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1.
The winding and unwinding of a pipeline onto a large diameter reel as practiced in the reeling installation method, induces bending strains of 1–3% followed by straightening, and reverse bending. The operator must ensure that such plastic deformations are sustained free of local buckling or rupture in the line. Such failures are for example precipitated by pipeline discontinuities in wall thickness and yield stress as they act as stress risers, lead to localized deformations severe enough to result in local buckling. The effect of such discontinuities is studied using a large-scale nonlinear finite element model that simulates the reeling/unreeling of a pipeline. Nonlinear kinematic hardening is used to capture the elasto-plastic behavior of the material imposed by the bending/reverse bending history. Discontinuities in wall thickness and yield stress are shown to result in sharp local changes in curvature that extend over 3–4 pipe diameters accompanied by severe local straining and ovalization. The extent of the disturbance is governed by the bending strain imposed by the ratio of pipe to reel diameter. It can be reduced by an increase in the applied tension but at the expense of additional ovalization of the pipeline. It can also be reduced by increasing the pipe wall thickness but with the consequent increase in costs. A parametric study of the effect of such discontinuities demonstrates that for some combinations of process parameters, the disturbance can lead to local buckling either during winding or unwinding. It is concluded that a modeling framework such as the one presented should be used to generate a design protocol for reel-installed pipelines. 相似文献
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采用卷管法进行海底管道铺设过程中,管道首先通过牵引作用上卷于卷筒进行储存。管道与卷筒发生非线性接触,可能会产生复杂的塑性变形和局部屈曲。通过全尺寸柔性管力学性能试验获得柔性管轴力—应变以及弯曲—曲率等非线性力学性能关系,将试验所得的非线性材料性能参数导入建立的两种柔性管上卷ABAQUS有限元模型（梁—实体单元模型与壳和桁架—实体单元模型）,实现柔性管较大轴向抗拉刚度和较小抗弯刚度的同步模拟以及管道与卷筒的非线性接触响应特征。通过对比分析两种有限元模型数值模拟得到的管道弯矩、弯曲曲率、管道轴力、管道与卷筒的接触压强等数据,发现在管道上卷过程中管道沿副法线方向的SM3弯矩占据其弯曲变形主导地位;管道与卷筒之间的摩擦效应对于管道轴力的影响较为显著;管道与卷筒的最大接触压强主要发生在卷管过渡段区域。 相似文献
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针对胜利石油管理局“滩海铺管敷缆船”总体设计情况，分别从设计指标、基本功能、主要性能参数、关键技术和总体布置等几个方面进行了较详细的介绍。该装备具有性能指标先进、设备装备精良、工艺流程合理、安全可靠和注重环保的特点，适用于我国浅海油田及其它相同情况海域。 相似文献
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A numerical approach for predicting motion and tension of extensible marine cables during laying operations in a rough sea is presented here. The solution methodology consists of dividing the cable into straight elements, which must satisfy an equilibrium equation and compatibility relations. The system of nonlinear differential equations is solved by the Runge–Kutta method, taking the effect of regular and/or irregular waves into account explicitly.
Illustrative applications of the method are given for a typical cable laying ship. The results are presented as rms values of the cable dynamic tension and corresponding dynamic factor for two different types of cable and several values of cable stiffness. The effect of axial deformation on the maximum tension at the shipboard pulley location is highlighted. 相似文献
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Yosuke Fujii 《Journal of Oceanography》2005,61(1):167-181
I present the derivation of the Preconditioned Optimizing Utility for Large-dimensional analyses (POpULar), which is developed for adopting a non-diagonal background error covariance matrix in nonlinear variational analyses (i.e., analyses employing a non-quadratic cost function). POpULar is based on the idea of a linear preconditioned conjugate gradient method widely adopted in ocean data assimilation systems. POpULar uses the background error covariance matrix as a preconditioner without any decomposition of the matrix. This preconditioning accelerates the convergence. Moreover, the inverse of the matrix is not required. POpULar therefore allows us easily to handle the correlations among deviations of control variables (i.e., the variables which will be analyzed) from their background in nonlinear problems. In order to demonstrate the usefulness of POpULar, we illustrate two effects which are often neglected in studies of ocean data assimilation before. One is the effect of correlations among the deviations of control variables in an adjoint analysis. The other is the nonlinear effect of sea surface dynamic height calculation required when sea surface height observation is employed in a three-dimensional ocean analysis. As the results, these effects are not so small to neglect. 相似文献
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In this paper a nonlinear dynamic PDE formulation for a pipe string suspended from a pipelay vessel to the seabed in a pipelay operation is developed. This model extends a three-dimensional beam model capable of undergoing finite extension, shearing, twist and bending, to apply for marine applications by adding the effects of restoring forces, hydrodynamic drag and seabed interaction. The model is validated against the natural catenary equation and the FEM code RIFLEX. The model is extended to include the pipelay vessel dynamics by applying a potential theory formulation of a surface vessel, suited for dynamic positioning and low speed maneuvering, as a boundary condition for the PDE. This system is found to be input-output passive and stable. Pipeline installation applications where the presented model is suited are e.g., analysis and simulation of the installation operation, operability analysis, hardware-in-the-loop (HIL) testing for vessel control systems, and automation of the pipelay operation. 相似文献
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Jean-François Balmat Frédéric Lafont Robert Maifret Nathalie Pessel 《Ocean Engineering》2009,36(15-16):1278-1286
This paper presents a fuzzy approach for the MAritime RISk Assessment (MARISA) applied to safety at sea. The aim of this work is to define automatically an individual ship risk factor which could be used in a decision making system. To achieve this purpose, a modular and hierarchical structure using fuzzy logic has been developed. It allows us to obtain a fuzzy risk factor (FRF) composed of a static risk factor (SRF) and a dynamic risk factor (DRF). The static risk factor assessment takes into account several static data relative to the ship (age, flag, gross tonnage, number of companies, duration of detention and type). The dynamic risk factor is evaluated by considering the meteorological conditions (sea state, wind speed and visibility) and the moment of the day. Moreover, the MARISA graphic interface developed with the Labview software is presented. This interface allows several simulations to be carried out to validate the fuzzy method proposed. Simulation results are presented. 相似文献
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This paper reports a study of the field measurements and monitoring of wastewater discharge in sea water at Bari East (Italy). A wastewater sea outfall system is an integral and fundamental part of each wastewater treatment with ultimate sink in the sea water. The design of a water treatment plant and wastewater outfall must take into account the use of the environmental water, the values of physicochemical parameters to be respected in order to safeguard the use itself and the quality of the environmental water where wastewater is issued. In the present study measurements of sea current velocity components were carried out with a VM-ADP (Vessel-Mounted Acoustic Doppler Profiler). Salinity, wind directions and velocities were assessed with, for one survey, the total faecal coliforms and other biochemical parameters. It was emphasized that the measurements necessary for monitoring cannot be concentrated in the wastewater outfall pipe zone only, but should be extended to a neighbouring area of the outfall pipe, with an extension depending on the wastewater discharge, the polluting charge and the magnitude of the sea currents and the winds typical of the zone of interest. The analyses presented in this paper confirm that the sea zones close to the wastewater outfall pipe are particularly sensitive and vulnerable. Such results must be considered in the planning of a wastewater outfall pipe. 相似文献
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Mostafa A. Foda 《Applied Ocean Research》1985,7(2):79-84
The vertical stability of a submarine pipeline laid half-buried on the sea floor under wave action is studied. As the wave-induced lifting force acts to detach the pipe from the sea floor, mud suction resistance will be developing at pipe-soil interface, acting to hold the pipe in place. This couples the pipe equilibrium with the seabed response which is modelled as a poroelastic media, following the formulation of Biot. Conditions for pipe detachment or breakout from the sea floor are investigated for typical seawave, pipe, and seabed parameters. A general power law will describe the slow quasistatic breakout of the pipe. In the case when the forcing wave period is much shorter than the quasistatic breakout time, the response function of the coupled pipe-seabed system will involve weak nonlinear terms of higher harmonics. The possibilities for resonating the system in such case are examined by including the inertia of the pipe in the analysis. 相似文献
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深海采矿系统中的长距离垂直输运管道在工作中具有复杂的流固耦合力学特性,在生产作业中其结构安全性和可靠性面临严峻考验。建立深海采矿系统从海底到水面的完整模型,采用集中质量法对于其中的长距离垂直输运管道的环境载荷进行了研究,并将计算结果与模型试验测量值进行对比验证,重点分析管道顶部轴向张力和剪力的大小关系以及变化规律。分析结果表明:在深海采矿系统的长距离垂直输运管道中,轴向张力在结构载荷占主要成分,由波浪引起的结构轴向张力增加会达到管体自重的38%～48%。因此,选择合适的作业工况对降低结构载荷,加强结构安全性能有很大帮助。 相似文献
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Ole Fabian 《Ocean Engineering》1981,8(3):295-330
A study of the elastic-plastic collapse behaviour of long, cylindrical tubes subjected to combined bending and pressure load is presented.Besides the plastic properties of the tube material, the non-linearities accounted for in the analysis cover the Brazier effect and the influence of geometrical imperfections. The imperfections considered are given either by initial ovalization of the tube cross-section or in terms of initial, short-wave axial buckles. Related to ocean pipe laying, i.e. for thick-walled tubes under combined bending and external pressure load, initial ovalization proves to be by far the more severe type of imperfection. 相似文献
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随着海洋科学技术的发展和人类对于海洋油气资源认识的不断增加,海洋油气资源的开发从近海走向远海。作为海洋油气运输主要方式的海洋管道,其铺设问题成为焦点。常见海洋管道工程铺设方法为:拖曳铺设、卷筒铺设、J型铺设、S型铺设。通过引入先进的国际海洋工程软件OrcaFlex并结合国内外关于海洋管道铺设的工程手册及相关规范、标准,如DNV、API、AWS等,实时模拟研究S型海洋管道铺设过程。结合作者工作经历及实际海洋铺管工程背景算例分析,研究铺管上弓段接触点、悬垂段及触底段在铺设过程中的各自静力、动力特性。对海洋管道S型铺设过程中应该注意的一些有关设计、工艺和HSE低成本安全高效铺设等方面提出几点有用的意见。 相似文献
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Offshore oil and gas exploration are gradually heading toward the deep sea and even the ultra-deep sea. According, the working temperature and pressure intensity of subsea oil and gas pipelines have increased by a considerable degree. This situation is accompanied by the global buckling problem in deep sea pipelines, which has become increasingly common. Meanwhile, ordinary single-layer pipelines cannot last for a long time under harsh deep-sea working conditions. Thus, multilayer pipelines, such as the pipe-in-pipe (PIP) structure and bundled pipelines, have gradually become top choices. However, the global buckling mechanisms of these multilayer pipelines are more complicated than those of single-layer pipelines. The sleeper–snake lay pipeline, which is an active control method for global buckling, was used in this study. The change and development laws of global buckling in a PIP structure at different wavelengths and amplitudes were determined through an experimental study. A dynamic solution method that considers artificial damping was adopted to establish finite element global buckling models of a PIP structure with initial imperfections. The effects of various factors, such as pipeline laying shape, sleeper–pipe function, and seabed–pipe function, on global buckling were analyzed. By the result of finite element method analysis, the initial imperfection, and sleeper–pipeline friction were determined to be the key factors that influenced critical pipeline buckling force. Accordingly, a reference for the design of PIP structures is presented. 相似文献
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An Overview of Deepwater Pipeline Laying Technology 总被引：1，自引：0，他引：1
The technology and methods involved in pipeline laying in shallow water have evolved to the level of routine and commonplace. However, regarding the unexpected deepwater complexity, the traditional pipeline laying techniques have to confront many new challenges arisen from the increase of the water depth, diameter of the pipe and the welding difficuhy, all of which should be modified and/or innovated based on the existed mature experiences. The purpose of this investigation is to outline the existing and new engineering laying techniques and the associated facilities, which can provide some significant information to the related research. In the context, the latest deepwater pipeline laying technology and pipe laying barges of the renowned companies from Switzerland, Norway, Italy etc., are introduced and the corresponding comparison and discussion are presented as well. 相似文献
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Geotextile Sand Containers (GSC) are increasingly used worldwide for shore protection structures such as seawalls, groins, breakwaters, revetments and artificial reefs. However, reliable design formulae for the hydraulic stability based on a good understanding of the processes involved in the wave-structure interactions are still needed.Although the effect of the deformations of the sand containers on the hydraulic stability is significant, no stability formula is available to account for those deformations and the associated processes leading to the observed failures. Therefore, based on the results of extensive experimental and numerical studies ([Recio J. 2008, Hydraulic Stability of Geotextile Sand Containers for Coastal Structures – Effect of Deformations and Stability Formulae – PhD Thesis, Leichtweiss Institute for Hydraulic Engineering and Water Resources, www.digibib.tu-bs.de/?docid=00021899]), analytical stability formulae are developed that account for the effect of the deformations of the individual GSCs for sliding and overturning stability. The required drag, inertia and lift coefficients are determined experimentally from hydraulic model experiments specially designed for this purpose. Several types of GSC configurations which are representative for a wide range of GSC-structure types are investigated under wave action. Moreover, deformation factors to account for the deformation of the containers on the stability are analytically derived and implemented in the stability formulae.Finally, Stability formulae for each type of coastal structures made of geotextile sand containers such as breakwaters, revetments, sea walls, dune reinforcement and scour protection systems are proposed and recommendations are given with respect to the practical application of the proposed hydraulic stability formula, including their limitations. 相似文献
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Numerical modelling of deep sea air-lift 总被引：2，自引：0，他引：2
Deep sea air-lifting of solid particles from depth of 1600 m is simulated with a mathematical model of the three-phase flow in an upward pipe. The computations are carried out for an axisymmetric domain in a transient way. Phase distributions, pressure and velocity profiles together with flow rates for all phases are presented and analysed. The influence of the pipe diameter on the air-lift efficiency was studied for air-lift pipes of different lengths and found to be significant. The lifting efficiency increases with the increase of the pipe diameter due to the reduction of the wall friction influence on the flow. In addition, the efficiency also increases with the increase of the solid particles volume fraction at the inlet. The presented numerical model can be utilized during various stages of the design of the air-lift pumps to help answer fundamental questions on the process, and during their operation to select optimal process parameters and to address possible problems. 相似文献
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Bao Yingbin Li Runpei Gu Yongning
Ph. D. Candidate School of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai Professor School of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai 《中国海洋工程》1998,(1)
This paper studies intensively the problems of ship-platform collision.The ship and platformare treated as one structural system connected with spring elements and then motion equation of the colli-sion system is established.A nonlinear force-displacement relationship is derived for the simulation of lo-cal dent in a hit member and the yield surface of a dented tubular section is developed to consider the re-duction of load carrying capacity of hit members.Large deformations,plasticity and strain-hardening ofthe beam-column element are taken into account by combining the elastic large displacement analysis theo-ry with the plastic node method.The effect of the hydrodynamic forces acting on the platform,the rubberfender the property of the local dent and the buckling behavior of beam-column on collision are analyzed.The numerical simulation of the nonlinear dynamic response is carried out by Wilson θ method with updat-ed Newton-Raphson iteration.And the numerical example of the dynamic response of a offs 相似文献