laboratory of Traction Power of China(No.2019TPL_T02)。
文摘With continuous changes to energy-saving requirements,the task of train aerodynamic optimization becomes important.Traditional aerodynamic optimization of a high-speed train is carried out assuming the same shape of the head and tail cars,which ignores the combined effect of the two cars on aerodynamic forces.The streamlined structure of the train has different effects on the aerodynamics of the head and tail cars.In-depth study of these effects will help engineers improve their shape design capabilities.Based on the surrogate model method,this paper studies the influence of five shape parameters of the streamlined area on the resistance of the head and tail cars and the lift force of the tail car of CRH380A,and compares the aerodynamic performance of the two optimization schemes.The research results show that the optimization direction for reducing drag of the head car is opposite to that for reducing the drag and lift of the tail car,while the optimization directions for reducing both drag and lift for the tail car alone,are roughly the same.Therefore,the same shaped head and tail cars are problematic for improving aerodynamic performance.After optimization,the head car’s resistance,the tail car’s resistance,and the tail car’s lift of the train with the same shape of head and tail cars are reduced by 1.7%,0.5%,and 3.5%,respectively.The train with different shapes had values decreased by 5.6%,1.4%,and 7.5%,respectively.The optimization effect of the latter is more than twice that of the former.
基金supported by the National Natural Science Foundation of China (No. 51375227)the Introduction of Talent Research Start-up Fund of Nanjing Institute of Technology(No. YKJ201960).
文摘Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis during blood delivery.In this paper,a new valveless piezoelectric(PZT)pump with streamlined flow tubes(streamlined pump)is proposed.The design method and the working principle of the pump are analyzed.The velocity streamlines are simulated,and the results demonstrate that there are no obvious vortexes in the flow tube of the streamlined pump.Five prototype pumps(two cone pumps and three streamlined pumps)are designed and fabricated to perform flow rate and flow resistance experiments.The experimental results illustrate that the maximum flow rate of the streamlined pump is 142 mL/min,which is 179%higher than that of the cone piezoelectric pump,demonstrating that the streamlined pump has a large flow rate performance.This research provides an inspiration for future research on simple structure,low vortex and large flow rate volume-type pumps,and also provides a useful solution for thrombosis preventing.
文摘In foundries a lot of effort is done to minimize energy consumption in the production to reduce costs and hence increase the competitiveness. At the same time the foundries must live up to the increased demands for high quality castings. Traditional gating systems are known for a straight tapered down runner, a well base and 90° bends in the runner system. Previous work has shown that the traditional way of designing gating systems creates high inconsistency in flow patterns during filling. In the streamlined gating systems there are no sharp changes in direction and a large effort is done to confine and control the flow of the molten metal during mould filling. The main objective in the work presented here is to use the principles of the streamlined gating systems to reduce the weight of the gating system relative to the traditional layouts. By reducing the weight of gating system and thereby improving yield, the amount of molten iron needed is also reduced, hence reducing the energy consumption for melting. Experiments in real production lines have proven that it is possible to achieve a reduction in the poured weight by using the streamlined gating systems. In a layout for casting of three valve housings in a vertically parted mould the weight of the gating system was reduced by 1.1 kg changing from the traditional layouts to the streamlined gating systems. This weight reduction corresponds in this case to a 20% weight reduction for the gating system. Using streamlined gating systems with fan gates to give a beneficial heat distribution in the castings may be an efficient tool to eliminate the need for heat treatment. In the experiments the change in gating system from the traditional layout to the streamlined layout removed the need for heat treatment. This obviously means a huge energy saving in the foundry. The energy consumption for heat treatment of iron has been found to be 0.489 kWh/ kg. The valve housing in the experiments weighs 3 kg so when the need for heat treatment is removed, around 1.5 kWh is saved per casting. Along with the reduction in energy used the foundry also save the cost of handling the castings for the heat treatment and the production times is reduced considerably When the moulds for the vertical layout is produced on a DISAMATIC that produces 350 moulds an hour the total energy saved per hour for both melting and heat treatment becomes 2,000 kWh and per eight hour work day 16,000 kWh. Seen in this perspective the potential for saving energy in the foundries is substantial. Furthermore the experiments where ductile iron valve housings was cast also proved that it is possible to lower the pouring temperature from 1,400℃ to 1,300℃ without the risk of cold runs. This is possible due to a high flow rate during mould filling in combination with low velocities due to the use of fan gates. All of this has also been investigated in experiments using glass plate fronted moulds.
文摘WANG Xianlong didn＇t expect it would take only five working days to register his business, an outdoor products company based in Yiwu, a city in east China＇s Zhejiang Province. ＂Previously, getting administrative approval used to take at least three weeks.＂ Wang said. ＂1 would have to go back and forth between several government departments. But now, the Yiwu Administration Service Center offers a onestop service for enterprises. It＇s much faster.＂
文摘Bathed in the golden light of September,Beijing’s Shougang Park hosted the 2025 China International Fair for Trade in Services(CIFTIS).At the heart of the event,a dynamic spirit of renewal was evident,as emerging patterns in cultural,tourism,and sports consumption unfolded throughout the fair.From the creative integration of the centuries-old Peking Opera with innovative business models,to immersive sports experiences and the rollout of streamlined tax refund procedures for international visitors,the fair showcased a nuanced yet significant shift in consumption practices.
基金funded by the National Natural Science Foundation of China(Grant No.52108435)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202404320)+1 种基金Chongqing Jiaotong University Postgraduate Research and Innovation Project(2024S0013)Chongqing Jiaotong University Undergraduate Innovation and Entrepreneurship Project(S202410618019).
文摘Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider bridge decks and larger aspect ratios(B/D).To obtain more effective and aerodynamic design shapes for streamlined box girders,it is essential to investigate the impact of B/D on their aerodynamic performance.Accordingly,in this study we investigate the buffeting responses of large-span suspension bridges using girders of varying aspect ratios(B/D of 7.5,9.3,and 12.7).First,the aerodynamic coefficients of these girders are estimated using computational fluid dynamics(CFD)simulations.Subsequently,spatial finite element(FE)models of three long-span suspension bridges with different girders(B/D of 7.5,9.3,and 12.7)are established in Ansys software,and the dynamic characteristics of these bridges are obtained.Then,the time-domain buffeting analysis is performed by simulating the fluctuating wind fields acting on the bridge through the spectral representation method.Ultimately,the buffeting responses are computed using Ansys software,and the impact of B/D on these responses is assessed.The results reveal that the root mean square(RMS)values of the main girder’s buffeting displacement are highest at the midspan position and are lowest at the ends of the bridge.A decrease in B/D of the main girder leads to a more severe buffeting response because both the range and the effective value of the displacement increase with the decreasing B/D.Comparing the buffeting displacements in three directions,B/D plays a significant role in the vertical buffeting displacement,moderately impacts the torsional displacement,and has the least effect on the lateral displacement.The findings of this study may help wind resistance analysis and design optimization for bridges.
基金Project supported by the National Natural Science Foundation of China(No.12250410244)the Jiangsu Funding Program for Excellent Postdoctoral Talent of China(No.2023ZB884)+2 种基金the Foreign Expert Project funding of China(No.WGXZ2023017L)the Shuang-Chuang(SC)Doctor Program of Jiangsu Provincethe Longshan Scholar Program of Nanjing University of Information Science&Technology。
文摘The unsteady magnetohydrodynamical(MHD)free convection flow of an incompressible,electrically conducting hybrid nanofluid within a vertical cylindrical geometry is investigated,incorporating the effects of thermal radiation,viscous dissipation,and internal heat generation.The system is subjected to a time-periodic boundary temperature condition.The Laplace and finite Hankel transforms are used to derive the exact solutions for the velocity and temperature distributions.The effects of various key physical parameters,including the Richardson number,the Eckert number,the radiation parameter,the heat source parameter,and the nanoparticle volume fraction,are considered.The numerical results reveal that increasing the volume fraction significantly enhances the thermal conductivity and temperature,while the magnetic field intensity and viscous dissipation strongly influence the fluid motion and heat transport.Additionally,the pulsating boundary conditions produce distinct oscillatory behaviors in both the velocity and temperature fields.These findings provide important insights into optimizing the heat transfer performance in cylindrical systems such as electronic cooling modules and energy storage devices operating under dynamic thermal conditions.
文摘AIM:To evaluate the one-year clinical outcomes of a novel canaloplasty device used in combination with cataract extraction(CE)in patients with mild to severe open angle glaucoma(OAG).METHODS:This study reviewed patients diagnosed with mild to severe OAG,who underwent canaloplasty with the STREAMLINE®Surgical System combined with CE.The primary outcome was surgical success,defined as achieving≥20%intraocular pressure(IOP)reduction and/or a reduction of≥1 glaucoma medication compared to baseline.Secondary outcomes included mean IOP,average number of glaucoma medications,and best-corrected distance visual acuity(BCDVA).Data was collected preoperatively and at multiple postoperative time points up to one year.RESULTS:A total of 68 eyes of 47 patients were included with mean age was 73.1±7.0y and 60%were females.Surgical success at one year was achieved in 68.8%of eyes,with 67.6%success in mild,80.0%in moderate,and 66.7%in severe OAG cases.IOP was significantly reduced from a baseline of 16.1±0.5 to 14.7±0.4 mm Hg at one year(P=0.0004).The number of medications decreased significantly in all eyes from a baseline of 1.2±0.1 to 0.6±0.1 at one year(P<0.0001).When stratified by glaucoma severity,only the mild group experienced a statistically significant decrease from a baseline of 1.1±0.1 to 0.4±0.1(P<0.0001).BCDVA improved significantly from baseline to one year.No sight-threatening complications were reported.CONCLUSION:Canaloplasty using the STREAMLINE®surgical system combined with CE effectively reduces IOP at one year in mild to severe OAG with minimal complications.IOP lowering efficacy,reduction in IOP lowering medications,and safety in moderate to severe OAG require further study.
基金The National Natural Science Foundation of China under contract No.42276003the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University under contract No.SL2021MS021.
文摘Using the satellite altimeter data from 1993 to 2021,this study investigates the seasonal and interannual variations of Kuroshio surface water intrusion into the East China Sea(ECS)with an emphasis on transports across different isobaths.The results reveal that the intrusion variability differs among the isobaths used to identify the intrusion.On the seasonal scale,the transport volume and proportion of intrusion into the outer shelf(across 200 m isobath)are greatest in spring compared to other seasons possibly because of the relief of northerly monsoon and the increase of Kuroshio transport.However,in the inner shelf regions(across 100 m isobath),the strongest intrusion occurs in summer,with a much longer residence period and broader spatial range,though the Kuroshio moves farthest away from the coast.This implies that the Kuroshio may have the highest exchange efficiency with the ECS shelf water during summer.On the interannual scale,increased upstream transport from the Kuroshio and shoreward movement of the current almost equally contribute to the enhancement of surface water intrusion into the outer shelf regions.In contrast to the seasonal characteristics,the interannual intrusion into the shallower shelf regions(across the 120 m and 100 m isobaths)is primarily correlated to the position of the Kuroshio axis,i.e.,the closer to the coast the Kuroshio is,the more water can enter the inner continental shelf.This result highlights that the importance of factors that control the intrusion variabilities may also change between seasonal and interannual time scales when different isobaths are used.
基金the support of EPIC-Energy Production Innovation Center,hosted by the University of Campinas(UNICAMP)sponsored by FAPESP-Sao Paulo Research Foundation(2017/15736e3 process).
文摘Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing excellent petrophysical properties,such as high porosity and permeability,these reservoirs typically exhibit a notably low recovery factor,sometimes falling below 10%.Previous research has indicated that various enhanced oil recovery(EOR)methods,such as water alternating gas(WAG),can substantially augment the recovery factor in pre-salt reservoirs,resulting in improvements of up to 20%.Nevertheless,the fluid flow mechanism within Brazilian carbonate reservoirs,characterized by complex pore geometry,remains unclear.Our study examines the behavior of fluid flow in a similar heterogeneous porous material,utilizing a plug sample obtained from a vugular segment of a Brazilian stromatolite outcrop,known to share analogies with certain pre-salt reservoirs.We conducted single-phase and multi-phase core flooding experiments,complemented by medical-CT scanning,to generate flow streamlines and evaluate the efficiency of water flooding.Subsequently,micro-CT scanning of the core sample was performed,and two cross-sections from horizontal and vertical plates were constructed.These cross-sections were then employed as geometries in a numerical simulator,enabling us to investigate the impact of pore geometry on fluid flow.Analysis of the pore-scale modeling and experimental data unveiled that the presence of dead-end pores and vugs results in a significant portion of the fluid remaining stagnant within these regions.Consequently,the injected fluid exhibits channeling-like behavior,leading to rapid breakthrough and low areal swept efficiency.Additionally,the numerical simulation results demonstrated that,irrespective of the size of the dead-end regions,the pressure variation within the dead-end vugs and pores is negligible.Despite the stromatolite's favorable petrophysical properties,including relatively high porosity and permeability,as well as the presence of interconnected large vugs,the recovery factor during water flooding remained low due to early breakthrough.These findings align with field data obtained from pre-salt reservoirs,providing an explanation for the observed low recovery factor during water flooding in such reservoirs.
文摘Purpose – The volume of passenger traffic at metro transfer stations serves as a pivotal metric for theorchestration of crowd flow management. Given the intricacies of crowd dynamics within these stations andthe recurrent instances of substantial passenger influxes, a methodology predicated on stochastic processesand the principle of user equilibrium is introduced to facilitate real-time traffic flow estimation within transferstation streamlines.Design/methodology/approach – The synthesis of stochastic process theory with streamline analysisengenders a probabilistic model of intra-station pedestrian traffic dynamics. Leveraging real-time passengerflow data procured from monitoring systems within the transfer station, a gradient descent optimizationtechnique is employed to minimize the cost function, thereby deducing the dynamic distribution of categorizedpassenger flows. Subsequently, adhering to the tenets of user equilibrium, the Frank–Wolfe algorithm isimplemented to allocate the intra-station categorized passenger flows across various streamlines, ascertainingthe traffic volume for each.Findings – Utilizing the Xiaozhai Station of the Xi’an Metro as a case study, the Anylogic simulation softwareis engaged to emulate the intra-station crowd dynamics, thereby substantiating the efficacy of the proposedpassenger flow estimation model. The derived solutions are instrumental in formulating a crowd controlstrategy for Xiaozhai Station during the peak interval from 17:30 to 18:00 on a designated day, yielding crowdmanagement interventions that offer insights for the orchestration of passenger flow and operationalgovernance within metro stations.Originality/value – The construction of an estimation methodology for the real-time streamline traffic flowaugments the model’s dataset, supplanting estimated values derived from surveys or historical datasets withreal-time computed traffic data, thereby enhancing the precision and immediacy of crowd flow managementwithin metro stations.
文摘This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re = 900. Three-dimensional streamlines and limiting streamlines on wall surface are used to analyze the three-dimensional flow characteristics. Topological theory is applied to limiting streamlines on inner walls of the channel and two-dimensional streamlines at several cross sections. It is also shown that the flow impinges on the end wall of turn and the secondary flow is induced by the curvature in the sharp turn.
文摘R-phycoerythrin, a light-harvesting protein in some marine algae, and can be widely used in medicine, was isolated and purified from a red alga, Palmaria palmata (Lannaeus) Kuntze, using the streamline column (expanded bed adsorption) combined with ion-exchange chromatography. Because the crude extract was applied to the column upwardly, the column would not be blocked by polysaccharides usually very abundant in the extract of marine alga, this kind of blockage could hardly lie overcome in ordinary chromatographic column. After applying the crude extract containing 0.5 mol/L (NH4)(2)SO4, (NH4)(2)SO4 solution of different concentrations (0.2 mol/L, 0.1 mol/L and 0.05 mol/L) was used to elute the column downwardly and the eluates were collected and desalted. The desalted eluates were then applied onto all ion-exchange chromatographic column loaded with Q-sepharose for further purification of the R-phycoerythrin. Through these two steps, the purity (OD565/OD280) of the R-phycoerythrin from P. palmata was up to 3.5, more than 3.2, the commonly accepted criterion for purity, and the yield of the purified R-phycoerythrin could reach 0.122 mg/g of frozen P. palmata, much higher than that of phycobiliproteins purified with the previous methods. The result indicated that the cost of R-phycoerythrin will drop down with the method reported in this article.
文摘Gyrnnarchus niloticus swims by undulations of a long-based dorsal fin, while its body axis is in many cases held straight during swimming. This paper provides a brief relevant introduction to Gyrnnarchus niloticus, which belongs to the African freshwater electric eels but can inspire our bionic interests in propulsion besides its abilities in electric sensing. A special larva of Gyrnnarchus niloticus was morphologically measured by photographing it with a piece of scale-calibrated paper as the background. Then we analyzed the data by a CFD-aided approach. Detailed flow patterns around the larva and a NACA0012 hydrofoil were respectively calculated and visualized at the Reynolds number of 7350 or so. The results show that the profile of Gyrnnarchus niloticus is well streamlined.
