Simulation of Vortex-Induced Vibrations of A Cylinder Using ANSYS CFX Rigid Body Solver

This article simulates the vortex-induced oscillations of a rigid circular cylinder with elastic support using the new ANSYS CFX rigid body solver. This solver requires no solid mesh to setup FSI (Fluid Structure Interaction) simulation. The two-way case was setup in CFX only. Specific mass of the cylinder and flow conditions were similar to previous experimental data with mass damping parameter equal to 0.04, specific mass of 1 and Reynolds number of 3800. Two dimensional simulations were setup. Both one-degree-of-freedom and two-degree-of-freedom cases were run and results were obtained for both cases with reasonable accuracy as compared with experimental results. Eight-figure XY trajectory and lock-in behavior were clearly captured. The obtained results were satisfactory.     

Hybrid particle swarm optimization for first-order reliability method

A reliability analysis method based on the combination of the first-order reliability method (FORM) and hybrid particle swarm optimization (SACPSO) is presented for the reliability optimization calculation. The new reliability method, named as SACPSO-FORM, can be utilized for those complex reliability problems with correlated non-normal variables and implicit performance functions. Three examples are performed to verify its validation, and stability reliability analysis on the complicated rock foundation of a practical gravity dam is demonstrated. The results show that the proposed method is accurate, stable, flexible and efficient for reliability analysis in engineering applications.     

二维粒子图像测速实验中三维涡旋可测性分析

现今二维粒子图像测速（PIV）广泛应用,为进一步提高PIV测量结果对紊流及水流和泥沙相互作用机理的理解,分析了二维PIV中三维涡旋的可测性。结合涡旋识别的旋转强度方法、坐标旋转定理和紊流经典Burgers涡模型,推导得出:二维PIV能否检测出三维涡旋,主要受涡旋环量和旋涡与测量平面之间的倾角两个因素影响,且仅当涡旋环量大于某一特定值（为倾角的函数）时,三维涡旋才可以被测量出。利用广泛使用的直接数值模拟（DNS）槽道紊流数据统计分析,得出了该条件下倾角和环量的相关曲线与拟合方程;结合环量概率密度累积分布可知,在常规二维PIV实验中,涡旋被测量出的概率越大,相应的倾角也越大,其中以90%、50%和10%的概率被测量出的三维涡旋与测量平面间分别呈20°、11°和5°的倾角。     

考虑薄膜水的利用介质粒度分布获取水土特征曲线的方法

利用介质粒度分布间接获取水土特征曲线（SWCC）是一种快速、经济的方法。由于该方法的传统模型（HP模型和MV模型）忽略了薄膜水,获得的SWCC在低含水率段存在显著误差。提出了一种考虑介质表面薄膜水的含水率估算方法,与HP模型和MV模型的吸力计算方法结合预测SWCC,选用土壤水力性质数据库UNSODA的17种土壤样品对两种修正模型的预测效果进行了验证。结果表明,采用薄膜水修正后的HP模型和MV模型可以显著改善传统模型中SWCC低含水率段含水率的低估,并能有效地预测砂土等粗粒介质的SWCC。另外,含水率估算中引入参数β后,修正的MV模型也可用于壤土和黏土等细粒介质的SWCC的预测。     

高黏性新近吹填淤泥真空预压试验颗粒流宏微观分析

为了从宏观和微观角度探讨颗粒组成对淤堵层形成机理和加固效果的影响规律,依托天津某新近吹填造陆工程,先进行直排式真空预压法室内模型试验,然后基于颗粒流理论和PFC2D程序,在解决模拟过程中颗粒级配和孔隙比的二维转换、排水边界的等效模拟、真空渗流场的施加等问题后,对模型进行有效的模拟计算,进而将结果推广,开展了不同颗粒组成吹填土真空预压试验的颗粒流模拟,总结了排水速率变化及颗粒运移规律。结果表明:对吹填土真空预压过程进行二维颗粒流数值模拟是有效可行的;真空预压过程中细颗粒沿渗透路径迁移,在沿途滞留,导致渗透路径变短变窄,从而形成淤堵层;对于高黏性新近吹填淤泥,在相同真空荷载作用下,黏粒质量分数越大,初期排水速率增长越快,并且随着土体不均匀系数的提高,淤堵层变得易于形成且致密,排水速率衰减越快;粉粒质量分数越大,土体孔隙率变化越均匀,尤其当粉粒质量分数大于黏粒质量分数时,真空预压加固效果有明显改善。     

基于粒子滤波的跨断层数据分析

以大同台和唐山台为例,对跨断层观测数据与降水量、气温等辅助观测数据进行粒子滤波处理,并与卡尔曼滤波结果进行比较。示例及统计结果表明,该算法在跨断层数据处理中是可行性的。     

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SPH simulation of free surface flow over a sharp-crested weir

In this paper the numerical simulation of a free surface flow over a sharp-crested weir is presented. Since in this case the usual shallow water assumptions are not satisfied, we propose to solve the problem using the full weakly compressible Navier–Stokes equations with the Tait equation of state for water. The numerical method used consists of the new meshless Smooth Particle Hydrodynamics (SPH) formulation proposed by Ferrari et al. (2009) [8], that accurately tracks the free surface profile and provides monotone pressure fields. Thus, the unsteady evolution of the complex moving material interface (free surface) can been properly solved. The simulations involving about half a million of fluid particles have been run in parallel on two of the most powerful High Performance Computing (HPC) facilities in Europe. The validation of the results has been carried out analysing the pressure field and comparing the free surface profiles obtained with the SPH scheme with experimental measurements available in literature [18]. A very good quantitative agreement has been obtained.     

基于微粒群算法的供水管网抗震优化设计

以管网年费用折算值为优化目标、管网拓扑结构与管径为优化参数、管网节点最低可靠度为约束条件,建立了供水管网抗震优化设计模型。利用微粒群算法对这一模型进行了求解,该算法以管网作为微粒个体,通过不断地更新微粒的位置来搜索最优的管网结构,直到最后给出优化的管网结构。利用上述方法对一典型供水管网进行了抗震优化设计分析,给出了3种不同节点最低可靠度约束条件下的优化改造方案。     

基于PSO-AHP的大坝致灾因子权重计算

提出了一种基于改进粒子群优化-层次分析法（SELPSO-AHP）的致灾因子权重计算模型,该模型依据大坝现场检测、原型监测和安全定期检查等成果,由层次分析法构建大坝风险分析的层次结构体系。为保证判断矩阵的一致性,引入改进粒子群算法和罚函数法用于层次分析法的权值计算,取得了比遗传算法更精确、更稳定的结果。将所建立的模型用于某混凝土重力坝的运行风险分析,得到了影响该坝运行风险的主要因素,为保障大坝安全提供了依据。