基于CFD的挑流泄洪雾化特性研究

针对泄洪雾化影响范围不易采用数学模型直接模拟的问题,以某高坝电站泄洪为研究对象,先采用三维数学模型计算挑流水舌入水流速、入水角度等水力特征值,再基于此特征值选用原型观测校正后的计算公式预报泄洪雾化范围,并通过物理模型试验对计算结果进行验证分析。结果表明,受比尺效应影响,物理模型试验预测的雾化影响范围小于公式计算的范围,但两者的变化趋势一致;雾流受惯性力和水舌风作用,沿水舌轴线做爬坡运动,与原型观测现象一致;受出口挑流影响,泄洪雾化影响集中在水舌落入点的下游,而水垫塘上游、右岸降雨强度较小,影响范围有限。     

United friction resistance in open channel flows

It is now over half a century since Keulegan conducted his open channel flow experiments.Over the past decades,many empirical formulae were proposed based on his results,however,there is still not a combined expression to describe the effects of friction over all hydraulic regions in open channel flows.Therefore,in this letter,based on the analysis of the implicit model and the logarithmic matching method,the results of Keulegan(for authentic experiment data are no longer available,here we adopt the analytical solutions given by Dou)are rescaled into one monotone curve by combining the Reynolds number and the relative roughness of the river bed.A united expression that could cover the entire turbulence regions and be validated with Dou’s analytical solutions is suggested to estimate the friction factor throughout the turbulent region in open channel flows,with higher accuracy than that of the previous formulas.     

抽水蓄能电站同发同抽水力特性VOF数值模拟

为了有效缓解电网突然出现的电力不平衡现象,同一个抽水蓄能电站不同水力单元机组同时分别发电及抽水运行,是对抽水蓄能运行及调度方式的一个重大创新措施。以某抽水蓄能电站上库为例,通过数学模型研究上库进/出水口在同发同抽工况下的库区水流流态、流道的水力特性、库区漩涡特性等水力参数的变化规律。结果表明,VOF方法可很好地模拟抽水蓄能同发同抽过程;同发同抽工况下,库区内进出水口附近局部水流流态与单向运行工况基本一致,但是两进/出水口之间形成连通的水流通道,库区内形成大范围横向流动,致使抽水单元大部分水流再次进入发电单元。     

城市行洪河道桥群阻水叠加效应量化研究

针对城市行洪河道桥梁群形成的叠加阻水效应问题,以南京市重要行洪通道秦淮河为例,考虑桥墩不过水边界等因素,建立了秦淮河涉水桥梁群的平面二维水流数学模型,对桥群阻水叠加效应进行量化分析。分析结果表明,河道上游水流受桥梁群阻水影响,水位壅高较为明显,壅水高度随桥墩数量的增加而增大。基于计算结果,推导出了桥梁群壅水高度计算公式,并通过滁河六合城区段桥群壅水叠加影响进行了验证,验证结果良好。同时,给出了桥墩在河道两侧及河道中心的位置影响系数值,阐明了桥群壅水叠加机理;所建立的壅水叠加公式较好地反映了河道桥群的阻水叠加效应,为城市河道桥群壅水叠加影响的量化分析研究提供了科学依据。     

桥群叠加阻水效应对河道过流能力影响研究

在桥墩概化、模型验证和参数分析率定基础上,建立秦淮新河涉水桥群二维整体数学模型,对秦淮新河不同水文条件下桥群叠加阻水对行洪能力的影响进行计算分析。结果表明:秦淮新河河道水流受桥群阻水叠加影响,尤其在中上游,桥墩布置密集,河道壅水明显,在一定程度上消弱了秦淮新河的行洪能力,对行洪安全造成一定影响。     

大古水电站坝前排沙运行方式与排沙漏斗形态

为给实际工程排沙设施的设计和布置提供依据,基于1∶60整体模型,根据淤积泥沙扬动流速相似原理,试验研究大古水电站2条排沙廊道和1个底孔在不同运行方式下坝前库区的排沙效果和排沙漏斗形态。结果表明:排沙洞开启顺序对最终排沙效果影响不大;深水条件下,坝前排沙漏斗形态主要受泥沙特性决定,非黏性沙的排沙漏斗坡度接近于淤积泥沙水下休止角;大古水电站排沙设施的设计方案具备保证电站进水口"门前清"的条件。     

高土石坝大交角挑流消能水垫塘优化布置

通过如美水电站整体模型试验,从水流流态、水垫深度、动水压力、下游河道流速分布等特性,对比研究了增设二道坝和降低底板高程两类优化方案。结果表明,大交角挑流消能水垫塘下游增设二道坝,其效果与二道坝高度、泄量、河谷宽度等密切相关,会恶化出流与下游河道的衔接;降低水垫塘底板高程对下游衔接影响较小,且可有效增加水垫深度,降低水垫塘临底水力指标。     

平原河道桥墩群阻水壅高试验研究

以南京秦淮新河为参考原型,建立河道桥群概化试验模型,定量研究平原河道桥群阻水叠加效应.试验结果表明:上游水流受桥墩阻水影响,水位壅高明显,壅水高度随桥墩数量的增加而增大,壅高范围随着桥墩数量的增多而延长;对于概化河道(流量1000 m3/s,流速2.5 m/s,阻水率6％),河道中心线最大壅水高度36 cm,壅水范围150 m;在桥梁群上游150 m位置处,6座桥梁组成的桥梁群引起的壅高值为单座桥梁壅高值的1.5倍.研究成果对评估桥梁等涉水建筑物引起的阻水影响具有参考意义.     

Numerical simulation of scouring funnel in front of bottom orifice

The scouring funnel in front of a bottom orifice under the condition of fixed water levels is simulated by using an Eulerian two-phase model, with onsideration of the flow-particle and particle-particle interactions. The predictions of the scouring funnel shape agree well with laboratory measurements. The flow-field characteristics of the two phases and the influences of the hydraulic and geometric parameters on the shape of the scouring funnel are analyzed on the basis of the computation results. It is revealed that the non-dimensional maximum scour hole parameters, the depth d_m / d_o, the length l_m / d_o, and the half-width w_m / d_o, are linear with the densimetric Froude number Fr_o, the main parameter describing the scour hole, the centerline scour depth D_c and the half-scour width W_r vary according to a power law, and the transverse scour profiles exhibit strong similarities, the velocity distribution of the water is confined within the sink-like area near the orifice, and the mutual impact of the flows at the azimuthal sections and the resistances of the walls and the sand layer produce a vortex in the scour hole, that makes the sand particles to be suspended in the water, the exchanging water in the pore water is the main contributor in forcing the sand to move, and transporting the sand in the same direction as the pore water along azimuthal sections.