Hydrodynamic interactions between two bodies in waves in 3D time domain

In this paper, a 3D time domain technique is adopted to calculate the coupled hydrodynamic interaction between two bodies without flare in waves. For verifying the code, two same cylinders are selected to calculate coupled hydrodynamic effects by comparison with the results obtained by 3D frequency method which has been proved to be efficient for solving such problems. In order to improve efficiency of calculation, the effect of history time has been discussed, and an improved method is presented. Moreover, the effect of lateral separation distance is also discussed in detail. The technique developed here may serve as a more rigorous tool to analyze the related transient problems of two ships doing underway replenishment in waves.     

Numerical simulation with a macroscopic CFD method and experimental analysis of wave interaction with fixed porous cylinder structures

Porous structures have been widely applied in the coastal and ocean engineering due to their wave energy dissipation mechanism. The macroscopic computational fluid dynamics (CFD) approach where the quadratic pressure drop condition of porous surface is introduced to model the wave interaction with porous cylinders. A series of CFD simulations of waves interacting with a single porous cylinder and the combined structure of a porous cylinder with a concentric inner solid column are performed, with corresponding tank tests conducted. The CFD method is compared with experiments, linear potential model, and the quadratic BEM (boundary element method) model. The effects of porosity and porous cylinder radius on wave force and wave heights inside porous cylinder are analyzed to evaluate the performance of porous shell reducing wave loads and wave surface elevation, and the wave force variation with incident wave amplitudes are also investigated. The results demonstrate that the established CFD model is reliable for engineering analysis and thereby being of great significance for reference purpose in the CFD simulations of waves interacting with porous structures.     

整体式悬挑结构与岩土共同作用研究

介绍了一种山区道路拓宽技术——整体式悬挑结构,运用有限元软件数值模拟了岩土对荷载的响应,提出了其简化计算方法；用visual c++编写了一种适用于该结构的计算程序,对该结构与岩土的共同作用进行了研究；得出了不同土体对结构受力的影响,实际工程选用老填土和碎石土是经济的.     

渗水作用下膨胀土中单桩承载变形特性研究

目前膨胀土中桩基设计仍基于非膨胀土力学的设计原则。基于FLAC3D采用热-力耦合方法实现吸热膨胀来模拟膨胀土的吸湿膨胀,并重点阐述温度场模拟湿度场的关键参数取值方法。建立膨胀土中单桩三维实体模型,得出渗水作用下膨胀土中单桩的荷载变形特性、桩侧摩阻发挥特征,并分析了桩长、桩径、膨胀系数等对单桩承载特性的影响规律。研究结论:非扩底桩最小桩长宜大于2倍膨胀影响深度;细长桩比短粗桩更能有效降低膨胀土中桩顶的位移。该方法可获得渗水作用下任一时刻的桩身受力变形特性,为研究膨胀土中桩基受荷性能提供一种可行的变通手段。     

Algorithmic formulation of clay and sand pipe–soil interaction models for on-bottom stability analysis

This paper presents a new algorithmic formulation of the clay and sand pipe–soil interaction models recommended by the DNV-RP-F109 code for dynamic on-bottom stability analysis of submarine pipelines. The pipe–soil force update algorithm is formulated within the framework of computational elasto-plasticity and applies Backward-Euler integration to ensure stability and robustness for large time step sizes. Algorithmic optimization techniques are developed by utilizing a closed-form solution and subincrementation. A numerical verification study covering full cyclic displacement ranges of a 12 inch pipeline is presented. The new formulation is shown to increase the time step size by a factor of up to 50 compared to commercial software tools for on-bottom stability analysis. This achievement will be particularly beneficial for long-duration 3D nonlinear time domain on-bottom stability analysis.     

Description of a flexible and extendable physical–biogeochemical model system for the water column

A modelling system for coupled physical–biogeochemical simulations in the water column is presented here. The physical model component allows for a number of different statistical turbulence closure schemes, ranging from simple algebraic closures to two-equation turbulence models with algebraic second-moment closures. The biogeochemical module consists of models which are based on a number of state variables represented by their ensemble averaged concentrations. Specific biogeochemical models may range from simple NPZ (nutrient–phytoplankton–zooplankton) to complex ecosystem models. Recently developed modified Patankar solvers for ordinary differential equations allow for stable discretisations of the production and destruction terms guaranteeing conservative and non-negative solutions. The increased stability of these new solvers over explicit solvers is demonstrated for a plankton spring bloom simulation. The model system is applied to marine ecosystem dynamics the Northern North Sea and the Central Gotland Sea. Two different biogeochemical models are applied, a conservative nitrogen-based model to the North Sea, and a more complex model including an oxygen equation to the Baltic Sea, allowing for the reproduction of chemical processes under anoxic conditions. For both applications, earlier model results obtained with slightly different model setups could be basically reproduced. It became however clear that the choice for ecosystem model parameters such as maximum phytoplankton growth rates does strongly depend on the physical model parameters (such as turbulence closure models or external forcing).     

城市地铁施工对近邻短桩桥基的影响研究

结合北京地铁10号线国贸站西北风道施工对邻近短桩桥基影响这一工程问题,运用ABAQUS软件,在对施工过程进行三维动态模拟的同时,重点研究了施工过程中桥基的变形和受力性态以及桩土相互作用机理,并将部分计算结果与量测结果作了比较。研究成果为该工程施工提供了决策和指导作用,也可供类似工程参考。     

考虑流固耦合影响的水中桩基结构振动特性分析

水-结构的耦合振动是一个比较复杂的问题,在设计中,只有考虑水体对结构基频及阻尼比等振动特性的影响,才能使结构设计更为合理、可靠。以往研究多分析水体的附加质量效应对桩柱基频的影响,对水深、桩径、上部结构等因素的影响尚缺乏进一步的研究,对水体的阻尼比增大效应也缺乏定量分析。鉴于工程的需要,利用有限元分析软件ADINA建立水体-桩基结构相互作用的三维有限元数值模型,对流固耦合作用下结构的基频和阻尼比进行计算,分析多种因素对水中结构振动特性的影响,并给出水体产生的阻尼比推荐值。结果表明,水体会引起结构基频降低及结构阻尼比增大,流固耦合作用对振动特性的影响不容忽视。