壁面喷流船用舵水动力的理论预测

本文提出具有壁面切向喷流的船用舵水动力学计算的一种方法,其中用Theodorsen方法求解钝尾有分离的势流问题。用Spalding统一边界层理论作粘性计算,以及用Lighthill的当量源方法考虑粘性/势流的耦合效应。通过对一个特定舵的计算,发现壁面喷流对提高舵效有较大潜力,预测了壁面喷流舵在船舶应用上有其研制开发的前景。     

轴对称面元上分布奇点在无界域中的诱导速度势和诱导速度

本文给出分布在轴对称面元上的奇点在无界域中的诱导速度势和诱导速度计算公式,奇点分布强度在轴向和径向采用高斯分点离散,周向采用富氏级数离散。用这种离散方法计算轴对称面元上分布奇点的诱导势和诱导速度,提高了计算效率和精度,可供用边界元方法求解势流问题时参考。     

粘性流中的二维兴波水翼水动力特性研究

本文采用边界层的概念来研究粘性流中的二维兴波水翼之水动力特性的数值计算方法。考虑到边界层与外部势流的相互干扰，运用了势流与边界层的相互迭代计算，从而求得两者相互匹配的解。用势流解求得的水翼升力系数往往比实验值明显偏大。而用本文的方法，从算例来看，计算结果比势流解减小１５％左右，而与实验值比较接近。本文还讨论了兴波阻力的计算方法，并有算例。     

掺气减蚀设施后二维空腔流动计算

本文发展了文献[4]中提出的求解自由面重力流的h2类边值问题理论。运用解析函数的Riemann-Hilbert混合边值问题的h3类边值问题理论，导出了计算有重力作用情况下双自由表面二维空腔势流流动的边界程分方程，提出了确定空腔区水舌下自由表面的计算格式，并在物理平面上进行了数值求解。表明，该数值方法具有收敛速度快、边界适应能力强、计算量小、计算精度高和对初值要求不高等特点。计算结果与实测资料对比分析表明，来流佛氏数Fr<7情况下，无需考虑阻力影响，采用势流模型即可获得与实测值相符合的结果；而在来流佛氏数Fr>7情况下，由于射流掺气加剧，需引入阻力修正。     

几何独立的高阶面元法在波-流-物相互作用问题mj项求解中的应用

mj项的计算是波-流-物相互作用问题的数值解的难点之一.该文给出了使用几何独立的高阶面元法求解mj项的方法,物面用任意的分片连续函数表示,定常兴波势用任意阶的B样条函数近似,直接对定常兴波势微分以得到mj项中定常兴波势的二阶导数.数值实例显示这一方法的计算结果非常准确.     

用时域法求解二维二阶非线性水波的绕射问题

本文用二阶理论在时期围内研究非线性水波的绕射问题。一、二阶问题分别满足各自的自由表面条件和物面条件。用一阶Ａｄａｍｓ格式并配合时步处理来计算自由表面上的波高和速度势，而流场内的速度势通过求解有限元方法得到。采用人工阻尼区来吸收反射波，对水平半圆柱在水面的绕射问题进行了计算，得到了自由表面波高时间历程和圆柱所受到的波浪力，计算结果和有关文献进行了比较，其符合程度是令人满意的。     

突体绕流的一种边界积分方程及数值解

本文应用复变函数理论,把管道中的突体绕流及半无限升坎绕流的流速分布和压力分布的计算问题化为上半平面解析函数的Dirichlet边值问题。在许瓦兹公式的基础上,再用索霍茨基-普来梅公式取边界值,在变量代换后,则问题化为求一个哥西型边界积分方程。用数值迭代方法求解,可得突体及升坎上的流速分布及压力系数。该方法的物理概念清楚,数值求解收敛速度快,计算效率高,数值解与试验资料吻合较好,是求解势流问题的一种有效而又简便的方法。     

溢流反弧段壁面势流流速计算方法的探讨

笔者在已有研究成果的基础上，考虑了溢流反弧段凹曲率的影响，应用急变流动断面平均概念，建立了求解溢流反派段壁面势流流速μpw的计算公式，经与已有的计算方法比较，其求得的u。值最大相差不超过1cm／s，壁面势流流速沿程增大的规律也是完全正确的，说明所推导的溢流反派段壁面劳流流速计算公式是正确可靠的．     

基于高阶谱方法与CFD计算的耦合模型在不规则波模拟中的应用

基于高阶谱(HOS)方法的势流造波模型可进行波浪的高效率非线性演化模拟,但由于忽略了黏性影响,在研究波浪与物体相互作用中,对于波浪破碎和边界层流场细节模拟等方面很难实现,而黏性波浪水池则有计算量大的局限性。该文建立了基于高阶谱(HOS)方法与CFD计算的耦合模型,外域波浪场依靠势流模型计算,而内域波浪场演化则通过求解Navier-Stokes方程获得,通过松弛区将二者结合,可以避免求解大范围的黏性波浪场而带来的巨大计算量,并且能在波浪与物体相互作用中考虑黏性影响。在对多种波浪类型的模拟以及网格尺度影响讨论中,黏势流耦合模型的适用性得到验证。并在多向不规则波的聚焦波模拟,以及基于势流基础上的大范围长时间演化下得到的极端海浪在CFD域内重构中,黏势流耦合模型都有其成功应用。     

由气水流场耦合求解圆板的垂直等速入水

为探讨气流对入水空泡的影响以及计算非定常空泡面上的压力分布，本文提出了一个用自由面和物面上的边值同时求解气、水流场的方法，对圆板垂直等速入水算例，获得了空泡深闭合的结果。空泡内压力在深闭合时的骤增趋势与实验一致。表明本方法用于计算存在自由面的二层不掺混不可压势流问题是有效的。     

MATLAB遗传算法工具箱(GAOT)在水资源优化计算中的应用

阐述了遗传算法的基本原理，对MATLAB遗传算法工具箱（GAOT）的参数使用进行了详细介绍，探讨了MATLAB遗传算法工具箱（GAOT）在水资源非线性规划和多目标规划时的应用，并用简单实例证明了这种应用具有良好的通用性、可行性和简便性，可以得到较满意的优化计算结果。     

Can we characterize river corridor evolution at a continental scale from historical topographic maps? A first assessment from the comparison of four countries

National historical map resources are assessed in four European countries to characterize river corridor features and associated channel changes, as well as identify issues limiting or promoting geomorphic assessment procedures at a continental scale. A geomorphic audit that launches potential data for diagnosis from reach to continental scales could offer a good resource for biology and ecology managers of river authorities or government agencies and engineers. The assessment compares the resources available by country in terms of period covered, spatial scale, history and chronology, and representation of the fluvial corridor features. We then applied the Historical Maps Vectorization Toolbox, initially developed for vectorizing river corridors from French maps, to detect and extract flow channels, unvegetated bars and riparian vegetation patches from historical topographical maps. We found that (a) it is difficult to apply an audit of channel changes to the whole continental scale because map legends differ between countries due to geographic and political specificity; (b) there exists an opportunity to get assessment information in all countries at reach or national scale where map resources are available; (c) the highest potential is observed in Switzerland and Belgium where there is high quality national map coverage from the 19th century; and (d) the algorithm Historical Maps Vectorization Toolbox applied to map resources works well with any of the countries, and its widespread application is encouraging.     

基于MATLAB的电力系统的潮流计算

随着计算机语言技术不断发展和成熟，基于MATLAB潮流计算研究近年来得到了长足的发展。针对这一现状，以P-Q分解法为例，分析了BASIC、FORTRAN和MATLAB高级语言潮流计算的异同，指出它们的优缺点，并针对潮流计算模型结构的特点，提出了基于MATLAB的潮流算法。     

基于MATLAB的泄洪洞气泡运动轨迹检测

针对高水头泄洪洞气泡运动轨迹难以测定的情况,设计并制造了比尺为1∶100的雅砻江锦屏一级水电站泄洪洞模型,首次采用图像测量方法对泄洪洞内气泡沿程运动特性进行测量。使用高速摄像机拍摄到清晰的气泡运动图像序列,并利用MATLAB图像处理方法实现了对流场中气泡的分割识别,得到气泡的面积、形心等参数,并进一步获取了泄洪洞流场中单个气泡运动轨迹。     

A COUPLING MODEL OF WATER FLOWS AND GAS FLOWS IN EXHAUSTED GAS BUBBLE ON MISSILE LAUNCHED UNDERWATER

The gas and water flows during an underwater missile launch are numerically studied. For the gas flow, the explicit difference scheme of Non-oscillation and Non-free-parameter Dissipation (NND) is utilized to solve the Euler equations for compressible fluids in the body-fitted coordinates. For the water flow, the Hess-Smith method is employed to solve the Laplace equation for the velocity potential of irrotational water flows based on the potential theory and the boundary element method. The hybrid Eulerian-Lagrangian formulation for the free boundary conditions is used to compute the changes of the free surface of the exhausted gas bubble in time stepping. On the free surface of the exhausted gas bubble, the matched conditions of both the normal velocities and pressures are satisfied. From the numerical simulation, it is found that the exhausted gas bubble grows more rapidly in the axial direction than in the radial direction and the bubble will shrink at its "neck" finally. Numerical results of the movement of the shock wave and the distribution of the Mach number and the gas pressure within the bubble were presented, which reveals that at some time, the gas flow in the Laval nozzle is subsonic and the gas pressure in the nozzle is very high. Influences of various initial missile velocities and chamber total pressures and water depths on both the time interval when the gas flow in the nozzle is subsonic and the peak of the gas pressure at the nozzle end were discussed. It was suggested that a reasonable adjustment of the chamber total pressure can improve the performance of the engine during the underwater launch of missiles.     

平面二维溃坝水沙输移动床数学模型研究

为数值模拟溃坝洪水作用下泥沙输移及河床变形,建立了无结构三角形网格的平面二维水沙耦合数学模型。水动力学模型采用浑水流动方程,考虑了泥沙输移及床面冲淤变化对水流动量的影响;泥沙输移采用不平衡泥沙输移模式。模型数值计算格式采用守恒性较好的有限体积法,单元界面的对流通量采用基于近似黎曼解的Roe格式计算,扩散通量采用中心格式,不平衡泥沙输移方程采用坡度限制的二阶空间精度格式离散。模型经经典算例和小尺度瞬间全溃的动床实验资料检验,水面、床面及流速等计算结果与实验资料或解析解等比较吻合,分析了动床与定床水面及洪水传播速度的差异。在上述检验的基础上,采用动床模型对某河道型水库溃坝诱发的水沙运动进行了数值模拟,结果表明溃坝洪水下水流、泥沙及河床变形发生强烈的相互作用,采用水沙及河床变形耦合的数学模型是必要的。     

Water medium retarders for heavy-duty vehicles: Computational fluid dynamics and experimental analysis of filling ratio control method

The water medium(WM) retarder is an auxiliary braking device that could convert the kinetic energy of the vehicle to the thermal energy of the coolant, and it is used instead of the service brake under non-emergency braking conditions. This paper analyzes the flow distribution based on a mathematical model and analyzes the key factors that could affect the filling ratio and the braking torque of the WM retarder. Computational fluid dynamics(CFD) simulations are conducted to compute the braking torque, and theresults are verified by experiments. It is shown that the filling ratio and the braking torque can be expressed by the mathematical model proposed in this paper. Compared with the Reynolds averaged Navier-Stokes(RANS) turbulent model, the shear stress transport(SST) turbulent model can more accurately simulate the braking torque. Finally, the flow distribution and the flow character in the WM retarders are analyzed.     

三维宽顶堰紊流场数值模拟及分析

本文利用三雏标准k-ε紊流数学模型,选择VOF方法追踪自由表面,采用气液两相流计算模型对宽顶堰流场进行了数值模拟,计算结果与试验数据较为吻合.模拟结果表明,数值模拟能够广泛应用于数值模拟带有复杂自由表面的泄水建筑物紊流场.     

瞬态压力分析方法在小型压裂地应力测试中的应用

小型压裂地应力测试是最可靠的深部岩体原位地应力状态测量方法,裂缝闭合压力等于最小水平主应力,故确定裂缝闭合压力是小型压裂测试分析的关键。小型压裂法分析基础为一维流体模型,考虑在一个竖直井旁产生交叉的垂直裂缝,该裂缝具有有限或无限的导流能力,这就自然引入了瞬态压力分析(PTA)的概念。尽管PTA方法已经广泛应用于石油/天然气行业,但在岩石力学工程的小型压裂测试分析中是新引入的概念,少有相关研究。首先回顾了瞬态压力分析的基本原理及其在小型压裂地应力测试中的应用;其次用偏微分方程描述小型压裂地应力测试过程中的压降过程,不同的流体状态代表张开状态的裂缝、正在闭合的裂缝以及闭合后的裂缝;这些不同的流体状态可以在压力导数曲线中表现出来,并利用这些特性识别裂缝的闭合压力;最后结合某深埋隧道小型压裂地应力测试,采用PTA方法分析确定了最小水平主应力,并与其他分析方法作了对比,为隧道工程小型压裂地应力测试分析提供一定的参考。     

NUMERICAL MODELING OF SUSPENDED SEDIMENT TRANSPORT IN CHANNEL BENDS

1. INTRODUCTION Due to the fact that three-dimensional (3D) numerical models are quite expensive to simulate flow and sediment transport processes, vertically-integrated two-dimensional (2D) models are extensively applied at present, even to the predictio…