反拱形水垫塘结构在拉西瓦水电站上的研究与应用

通过自行设计的拉西瓦水电站反拱型水垫塘模型,并通过在模型底板上铺设脉动压力传感器和流速传感器的方法,研究了在不同的上下游水位时反拱形水垫塘的动水荷载特性。研究表明:脉动压强的概率密度曲线与正态分布曲线具有相似的变化规律,最大流速发生在水舌冲击点下游的壁射流区,其结果可为反拱形水垫塘的设计与施工提供参考。更多还原     

高重力坝防冲建筑物体型参数对水力特性的影响

高重力坝防冲建筑物体型参数的选取决定了泄洪消能水流的水力特性,从而影响水电站的安全运行。采用水工模型试验的方法,研究了防冲建筑物体型参数对水流的水力特性影响规律。研究结果表明：水垫塘长度的减小,使塘内淹没冲击射流的扩散空间减小、冲击区的紊动增强,导致塘内底板时均压强谷值减小、脉动压强均方根峰值增大、底板安全风险增大;二级消力池池长的减小,使出池临底流速增大、下游冲刷风险增大;二道坝高度的降低,导致水垫塘底板沿程时均压强减小、脉动压力均方根峰值增大、底板安全风险增大,同时导致二级消力池内水跃收缩断面水深增加、跃首区临底流速降低、紊动强度降低、脉动压力均方根峰值减小,但出池临底流速增大。     

高重力坝挑坎体型及水力特性对比

基于水工模型试验方法,利用几何比尺为60的黄河古贤水利枢纽水工模型,研究了连续式、窄缝式、差动式、燕尾式、直边窄缝燕尾式及曲面窄缝燕尾式共6种体型挑坎的水舌特性及水垫塘底板的压强特性。结果表明:连续式挑坎水舌呈连续且集中的形态;当挑角为30°时,窄缝式挑坎并未呈现纵向拉伸的水舌形态,内外缘挑距大,入水宽度小,冲击压强与脉动强度较大;差动式挑坎水舌呈现分层分股的形态特征,入水宽度变大,冲击压强与脉动强度减小;燕尾式挑坎水舌纵向呈扫帚状,水舌面积增大,在空中扩散、掺气、摩擦消散充分,入水宽度大大增加,沿程时均压强未出现冲击压强且脉动强度最大值比连续式、窄缝式及差动式挑坎分别降低59.5%、69.8%和39.4%;曲面窄缝燕尾式挑坎横向收缩与纵向拉伸效果比直边窄缝燕尾式挑坎好,且横向收缩有利于近坝区水体紊动及削弱二道坝区水体紊动;燕尾式挑坎有利于水垫塘底板稳定和下游消能防冲,对于类似高重力坝挑坎体型选择具有一定参考价值。     

水垫塘内淹没冲击射流中的大尺度涡结构及其特征

高坝下游水垫塘消能与防护问题目前尚未得到妥善解决。本文应用现代紊流理论的观点，对水垫塘内的复杂流动结构进行了系统的研究，对主射流区的大尺度涡体和壁射流区的紊动涡体的拟序结构进行了分析，从紊流力学的角度对脉动压力的起源及水垫塘内水体能量的转移与耗散做了机理性解释，为高坝下游水垫塘的消能与防护的进一步研究提供了理论依据。     

高含沙水流脉动特性试验研究

以某工程的表孔为依托,建立1∶100单体模型。通过配置不同含沙量的水流,对水垫塘底板含沙水流的脉动压强进行试验。结果表明,在试验范围内,水流条件不同,含沙量对脉动强度的影响不同:水流条件较强时,脉动压强随着含沙量的增大,呈现先减小后又增大的趋势,含沙水流最大脉动压强比清水最多减小24.73%;水流条件较弱时,脉动压强随着含沙量的增大,呈现先增大后减小的趋势,含沙水流最大脉动压强比清水最大增加78.74%。冲击区含沙水流脉动压力分布比清水更接近正态分布,脉动压力能量大部分集中在0.4 Hz以内,功率谱无明显的优势频率,水流主要以低频大尺度漩涡为主。通过对高含沙水流水垫塘底板的脉动压强进行观测,总结分析了不同因素影响下高含沙水流脉动压强特性的变化规律,为相关工程提供参考。     

水垫塘冲击区掺气浓度对脉动压强作用的试验研究

采用水工模型试验,研究泄流进入水垫塘后在水垫塘底板冲击区内掺气浓度对脉动压强的作用。通过改变掺气量,使水垫塘内水体的掺气浓度发生变化,开展不同的掺气浓度对水垫塘冲击区底板脉动压强影响的研究。结果表明:在保持水垫深度和泄流流量不变的情况下,增加掺气量,水垫塘冲击区同一测点水体掺气浓度值随掺气量的增加而增加。水垫塘冲击区内掺气浓度分布规律为在冲击点处达到最大值,由冲击点向上、下游递减;冲击区底板总动水压强的峰值随掺气量的增加而降低;脉动压强的方差值随掺气量的增加而减小,即脉动变幅减小。脉动压强的概率密度分布为正态分布,分布曲线随掺气量的增加而变陡、变窄,脉动强度系数分布集中,即方差变小,压强峰值减小,脉动强度减小。同一测点脉动压强的频谱分布规律一致,其优势频率集中在低频范围,随掺气量的增加,脉动幅值降低,即脉动压强降低。     

山区泄水建筑物斜向进水消力井直径优化研究

通过水工模型试验,研究在斜向进水条件下,狭窄河谷泄水建筑物消力井沿径向不同井径下的底板动水压强时均值及不均匀系数、脉动压强方差和频谱特性的变化规律。成果表明:在一定泄洪功率时,受下附壁射流和底部潜流影响,射流远端冲击区底板区域动水压强时均值、不均匀系数以及脉动强度方差均明显大于射流轴线左、右侧底板和靠近泄槽末端消力井底板区域。相较于消力井井径由0.15m增大到0.30m,在井径进一步增大到0.45m时,无论消力井底板动水压强,还是底板脉动压强均呈下降趋势。     

热膜测速技术在挑射水流运动特性及高坝消能机理研究中的应用

本文为探讨挑射水流在冲坑内的基本特征与消能机理，首次利用热膜测速技术量测定床冲坑中淹没射流的沿程时均流速和脉动流速分布，并同时量测沿坑底的压强场，给出入射区、冲击区和壁射流区三个子区的流速和压强的变化规律；计算坝面摩阻消能、空中扩散消能和冲坑水垫中紊动剪切消能三部分的消能效率。     

热膜测速技术在挑射水流中的应用及高坝消能机理的研究

为探讨挑射水流在冲坑内的基本特征与消能机理，首次利用热膜测速技术量测定床冲坑中淹没射流的沿程时均流速和脉动流速分布，并同时量测沿坑底的压强场，给出入射区、冲击区和壁射流区３个子区的流速和压强的变化规律；计算坝面摩阻消能，空中扩散消能和冲坑水垫中紊动剪切消能３部分的消能效率。     

正冲击射流脉动壁压的正交分解与低阶近似

为更好地了解冲击射流脉动壁压的统计特性,通过实验对其脉动壁压强度与频谱特性进行了研究,并对冲击射流脉动壁压时序信号的正交分解与低阶近似进行了探讨。根据实验结果得到了脉动壁压强度的拟合公式,其壁压表现为窄带低频过程。     

CHARACTERISTICS OF CORRELATION AND SPECTRUM BETWEEN WALL FLUCTUATING PRESSURE AND FLUCTUATING VELOCITY OF IMPINGING JET

The correlation, the spectrum and the turbu-lent scale between wall fluctuating pressure and fluctuating ve-locity, on the bed of plunging pool under the action of single and twin impinging jet, are investigated in the paper by using 2-D LDA and the dynamic pressure scanning system of multi-ple points. It is found that the cross correlation between the horizontal fluctuating velocity and the fluctuating pressure of twin jet is bigger than that of sinlge jet, and the spectrum be-tween horizontal fluctuating velocity and fluctuating pressure obviously has approximately dominant frequency. The rela-tionship between the fluctuation pressure coefficient on wall and the turbulent intensity near the wall can be described with logarithmic curve.     

浑水脉动压力试验研究

在对量测技术进行研究和改进的基础上，对不同流态区清水和浑水脉动压力进行了系统的对比观测。试验结果表明：高含沙浑水不再属牛顿体而变为宾汉体，浑水的紊流结构发生变化。浑水脉动太力均方根和经度系数随含沙量增加呈直线关系增大，以常水水柱表示的脉动压力均方根和强度系数，浑水和清水没有区别。水流含沙后，浑水紊流结构的变化，并没有改变紊流结构中旋涡含能分布规律，紊动能仍然集中在大，中尺度旋涡中，所以，浑水和清水     

NUMERICAL STUDY OF TURBULENT IMPINGING JET WITH A REFINED k-ε MODEL

1.　INTRODUCTIONJet impingement flows are frequently used in industrial practice for their high rate ofheat and mass transfer.Their employment is common but also diverse and typical applica-tions includemany heating,cooling and drying processessuch asthe manufacturing of print-ed wiring board,printing processes,production of foodstuffs,de-icing of aircraft wings,cooling of electronic elements and package and cooling of turbine aerofoils.The high heattransfer rate are especially needed to a…     

基于AR模型的海上风机脉动风速时程模拟

为分析海上风机支撑结构及叶片的风振动力响应特性,基于线性滤波法中自回归AR模型,采用Kaimal脉动风速功率谱编制了具备时空相关特性的MATLAB脉动风速时程模拟程序;针对江苏如东黄海海域某4 MW级风机塔筒、叶片等结构进行了实例分析,得到结构表面各控制点模拟脉动风速时程曲线,并结合计算功率谱与目标谱进行对比验证;利用TurbSim软件对自编程序计算精度和效率进行比较。相关计算结果表明该程序简单易操作,所需参数较少;虽无法考虑湍流强度,但具有适用多种风机结构的优点;同时整体模拟效果良好,可有效解决风荷载输入问题。     

NUMERICAL STUDY OF HYDRODYNAMICS OF MULTIPLE TANDEM JETS IN CROSS FLOW

The hydrodynamics of a single jet and four tandem jets in a cross flow are simulated by using the Computational Fluid Dynamics (CFD) software Fluent. The realizable model is used to close the Reynolds-Averaged equations. The flow characteristics of the jets, including the jet trajectory, the velocity field and the turbulent kinetic energy are obtained with various jet-to-cross flow velocity ratios in the range of 2.38-17.88. It is shown that a single jet penetrates slightly deeper than the first jet in a jet group at the same , although the difference decreases with the decrease of . It is also found that the way in which the velo-city decays along the centerline of the jet is similar for both a single jet and the first jet in a group, and the speed of the decay increases with the decrease of . The downstream jets in a group are found to behave differently due to the sheltering effect of the first jet in the group. Compared with the first jet, the downstream jets penetrate deeper into the cross flow, and the velocity decays more slowly. The circulation zone between the two upstream jets in the front is stronger than those formed between the downstream jets. The Turbulent Kinetic Energy (TKE) sees a distinct double-peak across the cross-sections close to each nozzle, with low values in the jet core and high values in the shear layers. The double-peak gradually vanishes, as the shear layers of the jet merge further away from the nozzle, where the TKE assumes peaks at the jet centerline.     

Expansion characteristics of twin combustion gas jets with high pressure in cylindrical filling liquid chamber

To deal with the problem of how to control the interior ballistic stability in the bulk-loaded liquid propellant gun, the expansion and mixing process of the twin combustion-gas jets with high temperat...     

葛洲坝工程二江泄水闸脉动压力原型观测

本文根据6组共71个测点的原型观测数据,探讨了作用于葛洲坝二江泄水闸消力池隔墙上的脉动压力特性;提出了估算类似条件下的脉动压力强度的经验公式。从荷载、振动以及空化三个方面对二江泄水闸的运行进行了分析。结果表明,就这三方面而言,二江泄水闸的运行是安全的。     

Velocity and concentration measurements in initial region of submerged round jets in stagnant environment and in coflow

Velocity and concentration fields are measured in submerged round jets in a stagnant environment and in coflow using laser Doppler anemometry and laser-induced fluorescence. Measurements are made in the initial region within distances of 40 jet exit diameter at jet Reynolds number between 1000 and 5000 and coflow-to-jet velocity ratio from 0 to 0.43. Different behaviors of jet spreading and dilution are found in jets at three different ranges of Reynolds number in which the jets are classified as initially laminar, transitional or turbulent. In the zone of established flow, the jet centerline velocity and concentration decay with downstream distance at different rates in the three groups of jets. For jets in coflow, axial development of normalized forms of centerline mean excess velocity and mean concentration at different velocity ratios can be reasonably well collapsed onto universal trends through the use of momentum length scale. Turbulence properties inside a jet are increased by the presence of a strong coflow. Inside the zone of flow establishment, some strange features are observed on jet turbulence properties. The length of zone of flow establishment increases from the turbulent jets, to the transition jets and to the laminar jets. The zone lengths for concentration are shorter than those for velocity by one to two jet exit diameters. Both lengths are shortened further in the presence of a coflow. For jets a stagnant environment and in the strong jet flow region of jets in coflow, jet widths increase linearly with downstream distance in transitional and turbulent jets. Self-similarity of radial profiles of mean velocity or excess velocity, mean concentration, turbulence intensities and concentration fluctuation level is explored in the zone of established flow.     

射流冲刷试验研究

为研究影响射流冲刷的因素，作者进行了７０组试验，分别研究了单管和多管，水平和有入射角，贴底和离开床面，静水和动水等情况。对试验结果的分析表明，在床沙一定、河流流速与射流流速相比不大的情况下，冲刷坑的几何尺寸与Ｖ＾２／３Ｄ＾５／６有较好的关系。     

多股水舌入射水垫塘底板脉动压力互相关特性及其灰色关联分析

本文对１：１００比尺的小湾水垫塘底板脉动压强进行了量测，对水舌冲击区附近各测点，进行了时空相关分析。结果表明，相关系数随水垫深度增加有所增大，随离冲击区距离的增大呈近似指数衰减。文中还首次引入了灰色关联分析方法对其进行了灰色关联分析，结果表明其关联度均在０．６以上，说明灰色关联分析在脉动压强相关分析中有其一定的优越性。