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1.
An integrated dynamic model of China’s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is built as a three-dimensional single-body model with six-degree-of-freedom. The track-terrain interaction is modeled by partitioning the track-terrain interface into a certain number of mesh elements with three mutually perpendicular forces, including the normal force, the longitudinal shear force and the lateral shear force, acting on the center point of each mesh element. The hydrodynamic force of the miner is considered and applied. By considering the operational safety and collection efficiency, two new mining paths for the miner on the seafloor are proposed, which can be simulated with the established single-body dynamic model of the miner. The pipeline subsystem is built as a three-dimensional multi-body discrete element model, which is divided into rigid elements linked by flexible connectors. The flexible connector without mass is represented by six spring-damper elements. The external hydrodynamic forces of the ocean current from the longitudinal and lateral directions are both considered and modeled based on the Morison formula and applied to the mass center of each corresponding discrete rigid element. The mining ship is simplified and represented by a general kinematic point, whose heave motion induced by the ocean waves and the longitudinal and lateral towing motions are considered and applied. By integrating the single-body dynamic model of the miner and the multi-body discrete element dynamic model of the pipeline, and defining the kinematic equations of the mining ship, the integrated dynamic model of the total deep ocean mining system is formed. The longitudinal reciprocating motion operation modes of the total mining system, which combine the active straight-line and turning motions of the miner and the ship, and the passive towed motions of the pipeline, are proposed and simulated with the developed 3D dynamic model. Some critical simulation results are obtained and analyzed, such as the motion trajectories of key subsystems, the velocities of the buoyancy modules and the interaction forces between subsystems, which in a way can provide important theoretical basis and useful technical reference for the practical deep ocean mining system analysis, operation and control. 相似文献
2.
海冰动力过程的改进离散元模型及在渤海的应用 总被引：1，自引：0，他引：1
海冰的断裂、重叠和堆积等离散分布特性广泛地存在于极区和副极区的不同海域,并对海冰的生消、运移过程有着重要影响。针对海冰在不同尺度下的离散分布特点,发展海冰动力过程的离散元方法有助于完善海冰数值模式,提高海冰数值模拟的计算精度。为此,本文针对海冰生消运移过程中的非连续分布和形变特性,发展了适用于海冰动力过程的改进离散元模型(MDEM)。不同于传统离散元方法,该模型将海冰离散为具有一定厚度、尺寸和密集度的圆盘单元。海冰单元设为诸多浮冰块的集合体,其在运移和相互接触碰撞过程中,依照质量守恒发生单元尺寸、密集度和厚度的相应变化。基于海冰离散性和流变性的特点,该模型采用黏弹性接触本构模型计算单元间的作用力,并依据Mohr-Coulomb准则计算海冰法向作用下的塑性变形及切向摩擦力。为验证该模型的可靠性,本文对海冰在规则水域内的运移和堆积过程进行了分析,离散元计算结果与解析值相一致;此外,对旋转风场下海冰漂移规律的模拟进一步验证了本文方法的精确性。在此基础上,对渤海辽东湾的海冰动力过程进行了48h数值分析,计算结果与卫星遥感资料和油气作业区的海冰现场监测数据吻合良好。在下一步工作中将考虑海冰离散元模拟中的热力因素影响,发展具有冻结、断裂效应的海冰离散元模型,更精确地模拟海冰动力-热力耦合作用下的生消和运移过程。 相似文献
3.
Static analysis of stiffened shells has been carried out using an eight-noded isoparametric element for the shell and a three-noded curved beam element for the stiffener. A same displacement function is used for the shell and the stiffener elements. A modified technique has been followed to analyse the shell, which is an improvement over the degenerated shell concept. The stiffness matrix of the curved beam element is generated irrespective of its position and orientation within the shell element. The stiffness matrix of the stiffener is then transferred to all the nodes of the shell element. Numerical examples of stiffened shells with concentric and eccentric stiffeners have been analysed and the results presented together with those available in published literature. 相似文献
4.
Mass loss caused by glacier calving is one of the direct contributors to global sea level rise. Reliable calving laws are required for accurate modelling of ice sheet mass balance. Both continuous and discontinuous methods have been used for glacial calving simulations. In this study, the discrete element method(DEM) based on dilated polyhedral elements is introduced to simulate the calving process of a tidewater glacier. Dilated polyhedrons can be obtained from the Minkowski sum of a sphere and a core polyhedron. These elements can be utilized to generate a continuum ice material, where the interaction force between adjacent elements is modeled by constructing bonds at the joints of the common faces. A hybrid fracture model considering fracture energy is introduced. The viscous creep behavior of glaciers on long-term scales is not considered. By applying buoyancy and gravity to the modelled glacier, DEM results show that the calving process is caused by cracks which are initialized at the top of the glacier and spread to the bottom. The results demonstrate the feasibility of using the dilated polyhedral DEM method in glacier simulations, additionally allowing the fragment size of the breaking fragments to be counted. The relationship between crack propagation and internal stress in the glacier is analyzed during calving process. Through the analysis of the Mises stress and the normal stress between the elements, it is found that geometric changes caused by the glacier calving lead to the redistribution of the stress. The tensile stress between the elements is the main influencing factor of glacier ice failure. In addition, the element shape,glacier base friction and buoyancy are studied, the results show that the glacier model based on the dilated polyhedral DEM is sensitive to the above conditions. 相似文献
5.
The dynamic analysis of a pipe system is one of the most crucial problems for the entire mining system.A discrete element method(DEM)is proposed for the analysis of a deep-ocean mining pipe system,including the lift pipe,pump,buffer and flexible hose.By the discrete element method,the pipe is divided into some rigid elements that are linked by flexible connectors.First,two examples representing static analysis and dynamic analysis respectively are given to show that the DEM model is feasible.Then the three-dimensional DEM model is used for dynamic analysis of the mining pipe system.The dynamic motions of the entire mining pipe system under different work conditions are discussed.Some suggestions are made for the actual operation of deep-ocean mining systems. 相似文献
6.
西太平洋边缘海区元素地层学研究及其古海洋学意义 总被引：5，自引：2，他引：5
应用X射线萤光能谱对西太平洋边缘海区的4个钻孔的沉积物进行了元素分析。结果表明,元素在地层中的分布方式与气候变化有极大关系,存在两种模式:CaCO_3溶解区元素高含量与气候暖期一致;CaCO_3保存区,元素高含量段与气候寒冷区相对应,因此元素在地层中的分布有明确的古海洋学意义。利用元素在地层中的分布,对深海地层进行气候地层学划分与对比精度很高,称之为元素地层学。 相似文献
7.
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
8.
Considering the discontinuous characteristics of sea ice on various scales,a modified discrete element model（DEM） for sea ice dynamics is developed based on the granular material rheology.In this modified DEM,a soft sea ice particle element is introduced as a self-adjustive particle size function.Each ice particle can be treated as an assembly of ice floes,with its concentration and thickness changing to variable sizes under the conservation of mass.In this model,the contact forces among ice particles are calculated using a viscous-elastic-plastic model,while the maximum shear forces are described with the Mohr-Coulomb friction law.With this modified DEM,the ice flow dynamics is simulated under the drags of wind and current in a channel of various widths.The thicknesses,concentrations and velocities of ice particles are obtained,and then reasonable dynamic process is analyzed.The sea ice dynamic process is also simulated in a vortex wind field.Taking the influence of thermodynamics into account,this modified DEM will be improved in the future work. 相似文献
9.
不同性味矿物药的特征元素组成 总被引：1，自引：0，他引：1
应用自适应模式识别的ＩＤ３方法，通过３０种和３６种矿物药模式，分别建立起矿物药的“性”与其溶出元素的种类及含量之间和矿物药的“味”与其溶出元素的种类及含量之间的一般关系．矿物药的性与Ｓｉ、Ｍｎ、Ａｌ、Ｓｒ的不同含量有关，矿物药的味与Ｃｕ、Ｆｅ、Ｍｎ、Ｃａ的不同含量有关．上述元素为决定矿物药性味的特征元素． 相似文献
10.
A Mobile Offshore Base (MOB) is a multi-purpose logistics base, which can be stationed in coastal or international waters. In the conceptual design of the MOB, attention should be paid to the dynamic responses of the inter-module connectors because tremendous loads occur in the connectors. In this paper, a study on dynamic responses of the MOB connectors is carried out by use of the Rigid Module Flexible Connector (RMFC) model which assumes that the module stiffness is significantly larger than that of the connector. In the analysis, the connector is modeled as a linear spring, which restricts relative translations but allows for relative rotations of modules. The 3-D source distribution method is adopted to determine the hydrodynamic forces of the modules, and the hydrodynamic interaction between modules is taken into account. The module motions and connector loads for 12 connector stiffness cases in regular and irregular waves are calculated with the multi-rigid-body motion equations. And the calculat 相似文献
11.
Tiezhu Mi Shibin Zhao Minzhi Qiu Bochao Xu Qingzhen Yao Yu Zhen Zhiqing Lai Fang Zhang Zhigang Yu 《海洋学报(英文版)》2022,41(11):81-87
Scyphozoan jellyfish outbreak events are drawing increasing attentions during the past decade. Elemental compositions of statoliths are helpful to understand jellyfish life history and blooming mechanisms, but very rare endeavor has been focused on the Scyphozoan class. In this work, we explored the feasibility of element analysis of Aurelia aurita (a representative Scyphozoan jellyfish outbreak species in China) which may be used as proxies of environment parameters during jellyfish living and moving. Statolith crystals of Aurelia aurita were found to be a gathering of hexahedron type trigonal needle with size of 10?50 μm long, and 5?10 μm in diameter. By using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) downhole profiling method, elements such as Ca, Sr, Mg, Na and P were found to be above the limit of detection and limit of quantification. The epidermis of statocyst could significantly impact the element analyses, so the real statolith element signal section needs to be selected based on elements and Ca profiles together with care. By laser ablated a signal spot repeatedly, the analytical uncertainty was about 3%?4% for Sr/Ca content ratio and Mg/Ca content ratio, but above 10% for other element/Ca content ratios (n=3). Based on the analysis of statolith from temperature-control cultured jellyfish, Sr/Ca content ratios among different statoliths of the same jellyfish were about 6% (n=14), demonstrating biological processes/vital effects causing small variations compared with analytical uncertainties. Therefore, Sr/Ca content ratios may be used as a potential proxy to reveal the living environment variations the Scyphozoan jellyfish has experienced, such as temperature history, which is helpful to understand jellyfish bloom mechanisms. 相似文献
12.
比例边界有限元法(SBFEM)是一种半解析的数值方法,比完全数值方法具有更高的精度,该方法结合了有限元和边界元的优点,采用相对少的剖分单元就可以得到较高精度的模拟结果。通过改变有限子域内部比例中心的位置,使这种方法可以应用到多种形式浮体在波浪作用下的水动力特性的计算中。同时还给出了各种形式浮体的波浪力及反射、透射系数的数值结果,并与边界元方法(BEM)计算结果和特征函数展开方法得到解析解进行了比较,均吻合良好。研究表明比例边界有限元不仅可以计算矩形的浮体结构,而且对于多种结构形式的浮体都可以计算,这为多种结构形式浮体的水动力分析提供了一个可行的方法。 相似文献
13.
Three-dimensional hydroelasticity theory is used to predict the hydroelastic response of flexible floating interconnected structures. The theory is extended to take into account hinge rigid modes, which are calculated from a numerical analysis of the structure based on the finite element method. The modules and connectors are all considered to be flexible, with variable translational and rotational connector stiffness. As a special case, the response of a two-module interconnected structure with very high connector stiffness is found to compare well to experimental results for an otherwise equivalent continuous structure. This model is used to study the general characteristics of hydroelastic response in flexible floating interconnected structures, including their displacement and bending moments under various conditions. The effects of connector and module stiffness on the hydroelastic response are also studied, to provide information regarding the optimal design of such structures. 相似文献
14.
介绍了海洋石油钻井设备水下连接器,以H-4型水下连接器在现场使用中出现的故障现象为例,通过对H-4型水下连接器的结构原理的分析,分析在现场使用连接器发生脱不开故障的原因,并根据原因介绍了其预防的措施;旨在为海洋浮式钻井平台现场使用水下连接器作业提供借鉴和指导作用. 相似文献
15.
A numerical model to compute wave field is developed. It is based on the Berkhoff diffraction-refraction equation, in which an energy dissipation term is added, to take into account the breaking and the bottom friction phenomena. The energy dissipation function, by breaking and by bottom friction, is introduced in the Berkhoff equation to obtain a new equation of propagation.The resolution is done with the hybrid finite element method, where lagrangians elements are used. 相似文献
16.
二维潮流数学模型的四边形等参单元法 总被引：4，自引：0，他引：4
本文在有限差分和有限元法的基础上，采用四边形等参单元，对在河海域进行了潮流数学模型计算，计算表明：该方法既能较好地拟合边界，又可减少网格划分等前期工作，所得结果与实测资料基本一致。 相似文献
17.
本文从特征值问题出发 ,结合结构系统的有限单元模型并引入单元损伤因子 ,导出了求解单元损伤因子的方程 ,从而可以确定结构的损伤位置和损伤程度。利用简支梁进行了数值模拟 ,建立了简支梁的有限单元模型 ,用不同单元弹性模量的降低来模拟各种不同的损伤工况 ,并对每种工况进行了损伤位置和损伤程度识别 ,数值模拟结果同实际情况吻合很好。 相似文献
18.
A stability analysis of reinforced foundation soil is presented in this paper. A method based on the discrete element method (DEM) is suggested for calculating the bearing capacity on strip footings over multilayer soils reinforced with a horizontal layer of geosynthetics. The proposed method can estimate the ultimate bearing capacity and the distribution of tensile force developed in the geosynthetics of the footing system by Winkler springs to account for the compatibility between soil blocks and tensile elements to consider the tensile behavior between soil and geosynthetics. For footings on various multilayer soils with or without reinforcement of geosynthetics, the results of the method were compared to the field test results as well as to those obtained by various methods proposed by other researchers. 相似文献
19.
水下采油树井口连接器是连接采油树和井口的关键设备,对深海水下勘探开发及采油树的安装连接具有不可或缺的重要意义。以一种锁块式水下连接器为例,介绍其结构组成和工作原理,通过有限元建立连接器的三维模型,分析连接器在下放安装工况、连接锁紧工况、正常生产工况和钻完井工况下的连接性能,得出井口与采油树本体接触面作用力、VX钢圈接触应力和锁块受力情况随外部载荷的相互关系。结果表明,VX钢圈在整个过程中都能够保持良好密封,井口与采油树本体接触面未发生分离,弯矩对连接器连接性能影响很大,在额定弯矩作用时连接器部分锁块已发生弹塑性失效。 相似文献
20.
We present the derivation of the discrete Euler–Lagrange equations for an inverse spectral element ocean model based on the shallow water equations. We show that the discrete Euler–Lagrange equations can be obtained from the continuous Euler–Lagrange equations by using a correct combination of the weak and the strong forms of derivatives in the Galerkin integrals, and by changing the order with which elemental assembly and mass averaging are applied in the forward and in the adjoint systems. Our derivation can be extended to obtain an adjoint for any Galerkin finite element and spectral element system.We begin the derivations using a linear wave equation in one dimension. We then apply our technique to a two-dimensional shallow water ocean model and test it on a classic double-gyre problem. The spectral element forward and adjoint ocean models can be used in a variety of inverse applications, ranging from traditional data assimilation and parameter estimation, to the less traditional model sensitivity and stability analyses, and ensemble prediction. Here the Euler–Lagrange equations are solved by an indirect representer algorithm. 相似文献