参激振动对顺应式垂直通路立管涡激振动的影响

顺应式垂直通路立管(CVAR)是目前处于研究阶段的一种新型的立管类型,在海流作用下产生涡激振动,在平台垂荡运动作用下产生参数激励振动。为了研究参数激励的影响,本文引入尾流振子模型模拟漩涡脱落对立管的作用,同时考虑浮式平台升沉运动产生的参数激励,建立了CVAR参激-涡激联合振动方程,获取联合作用下的动力响应,并与纯涡激振动响应进行对比。结果表明,在相同的流速下CVAR中部涡激振动幅值最大,流速的增大会导致涡激振动的频率增大,发生高阶锁振,高阶锁振振动幅值比低阶锁振振动幅值小。考虑参数激励之后,较纯涡激振动而言,立管的振动幅值增大;当参激频率与涡激振动频率接近时,立管的振动幅值最大。     

Experimental and numerical study of the shielding effect of two tandem rough cylinders in flow-induce oscillation

The shielding effect of the downstream cylinder in flow induced oscillation (FIO) of two cylinders arranged in tandem is studied experimentally and numerically at Reynolds number 30,000 to 120,000. Both cylinders are in one degree-of-freedom, transverse-oscillations, and have turbulence stimulation in the form of selective surface roughness to expand FIO beyond vortex-induced vibration (VIV) into galloping. Shielding of the downstream cylinder has a negative effect on harnessing hydrokinetic energy. To study its effect and mechanics, selective cases are studied both numerically and experimentally and discussed to demonstrate the shielding effect on the downstream cylinder and understand its cause. The main conclusions are: (1) The shielding effect for the downstream cylinder shows a strong relation to the damping ratio. As the damping ratio increases, the shielding effect is mitigated. Additionally, the oscillation of the rear cylinder becomes stable and shows stable frequency. (2) In the VIV region, as the stiffness and natural frequency increase, the shielding effect decreases substantially. (3) In the VIV region, the vorticity of the vortices shedding from both the upper and the lower sides of the downstream cylinder does not accumulate enough due to the attraction by the vortices shed from the upstream cylinder, thus resulting in partial suppression of the oscillation on the downstream cylinder. (4) In the galloping region, the shielding effect for the downstream cylinder depends on whether the vorticity near the downstream cylinder is strengthened by the vortices generated by the shear layers of the upstream cylinder or weakened.     

海流作用下悬浮隧道缆索的运动响应

考虑参数激励频率,利用涡激振动方程,应用伽辽金和龙格库塔数值积分法,计算出不同流速下参数激励对缆索1阶振动的影响;进一步计算隧道—缆索耦合作用下缆索的振动响应。计算结果表明参数激励为缆索固有频率2倍时,缆索响应最大;隧道对缆索振动有明显的抑制作用。     

船舶低速横甩机理研究

本文利用非线性振动理论研究了参数激励频率和波浪的强迫激励频率相同且等于艏摇固有频率2倍时的船舶1/2亚谐共振运动,揭示了船舶在低速航行、遭遇频率相对较高时,积累艏摇运动导致横甩发生的机理.     

一种无变频器式舰船交流电力推进系统稳态特性分析

为提高舰船电力推进系统功率密度,降低振动噪声,提出了一种基于永磁同步电机的无变频器式舰船交流电力推进系统。该系统将永磁同步电机作为推进电机,原动机与电励磁发电机直连,发电机与推进电机通过电缆直连。通过原动机调速实现推进电机转速调节,通过发电机励磁调节实现推进电机电压调节。建立了该电力推进系统静态数学模型,推导了系统主要电气量与发电机励磁电流及推进电机负载转矩间的函数关系,分析了系统的静态稳定性条件,分析了不同转速工况下和电机参数匹配条件下各电气量随发电机励磁电流的变化规律。数字仿真结果验证了所建立的静态数学模型及理论分析结果的准确性。     

新型FDPSO涡激运动试验研究

以一座工作水深为1500m的新型深吃水变截面多立柱式FDPSO为研究对象,对其在300m等效截断水深锚泊系统系泊时的涡激运动特性开展了模型试验研究.模型试验在上海交通大学海洋工程国家重点实验中进行,缩尺比取为1:80.本文重点对不同工况下平台的横向涡激运动、响应谱和运动轨迹进行了系统性研究.研究结果表明:平台的横向运动频率未出现典型"锁定"现象,而是一直保持在接近固有横荡频率的范围内;同一流向下,平台纵向运动的平衡位置与最大振幅均随着折合速度的增加而增加.与其他经典平台相比,本文新型FDPSO最大横荡振幅值随折合速度的变化呈现不同的趋势.随着折合速度的增加,横荡运动的最大振幅与标称振幅之间的差值增大.     

基于PSCAD的船用柴油发电机组仿真分析

船舶电力系统容量小,在受到较大扰动时,频率和电压不再保持为恒定,而是一个动态变化的过程。为了对船舶电力系统的过渡过程进行分析,本文利用PSCAD／EMTDC软件建立了柴油机及其调速系统以及发电机励磁系统的数学仿真模型,并对其各组成部分进行详细分析。最后利用分级突加突卸负载的方式对机组模型的正确性进行验证,指出通过对船舶电站同步发电机的励磁控制和柴油机的转速控制可以提高船舶电力系统稳定性。     

船舶参数激励非线性随机横摇运动分析

研究了随机纵浪中船舶的参数激励横摇运动。将船舶初稳性高作为时变的随机参数激励,应用随机平均法和FPK方程,分析了船舶的参数激励横摇运动微分方程。考虑航速、船舶瞬时湿表面积及随机波浪,建立了船舶横摇幅值概率密度、概率分布函数及其均值的计算方法。以某渔政船为例,计算了不同航速时船舶随机横摇幅值的概率密度、概率分布函数及其均值。结果表明,参数激励谱峰频率为横摇固有频率的2倍时,发生主参数共振,船舶横摇严重,船舶倾覆发生的概率增加。     

Time domain approach for coupled cross-flow and in-line VIV induced fatigue damage of steel catenary riser at touchdown zone

Existing VIV prediction approaches for steel catenary riser (SCR) typically employ truncation model without considering the interaction between the SCR and soil, and only allow for cross-flow (CF) VIV. In this study, a time domain approach accounting for the SCR-soil interaction is proposed to predict the CF and in-line (IL) VIV induced fatigue damage of a SCR at touchdown zone (TDZ). The hydrodynamic force resulting from the vortex shedding is modeled using the forced oscillation test data of a rigid cylinder and an empirical damping model, which are defined as functions of the non-dimensional dominant frequency and amplitude of the SCR response. Due to the coupling effect, the IL VIV force is magnified based on the CF VIV amplitude. By combining a linear hysteretic interaction model with a trench shape model, some particular phenomena during the vertical SCR-soil interaction are captured and qualitatively discussed, while for the horizontal direction, the seabed is simplified as nonlinear spring model. Based on these models, parametric studies are conducted to broaden the understanding of the sensitivity of VIV induced fatigue damage to the seabed characteristic. The results indicate trench depth, vertical and lateral stiffness, and clay suction are significantly affect the VIV induced maximum fatigue damage at TDZ.     

基于一种固体区域迭代算法的圆柱涡激振动数值计算

利用Fluent平台的用户自定义程序（UDF）以及动网格模型,实现了圆柱运动方程的一种迭代求解算法,分别对层流、湍流状态下,弹性支承圆柱体在一定约化速度下的涡激响应进行了数值模拟,探讨了不同阻尼比对涡激响应的影响。结果表明：采用该迭代求解算法对弹性支承圆柱涡激振动的预测结果较为合理;随着阻尼比的逐渐增加,初始支振幅、升阻力系数时程曲线将由多频率拍振,最终变为单一频率主导的振动,且涡激振幅逐渐减小;除了质量-阻尼比联合参数m*ζ外,阻尼比ζ本身也应作为一个重要的涡激影响参数单独进行考量。     

Slow drift damping force acting on a horizontal cylinder

The hydrodynamic forces acting on a circular cylinder and a rectangular cylinder undergoing slow drift oscillation in regular waves were investigated experimentally and numerically. Forced oscillation tests with low frequency and large amplitude in regular waves and forced two-harmonic oscillation with combined low and high frequencies were carried out in the experimental study. In the numerical study a finite-difference method was used to simulate viscous flow around a two-dimensional oscillating cylinder. The results of experiments showed that a horizontal rectangular cylinder oscillating slowly in waves has much higher damping coefficients than one oscillating in two-harmonic mode, while the numerical study indicated that such differences in the damping coefficient arise partly from the different effects of one-direction harmonic flow and rotating flow on the vortex shedding caused by the slow drift oscillation.     

磁流体推进稳定性的解析研究（英文）

In this paper an analytical solution for the stability of the fully developed flow drive in a magneto-hydro-dynamic pump with pulsating transverse Eletro-magnetic fields is presented. To do this, a theoretical model of the flow is developed and the analytical results are obtained for both the cylindrical and Cartesian configurations that are proper to use in the propulsion of marine vessels. The governing parabolic momentum PDEs are transformed into an ordinary differential equation using approximate velocity distribution. The numerical results are obtained and asymptotic analyses are built to discover the mathematical behavior of the solutions. The maximum velocity in a magneto-hydro-dynamic pump versus time for various values of the Stuart number, electro-magnetic interaction number, Reynolds number, aspect ratio, as well as the magnetic and electrical angular frequency and the shift of the phase angle is presented. Results show that for a high Stuart number there is a frequency limit for stability of the fluid flow in a certain direction of the flow. This stability frequency is dependent on the geometric parameters of a channel.     

电力推进船舶供电单元建模与仿真

本文分析了电力推进船舶电力系统的特点,建立了带有PID调速系统的柴油发电机组仿真模型,同步发电机采用相复励励磁系统。针对电力推进船舶的电力系统特点,分析了电力系统常见的三相故障对同步发电机励磁电压和端电压的影响。     

Analytical study of magnetohydrodynamic propulsion stability

In this paper an analytical solution for the stability of the fully developed flow drive in a magneto-hydro-dynamic pump with pulsating transverse Eletro-magnetic fields is presented. To do this, a theoretical model of the flow is developed and the analytical results are obtained for both the cylindrical and Cartesian configurations that are proper to use in the propulsion of marine vessels. The governing parabolic momentum PDEs are transformed into an ordinary differential equation using approximate velocity distribution. The numerical results are obtained and asymptotic analyses are built to discover the mathematical behavior of the solutions. The maximum velocity in a magneto-hydro-dynamic pump versus time for various values of the Stuart number, electro-magnetic interaction number, Reynolds number, aspect ratio, as well as the magnetic and electrical angular frequency and the shift of the phase angle is presented. Results show that for a high Stuart number there is a frequency limit for stability of the fluid flow in a certain direction of the flow. This stability frequency is dependent on the geometric parameters of a channel.     

中频同步发电机快速励磁的仿真与试验研究

讨论了影响同步发电机瞬态电压变化的主要因素,建立了基于MATLAB／SIMULINK的中频同步发电机励磁控制系统仿真模型,在试验验证模型正确性的基础上,对如何提高励磁控制系统响应的快速性进行了仿真分析,并结合一台无刷中频同步发电机的试验研究,总结提出了在对瞬态电压指标有较高要求的应用背景下,应注意的问题与对策,这对于同步发电机的设计与工程应用具有一定的指导意义。     

分舱形式对圆柱壳结构声学性能影响研究

为研究舱壁布置形式对圆柱壳结构声学性能的影规律,文章应用有限元方法对等间距与不等间距分舱圆柱壳模型的振动响应进行了计算,以此为输入可计算获得壳体的均方法向速度级声学传递函数,并在典型频率处应用波数谱分析方法将壳体空间域振动场转换到波数域上,对壳体的振动进行波形分离与量化,分析获得了舱壁等间距布置与不等间距布置圆柱壳在典型激励下的结构声学性能,并解释其机理.研究表明:对垂向激励,圆柱壳不等间距分舱相比等间距分舱具有较好的结构声学性能,但对轴向激励,两者区别不明显.若将不等间距分舱与局部结构补强措施相结合,则可使得圆柱壳在两典型工况下均能获得更优的结构声学性能.     

不同间距比方柱涡激运动特性研究

采用有限体积法对间距比为3.0,4.0,5.0的方形四立柱涡激运动特性进行了数值研究。着重探讨了间距比对振动幅值,升力系数频谱特性,涡脱模式的影响。引入动网格技术来实现立柱和流场之间的流—固耦合模拟。研究表明：三种间距比下,流向振幅随折合速度先增大后振荡。从升力系数谱分析,在不同折合速度下,系统能量出现多个或单个峰值,但能量相对仍比较集中。当间距比较小时,由于流场的干扰作用,柱体的尾涡结构凌乱而不规则;当间距比较大时,各柱体都有各自单独的涡街,但干扰现象依然存在。     

海洋地震拖缆阻力试验研究

海洋地震拖缆是海洋油气资源勘探中的重要设备,为研究海洋地震拖缆在拖曳状态以及有横向干扰时的阻力特性,进行了缩比模型实验。基于应变测试技术,设计研发了一套高灵敏度测力机构,用于间接测量拖缆及其附件的首端张力值,以求得拖缆的实际阻力。通过对实测数据比较,分析了拖缆速度及横向干扰对拖缆阻力的影响。实验结果表明,在低速拖曳下拖缆阻力与速度的三次方成正比关系;在有横向干扰时,拖缆阻力可看作无干扰时的平衡力和与干扰频率有关的正弦脉动力的叠加,当干扰频率一定时,脉动阻力幅值与平衡阻力的比值基本为常数。基于以上实验结果,结合量纲分析法,能够对实际拖缆阻力进行较好的估算。     

气动式造波机中的横向波

本文讨论了用于产生二维波动的气动式造波机中,一种横向表面重力波的发生及其非线性特性。当输入频率接近于横向波的基频两倍时,利用奇摄动方法,可以得到横向波的振幅发展方程。振幅的理论预测与实验观察是定性相符的。     

幂律流体阻尼的隔冲特性研究

基于幂律流体阻尼特性,建立了单自由度冲击隔离系统数学模型,分析了幂律流体的分段阻尼力特性与隔冲耗能特性,并讨论了速度相关指数、固有频率、冲击载荷幅值等因素对系统隔冲性能的影响。研究结果表明:当激励信号产生的流体相对速度较小时,剪切稀化流体的隔冲性能优于线性阻尼和剪切稠化流体阻尼,流体相对速度较大时,剪切稠化流体的隔冲性能优于线性阻尼和剪切稀化流体。幂律流体的参数影响分析为幂律流体阻尼器的设计和实际应用提供了一定的参考。