共查询到20条相似文献，搜索用时 44 毫秒
1.
基于有限体积方法的海洋数值模式FVCOM,计算了南黄海西部六月份潮致余流及风生环流,分析了潮致余流、初夏风生环流各自的环流结构,得出六月份该区域风生环流占主导,偏南风的作用较为显著,潮致余流相对较弱。最后将风和潮汐进行耦合计算,得出该区域初夏的环流结构,表层海水大体为由南至北的流动,说明该区域风力为主要驱动力。计算结果与流速及环流实测资料吻合较好,为进一步研究浒苔的漂移轨迹等奠定了动力基础。 相似文献
2.
当FPSO服役于目标油田时,将受到风浪流的作用力。其中,风力给FPSO一个恒定的静力,使其偏离原来的位置。风力计算在FPSO系泊系统的分析过程中是非常重要的。设计人员常常参考OCIMF进行风力计算,或者参考API规范得出。OCIMF为针对油轮的计算规范,但使用OCIMF计算FPSO风力及流力的方法,与FPSO的适应性仍需要进一步论证。API规范针对海上浮式系统,其计算风流力的方法使用也非常广泛,其原理为将FPSO上部各个模块风力叠加得出。以FPSO风载荷为研究对象,开展了风洞模型试验,获得了典型FPSO风载荷特性曲线,并将试验结果分别与OCIMF结果和API规范计算结果进行对比分析,最终给出FPSO风力计算方法的建议。本数据可用于FPSO的风力计算,也可为FPSO运动、系泊的设计研究提供参考。 相似文献
3.
管内流动会影响输流管的振动响应,目前关于输流弹性管涡激振动方面的研究较少。基于计算流体力学(CFD)方法,开展内外流对细长输流弹性管振动特性影响的研究。首先在不考虑内流的情况下将弹性管涡激振动数值预报结果与模型试验数据进行对比,验证了数值方法的可靠性。再者考虑内外流耦合作用情况下,对不同内流流速下细长输流弹性管振动位移时—空分布、顺流向最大平均偏移、振动轨迹、内部横向涡的形成与分布等进行了对比分析。结果发现,与外流流速相比,内流流速的增加虽然难以改变弹性管的主振模态,但对沿管体的振动强度影响显著。顺流向最大偏移处管体运动轨迹发生明显的变形和跳跃。在剪切外流和均匀内流对弹性管的联合作用下,沿管跨方向模态间能量转换频繁,伴随着间歇性出现或消失的沿弹性管传播的行波组分,这主要归因于复杂的双重流固耦合系统(外流—管体,内流—管体)。在内流以附加质量力、离心力和科氏力形式的激励下,弹性管内二次流现象明显。在振动过程中,内部横向涡沿管壁生成、脱落并逐渐散布于整个横截面。 相似文献
4.
Subrata K. Chakrabarti 《Applied Ocean Research》1984,6(2):73-82
The contribution of the steady drift force on a floating structure may arise from waves, wind and current. The component of the wave drift force may be due to the second-order diffraction theory or potential effect and may be due to the velocity squared force or viscous effect. The presence of current in waves increases the effect of the viscous force. The expressions for these terms for a vertical cylinder are derived and their relative importance is investigated. Plots are presented showing the regions where the viscous or potential drift force predominates. Experiments were conducted with both small and large diameter cylinders. The mean drift forces obtained in these tests are compared with the theory. 相似文献
5.
6.
辽河三角洲潮道沉积物为软弱淤泥质土，管桩在波流荷载作用下的弹性变形或振动，可以导致潮道软土强度衰减并发生变形位移，随着悬臂段加长和波流荷载振动作用，下部扮土会自上而下发生液化。简单管桩的抗倾验算可以按照波流力与被动土压力的作用力矩分析，并考虑到海底的冲刷淘空深度。管桩打入下卧高强度粉土时，在保证打入深度的同时，应适当增大管桩的强度，加大管桩自振周期与波浪周期的差值。 相似文献
7.
Influence of wave-current interactions on fluid force on a single cylinder and on two cylinders in tandem is examined. Quantities obtained are spectra of fluid force on elements, total fluid force and its statical moment. Comparisons are made of the cases in which wave-current interactions are considered and ignored. It is shown that interactions affect spectra of element force and statical moment more than do total force spectrum. For two cylinders in tandem, for cylinder spacings, current conditions and frequency range of practical interest, the effect of interactions is slightly reduced. 相似文献
8.
Combined effects of current and waves on fluid force 总被引：2，自引：0，他引：2
Combined effects of current and waves on the force exerted on an element of a cylinder in a random gravity wave field in deep water are studied. Wave-current interactions are taken into account. Statistical quantities of the fluid force such as force spectrum and root mean square value of the force are obtained numerically and presented in graphical forms. Comparisons are made of the cases in which wave-current interactions are considered and ignored. It is shown that wave-current interactions contribute to changes in fluid force to an appreciable extent and therefore should be considered in the evaluation of fluid forces on objects. 相似文献
9.
以Spar型浮式风机为研究对象,研究涡激力对于浮式风机系统运动的影响。对多体动力学软件FAST进行二次开发,加入涡激力的计算接口,实现了在平台涡激、波激、空气动力载荷及系泊联合作用下的Spar浮式风机系统的运动响应的计算。计算了在风、浪、流联合作用下,频率锁定现象发生时,Spar基础的运动响应,分析了风浪下Spar风机运动响应的涡激运动特性,并研究了不同的入流角度的影响。结果表明:考虑涡激力后,Spar基础的横荡运动明显增大;风浪流同向时,风浪的存在会抑制流载荷引起的横荡在涡泄频率的运动;在流与风浪垂直时,会激发Spar基础的更大的纵荡运动响应。 相似文献
10.
—The forces of random wave plus current acting on a simplified offshore platform(jacket)mod-el have been studied numerically and experimentally.The numerical results are in good agreement withexperiments.The mean force can be approximated as a function of equivalent velocity parameter and theroot-mean-square force as a function of equivalent significant wave height parameter. 相似文献
11.
Internal solitons can bring about strong force on the oil drilling platform and pipeline at sea, which causes severe threat to the ocean engineering. Cai et al. (2003) introduced Morison's empirical formula, modal separation method and regression analyses to estimate the forces exerted by internal soliton on cylindrical piles. However, this method is very complicated and it requires some observational current data which are generally very difficult to obtain synchronically. In this paper, it is shown that the force by the first mode internal wave dominates most part of the global force, thus a new simple estimation method of the force based on only the first mode internal wave is put forward without some complicated steps and observational current data in the old method. The force can be estimated by the local vertical observational temperature, salinity data and amplitude of internal soliton. 相似文献
12.
研究了茅家港环抱式突堤航道防护工程对茅家港犀段的海犀水动力和海犀地貌的影响,分析了该岸段海犀水动力变化和海岸地貌演变的原因,结果表明,堤内和东堤外侧的水动力变弱,滩面淤积;西堤外侧的水动力变强,滩面冲蚀;口门处的水动力增强,航道位置稳定且冲蚀加深;口门以外的水动力未变化,航道不稳定． 相似文献
13.
A. E. Gledzer E. B. Gledzer A. A. Khapaev O. G. Chkhetiani 《Izvestiya Atmospheric and Oceanic Physics》2013,49(2):187-200
The results of experiments on turbulent flows excited by the Ampere force in a thin layer of a conducting fluid over a solid surface upon the passage of a current and the action of a spatially periodic magnetic field are considered. Third-order longitudinal structure functions of the velocity field are shown to be approximately linear in the spatial shift and negative even at horizontal scales that exceed the layer thickness by an order of magnitude. This is how the three-dimensional dynamics is manifested as a result of the dominant contribution of energy dissipation when the no-slip boundary condition is satisfied on the lower surface. Dissipation and the main summands of energy production have been estimated for the energy-balance equation. 相似文献
14.
A numerical model of the steel catenary riser(SCR) is built based on the slender rod model. The slender rod model,which describes the behavior of the slender riser in terms of the center line position, can solve the geometrical nonlinearity effectively. In a marine environment, the SCR is under the combined internal flow and external loads,such as wave and current. A general analysis considers only the inertial force and the drag force caused by the wave and current. However, the internal flow has an effect on the SCR; it is essential to explore the dynamic response of the SCR with the internal flow. The SCR also suffers the lift force and the fluctuating drag force because of the current. Finite element method is utilized to solve the motion equations. The effects of the internal flow, wave and current on the dynamic response of the SCR are considered. The results indicate that the increase of the internal flow density leads to the decrease of the displacement of the SCR, while the internal flow velocity has little effect on the SCR. The displacement of the SCR increases with the increase of the wave height and period. And the increasing wave period results in an increase in the vibration period of the SCR. The current velocity changes the displacements of the SCR in x-and z-directions. The vibration frequency of the SCR in y-direction increases with the increase of the current velocity. 相似文献
15.
Ice loads on a ship hull affect the safety of the hull structure and the ship maneuvering performance in ice-covered regions. A discrete element method （DEM） is used to simulate the interaction between drifting ice floes and a moving ship. The pancake ice floes are modelled with three-dimensional （3-D） dilated disk elements considering the buoyancy, drag force and additional mass induced by the current. The ship hull is modelled with 3D disks with overlaps. Ice loads on the ship hull are determined through the contact detection between ice floe element and ship hull element and the contact force calculation. The influences of different ice conditions （current velocities and directions, ice thicknesses, concentrations and ice floe sizes） and ship speeds are also examined on the dynamic ice force. The simulated results are compared qualitatively well with the existing field data and other numerical results. This work can be helpful in the shil3 structure design and the navigation securitv in ice-covered fields. 相似文献
16.
Non-linear loads on a fixed body due to waves and a current are investigated. Potential theory is used to describe the flow, and a three-dimensional (3D) boundary element method (BEM), combined with a time-stepping procedure, is used to solve the problem. The exact free-surface boundary conditions are expanded about the still-water level by Taylor series so that the solution is evaluated on a time-invariant geometry. A formulation correct to second order in the wave steepness and to first order in the current speed is used. Numerical results are obtained for the first-order and the second-order oscillatory forces and for the second-order mean force on a fixed vertical circular cylinder in waves and a current. The second-order oscillatory forces on the body in waves and current are new results, while the remaining force components are verified by comparison with established numerical and analytical models. It is shown that the current can have a significant influence on the forces, and especially on the amplitude of the second-order oscillatory component. 相似文献
17.
海底管道掏空与波浪力变化关系试验 总被引：1，自引：0，他引：1
鉴于海底油气管道在海洋能源开发中的特殊意义,前人开展了大量管道安全试验研究,特别注重不同底床、不同波浪条件、不同埋置深度等方面的组合试验,本次试验针对危害管道安全的掏空和悬跨开展了波浪水槽试验,探讨黄河三角洲为主的粉土海床上掏空与管道受力关系,弥补这方面研究的不足,结果表明,海底管道受力变化与掏空过程密切相关。连续试验过程表明,海底管道与海床土、波浪水体之间存在密切关系。海底管道在波浪作用下冲刷掏空经历了3个演变阶段:泥沙起动阶段、水流隧道发育阶段、快速掏空阶段和冲刷平衡阶段。水流隧道伴随的管涌对冲刷掏空起重要作用。伴随冲刷掏空,管道波浪力出现规律性转化,从正向作用逐渐过渡到负向作用,也可以分出4个演化阶段:冲刷初始阶段,管道波浪力以正向为主,管道表现为正向力作用下的振动;隧道发育阶段,管道受到的作用力主要是波峰上举力和波谷下拉力,表现为上下振动;管道悬空阶段,波峰负向作用力和波谷正向力交替出现,管道在波浪作用下表现为前后振动;冲刷平衡阶段,管道主要在负向作用力下振动。 相似文献
18.
基于三维频域势流理论,计算船体的水动力参数;采用动态耦合方法分析了深海半潜式生产平台各系统之间的相互作用特征,研究了立管系统对锚泊系统定位能力的影响。计算结果表明,立管系统在一定程度上增加了整个系统的刚度,其所受的附加质量和阻尼可降低平台的低频响应,从而降低平台的偏移和系泊缆的张力;海流将增大立管上的拖曳力,使平台偏移更远,锚索上的张力更大;立管系统对锚泊系统定位性能的最终影响需综合考虑多种因素的叠加。对目标平台而言,由于服役海域的流速较大,对立管的拖曳作用较为明显。因此,为确保平台的安全性,当服役海域流速较大时,带有多立管的平台,其锚泊系统的设计应考虑立管的影响。 相似文献
19.
本文用多元统计分析阐述了连云港附近岸滩表层沉积物的粒度特征,以及沉积物的平均粒径与波浪、潮流最大底切速之间的密切关系,从而得到沉积物运动的判据,它对预测岸滩冲淤亦具有一定的实际意义。 相似文献
20.
海上浮体动力定位外力计算 总被引：5，自引：1，他引：4
动力定位系统（dynamic positioning system）是一种闭环自动控制系统,采用推力器来抵抗风、浪、流等作用在浮体上的境力,使其保持在所要求的位置上。船舶的风和流作用力由经验公式求得,波浪力主要考虑二阶漂移力,由三维势流理论的直接积分法求得。通过模拟仿真,表明其结果能够用于船舶动力定位系统研究。 相似文献