A coupled FDM–FEM method for free surface flow interaction with thin elastic plate

A partitioned approach by the coupling finite difference method (FDM) and the finite element method (FEM) is developed for simulating the interaction between free surface flow and a thin elastic plate. The FDM, in which the constraint interpolation profile method is applied, is used for solving the flow field in a regular fixed Cartesian grid, and the tangent of the hyperbola for interface capturing with the slope weighting scheme is used for capturing free surface. The FEM is used for solving structural deformation of the thin plate. A conservative momentum-exchange method, based on the immersed boundary method, is adopted to couple the FDM and the FEM. Background grid resolution of the thin plate in a regular fixed Cartesian grid is important to the computational accuracy by using this method. A virtual structure method is proposed to improve the background grid resolution of the thin plate. Both of the flow solver and the structural solver are carefully tested and extensive validations of the coupled FDM–FEM method are carried out on a benchmark experiment, a rolling tank sloshing with a thin elastic plate.     

Monolithic coupling of the pressure and rigid body motion equations in computational marine hydrodynamics

In Fluid Structure Interaction(FSI) problems encountered in marine hydrodynamics, the pressure field and the velocity of the rigid body are tightly coupled. This coupling is traditionally resolved in a partitioned manner by solving the rigid body motion equations once per nonlinear correction loop, updating the position of the body and solving the fluid flow equations in the new configuration. The partitioned approach requires a large number of nonlinear iteration loops per time–step. In order to enhance the coupling, a monolithic approach is proposed in Finite Volume(FV) framework,where the pressure equation and the rigid body motion equations are solved in a single linear system. The coupling is resolved by solving the rigid body motion equations once per linear solver iteration of the pressure equation, where updated pressure field is used to calculate new forces acting on the body, and by introducing the updated rigid body boundary velocity in to the pressure equation. In this paper the monolithic coupling is validated on a simple 2D heave decay case. Additionally, the method is compared to the traditional partitioned approach(i.e. "strongly coupled" approach) in terms of computational efficiency and accuracy. The comparison is performed on a seakeeping case in regular head waves, and it shows that the monolithic approach achieves similar accuracy with fewer nonlinear correctors per time–step. Hence, significant savings in computational time can be achieved while retaining the same level of accuracy.     

Non-linear dynamic analysis of the response of moored floating structures

The complexity of the dynamic response of offshore marine structures requires advanced simulations tools for the accurate assessment of the seakeeping behaviour of these devices. The aim of this work is to present a new time-domain model for solving the dynamics of moored floating marine devices, specifically offshore wind turbines, subjected to non-linear environmental loads. The paper first introduces the formulation of the second-order wave radiation-diffraction solver, designed for calculating the wave-floater interaction. Then, the solver of the mooring dynamics, based on a non-linear Finite Element Method (FEM) approach, is presented. Next, the procedure developed for coupling the floater dynamics model with the mooring model is described. Some validation examples of the developed models, and comparisons among different mooring approaches, are presented. Finally, a study of the OC3 floating wind turbine concept is performed to analyze the influence of the mooring model in the dynamics of the platform and the tension in the mooring lines. The work comes to the conclusion that the coupling of a dynamic mooring model along with a second-order wave radiation-diffraction solver can offer realistic predictions of the floating wind turbine performance.     

玄武岩纤维复合材料层合加筋板轴向动力压缩破坏分析

基于通用有限元软件,结合复合材料失效准则对玄武岩纤维复合材料层合加筋板在轴向动力压缩载荷作用下的破坏问题进行了研究,并比较了玄武岩纤维复合材料层与S-2玻璃纤维增强复合材料帽形层合加筋板轴向动力压缩破坏的差异.研究结果表明,玄武岩纤维复合材料层合加筋板具备与S-2玻璃纤维复合材料层合加筋板相当的轴向压缩性能.本研究可以为选用玄武岩纤维作为高速舰船船体材料提供参考依据.     

Numerical simulation of the solitary wave interacting with an elastic structure using MPS-FEM coupled method

Fluid-Structure Interaction (FSI) caused by fluid impacting onto a flexible structure commonly occurs in naval architecture and ocean engineering. Research on the problem of wave-structure interaction is important to ensure the safety of offshore structures. This paper presents the Moving Particle Semi-implicit and Finite Element Coupled Method (MPS-FEM) to simulate FSI problems. The Moving Particle Semi-implicit (MPS) method is used to calculate the fluid domain, while the Finite Element Method (FEM) is used to address the structure domain. The scheme for the coupling of MPS and FEM is introduced first. Then, numerical validation and convergent study are performed to verify the accuracy of the solver for solitary wave generation and FSI problems. The interaction between the solitary wave and an elastic structure is investigated by using the MPS-FEM coupled method.     

玄武岩纤维复合材料舰船船体结构性能分析

玄武岩纤维复合材料在耐高温、耐酸碱、介电等性能方面有一定的优势,且价格低廉.采用有限元方法,分别针对玄武岩纤维复合材料和玻璃纤维增强复合材料建造的典型舰体舱段,计算不同载荷下的结构力学性能.比较了不同载荷时舰体舱段总体变形及局部关键位置的变形大小及应力水平.结果表明,玄武岩纤维复合材料应用于舰船结构制造,将能提高船体强度、降低制造成本,为舰船结构选用玄武岩纤维复合材料建造提供了参考依据.     

基于ANSYS的钢筋混凝土构件裂缝宽度计算方法

以大型通用有限元计算软件ANSYS为平台,建立了荷载作用下钢筋混凝土构件裂缝宽度的一种计算方法。采用ANSYS中的Solid 65单元模拟混凝土,Link 8单元模拟钢筋,三维非线性弹簧单元Combine 39模拟钢筋-混凝土界面的粘结滑移关系,将Houde提出的钢筋-混凝土间的粘结滑移本构模型引入ANSYS中以确定Combine 39弹簧单元的荷载-位移关系式。此外,在现有混凝土裂缝宽度计算方法的基础上,推导出适用于有限元分析的裂缝宽度计算公式,并应用ANSYS软件提供的二次开发工具——参数化编程语言(APDL)编制程序,在ANSYS后处理中实现混凝土构件裂缝宽度的计算功能。算例分析表明,与现有方法相比,该方法能更准确地计算各级荷载作用下钢筋混凝土构件的裂缝宽度。     

粉砂质条件下岸壁式舾装码头的设计与应用

钢筋混凝土板桩码头一向以造价低、结构简单等因素而应用较广,但在以粉砂质土层为主的地质条件下,沉桩问题成了其是否可行的关键。对适用本工程的舾装码头的结构型式进行了方案的技术经济比选,并对在实施低成本的混凝土板桩方案中出现的沉桩问题进行了分析探讨和经验总结。     

PVA纤维增强水泥基复合材料的耐久性能

混凝土结构的耐久性是工程领域需要迫切解决的问题之一。PVA（聚乙烯醇）纤维增强水泥基复合材料（PVA—ECC）在水泥基制品开发、桥梁道路施工、结构加固补强等领域有着广阔的应用前景。文中阐述了各种因素对PVA纤维增强水泥基复合材料的耐久性能的影响及目前研究的不足,以进一步研究优化该材料的耐久性能,更好地应用于实际工程。     

53000DWT散货船上层建筑整体吊装工艺设计

介绍了53000DWT散货船上层建筑整体吊装工艺设计,在技术上,通过对上层建筑整体吊装过程中结构的静力有限元分析,由分析结果找到受力薄弱环节,对薄弱环节提出加强方案,并对加强后的上层建筑结构再次有限元分析校核强度,将加强后的上层建筑整体吊装,生产实践表明,上层建筑整体吊装工艺设计相当成功,对后续船舶上层建筑整体吊装和其它船舶实施上层建筑整体吊装具有较强的指导和借鉴意义.     

Two-dimensional numerical simulation of an elastic wedge water entry by a coupled FDM-FEM method

Hydroelastic behavior of an elastic wedge impacting on calm water surface was investigated. A partitioned approach by coupling finite difference method (FDM) and finite element method (FEM) was developed to analyze the fluid structure interaction (FSI) problem. The FDM, in which the Constraint Interpolation Profile (CIP) method was applied, was used for solving the flow field in a fixed regular Cartesian grid system. Free surface was captured by the Tangent of Hyperbola for Interface Capturing with Slope Weighting (THINC/SW) scheme. The FEM was applied for calculating the structural deformation. A volume weighted method, which was based on the immersed boundary (IB) method, was adopted for coupling the FDM and the FEM together. An elastic wedge water entry problem was calculated by the coupled FDM-FEM method. Also a comparison between the current numerical results and the published results indicate that the coupled FDM-FEM method has reasonably good accuracy in predicting the impact force.     

三峡库区港口边坡生态防护技术研究

针对三峡库区复杂工程地质与水位条件下的港口高边坡稳定性与生态防护技术进行了深入研究,在国内外库区岸坡防护技术的基础上进行了优化比选,提出了采用香根草护面加筋边坡这一新型结构体系对三峡库岸边坡进行防护,并采用有限元仿真模拟计算与工程试验相结合的方法进行了论证。实践表明,该防护技术满足三峡库岸边坡防护的安全经济、环保性要求,是一种新型有效的库区港口边坡生态防护技术。     

Three-dimensional fluid-structure interaction case study on cubical fluid cavity with flexible bottom

In this paper, we report our study on a numerical fluid-structure interaction problem originally presented by Mok et al.(2001) in two dimensions and later studied in three dimensions by Valdés Vazquez(2007), Lombardi(2012), and Trimarchi(2012). We focus on a 3D test case in which we evaluated the sensitivity of several input parameters on the fluid and structural results. In particular, this analysis provides a starting point from which we can look deeper into specific aspects of these simulations and analyze more realistic cases, e.g., in sails design. In this study, using the commercial software ADINATM, we addressed a well-known unsteadiness problem comprising a square box representing the fluid domain with a flexible bottom modeled with structural shell elements. We compared data from previously published work whose authors used the same numerical approach, i.e., a partitioned approach coupling a finite volume solver(for the fluid domain) and a finite element solver(for the solid domain). Specifically, we established several benchmarks and made comparisons with respect to fluid and solid meshes, structural element types, and structural damping, as well as solution algorithms. Moreover, we compared our method with a monolithic finite element solution method. Our comparisons of new and old results provide an outline of best practices for such simulations.     

复合材料冷藏箱电源插座支架在自动化集装箱码头中的应用

针对集装箱码头传统冷藏箱钢结构电源插座支架易腐蚀、维护工作量大的特点,采用防腐性能优异的连续纤维增强树脂基复合材料代替传统钢结构制作冷藏箱支架。对复合材料冷藏箱电源插座支架的设计、计算、制造、安装进行研究,研究表明复合材料冷藏箱电源插座支架在整个生命周期维护需求小、综合成本低,对自动化集装箱堆场作业干扰小,适合自动化集装箱码头作业特点。     

圆锥壳和圆柱壳声辐射模态特性比较

单层加筋圆锥壳和圆柱壳是舰艇结构中最常见的结构,其噪声的辐射也受到广泛关注.本文以有限元法和边界元法为基础,在中、低频段研究比较了水中单层加筋圆锥壳和圆柱壳声辐射模态特性.对于相同尺寸的圆锥壳和圆柱壳而言,圆锥壳前10阶模态占主导时的频率f0高于圆柱壳的f0,并且辐射效率随着阶数的衰减要比圆柱壳的衰减快;圆锥壳的辐射效率总体高于圆柱壳的辐射效率;圆锥壳和圆柱壳的声辐射模态振速分布有着相同的规律,为振动噪声的主动控制提供了一些参考.     

基于近似模型技术的复合材料耐压壳性能研究

基于纤维增强复合材料具有高比模量,高比强度的特点,提出内部环肋金属内衬外部缠绕复合材料的潜水器耐压壳结构形式,结合有限元方法和近似模型技术对该种结构形式的耐压壳进行研究。得到复合材料加强纤维的含量与耐压壳结构性能参数的关系以及不同铺层角对耐压壳临界失稳压力的影响,为该种形式复合材料耐压壳的设计提供设计依据。     

Numerical computation of motions and structural loads for large containership using 3D Rankine panel method

In this paper, we present the results of our numerical seakeeping analyses of a 6750-TEU containership, which were subjected to the benchmark test of the 2 nd ITTC–ISSC Joint Workshop held in 2014. We performed the seakeeping analyses using three different methods based on a 3D Rankine panel method, including 1) a rigid-body solver, 2) a flexible-body solver using a beam model, and 3) a flexible-body solver using the eigenvectors of a 3D Finite Element Model(FEM). The flexible-body solvers adopt a fully coupled approach between the fluid and structure. We consider the nonlinear Froude–Krylov and restoring forces using a weakly nonlinear approach. In addition, we calculate the slamming loads on the bow flare and stern using a 2D generalized Wagner model. We compare the numerical and experimental results in terms of the linear response, the time series of the nonlinear response, and the longitudinal distribution of the sagging and hogging moments. The flexible-body solvers show good agreement with the experimental model with respect to both the linear and nonlinear results, including the high-frequency oscillations due to springing and whipping vibrations. The rigid-body solver gives similar results except for the springing and whipping.     

Evaluation of ultimate strength of stiffened panels under longitudinal thrust

A series of collapse analyses is performed applying nonlinear FEM on stiffened panels subjected to longitudinal thrust. MSC.Marc is used. Numbers, types and sizes of stiffeners are varied and so slenderness ratio as well as aspect ratio of local panels partitioned by stiffeners keeping the spacing between adjacent longitudinal stiffeners the same. Initial deflection of a thin-horse mode is imposed on local panels and that of flexural buckling and tripping modes on stiffeners to represent actual initial deflection in stiffened panels in ship structures. On the basis of the calculated results, buckling/plastic collapse behaviour of stiffened panels under longitudinal thrust is investigated. The calculated ultimate strength are compared with those obtained by applying several existing methods such as CSR for bulk carriers and PULS. Simple formulas for stiffened panels, of which collapse is dominated fundamentally by the collapse of local panels between longitudinal stiffeners, are also examined if they accurately estimate the ultimate strength. Through comparison of the estimated results with the FEM results, it has been concluded that PULS and modified FYH formulas fundamentally give good estimation of the ultimate strength of stiffened panels under longitudinal thrust.     

龙溪口航电枢纽现浇钢筋混凝土排架结构应用

针对钢筋混凝土排架结构与附属设备安装联合施工时出现的精度控制差、质量难以保障的问题，依托龙溪口航电枢纽工程泄洪闸启闭机房钢筋混凝土排架结构工程，进行了钢筋混凝土排架结构施工工艺标准化和施工质量控制要点的研究。通过优化施工组织、施工工艺，提出工期、质量优化措施，明确排架结构施工过程中支架搭设和模板组装为主要控制要点，为同类航电枢纽工程中的排架结构应用提供参考。     

New method for ship finite element method preprocessing based on a 3D parametric technique

A new method for ship finite element method (FEM) preprocessing is presented as well as its program development. The method is applicable for all kinds of ships at different levels, such as a whole ship, cargo hold parts or detailed structures. The 3D parametric technique is used when creating ship structures, which improves the modeling efficiency greatly and makes the model easy to modify. A 3D geometric constraint solver is developed to solve the constraint system of the parametric model. A meshing procedure is presented to automatically convert the parametric structure model into a finite element model, by which high quality mesh is generated in the stress concentrated area. It also becomes possible to create finite element models for different levels from the same structure model. Using this method, the engineers avoid much of the complex and laborious work of FEM preprocessing, which consumes a very significant amount of time in finite element analysis, and can pay more attention to post-processing. This method has proved to be practical and highly efficient by several engineering trials. This work is sponsored by “Liaoning BaiQianWan Talents Program”.