This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of v...This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of vortex shedding is modeled based on the classical van der Pol equation, combined with the equation for the oscillatory motion of the body. An appropriate approach is developed to estimate the empirical parameters in the wake oscillator model. The present predicted results are compared to the experimental data and previous wake oscillator model results. Good agreement with experimental results is found.展开更多
建立一种新的预报并列双圆柱涡激振动响应的经验性模型,根据特定间距比条件下旋涡脱落频率出现分支的现象,提出以两个具有不同固有频率的尾流振子来共同描述结构的近壁尾涡动力特性,同时两个振子均满足van der Pol方程,进而得到结构振...建立一种新的预报并列双圆柱涡激振动响应的经验性模型,根据特定间距比条件下旋涡脱落频率出现分支的现象,提出以两个具有不同固有频率的尾流振子来共同描述结构的近壁尾涡动力特性,同时两个振子均满足van der Pol方程,进而得到结构振子和流体振子的耦合方程组。使用该模型分别对中高质量比和低质量比的并列圆柱涡激振动问题进行数值计算,结果表明,结构的位移响应和最大振动幅值等变化规律与实验结果趋势一致,数值基本吻合。展开更多
为了研究大跨度斜拉桥超长拉索在不同流场特性下的高阶多模态涡激振动问题,以牛顿定律为基础,建立了考虑张力变化以及垂度效应的拉索结构振子方程,引入改进的Van Der Pol式尾流振子模型,以加速度耦合两非线性振子,提出了一种简便的拉索...为了研究大跨度斜拉桥超长拉索在不同流场特性下的高阶多模态涡激振动问题,以牛顿定律为基础,建立了考虑张力变化以及垂度效应的拉索结构振子方程,引入改进的Van Der Pol式尾流振子模型,以加速度耦合两非线性振子,提出了一种简便的拉索涡激振动流固耦合预报模型;采用二阶中心差分法,对两振子方程在空间域和时间域进行离散迭代求解,编制了拉索涡激振动的MATLAB计算程序,并验证了其可靠性。该方法为研究拉索涡激振动提供了一种新思路,可解决风洞试验和数值软件(CFD)不便模拟大长细比拉索结构的问题。基于提出的预报模型,以1根330 m超长拉索为研究对象,分析了拉索多模态涡激振动特性,探讨了不同流场特性对拉索涡激振动的影响。研究结果表明:均匀流作用下,拉索发生涡激锁定现象,以单一模态发生振动,随着风速的增加,拉索涡激锁定区间增大而最大振幅不发生改变;剪切流作用下,拉索发生多模态涡激振动,位移响应呈现"拍"的特点,振动频率分布在Strouhal涡脱频率范围内,存在2个或3个主导频率,主导频率全程参与振动,非主导频率间歇参与振动;拉索多模态涡激振动位移响应表现为行波-驻波并存的状态,随着风剖面指数的增加,涡激振动行波效应显著。展开更多
The fluctuating furces of the fluid exerted on the top terrsioned riser （＇FIR） in the in-line and cross-flow directions are both modeled by van del Pol wake oscillator model and the nonlinear coupled dynamics of th...The fluctuating furces of the fluid exerted on the top terrsioned riser （＇FIR） in the in-line and cross-flow directions are both modeled by van del Pol wake oscillator model and the nonlinear coupled dynamics of the in-line and cross-flow vortex-induced vibrations （VIV） of the riser are analyzed in time domain in this papar. The numencal shnulation results of the riser＇s in-line and cross-flow displacements and curvatures are compared with experimental measurements and the comparison shows the validity of this method in modeling some main features of the riser＇s VIV. Finally, the effects of the riser＇s top tensions and internal flow velocities on the coupled vibrations of the riser are investigated.展开更多
A numerical study based on a wake oscillator model was conducted to determine the response performance of vortex-induced vibration(VIV) on a long flexible cylinder with pinned-pinned boundary conditions subjected to l...A numerical study based on a wake oscillator model was conducted to determine the response performance of vortex-induced vibration(VIV) on a long flexible cylinder with pinned-pinned boundary conditions subjected to linear and exponential shear flows. The coupling equations of a structural vibration model and wake oscillator model were solved using a standard central finite difference method of the second order. The VIV response characteristics including the structural displacement, structural frequency, structural wavenumber, standing wave behavior,travelling wave behavior, structural velocity, lift force coefficient and transferred energy from the fluid to the structure with different flow profiles were compared. The numerical results show that the VIV displacement is a combination of standing waves and travelling waves. For linear shear flow, standing waves and travelling waves dominate the VIV response within the low-velocity and high-velocity zones, respectively. The negative values of the transferred energy only occur within the low-velocity zone. However, for exponential shear flow, travelling waves dominate the VIV response and the negative energy occurs along the entire length of the cylinder.展开更多
It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV) of cylinders. In this paper, a novel in-line(IL) and cross-flow(CF) coupling VIV prediction model for circular c...It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV) of cylinders. In this paper, a novel in-line(IL) and cross-flow(CF) coupling VIV prediction model for circular cylinders has been proposed, in which the influence of the Reynolds number was comprehensively considered. The Strouhal number linked with the vortex shedding frequency was calculated through a function of the Reynolds number. The coefficient of the mean drag force was fitted as a new piecewise function of the Reynolds number, and its amplification resulted from the CF VIV was also taken into account. The oscillating drag and lift forces were modelled with classical van der Pol wake oscillators and their empirical parameters were determined based on the lock-in boundaries and the peak-amplitude formulas. A new peak-amplitude formula for the IL VIV was developed under the resonance condition with respect to the mass-damping ratio and the Reynolds number. When compared with the results from the experiments and some other prediction models, the present model could give good estimations on the vibration amplitudes and frequencies of the VIV both for elastically-mounted rigid and long flexible cylinders. The present model considering the influence of the Reynolds number could generally provide better results than that neglecting the effect of the Reynolds number.展开更多
The streamwise flow-induced vibration of a circular cylinder with symmetric vortex shedding in the first instability range is investigated, and a wake oscillator model for the dynamic response prediction is proposed. ...The streamwise flow-induced vibration of a circular cylinder with symmetric vortex shedding in the first instability range is investigated, and a wake oscillator model for the dynamic response prediction is proposed. An approach is applied to calibrate the empirical parameters in the present model; the numerical and experimental results are compared to validate the proposed model. It can be found that the present prediction model is accurate and sufficiently simple to be easily applied in practice.展开更多
基金supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA09Z350)the National Natural Science Foundation of China(Grant No.10702073)the Knowledge Innovation Program of Chinese Academy of Sciences(Grant No.KJCX2-YW-L02)
文摘This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of vortex shedding is modeled based on the classical van der Pol equation, combined with the equation for the oscillatory motion of the body. An appropriate approach is developed to estimate the empirical parameters in the wake oscillator model. The present predicted results are compared to the experimental data and previous wake oscillator model results. Good agreement with experimental results is found.
文摘建立一种新的预报并列双圆柱涡激振动响应的经验性模型,根据特定间距比条件下旋涡脱落频率出现分支的现象,提出以两个具有不同固有频率的尾流振子来共同描述结构的近壁尾涡动力特性,同时两个振子均满足van der Pol方程,进而得到结构振子和流体振子的耦合方程组。使用该模型分别对中高质量比和低质量比的并列圆柱涡激振动问题进行数值计算,结果表明,结构的位移响应和最大振动幅值等变化规律与实验结果趋势一致,数值基本吻合。
文摘为了研究大跨度斜拉桥超长拉索在不同流场特性下的高阶多模态涡激振动问题,以牛顿定律为基础,建立了考虑张力变化以及垂度效应的拉索结构振子方程,引入改进的Van Der Pol式尾流振子模型,以加速度耦合两非线性振子,提出了一种简便的拉索涡激振动流固耦合预报模型;采用二阶中心差分法,对两振子方程在空间域和时间域进行离散迭代求解,编制了拉索涡激振动的MATLAB计算程序,并验证了其可靠性。该方法为研究拉索涡激振动提供了一种新思路,可解决风洞试验和数值软件(CFD)不便模拟大长细比拉索结构的问题。基于提出的预报模型,以1根330 m超长拉索为研究对象,分析了拉索多模态涡激振动特性,探讨了不同流场特性对拉索涡激振动的影响。研究结果表明:均匀流作用下,拉索发生涡激锁定现象,以单一模态发生振动,随着风速的增加,拉索涡激锁定区间增大而最大振幅不发生改变;剪切流作用下,拉索发生多模态涡激振动,位移响应呈现"拍"的特点,振动频率分布在Strouhal涡脱频率范围内,存在2个或3个主导频率,主导频率全程参与振动,非主导频率间歇参与振动;拉索多模态涡激振动位移响应表现为行波-驻波并存的状态,随着风剖面指数的增加,涡激振动行波效应显著。
基金supported by the High Technology Research and Development Program of China (863 Pro-gram, Grant No.2010AA09Z303)the Key Project of National Natural Science Foundation of China (Grant No.50739004)
文摘The fluctuating furces of the fluid exerted on the top terrsioned riser （＇FIR） in the in-line and cross-flow directions are both modeled by van del Pol wake oscillator model and the nonlinear coupled dynamics of the in-line and cross-flow vortex-induced vibrations （VIV） of the riser are analyzed in time domain in this papar. The numencal shnulation results of the riser＇s in-line and cross-flow displacements and curvatures are compared with experimental measurements and the comparison shows the validity of this method in modeling some main features of the riser＇s VIV. Finally, the effects of the riser＇s top tensions and internal flow velocities on the coupled vibrations of the riser are investigated.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51609206,51522902 and 51579040)
文摘A numerical study based on a wake oscillator model was conducted to determine the response performance of vortex-induced vibration(VIV) on a long flexible cylinder with pinned-pinned boundary conditions subjected to linear and exponential shear flows. The coupling equations of a structural vibration model and wake oscillator model were solved using a standard central finite difference method of the second order. The VIV response characteristics including the structural displacement, structural frequency, structural wavenumber, standing wave behavior,travelling wave behavior, structural velocity, lift force coefficient and transferred energy from the fluid to the structure with different flow profiles were compared. The numerical results show that the VIV displacement is a combination of standing waves and travelling waves. For linear shear flow, standing waves and travelling waves dominate the VIV response within the low-velocity and high-velocity zones, respectively. The negative values of the transferred energy only occur within the low-velocity zone. However, for exponential shear flow, travelling waves dominate the VIV response and the negative energy occurs along the entire length of the cylinder.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51379144,51479135 and51679167)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51621092)
文摘It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV) of cylinders. In this paper, a novel in-line(IL) and cross-flow(CF) coupling VIV prediction model for circular cylinders has been proposed, in which the influence of the Reynolds number was comprehensively considered. The Strouhal number linked with the vortex shedding frequency was calculated through a function of the Reynolds number. The coefficient of the mean drag force was fitted as a new piecewise function of the Reynolds number, and its amplification resulted from the CF VIV was also taken into account. The oscillating drag and lift forces were modelled with classical van der Pol wake oscillators and their empirical parameters were determined based on the lock-in boundaries and the peak-amplitude formulas. A new peak-amplitude formula for the IL VIV was developed under the resonance condition with respect to the mass-damping ratio and the Reynolds number. When compared with the results from the experiments and some other prediction models, the present model could give good estimations on the vibration amplitudes and frequencies of the VIV both for elastically-mounted rigid and long flexible cylinders. The present model considering the influence of the Reynolds number could generally provide better results than that neglecting the effect of the Reynolds number.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(SRFDP,Grant No. 20100032120047)State Key Laboratory of Ocean Engineering of Shanghai Jiao Tong University (Grant No.1104)the National Natural Science Foundation of China (Grant No. 51209161)
文摘The streamwise flow-induced vibration of a circular cylinder with symmetric vortex shedding in the first instability range is investigated, and a wake oscillator model for the dynamic response prediction is proposed. An approach is applied to calibrate the empirical parameters in the present model; the numerical and experimental results are compared to validate the proposed model. It can be found that the present prediction model is accurate and sufficiently simple to be easily applied in practice.
