In recent decades,control performance monitoring(CPM)has experienced remarkable progress in research and industrial applications.While CPM research has been investigated using various benchmarks,the historical data be...In recent decades,control performance monitoring(CPM)has experienced remarkable progress in research and industrial applications.While CPM research has been investigated using various benchmarks,the historical data benchmark(HIS)has garnered the most attention due to its practicality and effectiveness.However,existing CPM reviews usually focus on the theoretical benchmark,and there is a lack of an in-depth review that thoroughly explores HIS-based methods.In this article,a comprehensive overview of HIS-based CPM is provided.First,we provide a novel static-dynamic perspective on data-level manifestations of control performance underlying typical controller capacities including regulation and servo:static and dynamic properties.The static property portrays time-independent variability in system output,and the dynamic property describes temporal behavior driven by closed-loop feedback.Accordingly,existing HIS-based CPM approaches and their intrinsic motivations are classified and analyzed from these two perspectives.Specifically,two mainstream solutions for CPM methods are summarized,including static analysis and dynamic analysis,which match data-driven techniques with actual controlling behavior.Furthermore,this paper also points out various opportunities and challenges faced in CPM for modern industry and provides promising directions in the context of artificial intelligence for inspiring future research.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
The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and propos...The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and proposed a co-simulation(CS)approach between computational fluid dynamics and multi-body dynamics.Firstly,the aerodynamic model was developed by employing overset mesh technology and the finite volume method,and the detailed train-track coupled dynamic model was established.Then the User Data Protocol was adopted to build data communication channels.Moreover,the proposed CS method was validated by comparison with a reported field test result.Finally,a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation(OS)methods.In terms of the presented case,the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar.Differences mainly lie in aerodynamic moments and transient wheel-rail impacts.Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m,respectively.And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS.Wheel-rail safety indices obtained by CS are slightly greater than those by OS.This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios,which has superiority in computational efficiency and stability.展开更多
The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ...The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ships.This paper investigated the hydrodynamic performance of a KRISO container ship in steady turning using experimental and numerical approaches.The rotating arm tests were carried out in rotating arm basin of Zhejiang University,while the numerical simulations were conducted in commercial computational fluid dynamics software.Hydrodynamic forces and moments,hull surface wave height,wave patterns,and vorticity are studied under different velocities,radii,and drift angles.The results show that the increase in velocity has a significant impact on the forces and moments of the hull.The changes in longitudinal and transverse forces reflect the complex fluid dynamic interactions between the hull and water.Under conditions of small radius and large drift angle,the hull experiences greater forces and moments,indicating that stability and maneuverability will be more challenged during sudden turns.This study can provide experimental data and numerical simulation references for the research of ship turning maneuvers.展开更多
To meet the intelligent detection needs of underwater defects in large hydropower stations,the hydrodynamic performance of a bionic streamlined remotely operated vehicle containing a thruster protective net structure ...To meet the intelligent detection needs of underwater defects in large hydropower stations,the hydrodynamic performance of a bionic streamlined remotely operated vehicle containing a thruster protective net structure is numerically simulated via computational fluid dynamics and overlapping mesh technology.The results show that the entity model generates greater hydrodynamic force during steady motion,whereas the square net model experiences greater force and moment during unsteady motion.The lateral and vertical force coefficients of the entity model are 4.32 and 3.13 times greater than those of the square net model in the oblique towing test simulation.The square net model also offers better static and dynamic stability,with a 24.5%increase in dynamic stability,achieving the highest lift-to-drag ratio at attack angles of 6°∼8°.This research provides valuable insights for designing and controlling underwater defect detection vehicles for large hydropower stations.展开更多
A novel bidirectional tuned rolling mass damper(Bi-TRMD)device is proposed,and its dynamic character-istics and vibration reduction performance are investigated.The device achieves the performance goal of bidirectiona...A novel bidirectional tuned rolling mass damper(Bi-TRMD)device is proposed,and its dynamic character-istics and vibration reduction performance are investigated.The device achieves the performance goal of bidirectional vibration reduction for a tuned rolling mass damper with a single concave structure.First,the Bi-TRMD device is introduced,and its three-dimensional(3D)mechanical model is established.The motion equations of the model are de-rived using the Gibbs-Appell equation,and a trajectory pre-diction method for the sphere and structure within the model is developed.This method demonstrates that the rolling motion of the sphere around orthogonal axes is nearly indepen-dent within a limited range,enabling the simplification of the 3D model into a two-dimensional(2D)model.The accuracy of this simplification is validated through case analysis.The vibration reduction parameters are optimized using the 2D model and Den Hartog theory,leading to the derivation of mathematical expressions for the optimal frequency ratio and damping ratio.Subsequently,the bidirectional vi-bration reduction performance of the Bi-TRMD is analyzed.The results show that under white noise excitation,the Bi-TRMD achieves a bidirectional peak acceleration reduction rate that is 9.92%and 7.79%higher than that of translational tuned mass dampers(TMD)with the same mass.These findings demonstrate that the proposed Bi-TRMD ef-fectively achieves two-directional vibration reduction with a single concave structure,offering superior vibration reduction performance.展开更多
Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was ...Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.展开更多
The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly ...The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.展开更多
This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators...This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators with different formulations. For this purpose, we used five formulations of Eucommia ulmoides gum isolators and set different fatigue test methods to study the static and dynamic performance changes of Eucommia ulmoides gum isolators with different formulations by changing the amplitude. The experimental results showed that the addition of Eucommia ulmoides gum had an impact on the performance of the isolator, and the number of fatigue cycles would lead to the hardening of the Eucommia ulmoides gum isolator and changes in its static and dynamic performance. In the range of two million vibrations, the performance change of the isolator was significant in the early stage and then tended to be flat, indicating that the impact of fatigue on the performance of the isolator would not continue to persist. It is worth noting that the study found that the addition of 30% Eucommia ulmoides gum had the least impact on the performance of the isolator under fatigue. Therefore, for long-term use of Eucommia ulmoides gum isolators, attention should be paid to their fatigue characteristics to ensure their stability and reliability. Additionally, this study provides a reference for the design and application of Eucommia ulmoides gum isolators. In summary, this study provides important reference value for a deeper understanding of the fatigue characteristics of Eucommia ulmoides gum isolators and for ensuring their stable and reliable performance. .展开更多
The Global-Regional Integrated forecast System(GRIST)is the next-generation weather and climate integrated model dynamic framework developed by Chinese Academy of Meteorological Sciences.In this paper,we present sever...The Global-Regional Integrated forecast System(GRIST)is the next-generation weather and climate integrated model dynamic framework developed by Chinese Academy of Meteorological Sciences.In this paper,we present several changes made to the global nonhydrostatic dynamical(GND)core,which is part of the ongoing prototype of GRIST.The changes leveraging MPI and PnetCDF techniques were targeted at the parallelization and performance optimization to the original serial GND core.Meanwhile,some sophisticated data structures and interfaces were designed to adjust flexibly the size of boundary and halo domains according to the variable accuracy in parallel context.In addition,the I/O performance of PnetCDF decreases as the number of MPI processes increases in our experimental environment.Especially when the number exceeds 6000,it caused system-wide outages(SWO).Thus,a grouping solution was proposed to overcome that issue.Several experiments were carried out on the supercomputing platform based on Intel x86 CPUs in the National Supercomputing Center in Wuxi.The results demonstrated that the parallel GND core based on grouping solution achieves good strong scalability and improves the performance significantly,as well as avoiding the SWOs.展开更多
The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts....The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.展开更多
The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pol...The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.展开更多
A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was...A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was obtained using the particle trajectory model.The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated.The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration.The hydr...展开更多
Static disorder plays a crucial role in the electronic dynamics and spec-troscopy of complex molecular sys-tems.Traditionally,obtaining ob-servables averaged over static disor-der requires thousands of realiza-tions v...Static disorder plays a crucial role in the electronic dynamics and spec-troscopy of complex molecular sys-tems.Traditionally,obtaining ob-servables averaged over static disor-der requires thousands of realiza-tions via direct sampling of the dis-order distribution,leading to high computational costs.In this work,we extend the auxiliary degree-of-freedom based matrix product state(MPS)method to handle system-bath correlated thermal equilibrium initial states,which can capture static disorder effects using a one-shot quantum dynamical simulation.We validate the effectiveness of the extended method by computing the dipole-dipole time correlation function of the Holstein model relevant to the emission spectrum of molecular aggregates.Our results show that the one-shot method is very accu-rate with only a moderate increase in MPS bond dimension,thereby significantly reducing computational cost.Moreover,it enables the generation of a much larger number of samples than the conventional direct sampling method at negligible additional cost,thus reducing sta-tistical errors.This method provides a broadly useful tool for calculating equilibrium time cor-relation functions in system-bath coupled models with static disorder.展开更多
In this paper,a modeling method for a pantograph-catenary system is put forward to investigate the dynamic contact behavior in space,taking into consideration of the appearance characteristics of the contact surfaces ...In this paper,a modeling method for a pantograph-catenary system is put forward to investigate the dynamic contact behavior in space,taking into consideration of the appearance characteristics of the contact surfaces of the pantograph and catenary.The dynamic performance of the pantograph-catenary system,including contact forces,accelerations,and the corresponding spectra,is analyzed.Furthermore,with the modeling method,the influences of contact wire irregularity and the vibration caused by the front pantograph on the rear pantograph for a pantograph-catenary system with double pantographs are investigated.The results show that the appearance characteristics of the contact surfaces play an important role in the dynamic contact behavior.The appearance characteristics should be considered to reasonably evaluate the dynamic performance of the pantograph-catenary system.展开更多
This paper presents a redundantly actuated and over-constrained 2 RPU-2 SPR parallel manipulator with two rotational and one translational coupling degrees of freedom.The kinematics analysis is firstly carried out and...This paper presents a redundantly actuated and over-constrained 2 RPU-2 SPR parallel manipulator with two rotational and one translational coupling degrees of freedom.The kinematics analysis is firstly carried out and the mapping relationship of the velocity,acceleration and the independent parameters between the actuator joint and the moving platform are deduced by using the vector dot product and cross product operation.By employing d′Alembert′s principle and the principle of virtual work,the dynamics equilibrium equation is derived,and the simplified dynamics mathematical model of the parallel manipulator is further derived.Simultaneously,the generalized inertia matrix which can characterize the acceleration performance between joint space and operation space is further separated,and the performance indices including the dynamics dexterity,inertia coupling characteristics,energy transmission efficiency and driving force/torque balance are introduced.The analysis results show that the proposed redundantly actuated and over-constrained 2 RPU-2 SPR parallel manipulator in comparison with the existing non-redundant one has better dynamic comprehensive performance,which can be demonstrated practically by the successful application of the parallel kinematic machine head module of the hybrid machine tool.展开更多
Logistical supply is costly for the deepwater oil and gas exploitation, thereby it is necessary to develop a novel power supply solution to improve the offshore structure’s self-holding capacity. The two-body point a...Logistical supply is costly for the deepwater oil and gas exploitation, thereby it is necessary to develop a novel power supply solution to improve the offshore structure’s self-holding capacity. The two-body point absorbers, as a renewable energy device, have achieved a rapid development. Heave plate is used to constrain the truss’ s motion in the two-body point absorber, and the floater moves along the truss up and down. This two-body point absorber can be considered to be an essentially mass-spring-damper system. And it is well known that the heave plates have been widely used in the Spar platform to suppress the heave motions. So if the two-body point absorber can be modified to combine with offshore floating structures, this system can not only offer electric power to support operations or daily lives for the platform, but also control the large motions in the vertical plane. Following this concept, a novel tuned heave plate(THP) system is proposed for the conventional semi-submersible platform. In order to investigate the dynamic performances of the single THP, two experiments are conducted in this paper. First, the hydrodynamic coefficients of the heave plates are studied, and then the THP experiments are carried out to analyze its dynamic performance. It can be concluded that this THP is feasible and achieves the design objective.展开更多
The main aims of this study are to investigate the hydrodynamic performance of an autonomous underwater vehicle(AUV),calculate its hydrodynamic coefficients,and consider the flow characteristics of underwater bodies.I...The main aims of this study are to investigate the hydrodynamic performance of an autonomous underwater vehicle(AUV),calculate its hydrodynamic coefficients,and consider the flow characteristics of underwater bodies.In addition,three important parts of the SUBOFF bare hull,namely the main body,nose,and tail,are modified and redesigned to improve its hydrodynamic performance.A three-dimensional(3D)simulation is carried out using the computational fluid dynamics(CFD)method.To simulate turbulence,the k-ωshear stress transport(SST)model is employed,due to its good prediction capability at reasonable computational cost.Considering the effects of the length-to-diameter ratio(LTDR)and the nose and tail shapes on the hydrodynamic coefficients,it is concluded that a hull shape with bullet nose and sharp tail with LTDR equal to 7.14 performs better than the SUBOFF model.The final proposed model shows lower drag by about 14.9%at u=1.5 m·s^-1.Moreover,it produces 8 times more lift than the SUBOFF model at u=6.1 m·s^-1.These effects are due to the attachment of the fluid flow at the tail area of the hull,which weakens the wake region.展开更多
Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. Th...Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face?contacting conditions. Structure?Function method is adopted to handle the surface profiles of typical carbon?graphite rings, proving the fractal con?tact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar?Bhushan(MB) fractal model and the Chang?Etsion?Bogy(CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D(nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.展开更多
This paper presents a novel semi-submersible(SEMI) platform concept, called the multiple small columns(MSC) SEMI that improves upon the hydrodynamic performance of the conventional SEMI. Unlike the conventional SEMI, ...This paper presents a novel semi-submersible(SEMI) platform concept, called the multiple small columns(MSC) SEMI that improves upon the hydrodynamic performance of the conventional SEMI. Unlike the conventional SEMI, the proposed MSC SEMI utilizes multiple small circular columns to support the deck and a large pontoon that increases the structural displacement. The novelty of the MSC SEMI is its reduction of the hydrodynamic load on the structure and suppression of its motion response, particularly in the heave direction. The MSC SEMI has the advantages of increasing the added mass, radiation damping, and natural period of the structure. A comprehensive investigation of the hydrodynamic performance of the novel MSC SEMI is conducted in both the time and frequency domains with a special focus on the resulting hydrodynamic load and motion response. Numerical simulation results demonstrate that the MSC SEMI concept can reduce the hydrodynamic load and motion response and improve the hydrodynamic performance of SEMIs as expected.展开更多
基金supported in part by the National Natural Science Foundation of China(62125306)Zhejiang Key Research and Development Project(2024C01163)the State Key Laboratory of Industrial Control Technology,China(ICT2024A06)
文摘In recent decades,control performance monitoring(CPM)has experienced remarkable progress in research and industrial applications.While CPM research has been investigated using various benchmarks,the historical data benchmark(HIS)has garnered the most attention due to its practicality and effectiveness.However,existing CPM reviews usually focus on the theoretical benchmark,and there is a lack of an in-depth review that thoroughly explores HIS-based methods.In this article,a comprehensive overview of HIS-based CPM is provided.First,we provide a novel static-dynamic perspective on data-level manifestations of control performance underlying typical controller capacities including regulation and servo:static and dynamic properties.The static property portrays time-independent variability in system output,and the dynamic property describes temporal behavior driven by closed-loop feedback.Accordingly,existing HIS-based CPM approaches and their intrinsic motivations are classified and analyzed from these two perspectives.Specifically,two mainstream solutions for CPM methods are summarized,including static analysis and dynamic analysis,which match data-driven techniques with actual controlling behavior.Furthermore,this paper also points out various opportunities and challenges faced in CPM for modern industry and provides promising directions in the context of artificial intelligence for inspiring future research.
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Supported by the Sichuan Science and Technology Program(Grant No.2023ZDZX0008)the National Natural Science Foundation of China(Grant No.52388102)the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and proposed a co-simulation(CS)approach between computational fluid dynamics and multi-body dynamics.Firstly,the aerodynamic model was developed by employing overset mesh technology and the finite volume method,and the detailed train-track coupled dynamic model was established.Then the User Data Protocol was adopted to build data communication channels.Moreover,the proposed CS method was validated by comparison with a reported field test result.Finally,a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation(OS)methods.In terms of the presented case,the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar.Differences mainly lie in aerodynamic moments and transient wheel-rail impacts.Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m,respectively.And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS.Wheel-rail safety indices obtained by CS are slightly greater than those by OS.This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios,which has superiority in computational efficiency and stability.
基金supported by the China Scholarship Council(Grant No.202306320084).
文摘The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ships.This paper investigated the hydrodynamic performance of a KRISO container ship in steady turning using experimental and numerical approaches.The rotating arm tests were carried out in rotating arm basin of Zhejiang University,while the numerical simulations were conducted in commercial computational fluid dynamics software.Hydrodynamic forces and moments,hull surface wave height,wave patterns,and vorticity are studied under different velocities,radii,and drift angles.The results show that the increase in velocity has a significant impact on the forces and moments of the hull.The changes in longitudinal and transverse forces reflect the complex fluid dynamic interactions between the hull and water.Under conditions of small radius and large drift angle,the hull experiences greater forces and moments,indicating that stability and maneuverability will be more challenged during sudden turns.This study can provide experimental data and numerical simulation references for the research of ship turning maneuvers.
基金supported by the National Key R&D Program of China(Grant No.2022YFB4703401).
文摘To meet the intelligent detection needs of underwater defects in large hydropower stations,the hydrodynamic performance of a bionic streamlined remotely operated vehicle containing a thruster protective net structure is numerically simulated via computational fluid dynamics and overlapping mesh technology.The results show that the entity model generates greater hydrodynamic force during steady motion,whereas the square net model experiences greater force and moment during unsteady motion.The lateral and vertical force coefficients of the entity model are 4.32 and 3.13 times greater than those of the square net model in the oblique towing test simulation.The square net model also offers better static and dynamic stability,with a 24.5%increase in dynamic stability,achieving the highest lift-to-drag ratio at attack angles of 6°∼8°.This research provides valuable insights for designing and controlling underwater defect detection vehicles for large hydropower stations.
基金The National Key Research and Development Pro-gram of China(No.2022YFC3801201)the National Natural Science Foundation of China(No.51921006,52478505)+1 种基金the Natural Science Foundation of Guangdong Province(No.2022A1515010403)Shenzhen Collaborative Innovation Project(No.CJGJZD20220517142401002).
文摘A novel bidirectional tuned rolling mass damper(Bi-TRMD)device is proposed,and its dynamic character-istics and vibration reduction performance are investigated.The device achieves the performance goal of bidirectional vibration reduction for a tuned rolling mass damper with a single concave structure.First,the Bi-TRMD device is introduced,and its three-dimensional(3D)mechanical model is established.The motion equations of the model are de-rived using the Gibbs-Appell equation,and a trajectory pre-diction method for the sphere and structure within the model is developed.This method demonstrates that the rolling motion of the sphere around orthogonal axes is nearly indepen-dent within a limited range,enabling the simplification of the 3D model into a two-dimensional(2D)model.The accuracy of this simplification is validated through case analysis.The vibration reduction parameters are optimized using the 2D model and Den Hartog theory,leading to the derivation of mathematical expressions for the optimal frequency ratio and damping ratio.Subsequently,the bidirectional vi-bration reduction performance of the Bi-TRMD is analyzed.The results show that under white noise excitation,the Bi-TRMD achieves a bidirectional peak acceleration reduction rate that is 9.92%and 7.79%higher than that of translational tuned mass dampers(TMD)with the same mass.These findings demonstrate that the proposed Bi-TRMD ef-fectively achieves two-directional vibration reduction with a single concave structure,offering superior vibration reduction performance.
文摘Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.
基金Project(KYLX15_0256)supported by the Funding of Jiangsu Innovation Program for Graduate Education,ChinaProject(SV2015-KF-01)supported by the Open Project of State Key Laboratory for Strength and Vibration of Mechanical Structures,ChinaProject(XZA15003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.
文摘This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators with different formulations. For this purpose, we used five formulations of Eucommia ulmoides gum isolators and set different fatigue test methods to study the static and dynamic performance changes of Eucommia ulmoides gum isolators with different formulations by changing the amplitude. The experimental results showed that the addition of Eucommia ulmoides gum had an impact on the performance of the isolator, and the number of fatigue cycles would lead to the hardening of the Eucommia ulmoides gum isolator and changes in its static and dynamic performance. In the range of two million vibrations, the performance change of the isolator was significant in the early stage and then tended to be flat, indicating that the impact of fatigue on the performance of the isolator would not continue to persist. It is worth noting that the study found that the addition of 30% Eucommia ulmoides gum had the least impact on the performance of the isolator under fatigue. Therefore, for long-term use of Eucommia ulmoides gum isolators, attention should be paid to their fatigue characteristics to ensure their stability and reliability. Additionally, this study provides a reference for the design and application of Eucommia ulmoides gum isolators. In summary, this study provides important reference value for a deeper understanding of the fatigue characteristics of Eucommia ulmoides gum isolators and for ensuring their stable and reliable performance. .
基金This work was supported by the National Key Research and Development Program of China under Grant No.2017YFC1502203.
文摘The Global-Regional Integrated forecast System(GRIST)is the next-generation weather and climate integrated model dynamic framework developed by Chinese Academy of Meteorological Sciences.In this paper,we present several changes made to the global nonhydrostatic dynamical(GND)core,which is part of the ongoing prototype of GRIST.The changes leveraging MPI and PnetCDF techniques were targeted at the parallelization and performance optimization to the original serial GND core.Meanwhile,some sophisticated data structures and interfaces were designed to adjust flexibly the size of boundary and halo domains according to the variable accuracy in parallel context.In addition,the I/O performance of PnetCDF decreases as the number of MPI processes increases in our experimental environment.Especially when the number exceeds 6000,it caused system-wide outages(SWO).Thus,a grouping solution was proposed to overcome that issue.Several experiments were carried out on the supercomputing platform based on Intel x86 CPUs in the National Supercomputing Center in Wuxi.The results demonstrated that the parallel GND core based on grouping solution achieves good strong scalability and improves the performance significantly,as well as avoiding the SWOs.
基金Supported by Science Fund for Creative Research Groups of National Natural Science Foundation of China(Grant No.51221004)National Natural Science Foundation of China(Grant No.50805127)Fundamental Research Funds for the Central Universities of China(Grant No.2011QNA4002)
文摘The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.
基金supported by the National Natural Science Foundation of China (Nos.51778522,and 51508450)the Program for Innovative Research Team in Shaanxi (No.IRT2013KCT-13)
文摘The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.
基金The authors are grateful to"Chemical Grid Project"of Beijing University of Chemical Technology for providingthe computer facilities.
文摘A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was obtained using the particle trajectory model.The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated.The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration.The hydr...
基金supported by the National Natural Science Foundation of China(No.22273005 and No.22422301)the Innovation Program for Quantum Science and Technology(No.2023ZD0300200)+1 种基金the National Security Academic Foundation(No.U2330201)the Fundamental Research Funds for the Central Universities.
文摘Static disorder plays a crucial role in the electronic dynamics and spec-troscopy of complex molecular sys-tems.Traditionally,obtaining ob-servables averaged over static disor-der requires thousands of realiza-tions via direct sampling of the dis-order distribution,leading to high computational costs.In this work,we extend the auxiliary degree-of-freedom based matrix product state(MPS)method to handle system-bath correlated thermal equilibrium initial states,which can capture static disorder effects using a one-shot quantum dynamical simulation.We validate the effectiveness of the extended method by computing the dipole-dipole time correlation function of the Holstein model relevant to the emission spectrum of molecular aggregates.Our results show that the one-shot method is very accu-rate with only a moderate increase in MPS bond dimension,thereby significantly reducing computational cost.Moreover,it enables the generation of a much larger number of samples than the conventional direct sampling method at negligible additional cost,thus reducing sta-tistical errors.This method provides a broadly useful tool for calculating equilibrium time cor-relation functions in system-bath coupled models with static disorder.
基金Project supported by the National Natural Science Foundation of China (No.51075341)the National Basic Research Program (973) of China (No.2011CB711105)
文摘In this paper,a modeling method for a pantograph-catenary system is put forward to investigate the dynamic contact behavior in space,taking into consideration of the appearance characteristics of the contact surfaces of the pantograph and catenary.The dynamic performance of the pantograph-catenary system,including contact forces,accelerations,and the corresponding spectra,is analyzed.Furthermore,with the modeling method,the influences of contact wire irregularity and the vibration caused by the front pantograph on the rear pantograph for a pantograph-catenary system with double pantographs are investigated.The results show that the appearance characteristics of the contact surfaces play an important role in the dynamic contact behavior.The appearance characteristics should be considered to reasonably evaluate the dynamic performance of the pantograph-catenary system.
基金supported by the Fundamental Research Funds for the Central Universities (Nos. 2018JBZ007, 2018YJS136 and 2017YJS158)China Scholarship Council (CSC) (No. 201807090079)National Natural Science Foundation of China (No. 51675037)
文摘This paper presents a redundantly actuated and over-constrained 2 RPU-2 SPR parallel manipulator with two rotational and one translational coupling degrees of freedom.The kinematics analysis is firstly carried out and the mapping relationship of the velocity,acceleration and the independent parameters between the actuator joint and the moving platform are deduced by using the vector dot product and cross product operation.By employing d′Alembert′s principle and the principle of virtual work,the dynamics equilibrium equation is derived,and the simplified dynamics mathematical model of the parallel manipulator is further derived.Simultaneously,the generalized inertia matrix which can characterize the acceleration performance between joint space and operation space is further separated,and the performance indices including the dynamics dexterity,inertia coupling characteristics,energy transmission efficiency and driving force/torque balance are introduced.The analysis results show that the proposed redundantly actuated and over-constrained 2 RPU-2 SPR parallel manipulator in comparison with the existing non-redundant one has better dynamic comprehensive performance,which can be demonstrated practically by the successful application of the parallel kinematic machine head module of the hybrid machine tool.
基金financially supported by the Fundamental Research Program of Shandong Province(Grant No.ZR2016EEQ23)the Youth Exploration Project of Shandong Province Mount Tai Scholar Advanced Disciplinary Talent Group
文摘Logistical supply is costly for the deepwater oil and gas exploitation, thereby it is necessary to develop a novel power supply solution to improve the offshore structure’s self-holding capacity. The two-body point absorbers, as a renewable energy device, have achieved a rapid development. Heave plate is used to constrain the truss’ s motion in the two-body point absorber, and the floater moves along the truss up and down. This two-body point absorber can be considered to be an essentially mass-spring-damper system. And it is well known that the heave plates have been widely used in the Spar platform to suppress the heave motions. So if the two-body point absorber can be modified to combine with offshore floating structures, this system can not only offer electric power to support operations or daily lives for the platform, but also control the large motions in the vertical plane. Following this concept, a novel tuned heave plate(THP) system is proposed for the conventional semi-submersible platform. In order to investigate the dynamic performances of the single THP, two experiments are conducted in this paper. First, the hydrodynamic coefficients of the heave plates are studied, and then the THP experiments are carried out to analyze its dynamic performance. It can be concluded that this THP is feasible and achieves the design objective.
文摘The main aims of this study are to investigate the hydrodynamic performance of an autonomous underwater vehicle(AUV),calculate its hydrodynamic coefficients,and consider the flow characteristics of underwater bodies.In addition,three important parts of the SUBOFF bare hull,namely the main body,nose,and tail,are modified and redesigned to improve its hydrodynamic performance.A three-dimensional(3D)simulation is carried out using the computational fluid dynamics(CFD)method.To simulate turbulence,the k-ωshear stress transport(SST)model is employed,due to its good prediction capability at reasonable computational cost.Considering the effects of the length-to-diameter ratio(LTDR)and the nose and tail shapes on the hydrodynamic coefficients,it is concluded that a hull shape with bullet nose and sharp tail with LTDR equal to 7.14 performs better than the SUBOFF model.The final proposed model shows lower drag by about 14.9%at u=1.5 m·s^-1.Moreover,it produces 8 times more lift than the SUBOFF model at u=6.1 m·s^-1.These effects are due to the attachment of the fluid flow at the tail area of the hull,which weakens the wake region.
基金Supported by China Postdoctoral Science Foundation(Grant No.2017M621458)National Science and Technology Support Plan Projects(Grant No.2015BAA08B02)National Natural Science Foundation of China(Grant No.11632011),National Natural Science Foundation of China(Grant No.11372183)
文摘Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face?contacting conditions. Structure?Function method is adopted to handle the surface profiles of typical carbon?graphite rings, proving the fractal con?tact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar?Bhushan(MB) fractal model and the Chang?Etsion?Bogy(CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D(nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.
基金the support by the National Science Fund for Distinguished Young Scholars (No. 51625902)the National Key Research and Development Program of China (No. 2016YFE0200100)+1 种基金the Major Program of the National Natural Science Foundation of China (No. 51490675)the Taishan Scholars Program of Shandong Province (No. TS201511016)
文摘This paper presents a novel semi-submersible(SEMI) platform concept, called the multiple small columns(MSC) SEMI that improves upon the hydrodynamic performance of the conventional SEMI. Unlike the conventional SEMI, the proposed MSC SEMI utilizes multiple small circular columns to support the deck and a large pontoon that increases the structural displacement. The novelty of the MSC SEMI is its reduction of the hydrodynamic load on the structure and suppression of its motion response, particularly in the heave direction. The MSC SEMI has the advantages of increasing the added mass, radiation damping, and natural period of the structure. A comprehensive investigation of the hydrodynamic performance of the novel MSC SEMI is conducted in both the time and frequency domains with a special focus on the resulting hydrodynamic load and motion response. Numerical simulation results demonstrate that the MSC SEMI concept can reduce the hydrodynamic load and motion response and improve the hydrodynamic performance of SEMIs as expected.
