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This paper aims to present the critical top tension for static equilibrium configurations of a steel catenary riser(SCR) by using the finite element method. The critical top tension is the minimum top tension that can maintain the equilibrium of the SCR. If the top tension is smaller than the critical value, the equilibrium of the SCR does not exist. If the top tension is larger than the critical value, there are two possible equilibrium configurations. These two configurations exhibit the nonlinear large displacement. The configuration with the smaller displacement is stable, while the one with larger displacement is unstable. The numerical results show that the increases in the riser's vertical distances, horizontal offsets, riser's weights, internal flow velocities, and current velocities increase the critical top tensions of the SCR. In addition, the parametric studies are also performed in order to investigate the limit states for the analysis and design of the SCR. 相似文献
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岬间砂质海岸平衡形态模型及其在华南海岸的应用 总被引:1,自引:0,他引:1
本文介绍了对数螺线、双曲线、抛物线三种岬间海湾平面平衡形态模型,并通过对比分析,表明抛物线为三种模型中较为理想的模型.根据抛物线模型的基本原理,本文提供了模型的可行性操作,并就抛物线模型对华南岬间海湾的应用展开了讨论. 相似文献
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静态平衡岬湾海岸理论及其在黄、渤海海岸的应用 总被引:6,自引:0,他引:6
岬湾海岸是一种稳定的海岸存在形式,在天然海岸中岬湾地貌占51%。岬湾海岸研究是研究砂质海岸稳定性及演变的重要内容。岬湾海岸理论在海岸稳定性、海岸工程预测以及海岸综合治理方面有其重要的工程价值。文中详细讨论了岬湾理论中最具工程意义的抛物线型岬湾海岸线及基于静态平衡岬湾海岸理论开发的可视化应用软件MEPBay在海岸工程中的应用,并验证了该理论对黄、渤海海岸的适用性。MEPBay软件不仅有助于理解海岸形态过程,也是海岸工程师在岸线保护及海岸管理实践中的有力辅助工具。 相似文献
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岬湾海岸是全球重要的海岸地形,约占全球岸线的51%。岬间海滩又是岬湾海岸地形中最重要的组成部分。20世纪40年代以来,海洋地质学家和海岸工程师们对岬湾海岸做了大量的研究。尤其在20世纪80年代,有关抛物线形状海湾方程的成果发表和后来相关计算机软件的开发,都对判断岬湾岸线稳定性和预测岬头下游海岸的静态平衡起到至关重要的作用。详细介绍了静态平衡岬湾的概念,并且通过在由动态平衡向静态平衡转化、以岸外坝群保护平直沙岸、提高单岬或丁坝下游的稳定性等方面的具体应用,验证了方程的有效性。通过适当的人工构筑物,配合人工养滩,创造静态平衡的海滩,对海岸带的开发和保护具有重要意义。 相似文献
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Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R~2 value ~96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of "torque" or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed. 相似文献
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对海岸侵蚀特征及防治措施效果的分析表明,人工养滩方法是最为环保、长效、经济的海岸侵蚀防治方法.在详细介绍静态平衡岬湾和人工养滩的基本原理的基础上,重点阐述了人工岬湾养滩综合法的设计原则和总体思路,并以北戴河西海滩恢复治理工程为例进行了方案设计. 相似文献
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为了研究三亚海岸带地质环境状况,本文通过遥感技术,采用1987年的TM、2000年的TM、2010年的Rapideye和2015年的QB2四个时相的卫星遥感数据,对比研究过去28年来三亚海岸带地质环境变化情况,利用平衡岬湾模型软件Mepbay对工程用海海岸进行静态平衡岸线模拟,在研究中发现三亚海岸带地质环境有较大变化,地质灾害点较多,岸线侵蚀、淤积问题突出,岸线变迁幅度较大,造成三亚海岸带地质环境变化的主要原因是人们过度开发海岸带资源,用海工程规划设计不合理,缺乏环境保护意识,其次是自然因素。 相似文献