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Fish passage conditions over spillways are important for the operations of hydroelectric dams because spillways are usually considered as a common alternative passage route to divert fish from the turbines. The objectives of this study were to determine the relative potential of fish injury during spillway passage both before and after the installation of baffle blocks at Boundary Dam, and to provide validation data for a model being used to predict total dissolved gas levels. Sensor Fish were deployed through a release system mounted on the face of the dam in the forebay. Three treatments, based on the lateral position on the spillway, were evaluated for both the baseline and post-modification evaluations: Left Middle, Right Middle, and Right. No significant acceleration events were detected in the forebay, gate, or transition regions for any release location; events were only observed on the chute and in the tailrace. Baseline acceleration events observed in the chute region were all classified as strikes, whereas post-modification events included strike and shear on the chute. While the addition of baffle blocks increased the number of severe events observed on the spillway chute, overall fewer events were observed in the tailrace post-modification. Analysis of lateral positioning of passage indicated that the Right Middle treatment was potentially less injurious to fish based on relative frequency of severe events at each location. The construction of baffle blocks on the spillway visibly changed the flow regime. Prior to installation the flow jet was relatively thin, impacting the tailrace as a coherent stream that plunged deeply, possibly contributing to total dissolved gas production. Following baffle block construction, the discharge jet was more fragmented, potentially disrupting the plunge depth and decreasing the time that bubbles would be at depth in the plunge pool. The results in this study support the expected performance of the modified spillway chute: the addition of the baffle blocks generally lessened the depth and impact of entry. This study provides information that can be used to help design and operate spillways for improving fish passage conditions. 相似文献
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Dam discharges over spillways are the main reason for the gas-supersaturated water generated in rivers.Local aquatic organisms,especially fish,readily develop gas bubble disease(GBD) in a river with total dissolved gas supersaturation(TDGS).Sometimes,fish will die after a specific exposure period,which negatively affects the biological equilibrium.In this study,the influence of TDGS on silver carp was explored.Silver carp were exposed to gas-supersaturated water with TDGS levels of 140%,135%,130%,125%,120%,and 110%to test the impact of TDGS.Some silver carp died when the TDGS level was 120%or higher,and all the silver carp exposed to a TDGS level of 140%died within10 h.In comparison with the Chinese sucker,Prenant's schizothoracin,and rock carp,silver carp seem less sensitive to TDGS.In addition,we tested the catalase(CAT) activity in the muscles and gills of silver carp after they were exposed to gas-supersaturated water with a TDGS level of140%.The CAT activity changed with time;it increased first and then decreased until it was lower than the initial CAT activity.The results of this study can provide basic data for developing a standard for environmental evaluation. 相似文献
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More and more high dams have been constructed and operated in China. The total dissolved gas (TDG) supersaturation caused by dam discharge leads to gas bubble disease or even death of fish. Through a series of experiments, the conditions and requirements of supersaturated TDG generation were examined in this study. The results show that pressure (water depth), aeration, and bubble dissolution time are required for supersaturated TDG generation, and the air-water contact area and turbulence intensity are the... 相似文献
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过饱和总溶解气体释放过程预测 总被引：2，自引：1，他引：1
通过室内试验,研究泄流水体中过饱和总溶解气体的释放过程,分析了影响气体从水中释放的主要因素。利用原型观测资料对已有的过饱和总溶解气体释放的数学模型进行验证,同时对释放系数公式进行了修正。在此基础上预测了金沙江某电站下游河段过饱和总溶解气体的沿程释放规律。 相似文献
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Elevated levels of the Total Dissolved Gas (TDG) may be reached downstream of dams, leading to increased incidences of gas bubble diseases in fish. The supersaturated TDG dissipates and transports more slowly in reservoirs than in natural rivers because of the greater depth and the lower turbulence, which endangers the fish more seriously. With consideration of the topographical characteristics of a deep reservoir, a laterally averaged two-dimensional unsteady TDG model for deep reservoir is proposed. The dissipation process of the TDG inside the waterbody and the mass transfer through the free surface are separately modeled with different functions in the model. Hydrodynamics equations are solved coupling with those of water temperature and density. The TDG concentration is calculated based on the density current field. A good agreement is found in the simulation of the Dachaoshan Reservoir between the simulation results and the field data of the hydrodynamics parameters and the TDG distribution in the vertical direction and their unsteady evolution with time. The hydrodynamics parameters, the temperature and the TDG concentration are analyzed based on the simulation results. This study demonstrates that the model can be used to predict the evolutions of hydrodynamics parameters, the temperature and the TDG distribution in a deep reservoir with unsteady inflow and outflow. The results can be used in the study of the mitigation measures of the supersaturated TDG. 相似文献
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从对总溶解气体(TDG)过饱和概念的分析入手,阐述TDG过饱和的危害。通过对不同典型水体TDG饱和度的测量,表明泄流可以导致水体TDG含量增加甚至过饱和。在此基础上,采用试验研究的方法,探讨了TDG过饱和产生原因及其释放过程,表明水利工程泄流引起的TDG过饱和与泄流掺气、压力、紊动强度、水温等要素相关,并由此提出减缓水利工程TDG过饱和影响的建议。 相似文献
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为提高垃圾填埋场防渗衬垫对可挥发性有机污染物(VOCs)的阻挡效果,在对流-扩散-吸附机理的基础上,考虑了夹气泡压实黏土的固结变形、VOCs固有生物降解和VOCs气液相转化效应,建立了VOCs在夹气泡的填埋场黏土衬垫系统中的传输数学模型,并针对某工程实例,利用多物理场有限元数值软件对数学模型进行求解,研究了填埋场黏土衬垫中典型VOCs的传输与转化。结果表明,夹气泡形成的蒸汽阻滞作用能在一定程度上延缓VOCs的穿透过程;当封闭气体为氧气时,氧气的存在所促发的固有生物降解能有效阻断VOCs的传输,且在垃圾填埋场现场常见污染物浓度水平下所需气泡墙厚度相对较薄。 相似文献
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CAVITATION NUCLEI： EXPERIMENTS AND THEORY 总被引：1，自引：1，他引：0
MφRCH K.A. 《水动力学研究与进展(B辑)》2009,21(2):176-189
The Swedish astrophysicist and Nobel Prize winner Hannes Alfvén said:Theories come and go─the experiment is here forever.Often a theory,which we set up to describe an observed physical phenomenon,suffers from the lack of knowledge of decisive parameters,and therefore at best the theory becomes insufficient.Contrary,the experiment always reveals nature itself,though at prevailing experimental conditions.With essential parameters being out of control and even maybe unidentified,apparently similar experiments ... 相似文献
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简述了钢筋混凝土结构非线性有限元分析的常用模型．针对工程中大型钢筋混凝土压力管道结构设计分析的特点,分析了弥散／分层加筋混凝土有限元模式,提出在大型钢筋混凝土压力管道结构非线性有限元分析中采用弥散／分层加筋混凝土有限元模式,较能符合管道结构的特征． 相似文献
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变压器油中溶解气体在线监测装置中的色谱柱和气敏传感器存在消耗被测气体和长期稳定性差等不足。光声光谱气体分析技术灵敏度高,不消耗被测气体,克服了传统油中溶解气体在线监测技术的缺点。文中对其在变压器油中溶解气体在线监测中的应用进行了研究。构建了用于变压器油中溶解气体分析的光声光谱平台,给出具有红外特征吸收峰的CH4 ,C2 H6 ,C2 H4 ,C2 H2 ,CO和CO2 这6种主要故障特征气体的特征频谱,采用加权最小二乘法对2种混合气体中的CH4 ,C2 H6 ,C2 H4 ,C2 H2 ,CO和CO2 进行了定性和定量分析。分析结果与气体各组分体积分数真实值或气相色谱仪测量值的比较表明,光声光谱技术能有效地对变压器油中溶解气体进行分析。 相似文献
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通用流域污染负荷方程(generalized watershed loading function,简称GWLF)作为一个简单有效的集总参数流域模型已经受到了国内外研究者的广泛认可。在笔者前期研究成果的基础上,对原始GWLF模型的算法和已有水文框架进行了深入修改,添加了河道模块内泥沙悬浮、沉积过程以及污染物衰减过程,进一步增加了模型在空间属性基础上的通用性。以安徽省新安江屯溪监测站为收口断面的上游流域为研究区域,对改进后的GWLF模型(revised GWLF)进行了应用测试,并在月尺度上针对流量、泥沙量、溶解性氮负荷量和溶解性磷负荷量的模型输出结果与原始GWLF模型进行了比较。3项统计学指标和时间序列图表明,改进版模型能够在不添加额外数据需求的前提下,更好地重现流域内水文、泥沙和水质的循环过程。 相似文献
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根据芬兰Valken-Kotinen湖2011年1—4月冰下溶解氧现场观测数据,经对这些数据进行统计分析,绘制出该湖冰下不同时刻溶解氧含量垂直分布图形,通过大量的数据拟合与优化辨识计算,得到了描述该结冰湖冰下溶解氧时空分布规律的一个新的正态分布数值模型。该数值模型中溶解氧含量的变化由深度和冰封持续时间来确定,与文献中的小波分析法和高斯拟合时间序列法的分析结果作比较,该数值模型计算出的冰下溶解氧含量值与实测值吻合效果更好,所绘制出的溶解氧含量曲面和等值线图形更光滑,最后讨论了进一步改进该模型需要考虑的一些因素。该研究结果可推广应用到其它寒区冰封湖泊或水产养殖池塘等水体环境的溶解氧问题研究中。 相似文献
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大涡模拟法的二维形式 总被引：7，自引：0，他引：7
本文给出了大涡模拟（ＬＥＳ０法的二维简化形式，选择了标准的后台阶湍流进行考题。计算结果与有关实验十分吻合。为大涡模拟法的工程应用打下了基础。 相似文献