Propagation and run-up of nearshore tsunamis with HLLC approximate Riemann solver

A numerical model describing the propagation and run-up process of nearshore tsunamis in the vicinity of shorelines is developed based on an approximate Riemann solver. The governing equations of the model are the nonlinear shallow-water equations. The governing equations are discretized explicitly by using a finite volume method. The nonlinear terms in the momentum equations are solved with the Harten-Lax-van Leer-Contact (HLLC) approximate Riemann solver. The developed model is first applied to prediction of water motions in a parabolic basin, and propagation and subsequent run-up process of nearshore tsunamis around a circular island. Computed results are then compared with available analytical solutions and laboratory measurements. Very reasonable agreements are observed.     

Investigation of unrestrained cylinders rolling in steady uniform flows

The goal of this study is to understand the movement of unexploded ordnance that may become unburied and forced by currents. Symmetrical, smooth, finite-length, unrestrained cylinders were studied in steady, uniform flows over a range of Reynolds numbers in a smooth-bottomed, horizontal flume. The study uses PIV tracking methods in the laboratory to identify the movement of ordnance simulated by unrestrained cylinders. The PIV is supported with a numerical analysis using a RANS flow solver. The simulations showed that at low Reynolds numbers the cylinders should roll at speeds near 70% of the free-stream flow.     

动态规划法在管道修复与更新中的应用

管道工程的全寿命管理中最重要的环节是管道运营期的控制管理;针对管道运营期的修复、更新成本的动态规划控制管理,采用决策分析,提出最优线路原则;采用动态规划法来控制管道的运营成本,从而提高管道成本效率最大化。     

用交错网格有限差分法计算三维频率域电磁响应

用交错网格有限差分法(SFD)，实现了三维频率域电磁场响应 的数值模拟. 该方法适用于任何方向的磁偶极子源. 经与解析方法、积分方程等 其他方法的计算结果对比表明，交错网格有限差分法结合散度校正和不完全乔累斯基分解预 处理的双共轭梯度迭代方法进行正演计算，速度快、精度高、结果稳定，能适应三维复杂介 质的数值模拟，为三维电磁反演奠定了基础.     

Forward plane-wave electromagnetic model in three dimensions using hybrid finite volume–integral equation scheme

We present a concept of the hybrid finite volume–integral equation technique for solving Maxwell's equation in a quasi-static form. The divergence correction was incorporated to improve the convergence and stability of the governing linear system equations which pose a challenge on the discretization of the curl–curl Helmholtz equation. A staggered finite volume approach is applied for discretizing the system of equations on a structured mesh and solved in a secondary field technique. The bi-conjugate gradient stabilizer was utilized with block incomplete lower-upper factorization preconditioner to solve the system of equation. To obtain the electric and magnetic fields at the receivers, we use the integral Green tensor scheme. We verify the strength of our hybrid technique with benchmark models relative to other numerical algorithms. Importantly, from the tested models, our scheme was in close agreement with the semi-analytical solution. It also revealed that the use of a quasi-analytical boundary condition helps to minimize the runtime for the linear system equation. Furthermore, the integral Green tensor approach to compute at the receivers demonstrates better accuracy compared with the conventional interpolation method. This adopted technique can be applied efficiently to the inversion procedure.     

不同浸没长度下串列双立管涡激振动数值模拟

深海柔性立管涡激振动问题广受关注,其中多立管涡激振动较传统单立管涡激振动更为复杂。使用基于Open FOAM自主开发的深海柔性立管流固耦合求解器viv-FOAM-SJTU,对阶梯流中串列双立管涡激振动展开研究。首先针对阶梯流中串列双立管模型试验工况开展验证计算,下游立管的位移响应以及频率响应与试验结果基本吻合;而后改变立管浸没长度,分别选取浸没长度为0.4L(工况1)、0.55L(工况2)以及0.7L(工况3)的三种工况进行数值计算,其中L为立管长度。数值结果表明:3种浸没长度下,上下游立管的横流向振动均为一阶模态,且工况2和工况3中上下游立管的横流向位移均方根均大于工况1;上下游立管的顺流向主振模态在工况2和工况3中均为二阶,而在工况1中为一阶,且下游立管在工况2和工况3中的顺流向振动均表现出明显的多模态振动特性。     

岛礁附近浮式平台运动响应特性数值分析

利用基于开源平台Open FOAM自主开发的船舶与海洋工程水动力性能求解器naoe-FOAM-SJTU,数值模拟了近岛礁环境下规则波的演化特性以及带有系泊系统的浮式平台在相应波浪作用下的水动力性能。对于平台的水动力性能的研究发现,仿真结果与试验结果在平台自由衰减运动固有周期及RAO(response amplitude operator)方面吻合良好。对于波浪在近岛礁地形下的演化现象的研究,分析了波浪演化不对称性特性的成因,并分别给出了不同参数下波浪在地形上爬升时演化的具体特性,对于波高变化及波浪演化的频率成分进行量化的探究。研究发现,波浪周期越大,波高变化越明显,演化的非线性现象越明显,且波浪随着传播距离的增大演化出的阶数也在增大。     

米波动态频谱仪快速数据采集系统及程序设计

介绍利用AST386 SX/20微型计算机、快速数据采集卡和光电二极管阵构成的512通道快速数据采集系统,以及对太阳米波爆发频谱进行观测和处理程序的设计及程序流程图。     

工程建设中坐标转换方法的运用

工程建设中常因为遇到不同的坐标系统,增加了施工的难度.本文主要就坐标换算的方法、运用和编程做介绍,以供施工人员在工程建设中参考运用坐标换算方法,以达到系统统一、简化施工的目的.