变参数非线性马斯京根分段演算模型研究与应用

为了更好地模拟天然河道中洪水演进的时空非线性特征,通过构建连续型可变参数的槽蓄方程,在前人研究基础上进一步改进了非线性马斯京根模型结构,并与河道分段演算方法相耦合,提出了一种变参数非线性马斯京根分段演算模型(CVPCS-NMM),并应用于实际案例中。结果表明:CVPCS-NMM取得了比分段马斯京根模型和变指数非线性马斯京根模型(CVEP-NMM)更好的效果,反映出了天然河道洪水过程在时空上的非线性变化特点,表明该模型是一种行之有效的河道演算方法,也为进一步探讨如何将河道分段演算方法与非线性马斯京根模型相结合提供了一种研究思路。     

马斯京根法在锦屏二级水电站减水河段洪水演算中的应用研究

不同场次洪水演算所采用的马斯京根模型的演算参数不同,演算参数的取值对洪水演算的结果有很大影响。传统的演算参数确定方法是试算法,本文提出了一种根据参数的含义运用河道相关数据直接推求马斯京根法演算参数,使参数自适应分段马斯京根模型的方法,本方法具有演算精度高、计算速度快、适应性强等特点,解决了演算参数求解复杂、精度差等问题,该实例验证了本方法的可行性和准确性,可应用于具备类似条件河段的洪水验算。     

马斯京根分段演算与水箱模型组合在区间洪水过程预报中的应用

介绍了马斯京根流量演算方法和水箱模型,提出了将马斯京根分段分步流量演算方法与水箱模型相结合进行区间洪水预报的方法,并将该方法应用于渭河林家村站、汉江安康水库站的洪水预报的研究中,实践证明该方法合理可行,可以推广应用到其它的区间洪水预报中。     

改进的马斯京根法在渭河洪水演算中的应用

针对马斯京根模型的演算参数不能较好地反映各河段水力特征的问题,提出了改进的参数估计方法。实例应用结果表明:改进方法确定的马斯京根模型参数具有较高的精度,且演算的出流过程反映了洪水的地区组成。     

反演法洪水演算问题探讨

在水利水电工程设计中，无论是推求入库洪水或设计洪水的地区组成，均涉及到反演法洪水演算问题。作者在目前较常用的马斯京根公式反演法的基础上，探讨了马斯京根图解反演法和马斯京根迭代反演法．本文详细地介绍了马斯京根公式反演法、图解反演法、迭代反演法，并进行了比较。     

入库洪水计算的马斯京根法探讨

本文对马斯京根法推求入库洪水的求解产生的误差进行了系统的研究,其中包括马斯京根法的顺时序顺演算、逆时序逆演算、逆时序顺演算和顺时序逆演算公式。同时对大藤峡水库入库洪水作了条件数的分析。     

江西柘林河段洪水的反演推求

马斯京根法是我国现行的河道流量演算方法中最常用的一种,在线性运动波演算中具有较高精度.马斯京根法反演主要用于河道断面资料缺乏的地区,通过下断面的洪水流量过程来反推求上断面的洪水过程.当坝址洪水资料缺失时,可以通过马斯京根法反演,分析建立入库洪水与坝址洪水的关系,使建库前后资料满足一致性.     

哈里斯鹰算法在广义非线性马斯京根参数优化中的应用——以洛河为例

马斯京根模型在河道洪水演算中发挥着重要作用,其演算精度在于参数的优选。针对目前马斯京根参数率定中存在的求解复杂、精度不高等问题,提出利用哈里斯鹰算法对其参数进行优化,这种方法具有广泛的全局搜索能力,且需要调节的参数较少。以黄河支流洛河为研究对象,利用广义非线性马斯京根模型对宜阳—白马寺段的河道进行洪水演算,且分别用哈里斯鹰算法、粒子群算法和蚁群算法对其参数进行优化。结果表明,基于哈里斯鹰算法的广义非线性马斯京根模型在洛河宜阳—白马寺段的演算精度较高,其Min.SSD为1 237,洪峰误差DPO仅为5,均优于粒子群算法和蚁群算法优化后的结果,其成果适合应用于洛河宜阳—白马寺段的洪水预报工作。     

马斯京根法模型在受闸门影响的预报断面中存在的问题分析——以北运河土门楼站为例

中国洪水预报系统内置的马斯京根法河道洪水演算模型,功能强大且明显简化了运算量,是北运河土门楼站作业洪水预报的重要工具.但在实际预报工作中发现该模型存在一些问题,为提高预报精度延长预见期,阐述了在实际应用中国洪水预报系统马斯京根法模型进行洪水预报工作时发现该模型存在的缺陷,并提出了解决建议,以期促进模型优化,提高洪水预报精度.     

用分层马斯京根法作河道洪水演算

针对复式河道中用马斯京根法作洪水演算时,常出现洪水参数K、x值难以概化,整个过程线高、低水段很难拟合的情况,根据马斯京根法的基本原理.结合复式河道中漫滩部分水体的影响,提出了把整个入流过程按河槽形态的变化进行分层处理的分层马斯京根洪水演算方法。该法经在渭河临潼至华阴河段实际运用,其精度较传统马斯京根法有明显的提高。     

汾河下游河道洪水预报

汾河下游石滩至河津全长约220km，流经临汾、运城两个地区，是山西省重要的工农业基地。多年来，由于黄河水流之顶托，汾河下游逐年淤积，行洪能力减小，致使1998年河津水文站出现5年一遇洪水，其淹没损失超过1954年100年一遇的洪水。本文从马斯京根法，圣维南方程法二个方面完成了汾河下游河道的洪水预报工作，计算值与实测值吻合良好。其目的是力图在大洪水来临之际，及时为决策部门提供水位、流量及峰现时间，把灾害减轻到最低程度。     

蓟运河降污规划方案实施效果的量化分析

为了改善蓟运河的水污染现状,研究河道水量、水质的时空变化规律,利用一维圣维南方程和一维对流-扩散方程建立水动力-水质耦合模型,并对模型进行率定、验证,所得计算值与实测值吻合较好。应用模型模拟了蓟运河的降污规划方案,得出不同方案下污染物的时空变化情况,为方案的最终确立及修复效果的合理预测提供了量化依据。     

明渠水流泥沙运动水深平均及力矩方程的理论和验证

首次提出了水流泥沙运动水深平均及其力矩方程的概念 ,并从理论上推导出这套方程组。提出水流泥沙运动力矩方程的目的有两个 ,一是在不增加空间维数的情况下可以有效地恢复水流泥沙因子沿水深分布信息 ,克服目前普遍使用的水深平均方程过多地忽略沿水深分布信息的缺点 ;二是增强模型的模拟能力。针对这两个目的是否能真正得到体现 ,分别从理论和实验室资料两个方面对新推导的力矩方程进行了全面的检验。理论验证结果表明 ,一维的力矩方程除了能模拟水深平均的流速和含沙量 ,还能够较好地模拟水流泥沙因子沿水深分布信息 ,这充分说明了一维力矩方程的二维特性。为了检验力矩方程的模拟能力 ,特别选取了一些极端的水流泥沙运动实验 ,如清水冲刷、点源加沙和深槽回淤等。模拟结果表明 ,力矩方程对于这些极端的水沙运动具有较好的模拟能力     

Numerical Models for the Simulation of Overland Flow in Fields Within Surface Irrigation Systems

Discharges in a network of drainage ditches generated by intense rainfall are influenced by overland flow dynamically interacting with infiltration. Therefore a detailed estimation of the overland flow, especially in agricultural fields prepared for surface irrigation, is essential to the design of drainage ditches. In order to simulate overland flow, which in that case may be considered unsteady and one dimensional, numerical models were developed based on the numerical solution of the Saint-Venant equations, externally coupled with the Green-Ampt equation to account for the dynamic interaction between surface flow and infiltration. The numerical solution of the Saint Venant equations in their complete form (dynamic model) and in the simplified forms of the diffusion (diffusion model) and the kinematic wave equations (kinematic model) was obtained by applying the MacCormack explicit computational scheme. Overland flow models’ simulations were conducted in order to study the effect of the soil surface parameters on the hydrographs at the downstream end of the fields, as well as the accuracy of the diffusion and kinematic equations. It was found that the kinematic wave equations were unable to describe overland flow, while the diffusion model results were close to the results of the dynamic model.     

Numerical simulation of flow and bed morphology in the case of dam break floods with vegetation effect

The purpose of this study is to establish a depth-averaged 2-D hydrodynamic and sediment transport model for the dambreak flows with vegetation effect. The generalized shallow water equations are solved using an explicit finite volume method with unstructured quadtree rectangular grid, and in the hydrodynamic model, a Harten-Lax-Van Leer(HLL) approximate Riemann solver is used to calculate the intercell flux for capturing the dry-to-wet moving boundary. The sediment transport and bed variation equations in a coupled fashion are calculated by including the bed variation and the variable flow density in the flow continuity and momentum equations. The drag force of vegetation is modeled as the sink terms in the momentum equations. The developed model is tested against lab experiments of the dam-break flows over a fix bed and a movable bed in vegetated and non-vegetated channels. The results are compared with experimental data, and good agreement is obtained. It is shown that the reduced velocity under vegetated conditions leads to a decrease of the peak discharge and a rise of the water level of rivers and also an enhancement of the sediment deposition.     

2-D NUMERICAL SIMULATION OF RADIONUCLIDE TRANSPORT IN THE LOWER YANGTZE RIVER

The assessment of the radiological impact of the liquid discharges from nuclear power plants is a major issue for the environmental protection. In this study, a numerical model for the radionuclide transport in the aquatic environment is built, based on the hydrodynamic equations, including the complete set of Saint-Venant equations, the sediment transport equations, with consideration of several different particle sizes and the deposition and erosion of the suspended sediments, and the radionuclide transport equations. The exchanges of radionuclides between water, suspended matter and bed sediments are described in terms of kinetic transfer coefficients. The model is used to simulate the transport of the radionuclides discharged from a planned nuclear power plant project to be sited along the lower Yangtze River. From the model results, one may see the detailed temporal-spatial evolution of the radionuclide contamination in the solution, in the suspended matter and in the bed sediments. The model can be used as a basic tool for studying the environmental impacts of the liquid discharges from nuclear facilities on a river system.     

环形井眼气液两相流流动规律研究

本文在１０００米深全尺寸模拟实验井上进行了气液两相流实验研究。利用自行研制的计算机实时数据采集系统及井眼数据测量与传输遥测系统，获取取大量实验数据。依据这些数据，根据质量与动量守恒定律及其状态方程，通过变系数法，建立并求解了描述环空气液两相流的一维拟线性双曲型偏微分方程组，从而得出了适合井眼环空情况下的气体上升速度模型，依据本文提出的流型过渡区及气体上升速度模型所计算的结果和现有国内外有关模型计算     

NUMERICAL SIMULATION OF 2D HORIZONTAL COOLING WATER DISCHARGE IN GENERALIZED CURVILINEAR COORDINATE

1. INTRODUCTIONResearch on the movement characteristics ofcooling water is a hot spot presently , which hasgreat significance to maintain the balance of eco-logical system. Mathematical models and physicalmodels are major means for this study .In recentyears , Chen[1 ,2]has presentsed a 2D horizontalmathematical model based on the hybrid methodand finite element mesh, Zhang[3]has provided afinite layer model for 2D thermal density flowinopen channel . Wu[4]has developped an unsteady2D h…     

EVOLUTION EQUATIONS FOR NONLINEAR WAVES IN A THREELAYER FLUID MODEL

ＥＶＯＬＵＴＩＯＮＥＱＵＡＴＩＯＮＳＦＯＲＮＯＮＬＩＮＥＡＲＷＡＶＥＳＩＮＡＴＨＲＥＥＬＡＹＥＲＦＬＵＩＤＭＯＤＥＬ￥ＺｈｕＹｏｎｇ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓａｎｄＭｅｃｈａｎｉｃｓ，Ｓｈａｎｇｈａｉ...     

Numerical simulation of the internal wave propagation in continuously densitystratified ocean

A numerical model is proposed to simulate the internal wave propagation in a continuously density-stratified ocean, and in the model, the momentum equations are derived from the Euler equations on the basis of the Boussinesq approximation. The governing equations, including the continuity equation and the momentum equations, are discretized with the finite volume method. The advection terms are treated with the total variation diminishing （TVD） scheme, and the SIMPLE algorithm is employed to solve the discretized governing equations. After the modeling test, the suitable TVD scheme is selected. The SIMPLE algorithm is modified to simplify the calculation process, and it is easily made to adapt to the TVD scheme. The Sommerfeld＇s radiation condition combined with a sponge layer is adopted at the outflow boundary. In the water flume with a constant water depth, the numerical results are compared to the analytical solutions with a good agreement. The numerical simulations are carried out for a wave flume with a submerged dike, and the model results are analyzed in detail. The results show that the present numerical model can effectively simulate the propagation of the internal wave.