Evaluation of numerical time‐integration schemes for real‐time hybrid testing     

P. A. Bonnet  M. S. Williams  A. Blakeborough 《地震工程与结构动力学》2008,37(13):1467-1490

We present a comparison of methods for the analysis of the numerical substructure in a real‐time hybrid test. A multi‐tasking strategy is described, which satisfies the various control and numerical requirements. Within this strategy a variety of explicit and implicit time‐integration algorithms have been evaluated. Fully implicit schemes can be used in fast hybrid testing via a digital sub‐step feedback technique, but it is shown that this approach requires a large amount of computation at each sub‐step, making real‐time execution difficult for all but the simplest models. In cases where the numerical substructure poses no harsh stability condition, it is shown that the Newmark explicit method offers advantages of speed and accuracy. Where the stability limit of an explicit method cannot be met, one of the several alternatives may be used, such as Chang's modified Newmark scheme or the α‐operator splitting method. Appropriate methods of actuator delay compensation are also discussed. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

An external–internal mode coupling for a 3D hydrodynamical model for applications at regional scale (MARS)     

Pascal Lazure  Franck Dumas 《Advances in water resources》2008

This paper presents a 3D model in sigma coordinates. Although the principles it is based on have been established for some time, some original aspects for this type of 3D mode splitting model are presented here. The model was designed to simulate flows in various coastal areas from the regional scale down to the inshore scale of small bays or estuaries where circulation is generally driven by a mix of processes. The processes to be modeled enable simplifications of the Navier–Stokes equations on the classic Boussinesq and hydrostatic hypotheses. These equations are transformed within a sigma framework to make free surface processing easier. The main point of our demonstration focuses on the original aspect of the coupling between barotropic and baroclinic modes especially designed for ADI. It explains how full consistency of the transport calculated within the 2D and 3D equation sets was obtained. Lastly, we describe the physical processes simulated on a realistic configuration at a regional scale in the Bay of Biscay.  相似文献   

基于OpenGIS的地球探测信息综合解释平台          下载免费PDF全文

郑文锋  银正彤  王绪本  阚瑷珂  李海蓉 《地球物理学进展》2008,23(2):605-611

地球探测出现了大量的新技术和新方法,其应用也日益广泛,由于其技术和方法的多样性,致使地球探测数据的记录文件格式、处理方法、图形显示也是多种多样,庞杂无序,不便于保存、使用和管理.本文提出一种基于OpenGIS的地球探测信息综合解释平台,对多源、多尺度、多方法、海量多维地球探测数据进行整合,结合OpenGIS中的GDAS、GLS和WMS、WFS等规范,通过GIS平台进行数据融合,为专家进行综合解释、评价提供一个便捷、有效的工具.目前系统已经被实验室应用于一些项目中,实现了各种探测数据的集中管理和数据融合,提高了综合解释和评价效果.  相似文献   

弹塑性无厚度接触面单元的本构积分算法及验证     

袁凡凡  詹云刚  栾茂田 《岩土力学》2008,29(3):734-740

对基于理想弹塑性理论框架、屈服准则为Mohr-Coulomb准则、采用非关联流动法则的无厚度接触面单元的本构积分算法进行了探讨,引入非关联的伪屈服函数和伪势函数,提出了将超出屈服面、处于角点应力区的试应力双向返回到屈服面的本构积分算法。据此编制了ABAQUS用户单元子程序,进行了算例验证。结果表明,提出的算法可以较好地实现土与结构物共同作用的有限元数值模拟。  相似文献   

基于对象关系数据库的矢栅一体化查询与操作研究     

尹双石  刘洋  方裕  陈斌  田晓婷  刘泽洋 《地理与地理信息科学》2009,25(4)

在分析矢量栅格数据特点的基础上,提出一系列矢栅一体化查询函数,基于PostgreSQL/PostGIS数据库,实现了支持栅格数据存储与组织的扩展数据类型,并对栅格数据类型与PostGIS矢量数据一体化查询函数进行了扩展实现。最后,通过实例验证了矢栅一体化查询函数的表达能力和解决实际问题的应用前景。  相似文献   

Determination of the wave climate for the southern Brazilian shelf     

D.C. Cuchiara  E.H. Fernandes  J.C. Strauch  J.C. Winterwerp  L.J. Calliari 《Continental Shelf Research》2009

The main objective of this study is the characterization of the wave climate in the Southern Brazilian Shelf (SBS) based on a thorough review of existing field data and on numerical modeling experiments. A quantitative knowledge about the wave climate of this area is important to understand the mechanisms driving episodic mud bank attachments to the sandy shore, and the interaction of these banks with the flow and waves. The statistical analysis of existent data on the wave climate throughout the SBS indicates that the predominant wave directions are 100° and 160° (E–SE), with wave heights varying between 1 and 1.50 m. The wave period varies between 6 and 14 s, with predominance of mean wave period of 8 s (sea conditions) and 12 s (swell conditions). The spectral wave model SWAN version 40.41 [Booij, N., Haagsma, I.J.G., Holthuijsen, L.H., Kieftenburg, A.T.M.M., Ris, R.C., van der Westhuysen, A.J., Zijlema, M., 2004. SWAN Cycle III Version 40.41 Users Manual, Delft University of Technology, Delft, The Netherlands, p. 118, http://fluidmechanics.tudelft.nl/swan/index.htm] is used to simulate the wave climate for the region. Special attention is given to Cassino Beach, describing the wave climate observed during the Cassino Experiment, carried out in 2005. The verification of the standard SWAN model was carried out based on the comparison between numerical modeling results and available data of significant wave height, peak period, mean wave direction and energy density for the period relative to February of 1998. Results showed satisfactory model predictions of significant wave height and reasonably accurate predictions of peak spectral wave period and direction. The model performance is also considered satisfactory in the representation of the wave climate of the region when the wave spectrum has only one spectral peak, but presents limitations for bimodal wave spectrum. When two spectral peaks are observed, the SWAN model agrees with the spectral level observed in the low frequency, but underestimates the spectral level in the high-frequency band. When considering the presence of mud deposits in the area, model results predict that although the presence of mud attenuates most of the wave energy on the low frequency peak, it has a smaller effect in attenuating the wave energy on the high frequency peak.  相似文献   

The application of finite-difference time-domain modelling for the assessment of GPR in magnetically lossy materials   总被引：2，自引：0，他引：2  

Nigel J. Cassidy  Tim M. Millington 《Journal of Applied Geophysics》2009,67(4):296-308

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Lava flow hazard at Nyiragongo volcano,D.R.C.     

Massimiliano Favalli  Giuseppe D. Chirico  Paolo Papale  Maria Teresa Pareschi  Enzo Boschi 《Bulletin of Volcanology》2009,71(4):363-374

The 2002 eruption of Nyiragongo volcano constitutes the most outstanding case ever of lava flow in a big town. It also represents one of the very rare cases of direct casualties from lava flows, which had high velocities of up to tens of kilometer per hour. As in the 1977 eruption, which is the only other eccentric eruption of the volcano in more than 100 years, lava flows were emitted from several vents along a N–S system of fractures extending for more than 10 km, from which they propagated mostly towards Lake Kivu and Goma, a town of about 500,000 inhabitants. We assessed the lava flow hazard on the entire volcano and in the towns of Goma (D.R.C.) and Gisenyi (Rwanda) through numerical simulations of probable lava flow paths. Lava flow paths are computed based on the steepest descent principle, modified by stochastically perturbing the topography to take into account the capability of lava flows to override topographic obstacles, fill topographic depressions, and spread over the topography. Code calibration and the definition of the expected lava flow length and vent opening probability distributions were done based on the 1977 and 2002 eruptions. The final lava flow hazard map shows that the eastern sector of Goma devastated in 2002 represents the area of highest hazard on the flanks of the volcano. The second highest hazard sector in Goma is the area of propagation of the western lava flow in 2002. The town of Gisenyi is subject to moderate to high hazard due to its proximity to the alignment of fractures active in 1977 and 2002. In a companion paper (Chirico et al., Bull Volcanol, in this issue, 2008) we use numerical simulations to investigate the possibility of reducing lava flow hazard through the construction of protective barriers, and formulate a proposal for the future development of the town of Goma.  相似文献   

Numerical modelling of the transverse dynamic behaviour of circular tunnels in clayey soils     

A. Amorosi  D. Boldini 《Soil Dynamics and Earthquake Engineering》2009

In this paper, different approaches aimed at investigating the dynamic behaviour of circular tunnels in the transverse direction are presented. The analysed cases refer to a shallow tunnel built in two different clayey deposits. The adopted approaches include 1D numerical analyses performed modelling the soil as a single-phase visco-elastic non-linear medium, the results of which are then used to evaluate the input data for selected analytical solutions proposed in the literature (uncoupled approach), and 2D fully coupled FE simulations adopting visco-elastic and visco-elasto-plastic effective stress models for the soil (coupled approach). The results are proposed in terms of seismic-induced loads in the transverse direction of the tunnel lining. The different constitutive hypotheses adopted in the coupled numerical approach prove to play a significant role on the results. In particular, the plasticity-based analyses indicate that a seismic event can produce a substantial modification of loads acting in the lining, leading to permanent increments of both hoop force and bending moment.  相似文献   

格林函数的奇异性处理   总被引：1，自引：0，他引：1       下载免费PDF全文

张金会  孙建国 《地球物理学进展》2009,24(6):2106-2116

格林函数在解决电磁场和直流电场问题的积分方程法和边界单元法等方法中有着广泛的应用.在应用格林函数时会遇到格林函数奇异性的问题,即其在源区域的内部,当场点和源点重合时,会碰到对格林函数为无穷大,积分为奇异积分.对于不同问题中遇到的不同形式的格林函数奇异性问题的各种处理方法进行了分析和评述.对于标量格林函数奇异性问题处理方法有：挖去法、级数展开法、绕开法和解析法等.对于并矢格林函数奇异性问题处理方法有：分量处理法、源并矢法和拟源并矢法等处理方法.通过对实际工作中所遇到的新方法新问题中的不同形式的格林函数的研究,提供了奇异性问题的处理的方法和途径.  相似文献