共查询到20条相似文献，搜索用时 31 毫秒
1.
《中国海洋工程》2021,(4)
In connection with the design of floating wind turbines, stochastic dynamic analysis is a critical task considering nonlinear wind and wave forces. To study the random structural responses of a newly designed submerged tension leg platform(STLP) wind turbine, a set of dynamic simulations and comparison analysis with the MIT/NREL TLP wind turbine are carried out. The signal filter method is used to evaluate the mean and standard deviations of the structural response. Furthermore, the extreme responses are estimated by using the mean upcrossing rate method. The fatigue damages for blade root, tower, and mooring line are also studied according to the simulated time-series. The results and comparison analysis show that the STLP gives small surge and pitch motions and mooring line tensions in operational sea states due to the small water-plane area. Additionally, in severe sea states, the STLP gives lower extreme values of platform pitch, slightly larger surge and heave motions and better towerbase and mooring line fatigue performances than those of the MIT/NREL TLP. It is found that the STLP wind turbine has good performances in structural responses and could be a potential type for exploiting the wind resources located in deep waters. 相似文献
2.
半潜浮式风机逐渐在深海风电开发中受到关注,建立风机、平台与系泊结构耦合数值计算模型,通过FAST与AQWA链接进行风机塔基荷载及平台运动响应相互耦合传递,基于随机波与极限波组合模型生成畸形波时程序列,进行半潜浮式风机系泊失效全过程时域模拟计算分析,得出系泊锚链张力、风机、塔筒和平台运动时程响应,探究系泊失效、风机停机和叶片变桨速率对浮式风机平台系泊结构动力响应的影响。结果表明：畸形波作用下浮式平台和系泊结构动力响应显著,系泊失效导致塔基剪力增加,平台纵荡和纵摇运动响应显著增大;风机停机会引起系泊锚链张力显著减小,转子推力、塔基剪力和叶尖挥舞位移响应逐渐衰减,平台纵荡、纵摇和横摇运动响应显著减小;随着叶片变桨速率增加,风机转子推力和塔基剪力波动幅值增大。 相似文献
3.
以三浮筒(Tri-floater)型半潜式风机系统为对象,采用时域方法,考虑垂荡板的黏性阻尼效应,研究系泊缆直径、长度、预张力和布置方式等参数对其在风浪流中动力响应特性的影响规律,提出了一种系泊参数优化方法。在此基础上,根据东海和南海三个不同水深区域百年一遇海洋环境条件,通过调整Tri-floater型浮式基础的吃水和垂荡板等参数,有效地提高了其运动响应周期,减小了其运动响应幅值。同时,根据风机浮式基础运动幅值的设计规范要求,针对三个不同水深区域特点,设计了Tri-floater型浮式基础的系泊系统。计算结果表明,改进后的Tri-floater型半潜式风机系统能满足百年一遇极端环境下的作业要求,适合于东海和南海海洋环境下海上风能资源的开发。 相似文献
4.
参考英国的Kincardine风机采用的新式的Semi-Spar概念,结合spar式基础和半潜式基础的特点,提出了一种新式海上浮式风机平台模型,并基于三维势流理论,利用AQWA软件进行水动力计算,验证新式平台可靠性。分析了在风、浪、流荷载联合作用下,锚链竖向夹角、系缆数量对风机浮式平台运动性能和系泊张力的影响,对系泊系统进行优化,并验证极端工况下的可靠性。结果证明风机平台水平运动和纵摇运动幅值较小,但垂荡幅值略大,而通过减小锚链竖向夹角可以控制平台运动响应幅值,增加系缆数量可以同时减小系泊张力大小。计算结果证明了新型Semi-Spar式海上风机平台可行性,为浮式风机平台及系泊系统的设计提供参考。 相似文献
5.
Experiment Study of Dynamics Response for Wind Turbine System of Floating Foundation 总被引：1，自引：1，他引：0
The floating foundation is designed to support a 1.5 MW wind turbine in 30 m water depth. With consideration of the viscous damping of foundation and heave plates, the amplitude-frequency response characteristics of the foundation are studied. By taking into account the elastic effect of blades and tower, the classic quasi-steady blade-element/momentum (BEM) theory is used to calculate the aerodynamic elastic loads. A coupled dynamic model of the turbine-foundation- mooring lines is established to calculate the motion response of floating foundation under Kaimal wind spectrum and regular wave by using the FAST codes. The model experiment is carried out to test damping characteristics and natural motion behaviors of the wind turbine system. The dynamics response is tested by considering only waves and the joint action of wind and waves. It is shown that the wind turbine system can avoid resonances under the action of wind and waves. In addition, the heave motion of the floating foundation is induced by waves and the surge motion is induced by wind. The action of wind and waves is of significance for pitch. 相似文献
6.
海上浮式风力机受风、浪、流等外部载荷影响,运营期间经常处于偏航工况,给风力机基础运动响应和锚泊载荷带来重要影响.基于经典叶素动量理论及势流理论,建立海上浮式风力机水—气动力耦合分析模型,对在非定常风、不规则波浪联合作用下,风力机偏航时基础运动响应及锚泊载荷等进行分析.研究发现,额定风速工况下,风力机偏航对平台纵荡和纵摇运动影响较大,偏航30°时纵荡和纵摇平均值比偏航0°时分别下降20.68％和37.36％,垂荡运动响应受风力机偏航影响较小;锚泊载荷变化趋势与平台运动及锚链布置有关,平台纵荡对锚泊载荷影响较大,偏航30°时锚链#1有效张力平均值比偏航0°时下降12.98％. 相似文献
7.
Both numerical calculation and model test are important techniques to study and forecast the dynamic responses of the floating offshore wind turbine (FOWT). However, both the methods have their own limitations at present. In this study, the dynamic responses of a 5 MW OC3 spar-type floating wind turbine designed for a water depth of 200 m are numerically investigated and validated by a 1:50 scaled model test. Moreover, the discrepancies between the numerical calculations and model tests are obtained and discussed. According to the discussions, it is found that the surge and pitch are coupled with the mooring tensions, but the heave is independent of them. Surge and pitch are mainly induced by wave under wind wave conditions. Wind and current will induce the low-frequency average responses, while wave will induce the fluctuation ranges of the responses. In addition, wave will induce the wavefrequency responses but wind and current will restrain the ranges of the responses. 相似文献
8.
概念性地设计了一种新型半潜式海上风力机基础,确定了结构的型式和尺寸,对风浪联合作用下不同工况的风力机基础稳性进行了校核.考虑黏性阻尼和二阶波浪力的作用,计算分析了风力机基础的水动力系数、幅频运动以及动力响应特性.结果表明,经过改进的新型风力机基础具有良好的稳性和水动力性能,特别是在垂荡性能上有大幅的提升.波浪入射角度对垂荡的影响不大,但对其他自由度RAOs影响较大.垂荡、横摇和纵摇RAOs均存在一个主峰值和次峰值,但峰值周期均远离波能集中区.此外还发现,不同工况下风浪入射角对风机系统的动力响应和系泊力均有较大影响,相对于工作工况,极端工况下所受风荷载较小,但是系泊力更大. 相似文献
9.
10.
针对张力腿系泊浮式风力机的基础运动,忽略柔性构件的影响,建立气动—水动—系泊非线性耦合运动方程。在运动控制方程中包含张力腿系泊系统的非线性回复刚度,桨距角控制以及浮式基础运动对空气动力载荷的影响。在波浪载荷的计算中考虑二阶波浪载荷的作用。采用随机频率相位角调制法生成畸形波波面时历,计算在畸形波作用下张力腿型浮式风力机的动力响应特性。数值模拟结果表明,在畸形波作用下,浮式基础的运动及空气动力性能均受到了显著的影响。其中浮式基础的纵荡和纵摇运动分别受二阶差频与和频波浪力的影响,而垂荡运动的增加则主要是受下沉运动的影响。在畸形波经过的时刻,风力机的功率系数迅速下降,水平方向的风载荷波动先减小,随后其数值急剧下降,而垂直方向的风载荷波动增大。 相似文献
11.
为研究顺应式海洋平台慢漂运动的影响因素,以截断圆柱和漂浮方箱为例进行了不规则波作用下的慢漂运动模型试验。测量了不同系泊刚度条件下的漂浮方箱以及相同系泊刚度条件下的截断圆柱和漂浮方箱在静水中自由衰减运动和在不规则波中的运动响应,并将运动响应分解成一阶波频运动响应和二阶低频运动响应,分析了系泊刚度和浮体形状对浮体运动的影响。通过物理模型试验发现了系泊刚度及浮体形状对顺应式系泊浮体一阶运动标准差和二阶低频运动平均漂移值和标准差的关系。结果表明由于顺应式浮体的固有周期远离波浪谱峰周期时,系泊刚度以及浮体形状对慢漂运动的一阶运动响应影响不大;二阶低频运动相对偏离平衡位置的平均值和标准差均随系泊刚度增大而减小,浮体形状同样对慢漂运动的二阶低频纵荡运动响应影响较大。试验结果为实际海洋工程的外形选择和系泊刚度选择提供数据支持。 相似文献
12.
波浪能是一种清洁、可再生的新型能源,波浪能发电装置在海上作业时会受到变化的风、浪、流载荷作用,需要系泊系统保证其稳性和安全性。以适用于中国南海500 m水深的振荡双浮体式波浪能发电装置为研究对象,运用频域计算与时域计算结合的方法对双浮体及其系泊系统的运动响应和动力载荷进行计算,获取极端海况与工作海况下浮体运动和系泊缆索张力的时历数据。参照BV船级社NR-493规定的海上浮式结构物系泊安全系数规范,对3种系泊方案进行安全校核和对比分析。选定其中一种系泊方案,通过改变系泊系统以及能量转换器（PTO）的参数,探究参数变化对双体波浪能装置运动响应以及系泊系统特性的影响,为类似应用于深水的双体波浪能装置系泊系统的设计提供参考。 相似文献
13.
The present work reports a Hybrid Modular Floating Structure (HMFS) system with typical malfunction conditions. The effects of both fractured mooring lines and failed connectors on main hydrodynamic responses (mooring line tensions, module motions, connector loads and wave power production) of the HMFS system under typical sea conditions are comparatively investigated. The results indicate that the mooring tension distribution, certain module motions (surge, sway and yaw) and connector loads (Mz) are significantly influenced by mooring line fractures. The adjacent mooring line of the fractured line on the upstream side suffers the largest tension among the remaining mooring lines, and the case with two fractured mooring lines in the same group on the upstream side is the most dangerous among all cases of two-line failures in view of mooring line tensions, module motions and connector loads. Therefore, one emergency strategy with appropriate relaxation of a proper mooring line has been proposed and proved effective to reduce the risk of more progressive mooring line fractures. In addition, connector failures substantially affect certain module motions (heave and pitch), certain connector loads (Fz and My) and wave power production. The present work can be helpful and instructive for studies on malfunction conditions of modular floating structure (MFS) systems.
相似文献14.
Tension Leg Platform (TLP) is one of the concepts which shows promising results during initial studies to carry floating wind turbines. One of the concerns regarding tension leg platform wind turbines (TLPWTs) is the high natural frequencies of the structure that may be excited by nonlinear waves loads. Since Computational Fluid Dynamics (CFD) models are capable of capturing nonlinear wave loads, they can lead to better insight about this concern. In the current study, a CFD model based on immersed boundary method, in combination with a two-body structural model of TLPWT is developed to study wave induced responses of TLPWT in deep water. The results are compared with the results of a potential flow theory-finite element software, SIMO-RIFLEX (SR). First, the CFD based model is described and the potential flow theory based model is briefly introduced. Then, a grid sensitivity study is performed and free decay tests are simulated to determine the natural frequencies of different motion modes of the TLPWT. The responses of the TLPWT to regular waves are studied, and the effects of wave height are investigated. For the studied wave heights which vary from small to medium amplitude (wave height over wavelength less than 0.071), the results predicted by the CFD based model are generally in good agreement with the potential flow theory based model. The only considerable difference is the TLPWT mean surge motion which is predicted higher by the CFD model, possibly because of considering the nonlinear effects of the waves loads and applying these loads at the TLPWT instantaneous position in the CFD model. This difference does not considerably affect the important TLPWT design driving parameters such as tendons forces and tower base moment, since it only affects the mean dynamic position of TLPWT. In the current study, the incoming wave frequency is set such that third-harmonic wave frequency coincides with the first tower bending mode frequency. However, for the studied wave conditions a significant excitation of tower natural frequency is not observed. The high stiffness of tendons which results in linear pitch motion of TLPWT hull (less than 0.02 degrees) and tower (less than 0.25 degrees) can explain the limited excitement of the tower first bending mode. The good agreement between CFD and potential flow theory based results for small and medium amplitude waves gives confidence to the proposed CFD based model to be further used for hydrodynamic analysis of floating wind turbines in extreme ocean conditions. 相似文献
15.
Based on the lumped-mass method and rigid-body kinematics theory, a mathematical model of a gravity cage system attacked by irregular waves is developed to simulate the hydrodynamic response of cage system, including the maximum tension of mooring lines and the motion of float collar. The normalized response amplitudes (response amplitude operators) are calculated for the cage motion response in heave and surge, and the mooring line tension response, in regular waves. In addition, a statistical approach is taken to determine the motion and tension transfer functions in irregular waves. In order to validate the numerical model of a gravity cage attacked by irregular waves, numerical predictions have been compared with the experimental observations in the time and frequency domain. The effect of wave incident angle on the float collar motion, mooring line tension and net volume reduction of the gravity cage system in irregular waves is also investigated. The results show that at high frequencies, the cage system has no significant heave motion. It tends to contour itself to longer waves. The variation amplitude of mooring line forces decreases as the wave frequency increases. With the increasing of wave incident angle, the horizontal displacement of the float collar increases. 相似文献
16.
随着风电产业向深远海发展,浮式风机已经成为海上风机未来的发展趋势.由于复杂的风浪联合环境载荷作用,浮式风机作业时通常会产生大幅度的运动响应,这一方面会使得浮式风机系统受到的水动力载荷更加复杂,另一方面会影响浮式风机的输出功率.因此,如何有效地抑制浮式风机系统的运动响应就成为了设计的关键.基于非稳态致动线模型和两相流求解器naoeFOAM-SJTU,进行了带垂荡板的浮式风机耦合性能研究.首先在OC3-Hywind Spar平台上附加垂荡板,并结合NREL-5 MW风力机建立带垂荡板的浮式风机模型.其次对比不同形状的垂荡板对Spar-5 MW型浮式风机气动—水动耦合结果,分析相同风浪联合作用条件下垂荡板形状对浮式风机耦合响应的影响.研究结果表明:垂荡板能够减小纵荡和垂荡等运动响应幅值,但是对纵摇运动响应影响较小;当垂荡板直径和吃水位置相同时,相同风浪条件下圆形垂荡板能使浮式风机的气动平均功率增大约0.844％,而正方形垂荡板却使平均功率减小1.492％,这说明圆形垂荡板对浮式风机系统的作用效果整体而言优于正方形. 相似文献
17.
《Applied Ocean Research》2007,29(1-2):45-54
Catenary mooring lines are typically subjected to bimodal loads, comprising of a wave frequency (WF) component due to the first-order wave forces and a low frequency (LF) component induced by the second-order wave forces. For moored vessels, the LF forces due to current and wind also play a role. Only dynamic wave loads are considered herein, while current and wind loads are modeled as constant forces. Because of the nonlinearities of the mooring line characteristics, the dynamic line tension and the second-order responses, both the WF and LF line tensions are in principle nonGaussian. These facts make it difficult to estimate the combined fatigue damage of mooring lines in the frequency domain. A fatigue combination rule based on the Jiao and Moan’s theory has been extended to cover the nonGaussian case. The purpose of this paper is to improve and validate the frequency-domain method by time-domain analysis based on a simplified, but accurate mechanical model of the dynamic line tension. Improvements on the LF and combined fatigue damage estimation have been made by considering the nonsymmetrical property of the LF line tension distribution. Both the WF and LF mooring line tensions due to wave loading have been simulated in the time domain for different sea states and the combined fatigue damage has been estimated by using the rainflow cycle counting algorithm. The accuracy of the frequency-domain method for estimating the bimodal nonGaussian fatigue damage of mooring lines has been verified by the time-domain simulations and is considered to be acceptable. 相似文献
18.
《中国海洋工程》2021,(3)
The fish cage design requires accurate predictions of long-term extreme loads and responses. Compared with the time-consuming full long-term analysis method integrating all the probability distribution of the short-term extremes,the environmental contour method gains much attention in predicting the long-term extreme values due to the less computational effort. This paper investigates the long-term extreme response of a fish cage using the environmental contour method. The fish cage is numerically simulated based on the lumped-mass method and the curved beam theory. Based on the one-dimensional(1D) and two-dimensional(2D) environmental contour, the extreme responses,including the surge and heave motions, mooring force, and vertical bending of the floater, are predicted for different return periods and compared with the full long-term analysis results. Results indicate that the 1D method greatly underestimates the extreme values. The 2D environmental contour method with a higher percentile level, namely90%, provides reasonable estimations and seems to be suitable for the long-term value analysis. Sensitivity studies show that the mooring arrangement and the bending stiffness have great effects on the bending moment and the mooring force and the mooring line pre-tension has minor effects on the fish cage response. 相似文献
19.
In this paper, motion response of a moored floating structure interacting with a large amplitude and steep incident wave field is studied using a coupled time domain solution scheme. Solution of the hydrodynamic boundary value problem is achieved using a three-dimensional numerical wave tank (3D NWT) approach based upon a form of Mixed-Eulerian–Lagrangian (MEL) scheme. In the developed method, nonlinearity arising due to incident wave as well as nonlinear hydrostatics is completely captured while the hydrodynamic interactions of radiation and diffraction are determined at every time step based on certain simplifying approximations. Mooring lines are modelled as linear as well as nonlinear springs. The horizontal tension for each individual mooring line is obtained from the nonlinear load-excursion plot of the lines computed using catenary theory, from which the linear and nonlinear line stiffness are determined. Motions of three realistic floating structures with different mooring systems are analyzed considering various combinations of linear and approximate nonlinear hydrodynamic load computations and linear/nonlinear mooring line stiffness. Results are discussed to bring out the influence and need for consideration of nonlinearities in the hydrodynamics and hydrostatics as well as the nonlinear modelling of the line stiffness. 相似文献
20.
我国南海海域海洋环境条件复杂且海水密度垂直层化现象显著,内孤立波活动频繁,因内孤立波而造成海洋开采平台破坏的案例屡见不鲜。依托水动力计算软件AQWA二次开发功能,采用Kdv方程,借助Fortran语言将深水半潜式平台立柱、浮箱、系泊系统3部分的内孤立波作用力叠加到外力项中,联合求解半潜式平台的6自由度动力响应特性。数值模拟结果表明,在内孤立波作用下,半潜式平台的运动及系泊线张力均受到了显著的影响。在不考虑系泊系统受内孤立波作用时,平台在纵荡和横荡方向上产生较大的漂移运动,最大偏移量较无内孤立波情况下增加了8倍;系泊线最大张力提高了17%,增加了系泊线断裂的风险。在考虑系泊系统受内孤立波作用时,平台的纵荡和横荡运动响应在原响应基础上继续提高15%,但是系泊线张力变化不大。内孤立波不同浪向下的平台纵荡和横荡响应相差也很明显;系泊系统合力在不同方向上的大小决定了平台不同方向上运动的大小。 相似文献