唐家山堰塞湖泄洪问题的研究

研究的是唐家山地震次生灾害引发的堰塞湖问题.首先对数字高程地图进行等高图像分析求解了堰塞湖不同高程水位对应的湖区面积,建立了蓄水量体积与堰塞湖水位高程的离散化模型,然后建立了神经网络模型和多元线性回归模型研究了北川降雨量与堰塞湖入库流量的关系,继而求解得到不同降雨量下每日堰塞湖水位高程.在研究泄洪过程时,首先通过对泄洪过程和溃坝过程内在机理的研究分别建立了正交多项式逼近模型和仿真模型得到溃坝时的溃口流量随时间变化的关系,继而分析求解得到溃坝时其他参数随时间变化的关系.针对淹没区的问题,综合数字高程地图和行政区域地图,利用数字地图计算了洪水到达各被淹没区域的时间,淹没范围,以便于确定撤离方案.     

唐家山堰塞湖泄洪问题研究

研究了唐家山堰塞湖的泄洪规律,并对其蓄水、溃坝、泛洪等三个过程进行了模型分析.     

基于故障树分析的堰塞湖溃坝概率估计方法

堰塞湖排险的一个关键问题是如何针对实施不同应对措施情况下的堰塞湖溃坝概率进行估计,这是一个值得关注的重要研究课题。本文提出了一种基于故障树分析(FTA)的堰塞湖溃坝概率估计方法。首先,通过堰塞湖排险问题的实际背景分析,基于FTA构建了堰塞湖溃坝故障树的基本架构;然后,通过相关领域知识、历史案例分析、专家主观判断和多位专家主观判断信息的融合,可以确定实施某一应对措施情形下故障树中各基本事件在不同时段内发生的概率;进一步地,依据构建的故障树和基本事件发生的概率,给出了在不同时段内堰塞湖溃坝事件发生的概率的估计方法。最后,通过一个实例分析说明了本文所提出方法的可行性与有效性。     

有限体积KFVS方法在二维溃坝中的应用

本文采用了基于KFVS格式的有限体积方法 (FVM)求解了控制水流运动的二维浅水方程 ,建立了二维水坝瞬间溃坝的洪水演进模型 .并应用此模型模拟了二维非对称溃坝和对称溃坝情形下坝左下角有障碍物时的洪水波演进过程 .模拟结果表明该数学模型对二维浅水运动的模拟很有效 .     

Finite element analysis of flood discharge atomization based on water–air two-phase flow

Flood discharge atomization is a phenomenon of water fog diffusion caused by the discharge of water from a spillway structure, which brings strong wind and heavy rainfall. These unnatural winds and rainfall are harmful for the safe operation of hydropower stations with high water heads. Compared to the method of prototype observations, physical models and mathematical models, which are semi-theoretical and semi-empirical, numerical simulation methods have the advantage of being not limited by a similar scale and are more economical. A finite element model is presented to simulate flood discharge atomization based on water–air two-phase flow in this paper. Equations governing flood discharge atomization are composed of partial differential equations of mass and momentum conservation laws with unknowns for pressure, velocity and the water concentration. The finite element method is used to solve the governing equations by adopting appropriate solution strategies to increase the convergence and numerical stability. Then, the finite element model is applied to a practical project, the Shuibuya hydropower station, which experienced a flood discharge in 2016. Simulation results show that the proposed model can simulate flood discharge atomization with efficient convergence and numerical stability in three dimensions, and good agreement was observed between numerical simulations and prototype observational data. Based on the simulation results, the mechanism of flood discharge atomization was analyzed.     

A method for the real time forecast of the outflow from a lake

An algorithm for the real time forecast of the outflow from a lake is described. It is assumed that the influent flows of the tributaries, the effluent flow and the lake level are measured hour by hour and used for the outflow prediction in future hours. The proposed method is tested in a real case, the 1957 spring flood of Lake Maggiore.     

鱼咀及丁坝对长江口航道分流分沙的影响

利用水平二维水流、盐度、泥沙数学模型研究了长江口航道整治工程(一期)实施前后,航道的分水分沙特点,重点讨论了束水丁坝的长度、潜堤的方向对航道分流比、分沙比的影响．数值模拟结果表明,双导堤工程减少了航道的分沙量,这有利于维护航道的畅通,但同时也使航道的分流比减小．航道分流分沙比的改变可通过调整各水工建筑物的布置或尺寸来实现．与束水丁坝长度的影响相比,鱼咀工程潜堤方向的改变对航道分流分沙比的影响更大．     

Modelling the impact of dam failure scenarios on flood inundation using SPH

Flooding resulting from collapse of a dam is a highly destructive event. It is important to accurately predict the flow behaviour so that potential mitigation strategies can be investigated for disaster management planning. The meshless SPH method has previously been able to model this class of extreme flow events. In this paper, we extend the method to include modelling of dam wall fragments. Collisions between dam wall fragments, between fragments and terrain and full two-way coupling between fragments and the free surface water flow is included. This gives a method that can specifically investigate the impact of the dam wall failure scenario on the subsequent inundation. The historical St. Francis dam failure is used to demonstrate the impact of including the dam fragments. It also provides a means of quantitatively investigating their effect in terms of arrival time and water height at a downstream power station. The scenario with multiple independently timed failures of different parts of the wall (which closely matches the historical failure) gives excellent agreement with the observed data and gives the best match of all failure scenarios. Traditionally such modelling is performed by solving the two dimensional shallow water equations which is not able to capture the three dimensional nature of the flow in earlier stages of dam flooding. We specifically investigate the three dimensional nature of flow structures and formation of multiple downstream hydraulic jumps. These strongly influence water height and therefore control the extent of flooding of tributary valleys.     

明渠层流失稳与沙纹成因机理研究

动床水流中,泥沙起动之后,往往要出现沙纹,沙纹成因各家的解释不一。白玉川,罗纪生的观点是:沙纹的尺度较小,主要是由于明渠层流不稳定性波或床面近壁流层中小尺度拟序结构发展演化所致。当床面边界附近扰动波或拟序结构以及水流自身所产生的床面底部切应力大于Shields切应力后,床面即产生响应,形成沙纹;如果扰动所产生的扰动切应力频率接近床面泥沙固有频率,则产生与泥沙颗粒的共振,这种现象也称之为“泥沙的检波性质”,此时床面发生最大响应,沙纹发展速度也最快。     

Numerical Investigation of Cavitation Interacting with Pressure Wave

A computational fluid dynamics solver based on homogeneous cavitation model is employed to compute the two-phase cavitating flow. The model treats the two-phase regime as the homogeneous mixture of liquid and vapour which are locally assumed to be under both kinetic and thermodynamic equilibrium. As our focus is on pressure wave formation, propagation and its impact on cavitation bubble, the compressibility effects of liquid water have to be accounted for and hence the flow is considered to be compressible. The cavitating flow disturbed by the introduced pressure wave is simulated to investigate the unsteady features of cavitation due to the external perturbations. It is observed that the cavity becomes unstable, locally experiencing deformation or collapse, which depends on the shock wave intensity and freestream flow speed.     

Mathematical modeling and numerical simulation of two-phase flows using Fourier pseudospectral and front-tracking methods: The proposition of a new method

In the present work, an extension of the Fourier Pseudospectral Method coupled with the Immersed Boudary Method for non-periodic problems (IMERSPEC) applied to numerical simulation of two-phase flow was developed. The proposed method was originally developed for single-phase, incompressible flow. Here, the method is extended to two-phase flows using the front-tracking method (IMERSPEC-FT) to model fluid-fluid interfaces. The proposed method was verified and validated through results involving spurious currents, mass conservation and numerical experiments analysis for rising bubbles. IMERSPEC-FT is shown to be a promising scheme for the two-phase computational fluid dynamics (CFD).     

Sediment Transport via Dam-Break Flows over Sloping Erodible Beds

When a semi-infinite body of homogeneous fluid initially at rest behind a vertical retaining wall is suddenly released by the removal of the barrier the resulting flow over either a horizontal or a sloping bed is referred to as a dam-break flow. When resistance to the flow is neglected the exact solution, in the case of a stable horizontal bed with or without "tail water," may be obtained on the basis of shallow-water theory via the method of characteristics and the results are well known. Discrepancies between these shallow-water based solutions and experiments have been partially accounted for by the introduction of flow resistance in the form of basal friction. This added friction significantly modifies the wave speed and flow profile near the head of the wave so that the simple exact solutions no longer apply and various asymptotic or numerical approaches must be implemented to solve these frictionally modified depth-averaged shallow-water equations. When the bed is no longer stable so that solid particles may be exchanged between the bed and the water column the dynamics of the flow becomes highly complex as the buoyancy forces vary in space and time according to the competing rates of erosion and deposition. It is our intention here to study dam-break flows over erodible sloping beds as agents of sediment transport taking into account basal friction as well as the effects of particle concentrations on flow dynamics including both erosion and deposition. We consider shallow flows over initially dry beds and investigate the effects of changes in the depositional and erosional models employed as well as in the nature of the drag acting on the flow. These models include effects hitherto neglected in such studies and offer insights into the transport of sediment in the worst case scenario of the complete and instantaneous collapse of a dam.     

边部注水时裂缝性油藏中水平井两相渗流

本文在流线不变的假定下研究边部注水时裂缝性油藏中水平井两相渗流问题,建立了双重孔隙介质中水平井两相流体垂直二维渗流的数学模型,并用特征线方法进行了精确求解,给出了裂缝系统和岩块系统中的饱和度分布以及水平井见水时间公式,从而为边部注水开发裂缝性油藏提供了必要的理论基础和工程计算方法。     

Creep damage modeling of a polycrystalline material

A polycrystalline material is investigated under creep conditions within the framework of continuum micromechanics. Geometrical 3D model of a polycrystalline microstructure is represented as a unit cell with grains of random crystallographical orientation and shape. Thickness of the plains, separating neighboring grains in the unit cell, can have non-zero value. Obtained geometry assigns a special zone in the vicinity of grain boundaries, possessing unordered crystalline structure. A mechanical behavior of this zone should allow sliding of the adjacent grains. Within the grain interior crystalline structure is ordered, what prescribes cubic symmetry of a material. The anisotropic material model with the orthotropic symmetry is implemented in ABAQUS and used to assign elastic and creep behavior of both the grain interior and grain boundary material. Appropriate parameters set allows transition from the orthotropy to the cubic symmetry for the grain interior. Material parameters for the grain interior are identified from creep tests for single crystal copper. Model parameters for the grain boundary are set from the physical considerations and numerical model validation according to the experimental data of the grain boundary sliding in a polycrystalline copper [2]. As the result of analysis representative number of grains and grain boundary thickness in the unit cell are recommended. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

赞比西河水资源调度

研究了赞比西河水资源的调度决策问题。赞比西河上的卡里巴大坝年久失修,赞比西河管理局给出了3种方案:维修、重建或用多个大坝代替现有的卡里巴大坝。通过查阅赞比西河相关资料及沿岸的地形地貌信息,首先确定了11个大坝的地理位置及每个大坝发电机组的装机容量,目标是满足水库附近居民及工农业的用水和用电需求;其次,根据投入产出比对管理局提出的3种方案进行了评价,以确定最优决策方案;最后,基于多坝替代系统建立了梯级水库的水资源调度模型,利用坐标轮换方法分别对平水年、丰水年和枯水年进行了水资源调度。模型的敏感性分析表明调度方案模型是稳健的,建立的调度模型符合实际,使得多坝系统水管理能力增强。     

Regularized shallow water equations and an efficient method for numerical simulation of shallow water flows

Regularized shallow water equations are derived as based on a regularization of the Navier-Stokes equations in the form of quasi-gasdynamic and quasi-hydrodynamic equations. Efficient finite-difference algorithms based on the regularized shallow water equations are proposed for the numerical simulation of shallow water flows. The capabilities of the model are examined by computing a test Riemann problem, the flow over an obstacle, and asymmetric dam break.     

Flow models and numerical schemes for single/two-phase transient flow in one dimension

In the two-phase flow field, a traditional mathematical model for simulating the transition of severe slugging flow presents a challenge when liquid slugs completely block pipelines. Accordingly, an advanced and practical slug model that is derived from a mixture model associated with a slip closure is essential to solving the problem in cooperation with the two-fluid model. The model can offset numerical instability that arises from the discontinuous function of the friction factor across the transition from one flow pattern to the other. Two numerical schemes, the non-iterative and the iterative, are developed, and the proposed schemes can stably predict the transient problems under the Courant–Friedrichs–Lewy (CFL) condition for semi-implicit/implicit schemes. In the present work, pressure transients produced by a complex phenomenon, named water hammer effect, are captured using the single-phase flow model in one-dimension to verify the applicability of the numerical schemes and the friction factor model. At last, the analysis of the two-phase transient flow in a pipeline-riser system indicates that the significant advantage of the present schemes is the robustness that the numerical prediction of the severe slugging behaviour is accurate and stable.     

交汇、分流河道洪水演进模型及其应用

通过引入水深连接方程,耦合了干、支流河道的水流运动,给出了它们的流量分配关系,建立了交汇、分流河道洪水演进模型．对交汇河道中水流顶托作用随河道参数的变化规律进行了研究．分析了干、支流洪峰遭遇现象,指出干流和支流的洪峰遭遇是1998年长江大洪水干流高洪水位的重要原因之一．并定性解释长江干流荆江河段的裁弯取直和长江分流河道的淤积对河道水流的影响．     

宾汉流体稠密两相湍流流动中的二阶矩模型

建立的Bingham流体稠密两相流动的二阶矩-颗粒动力论湍流模型（USM-theta模型）既体现了两相的作用,又体现了屈服应力所引起的附加项,并提出了USM-theta模型下考虑浓度修正值影响的两相湍流流动的算法．利用该模型对圆管内Bingham流体的单相湍流流动、稠密液固两相的湍流流动进行了计算,并和五方程湍流模型进行了比较,结果表明该模型的预测效果更好．利用USM-theta模型对含颗粒的Bingham流体的两相湍流流动进行了模拟,随着屈服应力的增加,Bingham流体相与颗粒相在管道中心附近的主流速度减小．液固两相湍流和Bingham流体两相湍流的计算结果表明屈服应力引起的附加项对流动有很重要的影响．