潜艇结构振动声辐射数值计算

采用有限元／边界元法对潜艇水下辐射噪声特性进行了研究。依据潜艇各种真实的结构尺寸和设备参数，利用有限元软件ANSYS建立了接近于真实潜艇的有限元模型，并利用该模型来计算潜艇在水下低速航行时200Hz以下频率段的辐射噪声。首先计算了潜艇在电机激励时非耐压壳体表面节点的位移，然后将计算所得的位移结果转换成节点速度导入SYSNOISE边界元模型，以作为边界元计算时的边界条件来研究潜艇的辐射噪声，最后将计算结果与实际测量结果进行了对比，结果显示，在63Hz以下的准确性较高，而在63—200Hz频率段的误差则较大。     

Multigrid fictitious boundary method for incompressible viscous flows around moving airfoils

In this paper, an efficient multigrid fictitious boundary method (MFBM) coupled with the FEM solver package FEATFLOW was used for the detailed simulation of incompressible viscous flows around one or more moving NACA0012 airfoils. The calculations were carried on a fixed multigrid finite element mesh on which fluid equations were satisfied everywhere, and the airfoils were allowed to move freely through the mesh. The MFBM was employed to treat interactions between the fluid and the airfoils. The motion of the airfoils was modeled by Newton-Euler equations. Numerical results of experiments verify that this method provides an efficient way to simulate incompressible viscous flows around moving airfoils.     

加强施工图设计阶段工程投资的控制

建设项目投资控制是工程设计中的重要内容之一,投资控制贯穿于项目建设的全过程。也就是在满足技术规范要求的基础上,采取技术措施,将工程投资控制在主管部门批文的幅度内。本文结合上海市嘉金(A5)高速公路建设设计过程,着重讨论施工图设计阶段设计优化的重要性和必要性。     

基于NURBS的船体与桥墩间水动干扰力及力矩的非定常计算

本文在一些假设下完成了船体与桥墩之间水动干扰力及力矩的数值计算工作，所采用的方法是基于非均匀有理B样条(NURBS)的三维Rankine源边界元法，即将船体、桥墩的几何形状以及流场中待求的物理量分布完全表达成NURBS的形式。给出了船体通过圆柱形桥墩时的水动干扰力及力矩的数值计算结果，并进行了一些分析。     

关于非齐次贝塞尔方程的奇边值问题

本文给出了贝塞尔方程的格林函数,并借助格林函数导出了非齐次贝塞尔方程的奇边值问题的解的表达式.     

The interaction of tidal advection, diffusion and mussel filtration in a tidal channel

Time series measurements of flow and pigment concentrations (Chl) in the Menai Strait have revealed that the strong residual flow in a tidal channel ( 500 m³ s^− 1) transports phytoplankton from the open sea into the channel where much of it is consumed by suspension feeders, mainly in commercial beds of Mytilus edulis. The progressive depletion of phytoplankton along the channel results in a strong horizontal gradient of plankton and hence Chl. Tidal displacement of this gradient causes large (± 50% of mean) oscillations of Chl in the vicinity of the mussel beds. Vertical mixing by the strong tidal flows is sufficiently vigorous for most of the tidal cycle to ensure that downward diffusion can resupply the near-bed layer although there are indications of some transient depletion around slack water.This paradigm of the interaction of advection, diffusion and filtration determining the distribution of plankton and its supply to mussels has been encapsulated in a series of simple models forced only by boundary values. In the first, a 1-D model of tidal flow in the channel reproduces the principal features of the observed currents including the unusually large spatial change in phase of the currents and the variation of the residual transport with tidal range. The flow field from this physical model is used to drive a second model based on the advection diffusion equation for Chl with a source at the Irish Sea boundary and a sink over the mussel bed. This model illustrates the formation of a strong Chl gradient along the channel and simulates the amplitude and phase of the M₂ oscillations of Chl and the development of the M₄ variation apparent in the observations. This second model has been extended to 2-D over the mussel beds to allow investigation of the effects of water column mixing. The model indicates that only for a short period ( 30 min), close to slack water, is mixing sufficiently reduced to permit the development of a depletion boundary layer and then only within  1 m from the bottom, a result which is consistent with the observations.     

列车作用下东巨寺沟铁路隧道围岩动力反应分析

东巨寺沟铁路隧道选取试验段中实施湿喷工艺喷射聚丙烯纤维混凝土,作为支护结构,并作永久性支护结构,免除二次衬砌;为研究该隧道在列车作用下的动力响应,从土－结构相互作用模型出发,采用粘－弹性人工边界条件,建立隧道支护结构－围岩相互作用的动力分析模型,采用时程积分法研究了列车荷载对铁路隧道围岩和支护结构的动力作用,分析了列车荷载作用下由于轨道不平顺引起的动力响应,并对该隧道围岩的稳定性进行了分析。分析结果表明:在列车动力作用下,隧道围岩和支护结构变形微小,处于稳定状态。     

Manufacturing Technology for the Mould of Plastic Cushion for Motorcycle Pedal

摩托车设计随着社会的发展更加人性化,外塑件的曲面也越来越复杂,在外塑件的曲面制作中越来越多地利用二次曲线、样条曲线等复杂的多阶函数曲线作为轮廓线或控制线来编辑曲面;在模具制作过程中,需要进行展开制作的踏皮等零件,如果设计者不提供展开的数据模型,制造者用手工测量进行展开的误差较大,需要进行修模修整,失去了3D设计的意义。     

基于AUTODYN的气泡与固定壁面相互作用数值模拟

阐述了AUTODYN软件模拟水下爆炸气泡的原理及过程,通过球对称模型以及重力场中气泡的实验数据与AUTODYN计算结果的对比,验证其在计算气泡脉动时间和压力等方面的计算精度,并以此为基础研究近壁面水下爆炸气泡的动力学特征以及影响因素,包括无量纲距离对气泡形状的影响,固壁面对气泡最大半径、脉动周期和射流时间的影响,以及近固壁面气泡射流速度及压力的变化等,总结相关规律,为气泡的数值模拟研究提供参考。     

大面积真空预压边界密封技术的应用

采用真空预压法对新吹填土及软弱地基进行加固时,边界密封通常采用密封沟的处理方法。但是,对于存在透水、透气的土层,边界密封仅采用密封沟方法不仅不经济,而且也不能达到加固效果。结合大面积真空预压地基处理工程中土层透气、工程造价、工期等实际情况,介绍区间采用密封沟与区域采用黏土密封墙相结合的边界密封技术。工程实践表明,加固效果良好,经济合理。