Development of Reasonable Numerical Methods For Predicting Complicated Hydraulic Appearance With Different Time and Space Scales

发展合理的数值方法来预测不同时间和空间尺度的复杂水力形态

基本信息

批准号：
08456116
负责人：
SHIMADA Masashi
金额：
$ 5.06万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

(1)The numerical methods are discussed theoretically and experimentally developed for predicting water surface of one dimensionally varied steady flows in open channels with a regular cross-section and locally varied resistance zone near the one-sided wall. The resistance zone is composed of pile series arranged like vegetation belt or rough stone zone. The lateral distribution of depth-averaged velocity within a cross section is firstly estimated from the equation of motion including the eddy diffusion effects due to interaction between distributed piles. The longitudinal water level is calculated using the one-dimensional energy equation in which the resistance effect of the pile zone is estimated as the lateral velocity distribution. The comparisons between the experimental and calculated values with respect to the velocities and water levels are very good to examine the usefulness of the analyses. The similar method is extended to the channels with compound sections. With that meth … More od, the cross sections of the flow were divided into three regions to predict the distribution of velocity and water level. With the previous methods the lateral velocity distribution assumes the uniform flow condition while we assume non-uniform flows. The longitudinal water level can be predicted by using the lateral velocity distribution and the energy slope obtained from that velocity distribution. The calculation method is validated by comparisons of the results obtained from the experiments made in the channels with regular and compound sections under the conditions of several kinds of pile zones.(2) To design reasonably grids for slow and rapid transient analysis using the method of characteristics is required to estimate the errors due to the discretizations and lime-line interpolations. The discretization errors for the linear valve closure problems in the simple piping systems is numerically and theoretically investigated with respect to pressure head rises, and formulated as the non-dimensional semi-theoretic equation, which is a function of the time scale of waves(valve closure time), pipe length, wavespeeds, number of pipes, and frictional coefficients. The combined time-line method for slow and rapid transient analysis is offered through designing adequate time-step sizes and grids, which satisfy the criteria for the discretization error and the error du to time-line interpolations. It is examined by numerical computations of transients using the pipeline model. Less

(1)从理论上和实验上讨论了预测具有规则截面和单侧壁附近局部变化阻力区的明渠中一维变化稳定流水面的数值方法。阻力区由桩组成。首先根据运动方程估计横截面内的深度平均速度的横向分布，包括由于分布桩之间的相互作用而产生的涡流扩散效应。一维能量方程，其中桩区的阻力效应被估计为横向速度分布，速度和水位方面的实验值和计算值之间的比较可以很好地检验分析的有用性。使用该方法，将流动的横截面分为三个区域来预测速度和水位的分布，而使用先前的方法，横向速度分布假设为均匀流动条件。纵向水位不均匀。可以利用横向速度分布和由该速度分布得到的能量斜率来预测，并通过对几种桩的条件下规则断面通道和复合断面通道的实验结果进行比较，验证了计算方法。 (2)采用特征法合理设计网格进行慢速和快速瞬态分析，以估计简单管道系统中线性阀门关闭问题的离散化误差和石灰线插值带来的误差。是数字和对压头上升进行了理论研究，并将其表述为无量纲半理论方程，它是波的时间尺度（阀门关闭时间）、管道长度、波速、管道数量和摩擦系数的函数。通过设计足够的时间步长和网格，提出了慢速和快速瞬态分析的组合时间线方法，该方法满足离散化误差和时间线插值误差的标准，并通过数值计算进行了检验。使用管道模型减少瞬态。