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海洋防腐工程中受阴极保护金属构筑物表面的电位电流分布常常是不均匀的,而金属表面的电位电流只有在一定范围内才能使构筑物受到有效和适当的保护.尤其是复杂而庞大的海洋钢结构物(如滨海电厂钛管凝汽器)阴极保护系统的设计和监测较复杂,此阴极保护下电化学场的计算,对评价阴极保护效果,优化阴极保护设计有重要意义.采用电化学场中的拉普拉斯(Laplace)方程,使用四节点四面体和合适的形状函数对水室表层和复杂结构体系周围场域进行离散.用有限元计算法,通过对各单元的分布和整个求解区域的总和,建立了两种不同金属组成复杂结构体系的三维有限元数学模型. 相似文献
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海洋平台复杂节点阴极保护电位分布的有限元法计算 总被引:1,自引:0,他引:1
了解阴极保护电位分布是合理设计阴极保护工程的必要条件和评价阴极保护效果的重要依据。本文应用有限元素法(FEM)计算海洋平台复杂节点表面的阴极保护电位分布。在实验室通过边界条件试验建立数学模型,计算海水中被保护的I,Y,K型复杂节点电位分布情况。计算结果与测量结果吻合得很好,说明FEM能够应用于海洋平台复杂节点阴极保护电位分布的计算,所获得的边界条件合理。 相似文献
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海洋钢结构阴极保护电场的数值模拟仿真和计算是当前海洋腐蚀、阴极保护研究和工程实践中一个重要的研究方向。研究海底管线的腐蚀状态就必须准确测定管线表面的电位分布,而实际测量中深海管线表面电位分布难以直接测量。构建了海水中钢管线的阴极保护数学模型,采用以边界元法为基础的数值计算方法,利用Matlab开发了均匀电解质中电位分布的计算软件,实测中通过对腐蚀电场海水区域环境电场的测量,就可实现不接触测量管线表面电位的目的。最后通过海洋实测验证了计算结果的可靠性,证明了基于Matlab的数值仿真计算引入阴极保护设计中是行之有效的。 相似文献
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通过表面观察及电化学方法研究X80钢在含有SRB的海水溶液中阴极保护准则的适用性,测试结果表明:腐蚀控制因素为阳极控制,对金属施加阴极极化第5天降低金属腐蚀速度主要通过增大金属表面SRB的附着电阻和电荷转移电阻实现;而施加阴极极化第10天,阴极保护主要通过改变金属表面电荷转移电阻控制腐蚀速度,且阴极极化电位越大控制效果越好。无阴级保护的金属试样腐蚀产物较多且附着力差,施加阴极保护的金属试样腐蚀产物较少且附着力较强。阴极保护的确能对存在SRB的海水溶液环境中X80钢起到阴极极化作用,但极化5 d时传统的阴极保护准则中-850 mVCSE(即-770 mVSCE)电位未达到85%的保护要求,-950 mVCSE(即-870 mVSCE)电位刚刚能满足保护要求;而极化10 d时2种极化电位下保护度都有所下降且都不能满足保护要求,因此还需要进一步实验确定其合适的阴极保护电位。 相似文献
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采用恒电位阴极极化和线性极化法研究了天然海水中不同动态条件、不同初始保护电位下,阴极保护初期碳钢表面钙质沉积层的形成规律.扫描电镜( SEM)和能谱X-射线分析(EDX)分析了保护后碳钢表面的产物.结果表明:-800 mV(vs.SCE,下同)保护电位下,在静态和动态海水中碳钢表面形成的钙质沉积层质量都较差;-900 mV保护电位下,静态海水中形成致密的钙质沉积层,动态下钙质沉积层形成困难;-1 000 mV保护电位下,静态和动态海水中都形成良好的钙质沉积层.随流速增大,阴极保护电流密度显著增大,钙质沉积层中Ca/Mg比值增加;动态条件下,较负的保护电位,有利于阴极保护初期钙质沉积层的形成. 相似文献
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In the last decade, offshore pipeline engineering extended its action field to very deep waters and continental slopes. This implied the necessity to deal with continental slope instability and mass gravity flows. Mass gravity flows are rare and have random occurrence; therefore, considering also the technical difficulties, the direct measurement of the phenomena is practically impossible. This has encouraged the development of physical and numerical models for investigating the characteristics and intensity of the phenomena (Proc. OTC Conf., Houston, TX (2000); Proc. 19th OMAE Conference, New Orleans, LA (2000)). In order to provide design activities with reliable predictive tools, two numerical models, one for debris flows and the other for turbidity currents, have been developed. The two models are coupled by the bottom boundary conditions of the turbidity current model that depends on the instantaneous velocity of the debris flow model. The two models used together provide a tool for the evaluation of a mass gravity flow event starting as a debris flow and evolving into a turbidity current. 相似文献
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This paper investigates the phenomena of wave refraction and diffraction in the slowly varying topography, as well as the current deflection due to wave actions. A numerical model is developed based on depth integrated mean continuity equation and momentum equations, and a 3rd-order wave equation which governs the wave diffraction, refraction and interaction with current. Examples to examine the above model are given comparing with the laboratory data or the numerical results of other researchers. An example simulating the inlet area shows the interesting velocity field which may be used as a pioneer to further study on the nearshore hydrodynamics and sedimentation. 相似文献
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通过对单点系泊潜标进行动力学分析,利用集中质量法建立系统的动力学模型,编制Matlab仿真程序,通过数值模拟获取不同海流条件下,分析潜标系统的姿态。文中将一个典型潜标系统的浮球、锚链、重力锚等部件,利用集中质量法简化为节点,通过模拟真实环境中的海流流速在垂直方向的分布,设计1~5 m/s的流速剖面分布。将节点的物理参数和海流参数代入仿真程序中,得到各节点的姿态、节点间张力以及重力锚与海底摩擦力等数据。分析仿真结果,海流流速与节点的偏降、节点间的张力以及重力锚与海底的摩擦力成正比,仿真结果与实际情况相符。文中设计的建模方法和仿真程序可以为单点系泊潜标的总体设计、姿态估算、锚系配置提供工程参考。 相似文献
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A 3-D baroclinic numerical model is established to study the temporal and spatial distribution of salinity in the Northern Branch(NB) of the Yangtze Estuary(YE) in response to river runoff, wind and currents. The idealized,process-oriented studies show that the lower river runoff in the dry season is the main driving factor for the spilling over from the NB to the Southern Branch(SB). The NB takes longer time to get in dynamic stable state compared with the SB, as the runoff transfers from the wet season to the dry season. The vertical stratification intensity of the NB has obvious periodic phenomena in the dry season, and the stratification strength is enhanced under the action of low runoff and north wind, which further weakens the vertical transport of water. Momentum balance analysis suggested that the landward net flux increases when considering the influence of the moderate north wind, and the landward flux will enhance if considering the boundary current during the spring tide. With the influence of the boundary current, increases the average salinity of the NB, as well as the intrusion degree from the NB to the SB.This indicates that the nearshore ocean current of the Yellow Sea is an important factor affecting the saltwater intrusion in the NB of the YE. 相似文献
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An analytical solution to shallow-water nonlinear equations determining the height of tsunami waves leaving the source is obtained. The initial water-level displacement in the source and the distribution of particle velocities are set. The numerical solution showed that analytical estimates fit well with source characteristics varying in a broad range, even if the waves produced by the source collapse. 相似文献
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We investigated the use of numerical methods to predict liquid sloshing phenomena in a moving tank and compared our results to model test measurements. The numerical techniques for the free surface, based on the so-called finite Volume-of-Fluid (VoF) approach, comprised an incompressible VoF method, an incompressible coupled Level-Set and Volume-of-Fluid (clsVoF) method, and a compressible VoF method. We assessed the capability of these three numerical methods to achieve suitable numerical predictions of sloshing phenomena, specifically, air pockets and bubbles on the free surface inside a test tank. To observe the described sloshing phenomena, we simulated tank motions leading to well defined single impact wave motions. We performed repeated physical tests for validation purposes. Computed velocity and pressure time histories were compared to experimental data we obtained from Particle Image Velocimetry (PIV) and pressure sensor measurement. Grid sensitivity and turbulence model studies were performed. We demonstrated that the compressible VoF method was the most suitable method to obtain accurate predictions of sloshing phenomena. 相似文献
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1 .IntroductionNumericalmodelsmostwidelyusedforseaenvironmentandsedimenttransportfocusonsolvingseriesofdifferentialequations .Theinputandoutputofanumericalmodelareconsideredasdecisivefactors .Butinrealitythecausesofnaturaleventssuchasmeteorological,astronomical,oceanograph ic ,geomorphologicandgeophysicalfactorsarerandom .Therearemanyuncertaintiesinvolvedininputfactorsinnumericalmodels .Correspondinglytheoutputsofnumericalmodelsarealsorandom .There fore ,theoutputparametersofnumericalmodelsca… 相似文献