压电俘能器能够为自然界中低功率的微机电系统持续供能.为了模拟机翼的沉浮-俯仰二自由度运动和有效俘获气动弹性振动能量,本文提出一种新颖的翼型颤振压电俘能器.基于非定常气动力模型,推导翼型颤振压电俘能器流-固-电耦合场的数学模型...压电俘能器能够为自然界中低功率的微机电系统持续供能.为了模拟机翼的沉浮-俯仰二自由度运动和有效俘获气动弹性振动能量,本文提出一种新颖的翼型颤振压电俘能器.基于非定常气动力模型,推导翼型颤振压电俘能器流-固-电耦合场的数学模型.建立有限元模型,模拟机翼的沉浮-俯仰二自由度运动,获得机翼附近的涡旋脱落和流场特性.搭建风洞实验系统,制作压电俘能器样机.利用实验验证理论和仿真模型的正确性,仿真分析压电俘能器结构参数对其气动弹性振动响应和俘获性能的影响.结果表明:理论分析、仿真模拟和实验研究获得的输出电压具有较好的一致性,验证建立数学和仿真模型的正确性.仿真分析获得机翼附近的压力场变化云图,表明交替的压力差驱动机翼发生二自由度沉浮-俯仰运动.当风速超过颤振起始速度时,压电俘能器发生颤振,并表现为极限环振荡.当偏心距为0.3和风速为16 m/s时,可获得最大输出电压为17.88 V和输出功率为1.278 m W.功率密度为7.99 m W/cm^(3),相比较于其他压电俘能器,能实现优越的俘获性能.研究结果对设计更高效的翼型颤振压电俘能器提供重要的指导意义.展开更多
Rain-wind-induced vibration of cable was studied based on previous research achievements. According to the quasi-steady assumption, the governing equation of vertical motion of the cable was derived and the criterion ...Rain-wind-induced vibration of cable was studied based on previous research achievements. According to the quasi-steady assumption, the governing equation of vertical motion of the cable was derived and the criterion for unstable motion and occurrence mechanism was studied. A comparison was performed between the oscillation responses of the stay cable obtained from calculated model and previous results. The results indicate that the analysis model can reflect the main characteristics of wind-rain-induced vibrationt of the cable which is amplitude- and velocity-restricted, and it is probably related with the periodic vortex shedding of wake flow. It is essential for the occurrence of rain-wind-induced or wind-induced vibration of cable that the derivative of lift coefficient with respect to transient angle of attack is less than zero. When rain-wind-induced vibration occurs, the aerodynamic force has a dual function for the vibration, and the maximum amplitude of stayed-cable is determined by the relative value of aerodynamic exciting force and aerodynamic damping force.展开更多
The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the p...The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the posture characteristics of the car-body based on the previous full-scale test results.And then the aerodynamic performance under different vibration cases(different car-body roll angles)is studied with an improved delayed detached eddy simulation(IDDES).The results revealed that car-body rolling had a significant impact on the aerodynamic behavior of bogies,which significantly increased the lateral force and yaw moment of a bogie and further may have aggravated the operational instability of the train.The unbalanced distribution of the longitudinal pressure on both sides of the bogie caused by the car-body rolling motion was the primary cause for the bogie yaw moment increase.The tail vortex of the train was also affected by the car-body rolling,resulting in vertical jitter.展开更多
Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formula...Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.展开更多
Wind tunnel tests were carried out to investigate the aerodynamic interference between a triple-box girder and trains,involving static aerodynamic forces and vortex-induced vibrations(VIVs).Static and dynamic sectiona...Wind tunnel tests were carried out to investigate the aerodynamic interference between a triple-box girder and trains,involving static aerodynamic forces and vortex-induced vibrations(VIVs).Static and dynamic sectional models of the girder and trains were employed for aerodynamic force measurement and VIV test,respectively.Results indicate that the aerodynamic interference effect on static aerodynamic forces of both the girder and trains is remarkable.When a single train exists,the horizontal position of the train has a small effect on aerodynamic coefficients of the girder.When two trains meet on the girder,the drag coefficient of the girder is significantly reduced compared with that of without train or with a single train;besides,during the whole meeting process,aerodynamic forces of the leeward train first drop and then increase suddenly.The fluctuation of aerodynamic force could cause redundant vibration of the train,which is unfavorable for safety and comfort.A train on the girder could worsen the girder VIV performance:a new vertical VIV appears in the triple-box girder when a train is on the girder,and the torsional VIV amplitude increases significantly when the train is on the windward side.展开更多
文摘压电俘能器能够为自然界中低功率的微机电系统持续供能.为了模拟机翼的沉浮-俯仰二自由度运动和有效俘获气动弹性振动能量,本文提出一种新颖的翼型颤振压电俘能器.基于非定常气动力模型,推导翼型颤振压电俘能器流-固-电耦合场的数学模型.建立有限元模型,模拟机翼的沉浮-俯仰二自由度运动,获得机翼附近的涡旋脱落和流场特性.搭建风洞实验系统,制作压电俘能器样机.利用实验验证理论和仿真模型的正确性,仿真分析压电俘能器结构参数对其气动弹性振动响应和俘获性能的影响.结果表明:理论分析、仿真模拟和实验研究获得的输出电压具有较好的一致性,验证建立数学和仿真模型的正确性.仿真分析获得机翼附近的压力场变化云图,表明交替的压力差驱动机翼发生二自由度沉浮-俯仰运动.当风速超过颤振起始速度时,压电俘能器发生颤振,并表现为极限环振荡.当偏心距为0.3和风速为16 m/s时,可获得最大输出电压为17.88 V和输出功率为1.278 m W.功率密度为7.99 m W/cm^(3),相比较于其他压电俘能器,能实现优越的俘获性能.研究结果对设计更高效的翼型颤振压电俘能器提供重要的指导意义.
基金Project(51078170) supported by the National Natural Science Foundation of ChinaProject(10JDG097) supported by Jiangsu University Talents Funds,China
文摘Rain-wind-induced vibration of cable was studied based on previous research achievements. According to the quasi-steady assumption, the governing equation of vertical motion of the cable was derived and the criterion for unstable motion and occurrence mechanism was studied. A comparison was performed between the oscillation responses of the stay cable obtained from calculated model and previous results. The results indicate that the analysis model can reflect the main characteristics of wind-rain-induced vibrationt of the cable which is amplitude- and velocity-restricted, and it is probably related with the periodic vortex shedding of wake flow. It is essential for the occurrence of rain-wind-induced or wind-induced vibration of cable that the derivative of lift coefficient with respect to transient angle of attack is less than zero. When rain-wind-induced vibration occurs, the aerodynamic force has a dual function for the vibration, and the maximum amplitude of stayed-cable is determined by the relative value of aerodynamic exciting force and aerodynamic damping force.
基金Project(BX2021379)supported by the China National Postdoctoral Program for Innovative Talents。
文摘The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the posture characteristics of the car-body based on the previous full-scale test results.And then the aerodynamic performance under different vibration cases(different car-body roll angles)is studied with an improved delayed detached eddy simulation(IDDES).The results revealed that car-body rolling had a significant impact on the aerodynamic behavior of bogies,which significantly increased the lateral force and yaw moment of a bogie and further may have aggravated the operational instability of the train.The unbalanced distribution of the longitudinal pressure on both sides of the bogie caused by the car-body rolling motion was the primary cause for the bogie yaw moment increase.The tail vortex of the train was also affected by the car-body rolling,resulting in vertical jitter.
基金Projects(50978203,51208254)supported by the National Natural Science Foundation of ChinaProject(BK2012390)supported by Natural Science Foundation of Jiangsu Province,ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.
基金Project(52025082) supported by the National Natural Science Foundation for Distinguished Young Scholars of ChinaProject(CX20190288) supported by Hunan Provincial Innovation Foundation for Postgraduate,China。
文摘Wind tunnel tests were carried out to investigate the aerodynamic interference between a triple-box girder and trains,involving static aerodynamic forces and vortex-induced vibrations(VIVs).Static and dynamic sectional models of the girder and trains were employed for aerodynamic force measurement and VIV test,respectively.Results indicate that the aerodynamic interference effect on static aerodynamic forces of both the girder and trains is remarkable.When a single train exists,the horizontal position of the train has a small effect on aerodynamic coefficients of the girder.When two trains meet on the girder,the drag coefficient of the girder is significantly reduced compared with that of without train or with a single train;besides,during the whole meeting process,aerodynamic forces of the leeward train first drop and then increase suddenly.The fluctuation of aerodynamic force could cause redundant vibration of the train,which is unfavorable for safety and comfort.A train on the girder could worsen the girder VIV performance:a new vertical VIV appears in the triple-box girder when a train is on the girder,and the torsional VIV amplitude increases significantly when the train is on the windward side.
