共查询到20条相似文献,搜索用时 62 毫秒
2.
朱昆鹏 《甘肃水利水电技术》2010,46(5):13-15,17
河道糙率作为表征水流能量沿程损失的重要参数,不仅仅是河流水沙输移模拟中必须考虑的问题,而且该参数的取值对河道治理规划设计也起到至关重要的作用,利用河道阻力学进行水流的分析计算对水利工程的施工等有着及其重要的作用。 相似文献
3.
4.
针对河道水体日趋营养化、污染物的浓度低、水量大等特色,本文将从河道的局部滩地方向出发,探讨人工湿地的构建方式与实际运用,净化河水。首先阐述了河道人工湿地构建的基本理论,在此基础上提出了河道人工湿地的具体构建方法,湿地床体的构建主要考虑其对湿地内部水流条件的影响,分析人工湿地对河道水流的影响,计算结果表明了该方法的合理性和可行性,这对构建该类河道人工湿地具有一定的指导意义。 相似文献
5.
6.
7.
8.
本文通过由流速分布推求冰期河道冰盖糙率系数,提出了由流速分布推算冰盖及河床糙率的计算方法,同时考虑冰盖影响区与河床的流速分布,确定最大流速位置,阐述了冰盖对水流的阻力是研究河道冰情演变及其运动规律的依据.并对河道冰期形成冰盖,其阻力使河道水位升高、过流能力降低、水位流量关系改变.流速分布推算冰盖及河床糙率的计算方法进行了分析.为北方地区基层测站的冰期测验工作提供参考. 相似文献
9.
弯曲型河道挟沙水流运动规律研究进展 总被引:11,自引:0,他引:11
弯道水流 (包括挟沙水流 )运动规律的研究 ,在水利工程学的许多领域中 ,占有重要的位置。本文着重对弯道水流水面横比降、横向环流、纵向垂线平均流速分布规律及弯道输沙特性研究进展进行了阐述分析 ,以便为生产科研方面服务。 相似文献
10.
11.
12.
在前人研究成果的基础上分析了水流挟沙的物理模式,以挟沙水流紊动能量方程为理论基础,得出了紊动能产生项和粘性耗散项的表达式,由此推导出适用于水流的紊流三区(光滑区、过渡区和粗糙区)的挟沙能力计算式,依据天然河流实测资料和室内水槽试验资料,验证了该水流挟沙能力计算式.针对该计算式分析了影响水流挟沙能力的因素. 相似文献
13.
山溪性河流河床稳定,受冲淤影响较小,具有良好的测站控制条件,Z-Q并系曲线基本呈单一线型。本文主要对其流量测验及方法进行了分析。 相似文献
14.
15.
利用和田河两支流1957-2010年的逐月实测流量资料,采用滑动平均法、Mann-Kendall秩次相关检验法及小波分析法,分析了和田河出山口枯水流量的变化特征。结果表明:和田河两支流出山口处实测枯水流量在20世纪90年代末之前变化趋势不明显,90年代末之后呈显著增大趋势;但两支流枯水流量均未发生突变现象;两支流枯水流量的周期性均不显著,其中最枯月流量周期性的优势尺度为1012 a。分析枯水流量的变化特点,主要与流域气温升高及出山口水库调节有关。 相似文献
16.
Alvaro Tena Fanny Ville Armengol Reñe Sarah M. Yarnell Ramon J. Batalla Damián Vericat 《河流研究与利用》2023,39(3):292-312
Streamflow in the Ésera and Upper Cinca Rivers (South Central Pyrenees) experiences alterations in the form of rapid pulses, commonly referred to as hydropeaks, associated with highly variable on-demand hydropower production from flowing or stored water. A hydrological characterization of the hydropeaks in these two rivers was carried out to examine their distinct hydropeaking pattern during hydrologically contrasted years. The Ésera demonstrated a hydropeaking regime characterized by a high frequency and magnitude, while the Upper Cinca presented a regime with higher frequency but of lesser magnitude. Additionally, this study classified hydropeaks following the shapes proposed in previous studies and assessed their temporal distribution (frequency), timing, and magnitude. Results indicated that hydropeaks were different in shape and magnitude in both rivers; a Front Step pulse shape dominated in the Ésera whereas a Rectangle pulse shape was the most frequent in the Cinca. The Front Step shape had the highest ramping rates during the rising limb of the hydrograph and the shortest time to the maximum flow; whereas the Rectangle shape had higher duration and a larger volume of water released. Hydropeaks in the Ésera were less frequent (one per day) than in the Cinca (two per day). The river Ésera presented, in general, high-magnitude hydropeaks, with double volume and duration, and three times larger up-ramping rates and time between flow pulses. Overall, hydropeak shapes in the Ésera varied depending on the hydrological year and the season, while in the Cinca, shape distribution followed the same temporal pattern regardless of year and season; thus, hydropeaking in the Ésera appeared to be much more dependent on the annual hydrology (whether the year is wet or dry) than in the Cinca. Hydropeaking regimes were characterized based on three categories of variables: magnitude (flow-based or hydrological variables), timing (duration), and frequency (occurrence). According to the variability of these variables, a total of three statistically significant groups were obtained in the Ésera, while two groups were identified in the Cinca. Hydropeaks can be statistically classified by their hydrological characteristics that in turn may have a direct effect on sediment entrainment and transport with implications to the ecological functioning of rivers. The different shape of the hydropeaks, however, will control the attenuation of the flows downstream and, consequently, the maintenance of the river's competence and capacity. This methodology provides a useful quantification of hydropeaking regimes to assess the potential impacts on physical and biological aspects of river systems. 相似文献
17.
18.
Invertebrates were compared upstream versus downstream from diversions on three small, headwater streams in the central Rocky Mountains, USA. Flow alteration of these streams varied from mild (some aspect of all natural flow components was transferred downstream) to severe (nearly 100% of the flow was diverted for 10–11 months of the year). The analysis was separated into periods of frequent (diversion gates often opened and closed; April–October) and infrequent flow fluctuations (stable low flows due to constant diversion; November–March). Invertebrates appeared resilient to mild flow alterations as neither the abundance, diversity, nor spatial and temporal variation in abundance and diversity differed upstream versus downstream during either period. In severely diverted streams, however, total invertebrate density downstream from the diversion was only 50% of upstream. Invertebrate diversity was also reduced; ten taxa abundant upstream were absent in downstream sections. Chironomids, ostracods and Ameletus spp. comprised 80% of total invertebrate density during constant, low flow conditions in the severely diverted streams. Although all taxa in the severely diverted streams recovered (drift) during the period of frequent flow fluctuations, spatial and temporal variation (coefficient of variation) in both density and the number of taxa was significantly greater downstream. Depending on the frequency with which free‐flowing conditions were re‐established, many invertebrate populations (especially mayflies and some stoneflies) declined or were even locally extirpated (e.g. Hesperoperla pacifica, Megarcys signata, Neothremma alicia, Polycelis coronata). Downstream communities in severely diverted tributaries appeared to fluctuate between two stable endpoints; a depauperate low‐flow community dominated by chironomids and ostracods and a more abundant and diverse natural‐flow community dominated by mayflies, chironomids, ostracods, stoneflies and caddisflies. Water abstraction (extent and timing of diversion) could be managed to minimize risks to downstream ecological resources. 相似文献
19.
坡面流阻力研究进展 总被引:8,自引:2,他引:8
坡面流阻力的研究对了解坡面流水流特性、汇流过程、土壤侵蚀和坡面产沙机理都非常重要。本文分5个方面总结了坡面流阻力研究的最新进展:(1)坡面流阻力系数与雷诺数的关系;(2)光滑床面上的坡面水流阻力;(3)粗糙床面上的坡面水流阻力;(4)降雨对坡面流阻力影响的研究;(5)坡面流阻力的计算模型。综合前人研究发现,阻力系数与雷诺数在不同的条件下呈正相关或负相关关系;用叠加法计算不同条件下的坡面流阻力有其合理的一面,也有不足之处;粗糙动床条件下的坡面水流阻力计算模型更接近实际情况。最后,本文指出了当前坡面流阻力研究存在的主要问题和未来需要突破的主攻方向。 相似文献