共查询到20条相似文献，搜索用时 140 毫秒
1.
在时域内分析深水钢悬链立管在平台运动和波流载荷共同作用下的非线性动力响应;采用雨流计数法处理立管节点应力的时间历程,选用DoE.E型S-N曲线分析立管在单一海况和平台运动联合作用下的疲劳损伤;将各方向含概率分布的疲劳损伤进行叠加,得到立管整体的全方向疲劳损伤及疲劳寿命。平台的运动为六自由度的运动预报数据,波流载荷由某海域实际的波浪统计数据采用Morison公式计算所得。计算结果表明钢悬链立管疲劳寿命的极值点分别位于悬挂点附近和触地点附近,对立管疲劳寿命极值点各方向疲劳损伤分布情况进行了分析。所提方法为钢悬链立管疲劳分析提供了新思路,给出的结论对钢悬链立管设计分析有一定借鉴意义。 相似文献
2.
研究海床土吸力对深海钢悬链线立管(SCR)与Spar平台整体波浪响应的影响。分别采用大挠度曲线梁模型、弹性地基梁模型模拟SCR的悬垂段和流线段,考虑SCR与Spar的动力耦合效应,提出整体分析法,并基于锚链/SCR分析程序Ca-ble3D开发V-Cable3D。考虑海床土吸力影响,时域动力响应分析获得一海况下SCR顶点和触地点的位移、张力、弯矩和应力时程。比较分析表明:SCR顶点和触地点附近分别存在波浪响应过程中的张力最大值和弯矩最大值,吸力对这两个特征量以及立管应力状态影响较大。提出的整体分析法为SCR波浪响应分析方法提供了新思路,对SCR与海床的相互作用分析有一定的参考意义。 相似文献
3.
非线性海床土深水缓波型立管动力响应分析 总被引：1，自引：1，他引：0
缓波立管的结构形式能够有效改善立管触地区的动力响应,达到保护立管触地区的目的。基于集中质量法和考虑土体弱化的非线性海床土模型,用等效浮力的方法将缓波立管浮力段简化,并在Orca Flex中建立传统钢悬链线立管和缓波立管的集中质量模型进行分析,考虑立管结构形式、浮力段长度和浮力段起始位置的影响,得到立管静态位形、触地点张力和弯矩、立管贯入深度以及触地点海床阻力等结果进行比较。结果表明:浮力段的配置会提高立管静态弯矩分布水平,但合理的缓波立管设计能有效改善立管触地区的动力响应,抑制海底沟槽的发展,达到保护立管触地区的目的。 相似文献
4.
钢悬链线立管(SCR)在上部浮体运动和波流荷载激励下会与海床土相互作用,传统的线性海床模型假定荷载位移关系是线性的,没有考虑管土相互作用的非线性过程和海床土吸力的影响,本文基于大挠度柔性索理论的钢悬链式立管动力分析程序CABLE3D,将立管受到线性海床的弹性支撑力扩充为立管受到的海床垂向力,充分考虑管土非线性相互作用,并考虑海床土吸力对钢悬链式立管触地点区域的影响,开发出新的动力分析程序。程序采用非线性有限元方法对控制方程进行离散,时域内采用Newmark-β法,求解给定上部浮体运动条件下,SCR的动力响应,通过算例对线性刚度海床和非线性刚度海床进行对比,并分析了不同海床刚度对SCR触地点动力响应和疲劳损伤的影响。结果表明:非线性海床刚度模型比线性海床刚度模型更接近真实的管土作用过程;在非线性海床刚度模型下,海床土刚度越大,SCR触地点区域垂向位移响应越小,应力幅值越大,疲劳损伤越严重。 相似文献
5.
《中国海洋大学学报(自然科学版)》2010,(Z1)
由于钢悬链线立管具有非线性特性,而海床土体又是软黏土,因此钢悬链线立管触地区域的管土的相互作用十分复杂。根据国外相关试验数据,采用ANSYS中的非线性弹簧单元模拟海床土体,考虑海床土体刚度退化和土吸力对管道的作用,建立海底管道拟静力有限元计算模型,计算分析管道与海床土体的相互作用,并探讨管道触地点区域关键点在顶端升沉运动下弯矩的变化规律,为进一步研究SCR与海床的动力相互作用提供参考。 相似文献
6.
采用弹性基础梁模型,模拟钢悬链线立管(steel catenary riser,SCR)与海床土的相互作用,推导了弹性基础梁模型的有限元公式,基于该模型编制了钢悬链式立管的动力分析程序,在此基础上,分析了在浮体运动及环境载荷作用下,钢悬链线立管触地点区域的动力响应特征,并与弹簧支撑模型进行了比较。研究表明,弹性基础梁模型对单元长度的敏感性较低,可采用较长的单元,从而减少计算量。 相似文献
7.
国外深水钢悬链线立管研究发展现状 总被引：2，自引：0，他引：2
介绍国外在新型深水立管系统--钢悬链线立管关键技术方面的研究发展现状,论述浮体一、二阶运动对钢悬链线立管疲劳寿命的影响、浮体升沉运动对钢悬链线立管触地点疲劳寿命的影响;钢悬链线立管与海底相互作用机制的实验研究及结果;钢悬链线立管涡致振动与疲劳的研究现状.并简要论述钢悬链线立管触地点问题的研究结论. 相似文献
8.
基于量纲分析理论,建立了钢悬链线立管(SCR)触地段的结构循环应变响应的相似准则。设计SCR立管触地段与土体相互作用装置,实验研究了典型工况下触地段床面形状变化对结构应变响应的影响。实验结果表明:水流载荷可使立管触地段下方土体局部冲刷的范围增大,立管结构应变幅值也相应增大;随着管土循环拍击作用和局部冲刷变形的发展,钢悬链线立管触地段的循环应变幅值逐渐增大并趋于稳定值;在立管脱离床面的瞬间,可观测到立管上缘拉应变突增的现象。拉应变突增幅度随着床面变形的发展逐渐增大,进而导致循环应变幅值的增加。 相似文献
9.
与海床的相互作用是钢悬链线立管特有的性质,是传统立管发展中不曾遇到的问题,也是控制立管疲劳寿命的主要因素,特别是触地区出现的峰值弯曲应力和管土接触模型的不确定,成为SCR触地区研究的难点。由于立管与海床的作用机理非常复杂,因此管土相互作用模型的提出大多是建立在模型试验的基础上。通过对国内外深水SCR触地区管土相互作用试验研究案例的分析,简要介绍了SCR触地点的动态响应取决于一系列参数,如海床土刚度、加载状况、立管的提升速度、土的重塑时间和土吸力等,并设计了一套三维管-土相互作用的试验装置,能够为深水钢悬链线立管触地区管-土相互作用的试验研究提供参考。 相似文献
10.
平台运动激励下钢悬链式立管触地点动态分析 总被引：1，自引：1，他引：0
平台运动和管土相互作用是引起钢悬链式立管(Steel Catenary Riser,SCR)触地点动态响应和疲劳损伤的关键因素。基于竖向土抗力-埋深曲线和侧向库伦摩擦双线模型模拟SCR触地区管土作用,并考虑竖向海床刚度的退化,研究平台三维运动激励下SCR触地区的动态响应与疲劳寿命,相对于简单的单向运动激励和仅考虑竖向管土作用,更符合工程实际。计算结果表明:①三维管土作用下,平台垂荡运动对立管触地区的影响最大,纵荡运动次之,横荡的影响最小;②平台三维运动的耦合,在一定程度上可降低立管触地区的动力响应和疲劳损伤,若仅考虑垂荡运动,结果偏于保守;③非线性海床模型相对于线弹性海床,引起的立管触地区的应力幅值、位移幅值显著增加,虽然贯入位移较小,但土抗力较大,选用线弹性海床的计算误差较大。平台运动和海床强度对SCR触地点动态响应和疲劳损伤的影响较大,因此在SCR响应分析与设计中,准确选择海床模型和平台运动方式,对于预测立管的疲劳寿命具有重要意义。 相似文献
11.
Numerical Simulation of Water Exchange Characteristics of the Jiaozhou Bay Based on A Three-Dimensional Lagrangian Model 总被引：1，自引：0，他引：1
Based on theory of three-dimensional hydrodynamics,an Euler-Lagrangian particle model is established to study the transport and water exchange capability in the Jiaozhou Bay.The three-dimensional hydrodynamic model,driven by tide and wind,is used to study the effects of wetting and drying of eatuarine intertidal flats by the dry-wet grid technology based on the Estuarine,Coastal and Ocean Model (ECOM).The particle model includes the advection and the diffusion processes,of which the advection process is simulated with a certain method,and the diffusion process is simulated with the random walk method.The effect of the intertidal zone,the turbulent diffusion and the timescales of the water exchange are also discussed.The results show that a moving boundary model can simulate the transport process of the particle in the intertidal zone,where the particles are transported for a longer distance than that of the stationary result.Simulations with and without the turbulent random walk show that the effect of turbulent diffusion is very effective at spreading particles throughout the estuary and speeding up the particle movement.The spatial distribution of residence time is given to quantify the water exchange capability that has very important ramifications to water quality.The effect of wind on the water exchange is also examined and the southeasterly wind in summer tends to block the water exchange near the northeast coast,while the northerly wind in winter speeds up the transport process.These results indicate that the Lagrangian particle model is applicable and has a large potential to help understanding the water exchange capability in estuaries,which can also he useful to simulate the transport process of contaminant. 相似文献
12.
Estuary/ocean exchange and tidal mixing in a Gulf of Maine Estuary: A Lagrangian modeling study 总被引：2，自引：0，他引：2
Ata Bilgili Jeffrey A. Proehl Daniel R. Lynch Keston W. Smith M. Robinson Swift 《Estuarine, Coastal and Shelf Science》2005,65(4):607-624
A Lagrangian particle method embedded within a 2-D finite element code, is used to study the transport and ocean–estuary exchange processes in the well-mixed Great Bay Estuarine System in New Hampshire, USA. The 2-D finite element model, driven by residual, semi-diurnal and diurnal tidal constituents, includes the effects of wetting and drying of estuarine mud flats through the use of a porous medium transport module. The particle method includes tidal advection, plus a random walk model in the horizontal that simulates sub-grid scale turbulent transport processes. Our approach involves instantaneous, massive [O(500,000)] particle releases that enable the quantification of ocean–estuary and inter-bay exchanges in a Markovian framework. The effects of the release time, spring–neap cycle, riverine discharge and diffusion strength on the intra-estuary and estuary–ocean exchange are also investigated.The results show a rather dynamic interaction between the ocean and the estuary with a fraction of the exiting particles being caught up in the Gulf of Maine Coastal Current and swept away. Three somewhat different estimates of estuarine residence time are calculated to provide complementary views of estuary flushing. Maps of residence time versus release location uncover a strong spatial dependency of residence time within the estuary that has very important ramifications for local water quality. Simulations with and without the turbulent random walk show that the combined effect of advective shear and turbulent diffusion is very effective at spreading particles throughout the estuary relatively quickly, even at low (1 m2/s) diffusivity. The results presented here show that a first-order Markov Chain approach has applicability and a high potential for improving our understanding of the mixing processes in estuaries. 相似文献
13.
This study extends previous two-dimensional research [Wang, S.D., Shen, Y.M., Zheng, Y.H., 2005. Two-dimensional numerical simulation for transport and fate of oil spills in seas. Ocean Engineering 32, 1556–1571] to three dimensions in order to investigate the vertical dispersion/motion of the spilled oil slick, which is a more realistic model of the motion of the spilled oil. To this end, a three-dimensional (3-D) model, based on the particle approach, is developed for simulating oil spill transport and fate in seas. The amount of oil released at sea is distributed among a large number of particles tracked individually. These particles are driven by a combination of water current, wave- and wind-induced speed and move in a 3-D space. Horizontal and vertical diffusion are taken into account using a random walk technique. The model simulates the most significant processes which affect the motion of oil particles, such as advection, surface spreading, evaporation, dissolution, emulsification, turbulent diffusion, the interaction of the oil particles with the shoreline, sedimentation and the temporal variations of oil viscosity, density and surface tension. In addition, the processes of hydrolysis, photo-oxidation and biodegradation are also considered in this model. The model has been applied to simulate the oil spill accident in the Bohai Sea. 相似文献
14.
This paper presents the development and application of two-dimensional and three-dimensional oil trajectory and fate models for coastal waters. In the two-dimensional model, the oil slick is divided into a number of small grids and the properties of each grid due to spreading, advection, turbulent diffusion, evaporation and dissolution are studied. This model can predict the movement of the oil slick on the water surface. In order to simulate the distribution of oil particles in the water column, a three-dimensional oil fate model is developed based on the mass transport equation and the concentration distribution of oil particles can be solved. A comparison of numerical results with the observed data shows good conformity. 相似文献
15.
水下溢油数值模拟研究 总被引：1，自引：0，他引：1
基于Lagrange积分法和Lagrange粒子追踪法建立了一个水下溢油数值模型。该溢油模型由两个子模型组成:羽流动力模型和对流扩散模型,其中羽流动力模型用以模拟溢油的喷发阶段和浮力羽流阶段;对流扩散模型用以模拟溢油的对流扩散阶段。通过数值实验,结合实验室水槽实验和水下溢油现场实验的观测资料进行模型验证。实验结果表明,模拟结果与观测资料一致性较好,从而验证了本文溢油模型的合理性和准确性;羽流动力模型为对流扩散模型提供源,海流、海水的垂向密度结构和油滴的直径分布是影响溢油在对流扩散阶段运动和分布的主要因素。 相似文献
16.
17.
The upper ocean response to a moving typhoon 总被引：1，自引：0，他引：1
The upper ocean response to the translation speed of typhoons is studied using a three-dimensional primitive equation model.
Similar models studied previously have applied stability criteria rather than the diffusion term to simulate the vertical
mixing process. This study retains the diffusion term and uses the level-2 turbulence closure scheme to estimate the vertical
eddy viscosity. The model results indicate that in the forced period, the mixed-layer temperature decrease is greater for
a slow-moving storm due to stronger upwelling caused by the longer residence time. A fast-moving storm can attain a similar
cooling intensity in the wake period if its residence time allows the wind to resonate with the current. The significant downward
momentum diffusion and advection in the first few inertial periods of these events leads to strong, persistent inertial pumping
throughout the upper ocean in the wake period. The mixed layer is further cooled by turbulent mixing supported by vertical
current shears. Meanwhile, the upper thermocline exhibits a compensating temperature increase. The vertical transfer magnitude
and penetration scale are smaller in the slow-moving case, when the inertial motion decays rapidly. The model results also
indicate that the dominant cooling process can be inferred from the non-dimensional storm speed. However, this value may be
misleading for rapidly moving storms in which the current response is so distant from the storm that little wind work is performed
on the ocean. 相似文献
18.
19.
Novel laboratory experiments and numerical modelling have been performed to study the advection scales of suspended sediment in the swash zone. An experiment was designed specifically to measure only the sediment picked up seaward of the swash zone and during bore collapse. The advection scales and settling of this sediment were measured during the uprush along a rigid sediment-free beach face by a sediment trap located at varying cross-shore positions. Measurements were made using a number of repeated solitary broken waves or bores. Approximately 25% of the pre-suspended sediment picked up by the bores reaches the mid-swash zone (50% of the horizontal run-up distance), indicating the importance of the sediment advection in the lower swash zone. The pre-suspended sediment is sourced from a region seaward of the shoreline (still water line) which has a width of about 20% of the run-up distance. An Eulerian–Lagrangian numerical model is used to model the advection scales of the suspended sediment. The model resolves the hydrodynamics by solving the non-linear shallow water equations in an Eulerian framework and then solves the advection–diffusion equation for turbulence and suspended sediment in a Lagrangian framework. The model provides good estimates of the measured mass and distribution of sediment advected up the beach face. The results suggest that the correct modelling of turbulence generation prior to and during bore collapse and the advection of the turbulent kinetic energy into the lower swash is important in resolving the contribution of pre-suspended sediment to the net sediment transport in the swash zone. 相似文献
20.
Simulation of Formation and Spreading of Salinity Minimum Associated with NPIW Using a High-Resolution Model 总被引：1，自引：2，他引：1
A series of numerical experiments were conducted with a high-resolution (eddy-permitting) North Pacific model to simulate
the formation and spreading of the salinity minimum associated with the North Pacific Intermediate Water (NPIW). It was found
that two factors are required to simulate a realistic configuration of the salinity minimum: a realistic wind stress field
and small-scale disturbances. The NCEP reanalyzed wind stress data lead to better results than the Hellerman and Rosenstein
wind stress data, due to the closer location of the simulated Oyashio and Kuroshio at the western boundary. Small-scale disturbances
formed by relaxing computational diffusivity included in the advection scheme promote the large-scale isopycnal mixing between
the Oyashio and Kuroshio waters, simulating a realistic configuration of the salinity minimum. A detailed analysis of the
Oyashio water transport was carried out on the final three-year data of the experiment with reduced computational diffusivity.
Simulated transport of the Kuroshio Extension in the intermediate layer is generally smaller than the observed value, while
those of the Oyashio and the flow at the subarctic front are comparable to the observed levels. In the Oyashio-Kuroshio interfrontal
zone the zonally integrated southward transport of the Oyashio water (140–155°E) is borne by the eddy activity, though the
time-mean flow reveals the existence of a coastal Oyashio intrusion. In the eastern part (155°E–180°) the zonally integrated
transport of the Oyashio water indicates a southward peak at the southern edge of the Kuroshio Extension, which corresponds
to the branching of the recirculating flow from the Kuroshio Extension.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献