桥渡非恒定流水工模型试验研究

扼要介绍非恒定流模型试验的理论基础(模型水流与原型水流的相似准则),我院为开展非恒定流试验研究而研制的试验设备与仪器,以及针对水库溃坝水流、潮汐水流、涌潮水流、天然河道水流等不同类型非恒定流对桥渡建筑物影响所进行的试验研究特点、研究成果和发展进程。     

设置保水堰管涵输水系统的水力瞬变数值仿真

为研究大型调水工程的水力瞬变过程，采用明渠非恒定流方程及Preissiman方法模拟无压管涵非恒定流、有压管涵水击和明满交替流，提出了设置保水堰的长距离管涵输水系统的水力学仿真模型。所建立的数值模型可模拟包括管涵明满交替和保水堰跌水等复杂的水流现象。数值仿真结果表明，在检修闸门和下游管涵之间设置保水堰，可以调节输水管道内的压力，避免紧急启闭时发生液柱分离以及检修闸门突然关闭时因明满流交替而产生强烈的冲击水压。     

高水头船闸反弧门后水流流态和收缩系数研究

用所建立的船闸反弧门段的局部模型，对反弧门后水流流态和结构进行了流动显示，通过以３８６微机为中心，ＶＰ３２图像板和ＣＣＤ图像传感器等组成的采集处理系统，获得了比较清晰的反弧门后水流流动图谱，给出恒定流条件下回流区长度的估算公式，比较了恒定与非恒定流门后流态的差异，并求得反弧门不同开度时的收缩系数。     

高水头船闸反弧门后水流流态和收缩系数研究

用所建立的船闸反弧门段的局部模型，对反弧门后水流流态和结构进行了流动显示。通过以３８６微机为中心、ＶＰ３２图像板和ＣＣＤ图像传感器等组成的采集处理系统，获得了比较清晰的反弧门后水流流动图谱。给出了恒定流条件下回流区长度的估算公式，比较了恒定与非恒定流门后流态的差异，并求得反弧门不同开度时的收缩系数。     

计算流体动力学(CFD)在建筑排水系统中的应用

建筑排水系统的设计依据是最大使用限度理念,该理念由概率论和恒定流理论发展而来.这种基于恒定流理论的现有方法,对排水立管流态、瞬态压强传播机理、系统内气体运动模式、虹吸雨水排水系统初始阶段的管道水流状态等问题的分析难以取得有效进展,而对排水系统内部非恒定水流运动情况的详细分析已成为该领域的研究趋势.介绍了研究建筑排水系统内气水运动模式的计算流体动力学(CFD)方法,并总结了CFD在国外排水系统中的应用情况.     

南水北调中线工程总干渠水力学 仿真模型研究

以节制闸为边界将南水北调中线总干渠分为若干子段,采用闸门过闸流量公式、能量方程、圣维南（Saint-Venant）方程组和低压管流方程分别计算闸门水位流量关系、明渠恒定流、明渠非恒定流和有压建筑物非恒定流,以此建立总干渠水力学计算模型。通过双重迭代方法对水流方程、过闸流量方程进行联合求解,以模拟总干渠运行调度动态过渡过程,以京石段2008年输水实测数据对水力学模型进行验证,结果表明模型具有良好的收敛性和较高的精度。     

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...     

关于建筑排水横管水流研究的探讨

建筑排水横管中水流状态属于非恒定、非满管的气、液、固三相流 ,对其进行研究也就相对复杂。但可以先对水流进行研究 ,进而引入固体 ,将固体作为一个移动的边界条件 ,最终建立起建筑排水横管的非恒定流数学模型并可将之用于对排水横管水流的模拟和预测。     

弧形闸门开启过程非恒定流流量系数研究

为探究非恒定流流量系数特点,采用RNG k-ε紊流模型结合动网格技术对某工程Y形宽尾墩表孔弧形闸门开启过程进行了三维动态数值模拟研究,根据过闸流量滞后的特点,将闸后水流分为滞后式、过渡式和平稳式3种流态。分析了闸门开启过程中水流流态及非恒定流流量系数与闸门开启速度和溢流堰顶水头的关系,指出非恒定流流量系数随闸门开启速度的加快及堰顶水头的降低而减小,并给出不同开启速度和堰顶水头情况下适于过渡式及平稳式水流的流量系数经验公式。部分结果与试验结果进行对比,吻合良好,验证了数值方法的可靠性。     

非恒定流作用下砾石推移质输移特性试验研究

基于水深与流量的变化率提出了反映水流非恒定强度的无量纲参数P。利用水槽非恒定流输沙同步测试系统试验研究了非恒定流作用下砾石推移质的输移特性。试验资料分析表明,非恒定流作用下的砾石推移质输移具有明显的随机性、间歇性与阵发性。水流的非恒定性对输沙率峰值的脉动性有影响,对P＞0.32的强非恒定流而言,若输沙率样本数少于20,将会给输沙率结果带来较大的偏差。非恒定流作用下输沙率与水流要素变化具有不同步性,并与水流非恒定强度有关。P＞0.32时,输沙率峰值一般滞后于流速峰值;当P＜0.32时,可能出现输沙率峰值先于流速峰值的现象。非恒定流作用下砾石推移质平均单宽输沙率（或输沙量）与单宽流量（或径流量）、非恒定强度参数P有关,随P的增强而加大。     

液体管道高频水力瞬变过程的数值模拟

目前在液体管道高频水力瞬变分析中,人们通常采用经典的拟稳态摩阻模型进行分析.但这种方法针对管壁切应力具有拟稳态特性的缓慢瞬变的分析是可行的,而对高频瞬变流动过程而言却不能准确预测水击压力波具体的衰减过程以及出现的波形畸变现象.介绍了一种新的考虑瞬时加速度对高频水力瞬变过程影响的非恒定摩阻模型,并结合特征线法给出了其数值解法,最后通过实例验证了该模型能比经典的拟恒定摩阻模型更为准确地模拟液体管道中高频瞬变流压力波的衰减和波形畸变.该模型对计算机的要求和计算耗时与经典的拟稳态摩阻模型相差不大,是一种具有良好工程应用潜力的液体管道高频瞬变分析数学模型.     

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.     

COMPUTER-AIDED ANALYSIS OF UNSTEADY PARTIALLY FILLED FLOWS IN DRAINAGE SYSTEMS

The partially filled pipeflows encountered in drainage systems belong to a family of unsteady flow problems capable of numerical solution via the method of characteristics.The defining equations in terms of flow depth,velocity and surface wave speed are developed and numerically solved by characteristic-difference method with time-lineinterpolation scheme.Boundary conditions for inflow,outflow,moving hydraulic jump and junctions are developed both experimentally and numerically.Full scale model experiments were carried out and it was consequently clarified that numerical model is capable of predicting flow characteristics in realistic drainage networks.     

ACCURATE PIPE TOP-ENTRY JUNCTION MODEL FOR STEADY AND UNSTEADY FLOWS

ＡＣＣＵＲＡＴＥ　ＰＩＰＥ　ＴＯＰ－ＥＮＴＲＹ　ＪＵＮＣＴＩＯＮ　ＭＯＤＥＬ　ＦＯＲ　ＳＴＥＡＤＹ　ＡＮＤ　ＵＮＳＴＥＡＤＹ　ＦＬＯＷＳＡＣＣＵＲＡＴＥＰＩＰＥＴＯＰ－ＥＮＴＲＹＪＵＮＣＴＩＯＮＭＯＤＥＬＦＯＲＳＴＥＡＤＹＡＮＤＵＮＳＴＥＡＤＹＦＬＯ...     

Unsteady Flow Simulation and Erosion Assessment in a Ditch Network of a Drained Peatland Forest Catchment in Eastern Finland

We developed and applied a computational model for simulating unsteady flow in a drainage network of a boreal forested peatland site. The input to the model was the hourly runoff produced by a hydrological model. The simulations of the flow in the ditch network were performed using an iterative procedure for solving the Saint-Venant equations that govern the flow in each of the network channels. These equations were solved separately for each ditch branch, and the flow depths at the junctions were corrected using the method of characteristics. The model was applied to the drainage network of a peatland catchment in Eastern Finland over a period of 15 months. Because flow resistance in the ditches depended strongly on flow conditions, flow resistance (Manning’s n) was introduced as a function of discharge. The model was calibrated and validated against field data and the simulation results were further applied to assess erosion risk. The highest risk of erosion occurred during long lasting flows induced by snowmelt at ditch sections with a steep slope and a large upstream area. These model results can aid in the design and siting of water protection measures within the drained area.     

滨海山丘区城市小流域设计洪水计算方法研究

我国滨海山丘区城市上游有山丘区,洪水下泄速度较快;下游受到潮水的顶托作用,内河洪涝水无法外排入海,洪涝灾害频发。城市化的进程也改变了原有下垫面的产汇流特性,既不能采用原有天然流域设计洪水计算方法,也不能采用城市排水的计算方法。论文针对快速城市化中的滨海山丘区的特点,分析了城市市政排水计算公式、水利推理公式和非恒定流法之间的区别,提出了利用推理公式、管道汇流和非恒定流法相结合计算小流域设计洪水的方法。以赣榆县柘汪-石桥片区为例,分别采用上述3种方法计算其设计洪水。结果表明:非恒定流方法的计算结果比推理公式方法小,该方法比较符合滨海山丘区的洪水特性,可为城市建设和河道规划提供依据。     

外河水位顶托下雨水管网排水能力变化的SWMM模拟

以沈阳市和平区雨水管网系统为例,选取芝加哥雨型为设计雨型,利用SWMM,模拟分析了不同暴雨重现期和外河设计洪水位下的雨水管网系统排涝过程。结果表明:随着降雨重现期增大,雨水管网排水能力增加,但积水程度加重;雨水管网系统有效排涝系数随着降雨重现期的增大而减小,且在高重现期时变化程度减缓;雨水管网系统总排水能力与外河水位和各节点(雨水井)的平均落差呈显著正相关,相关系数R为0.992,并呈近似线性关系;泵站排水在淹没出流地区至关重要,本例中可提升36.3%的管网系统排水能力,而对于自由出流地区,泵站对系统排水能力基本没有贡献。     

河道边界水位对管道排水能力的影响分析

为保证城市排水安全,缓解城市内涝,针对河道排涝水位对管道排水的动态影响问题,选用宿迁市马陵河排水片区为研究区,基于SWMM模型,模拟2、3和5 a重现期暴雨条件下出水口管道分别为自由出流、半淹没出流和完全淹没出流3种情形的管道相对排水能力变化,并在此基础上探求马陵河各分段控制水位。结果表明:管道水流主要受河道高水位作用,即管道完全淹没出流时,排水能力随水位的升高而不断减小,减小程度与末管道高差和水位动态顶托管道水流有关。此结论可为城市排水管网改造及河道调控水位除涝提供科学参考。     

An Unsteady Subsurface Drainage Equation Incorporating Variability of Soil Drainage Properties

Almost all unsteady subsurface drainage equations developed so far use constant value of drainable porosity and hydraulic conductivity which may not be representative of entire drainage flow region. A drainage equation was, thus, developed incorporating depth-wise variability of drainable porosity (f) and hydraulic conductivity (K) of saline soils of Haryana state in India. The drain spacing with measured hydraulic heads at different periods of drainage were estimated by the developed equation and compared with the corresponding drain spacing estimated by commonly used unsteady drainage equations. The study revealed that the developed equation estimated the drain spacing that was nearest to the actual drain spacing of the existing subsurface drainage system, when a generally used design criterion of 30 cm water table drop in 2 days is considered. For a criterion of desired water table drop in 3 days and beyond, Glover equation was found to be the most superior. Hence, both the developed equation and Glover equation can be readily used with the associated design criteria for designing unsteady subsurface drainage systems in saline soils of the state of Haryana, India.