SOLUTION OF THE ENSO DELAYED OSCILLATOR WITH HOMOTOPY ANALYSIS METHOD

An ENSO delayed oscillator is considered.The El Nino atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions.The conceptual oscillator model should consider the variations of both the eastern and western Pacific anomaly patterns.Using the homotopy analysis method,the approximate expansions of the solution of corresponding problem are constructed.The method is based on a continuous variation from an initial trial to the exact solution.A Maclaurin series expansion provides a successive approximation of the solution through repeated application of a differential operator with the initial trial as the first term.This approach does not require the use of perturbation parameters and the solution series converges rapidly with the number of terms.Comparing the approximate analytical solution by homotopy analysis method with the exact solution,we can find that the homotopy analysis method is valid for solving the strong nonlinear ENSO delayed oscillator model.     

洪泽湖混合流数值模拟

本文通过构造一个二维开边界数值模式，对不同风情及出入湖流量组合情况下的洪泽湖混合流流态进行模拟研究，探讨其混合流特征。     

隔水边界附近围岩渗透性变化时隧道涌水的渗流模型

根据各向同性岩石中隔水边界与水平方向的夹角,在岩石渗透性随深度呈负指数衰减条件下,分两种情况给出了二维稳定流隧道涌水量的解析解和数值解.分别对隔水边界距离和隧道埋深对隧道涌水强度的影响,以及岩体中上下水位的巨大差异进行了理论分析.此法可用于预测隧道涌水量,并给出了算例及关系曲线.     

水库异重流的三维数值模拟及影响因素分析

不同水沙条件下异重流的潜入位置以及潜入后流速和含沙量的垂向分布规律是研究异重流运动规律的关键要素,对优化水库异重流的排沙调度、提高水库运用效益等至关重要。本文利用SCHISM三维水沙数学模型对水库异重流水槽试验进行了数值模拟,结果表明模型能够得到符合实际情况的垂线流速和含沙量分布,且异重流潜入后的平均厚度、平均流速和平均含沙量均与实测值吻合较好。对异重流模拟结果的分析发现,入口流量和含沙量的增加造成异重流运动速度越快,而入口含沙量的减小和流量的增加会造成异重流厚度增加。异重流垂向流速和含沙量的无量纲化分布受到入口水沙条件的影响,表现在其与断面Froude数的相关性,Froude数越大,则最大流速点与河床的距离越小,最大流速越大;含沙量致密层的厚度越小,对应的含沙量也越大。此外,潜入点位置也受入口水沙条件的影响,表现在潜入水深与入口水深之比随入口Froude数增加而增加的定量关系,由此可以利用入口水沙条件预报异重流潜入的位置。研究结果不仅验证了SCHISM模型用于模拟水库异重流运动的优势,而且丰富和完善了关于异重流潜入点位置及流速和含沙量垂向分布受入口水沙条件影响的变化规律。     

基于随机森林与支持向量机的水库长期径流预报

水库长期径流预报对于研判水文情势变化和指导水库调度管理具有重要意义。针对云南龙江水库年、汛期和枯水期平均入库径流,利用随机森林从环流指数、海温、气压和前期月径流中选取关键预报因子,基于粒子群与交叉验证相结合的算法优选参数,建立随机森林与支持向量机模型,开展龙江水库入库径流预报研究。结果表明:太平洋中北部与西部气候因子对径流预报的影响较大,前期月径流对年、汛期径流的重要性偏低,但对枯水期的影响程度与部分气候因子相当。随机森林与支持向量机模型总体精度较高,模拟与预报的合格率均达到85%以上,平均绝对百分比误差均低于15%,支持向量机的泛化能力强于随机森林,但二者在局部极值流量处的预报精度尚有待提升。     

水库异重流淤积成因分析及前锋运动规律

汛期暴雨冲刷河道两岸形成浑水入库,在一定条件下会潜入水库底部形成异重流。若上游降雨历时较短,形成的异重流因失去后续浑水补给而停止运动进而造成水库淤积。针对这一问题,基于水库异重流挟沙能力的计算公式,分析异重流造成水库淤积的原因,即异重流的超饱和输沙和沿程流量损失。针对异重流因沿程流量损失而发生的水库淤积,对失去后续浑水补给的异重流进行水槽试验,分析坡度和浑水入流流速对异重流前锋厚度及运动速度的影响。试验结果表明:坡度或浑水入流流速越小,失去浑水补给的异重流前锋运动速度越慢,前锋厚度减小越快。     

THE ANALYSIS OF INTRASEASONAL LONG ROSSBY WAVE SPEED IN THE SUBTROPICAL PACIFIC OCEAN

1. INTRODUCTIONLong Rossby waves are the main mechanis mwherebyinformation about one part of the oceanistransferred to another part and a nonequilibriumo-cean state adjusts to an equilibriumone . The studyon the beta views of long Rossby waves is an i m-portant aspect of ocean circulation. In a recentstudy , Chelton and Schlax[1]conducted a thoroughanalysis of the satellite alti meter data from thefirst 3 years TOPEX/POSEIDON mission. Theyfound two interesting properties of long Ro…     

Relationships between wind-driven and hydraulic flow in Lake St. Clair and the St. Clair River Delta

A three-dimensional hydrodynamic forecasting model of the Great Lakes Huron-Erie Corridor is used to investigate mixing and the relationship between hydraulic and wind-induced currents in a shallow lake system in which lake inflows come through several channels of a river delta. The hydrodynamics in Lake St. Clair and the channels of the St. Clair River Delta are evaluated for (1) a one-year simulation from 1985 including water age calculation, (2) 8 different wind direction scenarios, and (3) a storm event. Observations and model simulations show distinct regions in the lake in which currents are forced by either hydraulic flow from the river system or from wind stress over the lake. However, during severe storm events, these regions are found to shift or even disappear due to changes in the delta channel inputs into the lake. These changes underscore the need for realistic, unsteady river flow boundary conditions at interfaces between a shallow lake and river delta. Steady inflow conditions will not allow for potential shifting of these current zones, and will also fail to resolve flow retardation or reversals during storm events.     

基于ARGO浮标资料的太平洋三维流场估算

针对实际海洋中三维海流观测困难和流场资料欠缺的问题,通过ARGO浮标观测资料与WOA09背景场资料进行最优插值融合,得到较精细的温盐网格化资料,并在此基础之上通过引入P矢量方法,对太平洋海区的三维流场进行了诊断推算。分析表明:ARGO浮标再分析融合数据能够较好表现太平洋温盐场分布结构,在此基础之上诊断推算的三维流场能够合理刻画太平洋流场的基本特征,为获取大尺度海洋三维流场信息提供了有效的途径。     

A LATTICE BOLTZMANN MODELING FOR THE WESTERN BOUNDARY CURRENT IN A LINEAR WIND-DRIVEN QUASI-GEOSTROPHIC MODEL

1 .　INTRODUCTIONLatticeBoltzmannMethod (LBM )isanewnumericalmethodforcomputationalfluid (ChenandDoolen 1998) ,whichisdevelopedfromLat ticeGasCellularAutomaton (LGCA )inthelate80satlastcentury .LBMusesthecontinuousdistri butionfunctiontoreplacetheBooleanvariablesusedinLGCA .Asaresult ,LBMovercomesmanyshortcomingsofitsancestor ,suchasnoise ,notconformingtoGalileoinvarianceetc .HeandLuo(1997)developedLBMasaself containedsystemconstructedtheamodelwithoutconnectiontoLGCA .LBMha…     

用聚类预报模型预报三峡水库来水量的探讨

为了开展三峡水库入库来水量长期预报,从北半球500 hPa高度场、太平洋海温场、北半球100 hPa高度场、北半球地面气压场与74项环流特征指数作为预报因子,采用回归方程求解和回归效果检验,建立回归聚类预报物理模型,对三峡水库6～8月各月平均来水量进行了长期预报分析。结果表明,三峡水库6~8月份各月来水量回归聚类预报的技术路线是可行的,正、负距平符号一致的概率能达到80%以上,效果较好,基本上可以满足生产需要。回归聚类预报物理模型具有一定的应用推广价值。     

金沙江干流山区水库通航流态三维数值模拟研究

采用三维水动力学模型,借助非结构网格重构地形,开展了金沙江干流山区水库通航流态的数值模拟研究。以攀枝花河段为例,选取不同的来流条件进行了模拟,重点关注了水深、流速、平面流场和典型弯道的环流结构等水动力学特性,进一步对河段可能的碍航点进行了分析。计算结果表明:在一定的出流边界条件下,河道水深整体呈沿程递增趋势,基本可满足三级航道标准;同时某些流量级下,局部卡口、突扩和弯道河段可能出现碍航流态。研究结果可为金沙江梯级水库群联合调度提供技术参考。     

FLUSHING TIME OF THE YANGTZE ESTUARY BY DISCHARGE: A MODEL STUDY

1 .　INTRODUCTIONTheYangtzeestuaryisamesotidalestuary .ThelengthoftheestuaryfromXuliujingtothemouthisabout 110km .Thewidthofestuarymouthisabout 90km .ThereachbetweenXuliujingandMouthiscalledestuary .Wherethetidalanddis chargeinteractswitheachother .Withthedevel opmentofeconomyandtheincreaseoflivinglev el,muchsewagehasbeendischargedintoopenseathroughtheYangtzeestusry .HydrodynamicandwaterqualityinvestigaionsoftheYangtzeestuaryhasbeenattractedtheattentionofcitizenscon cernedwithenvironme…     

NUMERICAL SIMULATION OF TWO-PHASE GRAVITY CURRENTS OVER A POROUS SUBSTRATE

1 .　INTRODUCTIONGravitycurrentsoccurinmanysituationsaris inginbothindustrialandnaturalsettings[1 2 ] .Commonlythecurrentisdrivenbycompositionalortemperaturedifference ,toleadtoahomoge nouscurrent ,orbysuspended particulatematter ,toleadtoaparticle drivencurrent.Combinationsbybothparticleandcompositionalortemperaturedifferencecanalsooccur[3] .Mostoftheresearchesareconcentratedonthesituationswherethecur rentsflowaboveanimpermeableboundary .How evertherearemanyimportantcaseswheregravitycurr…     

THREE-DIMENSIONAL NUMERICAL MODELLING OF THE WAVE-IN- DUCED RIP CURRENTS UNDER IRREGULAR BATHYMETRY

A process-based 3-D hydrodynamic model is established to simulate the rip current structures under irregular bathymetry.The depth-varying wave-induced residual momentum,the surface rollers,the turbulent mixing and the wave-current interactions are considered.Experimental datasets are used to validate the model,and it is shown that the model can effectively describe the 3-D structures of the rip currents in both normal and oblique wave incident cases.The flow patterns of the rip currents see various characteristics for different incident wave directions.In the normal incident case,pairs of counter-rotating primary circulation cells are formed,and an offshore rip flow occurs in the embayment troughs.The peak seaward velocities occur at the top of the bed boundary layer,and the undertow is incorporated in addition to the rip currents.In the oblique incident case,the longshore currents are dominant,which result in a meandering flow along the depth contour,and the undertow is weaker compared to that in the normal incident condition.     

AN EXTENDED MODELING OF TIDE-WAVE MOTION

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｏｓｔｕｄｙｔｈｅｍｏｔｉｏｎｏｆｔｈｅｔｉｄｅ ｗａｖｅｓ,ｔｈｅｓｈａｌｌｏｗｗａｔｅｒｅｑｕａｔｉｏｎｓ ,ｉ.ｅ .ｔｈｅｖｅｒｔｉｃａｌｉｎｔｅｒｇｒａ ｔｉｏｎｏｆｔｈｅｃｏｎｔｉｎｕｉｔｙｅｑｕａｔｉｏｎａｎｄｍｏｍｅｎｔｕｍｅｑｕａ ｔｉｏｎ ,ｉｓｃｏｎｓｉｄｅｒｅｄａｓｔｈｅｇｏｖｅｒｎｉｎｇｅｑｕａｔｉｏｎｓ.Ｂｙａｂｏｖｅｅｑｕａｔｉｏｎｓｔｗｏｅｑｕａｔｉｏｎｓｒｅｌａｔｅｄｔｏｔｈｅｈｏｒｉｚｏｎ ｔａｌｆｌｕｘｏｆｔｈｅｔｉｄｅ ｃｕｒｒｅｎｔｓａ…     

边界条件对自然河流形成及演变影响机理的实验研究

运用自然模型法,采用清水冲刷成功地塑造了室内天然小河。实验研究了不同的初始河流几何边界条件以及水流条件对河流演变的影响。研究发现流量对河流展宽幅值影响最大。水流入射角的大小与河流展宽幅度及河流弯曲度的变化没有必然的联系,30°入射角时小河的河流展宽及弯曲度变化最明显。入射角对河流演变的作用只是短期的,且在演变初始阶段影响较大。受初始边界条件的影响,河流向下游演变具有滞后性及曲率变化的传递性等特点。本文最后分析了河流演变过程中的泥沙分选现象。     

南沙河流域来水量分析计算

南沙河是鞍山市城市河流,目前正在进行河道综合整治,拟修建多个蓄水工程。每个工程都必须进行水资源论证,来水量分析计算是水资源论证中最重要的组成部分之一,不同保证率的来水量和来水过程计算成果与立山站降水一径流深相关关系图及降水一径流历年过程线图的变化趋势基本一致,所以来水量的计算是合理的。     

非恒定流作用下的阶梯形丁坝局部冲刷特性

阶梯形丁坝是常见的航道整治建筑物,天然河道中的水流多为非恒定流,非恒定流作用下的阶梯形丁坝局部冲刷特性研究,对丁坝结构设计和水毁防护等具有重要意义.采用自回归马尔柯夫模型,将天然来流过程概化为波谷起冲和波峰起冲2种情况,基于平面二维水流泥沙数学模型,探讨非恒定流作用下的阶梯形丁坝局部冲刷特性.结果表明:① 不同流量过程...     

ANALYTICAL STUDY OF WAVE MAKING IN A FLUME WITH A PARTIALLY REFLECTING END-WALL

Based on the eigenfunction expansion technique, the wave generation by a piston wave maker in a wave flume with a partially reflecting end-wall is studied. The corresponding velocity potential and wave elevation in the flume are obtained. The present analytical solution is verified by the numerical results obtained from a time-domain higher-order boundary element method in a closed flume. Numerical experiments are further carried out to study the difference between the partial/full reflection boundary and the transmission boundary and the effects of the reflection coefficient and the motion period of the wave maker on the wave height. Meanwhile, the natural frequency of the wave flume can be obtained from the analytical expression. The resonance occurs when the motion frequency is equal to the natural frequency. Even the partial reflection of the end-wall in the wave flume experiments has a great influence on the wave height, therefore, inaccurate measurements would be resulted in long-time simulations, especially when the wave frequency approaches the wave flume natural frequency. The present study can serve as a guidance for the physical experiment in wave flumes.