Numerical Simulation of Local Scour Around A Large Circular Cylinder Under Wave Action   总被引：1，自引：0，他引：1  

赵明  滕斌 《中国海洋工程》2001,(3):371-382

A horizontal two- dimensional numerical model is developed for estimation of sediment transport and sea bed change around a large circular cylinder under wave action. The wave model is based on an elliptic mild slope equation. The wave-induced current by the gradient of radiation stress is considered and a depth integrated shallow water equation is applied to the calculation of the current. The mass transport velocity and the bed shear stress due to streaming are considered, which are important factors affecting the sediment transport around a structure due to waves, especially in reflective areas. Wave-current interaction is taken into account in the model for computing the bed shear stress. The model is implemented by a finite element method. The results of this model are compared with those from other methods and agree well with experimental data.  相似文献   

三氮循环与地下水污染——以辛店地区为例   总被引：3，自引：0，他引：3  

邱汉学  刘贯群  焦超颖 《中国海洋大学学报(自然科学版)》1997,(4)

以往对三氮循环转化的室内实验表明吸附作用在浅表地带起很大作用。对辛店地区的实际资料研究表明，包气带岩性、厚度、理化性质对三氮的吸附与转化起着决定性作用。进入地下水中的三氮因受到水中污染物种类、数量，氧化还原条件的影响，可呈氧化或还原状态。  相似文献   

Three-Dimensional Instability of Flow Around Two Circular Cylinders in Tandem Arrangement     

邓见任安禄  邹建锋 《中国海洋工程》2005,19(1):73-82

The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the virtual boundary method is used here. A Reynolds number range between 220 and 270 has been considered, and the spacing between two cylinders is selected as L/D = 3 and L/D = 3.5. When L/D = 3, the secondary vortices of Mode-A are seen to appear at Re = 240 and persist over the range of the Reynolds number of 240 - 270. When L/D = 3.5, the similar critical Reynolds number has been found at Re = 250. No obvious discontinuity has been found in the Strouhal-Reynolds number relationship, and this is different from three-dimensional flow around a single cylinder at the critical Reynolds number. The spanwise wavelength is about four times the diameter of the cylinder, and it is the characteristic wavelength for ModeA instability. This paper can give some foremost insight into the three-dimensional instability of flow by complicated geometrical configuration.  相似文献   

Analytical and experimental investigation on transverse vibrations of solid, circular and annular plates carrying a concentrated mass at an arbitrary position with marine applications     

D.V. Bambill  S. La Malfa  C.A. Rossit  P.A.A. Laura 《Ocean Engineering》2004,31(2):127-138

This investigation arose from the practical necessity of placing a centrifugal pump rigidly attached to a thin, circular cover plate of a water tank in a medium size ocean vessel. Due to lack of space, it was necessary to locate the system off—center of the circular configuration. It was considered necessary to calculate the fundamental frequency of the coupled system.The first part of the present study is concerned with the determination of the fundamental frequency of vibration of a circular plate carrying a concentrated mass at an arbitrary position, using a variational approach.Numerical results are obtained for the stated problem for several combinations of the intervening geometric and mechanical parameters.An experimental investigation is also performed in the case of clamped plates.Based on the results for solid circular plates, the fundamental frequency of annular plates with a free inner edge and a concentrated mass is also obtained.Circular plates are fundamental structural elements in ocean engineering applications: from off-shore platforms to underwater acoustic transducers. In a great variety of circumstances, they must carry operational systems in an eccentric fashion. Since the dynamic performance is always of interest, one must know at least some of the basic dynamic parameters.  相似文献   

区域循环经济的能值分析与评估——以徐州市为例     

仇方道  佟连军  丁宁凯 《地域研究与开发》2007,26(6):69-74

循环经济是区域实现向可持续发展转型的重要模式.基于能值分析理论,构建了区域循环经济能值分析指标体系,并以此对1991-2004年徐州市的能值使用与转移情况进行了深入分析.结果表明,1991-2004年徐州市经济社会发展主要依赖于本地不可更新资源的利用,能值自给率都在98%以上;资源利用效率呈现先提高后下降的演变过程,具有明显阶段性特征;环境压力的变化与经济增速的周期性波动相一致,并呈现波浪式加大;徐州市循环经济系统处于比较有活力的发展状态区间,但持续性能力逐渐减弱.  相似文献   

基于损伤理论的圆形巷道围岩应力场分析   总被引：8，自引：1，他引：8  

李忠华  官福海  潘一山 《岩土力学》2004,25(Z2):160-163

由于巷道掘进破坏了原岩地应力场,使围岩应力重新分布,应力集中区的高应力造成巷道变形破坏.特别是布置在高地应力区的巷道变形破坏更加严重.因此必须合理准确地计算巷道围岩应力场,为巷道变形破坏计算及稳定性分析提供理论依据.岩体内部存在微裂纹,其发生、扩展、并合,决定了岩石材料的宏观力学性能,因此巷道围岩应力场的计算应该考虑岩石材料的损伤特性.本文基于损伤理论计算得到的不同地应力情况下的圆形巷道围岩应力场,计算结果与实际情况符合得较好.  相似文献   

A macro‐element for a circular foundation to simulate 3D soil–structure interaction     

S. Grange  P. Kotronis  J. Mazars 《国际地质力学数值与分析法杂志》2008,32(10):1205-1227

This paper presents a non‐linear interface element to compute soil–structure interaction (SSI) based on the macro‐element concept. The particularity of this approach lies in the fact that the foundation is supposed to be infinitely rigid and its movement is entirely described by a system of global variables (forces and displacements) defined in the foundation's centre. The non‐linear behaviour of the soil is reproduced using the classical theory of plasticity. Failure is described by the interaction diagram of the ultimate bearing capacity of the foundation under combined loads. The macro‐element is appropriate for modelling the cyclic or dynamic response of structures subjected to seismic action. More specifically, the element is able to simulate the behaviour of a circular rigid shallow foundation considering the plasticity of the soil under monotonic static or cyclic loading applied in three directions. It is implemented into FedeasLab, a finite element Matlab toolbox. Comparisons with experimental monotonic static and cyclic results show the good performance of the approach. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Tests and model calibration of high‐strength steel tubular beam‐to‐column and column‐base composite joints for moment‐resisting structures          下载免费PDF全文

Raffaele Pucinotti  Nicola Tondini  Gabriele Zanon  Oreste S. Bursi 《地震工程与结构动力学》2015,44(9):1471-1493

Performance‐based engineering (PBE) methodologies allow for the design of more reliable earthquake‐resistant structures. Nonetheless, to implement PBE techniques, accurate finite element models of critical components are needed. With these objectives in mind, initially, we describe an experimental study on the seismic behaviour of both beam‐to‐column (BTC) and column‐base (CB) joints made of high‐strength steel S590 circular columns filled with concrete. These joints belonged to moment‐resisting frames (MRFs) that constituted the lateral‐force‐resisting system of an office building. BTC joints were conceived as rigid and of partial strength, whereas CB joints were designed as rigid and of full strength. Tests on a BTC joint composed of an S275 steel composite beam and high‐strength steel concrete‐filled tubes were carried out. Moreover, two seismic CB joints were tested with stiffeners welded to the base plate and anchor bolts embedded in the concrete foundation as well as where part of a column was embedded in the foundation with no stiffeners. A test programme was carried out with the aim of characterising these joints under monotonic, cyclic and random loads. Experimental results are presented by means of both force–interstory drift ratio and moment–rotation relationships. The outcomes demonstrated the adequacy of these joints to be used for MRFs of medium ductility class located in zones of moderate seismic hazard. Then, a numerical calibration of the whole joint subassemblies was successfully accomplished. Finally, non‐linear time‐history analyses performed on 2D MRFs provided useful information on the seismic behaviour of relevant MRFs. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

考虑轴向力和渗透力时圆形隧道广义Hoek-Brown解     

许渊  李亮  邹金锋  袁臻 《岩土力学》2015,36(10):2837-2846

为了研究渗透水压力和轴向应力共同作用时隧道围岩的应力和位移变化趋势,将圆形隧道简化为轴对称模型,假定渗透场以渗透体积力作用在原应力场,以围岩开挖断面为假定平面,引入垂直于该平面的轴向应力。基于广义Hoek-Brown强度准则和非关联流动法则,推导出考虑轴向应力和渗透场共同作用时弹-脆-塑性围岩的应力和位移非线性解,采用数值算例分析了轴向应力和渗透力共同作用时隧道围岩塑性区应力场和位移场的分布规律。计算结果表明：与无渗透水压力作用下的模型相比,渗透力作用使得围岩塑性区各点位移增大,并且内外水头差越大,位移增大越明显。当轴向应力为中主应力时,围岩塑性区半径和塑性区各点应力增大,轴向应力为大主应力和小主应力时,围岩塑性区半径和塑性区应力变化较小。因此,渗透力的存在不利于隧道围岩的稳定性,并且轴向应力的大小对于富水地区隧道围岩的应力和位移分布具有较大影响。在施工设计时考虑渗透力以及轴向应力的共同影响对于保证隧道围岩稳定性具有重要意义。  相似文献   

Axisymmetric vibration of an elastic circular plate bonded on a transversely isotropic multilayered half-space     

《Soil Dynamics and Earthquake Engineering》2014

Based on the analytical layer-element method, an analytical solution is proposed to determine the dynamic interaction between the elastic circular plate and transversely isotropic multilayered half-space. The dynamic response of the elastic circular plate is governed by the classical thin-plate theory with the assumption that the contact surface between the plate and soil is frictionless. The total stiffness matrix of the transversely isotropic multilayered half-space is acquired by assembling the analytical layer-element of each soil layer with the aid of the continuity conditions between adjacent layers. According to the displacement condition of coordination between the plate and soil, the dynamic interaction problem is reduced to that of multilayered transversely isotropic half-space subjected to axisymmetric harmonic vertical loading. Some numerical examples are given to study the vertical vibration of the plate, and the results indicate that the dynamic response of elastic circular plate depends strongly on the material properties of the soils, the rigidity of the plate, the frequency of excitation and the external load form.  相似文献