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《中国农村水利水电》2019,(4)
应用HEC-RAS和MIKE11模型对江西省高安市锦江河段进行水面线计算,并与实测水位数据进行对比,计算模型精度,综合考虑参与建模的主要水文参数初始水位和河道糙率,并对其进行敏感性分析。结论如下:MIKE11模型计算的水面线精确度更高,其水位结果也略高于HEC-RAS模型,两个模型对河道糙率的敏感性不同是造成水面线结果差异的一个重要因素。经计算,MIKE11模型对糙率更为敏感。MIKE11模型对锦江河道水面线的推算具有更加重要的意义。 相似文献
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陈阳生 《中国农村水利水电》1989,(1)
本文根据天然河道水面线计算的特点,运用分段插值法,以牛顿二次插值多项式替代基本方程式中的断面函数,将基本方程式转化为仅含待求断面水位这一个未知量的一元二次方程。通过解该一元二次方程直接推求水面线。本文中还引用了相对水位的概念,使计算进一步简化。 相似文献
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结合DHI-MIKE一维模型的捞刀河天然河道水面线简化复核计算 总被引：1，自引：0，他引：1
孙翔 《中国农村水利水电》2012,(8):70-71
河道治理的前期规划阶段,设计水位是控制性条件之一。但因为前期资料的细致程度所限,往往只能采用洪痕调查、既有成果确定设计水位,难以反映河道经多年演变的设计水位现状。介绍一种复核水面线的简化算法,在基础资料精度不高的情况下,对天然河道水面线进行复核,为前期设计提供可靠性相对较高的设计水位成果。 相似文献
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水库对下游河段水环境影响的评价 总被引：3，自引：0，他引：3
水库对下游河段水环境的改善，主要是通过蓄水和合理运用等手段来实现。水库调节的作用，改善了天然河道来水过程不均匀的缺陷，将洪水期的水量调配到枯水期，从而大大减轻枯水期天然河道的污染程度。评价水库对下游河段水环境的影响是一个复杂的问题，因为天然来水、水库下泄量以及河道流态都是变化的。提出列表计算法，根据水库的运用情况，逐时段列表计算。 相似文献
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《中国农村水利水电》2020,(3)
山丘、平原地区混合地区的河道,产汇流条件复杂,单一计算方法难以有效地模拟河道的洪水情况。以北方小流域的某山丘、平原复合河道为例,基于HEC-RAS模型,在缺乏水文资料的情况下,采用对河道划分山丘、平原区域的方法对河道进行了10年一遇洪水的模拟。结果表明HEC-RAS模型采用山丘、平原区域划分的计算方法与不划分相比较,前者更为符合实际情况。同时,此方法能够适用于流态复杂的河道水面线推求,可为防洪规划与防洪预报提高精度作为参考。 相似文献
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杨亮亮 《国际沙棘研究与开发》2021,(3):6-13
为克服能量方程逐段试算方法在河道水面线计算上存在的不足与局限,本文以黄河干流白银市水川段为例,采用二维水动力数值计算模型,对4种洪水频率工况下黄河干流白银市段的水面线高程进行计算,并将二维数值计算结果与能量方程计算结果进行复核和评价.经计算可知两种计算方法在计算结果上存在偏差,能量方程在河道水面线计算上是一种近似成果,... 相似文献
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基于最大熵法的河道行洪风险评估 总被引：1，自引：0，他引：1
通过随机模拟的方法将不确定因素引入河道水面线的推求过程,来定量描述河道水面线的不确定性。在此基础上,建立了基于最大熵原理（准则）的河道行洪风险评估模型,此方法可以得到水面线的最大熵密度函数具体表达式,再进行风险率的计算,并用实例验证了该模型的可行性和实用性,从而为河道行洪风险评估提供了一条简便可行的途径。 相似文献
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黄朝轩 《中国农村水利水电》2012,(10)
对马蹄形无压隧洞的恒定非均匀流沿程水面线进行了深入研究,基于恒定渐变流基本微分方程,通过采用数值分析理论,得到流程S与始、末段水深h1、h2的解析函数,通过该函数可直接计算沿程水面线。该方法比《水工隧洞设计规范》中推荐的分段求和试算法更简单、便捷,特别对水深较敏感段,规范推荐试算法误差较大,并且逐段试算推求水深将导致末端断面水深误差逐步累积,导致误差大,精度下降。最后通过工程实例计算比较得出：新解析法计算成果与规范推荐法（程序）计算成果基本一致,甚至优于规范推荐的分段试算法,完全满足工程实践要求。 相似文献
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Linking water market functioning, access to water resources and farm production strategies: example from Pakistan 总被引：3，自引：0，他引：3
Jean-Daniel Rinaudo Pierre Strosser Thierry Rieu 《Irrigation and Drainage Systems》1997,11(3):261-280
As a response to inadequacy in canal water supplies, farmers in Pakistan have invested in private tubewells to control irrigation water resources. Also, they participate in surface water and groundwater markets that take place within tertiary units of the irrigation system.The present paper describes the functioning and organization of these water markets, using information collected in sample watercourses of the Fordwah Branch irrigation system, South-Punjab, Pakistan. The variability in type and intensity of water markets is investigated with regard to access to water resources and farm production strategies and constraints. 相似文献
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基于传统水泵,设计了一种由多组单元泵组插装而成的二维插装水泵。单元泵组由两个单元泵组成,通过两个单元泵的配合可以消除流量脉动。基于其中的基础组件,即两个单元泵的组合特性展开了研究。通过理论分析与对比,阐述了二维插装水泵的工作原理,说明了二维插装水泵的潜在优势,包括结构力平衡、排量大、油水分离、无结构性流量脉动等。同时,针对凸轮与滚子之间的接触曲面进行了数学建模与分析。有别于二维取点后补偿得到接触点的方式,接触曲面的数学建模方法采取分析滚子与凸轮的空间接触关系,基于空间关系建立接触曲面的坐标模型,接触曲面的数学模型在精度上优于二维取点补偿法。通过对活塞运动规律和两个单元泵组流量特性的试验研究,验证了接触曲面数学模型的正确性和二维插装水泵无结构性流量脉动的优点。 相似文献
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《Agricultural Water Management》2005,74(1):77-85
Water diverted from rivers to canals and then to fields brings along a heavy sediment load. According to estimates, the elevation of irrigated fields in the Indus Basin has increased up to 8 cm due to deposition of sediment from irrigation water. The deposition of sediment in the canals, distributaries and watercourses is a common concern. Each year during the winter, the canals are closed for desilting the conveyance system. Sediment deposited in the farmer-managed watercourses is piled along the watercourse banks, which takes fertile land out of production. This study was conducted to evaluate the possibilities of preparing cement blocks with soils and with sediments removed from the watercourses and using them in low cost linings to decrease losses from watercourses. Soil–cement and sediment–cement blocks were prepared, and tested for strength, durability and ability to reduce losses from watercourses. Compositions of the soil and of the sediments removed from the channels were determined. Blocks mortared into walls lining the sides of these channels reduced losses to less than 20% of losses in unlined old channels. Plastering the inside of these walls reduced water losses to less than 1% of the losses occurring in old unlined channels. Sediment–cement blocks were easier to make and they develop greater strength than soil–cement blocks. Cost of channel lining, using these blocks, appears to be about 2/3 of costs using fired brick masonry. 相似文献
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The 2-year field experiments were carried out to research the effect of different irrigation methods, namely border irrigation,
sprinkler irrigation, and surface drip irrigation, on root development and profile water uptake in winter wheat. Results showed
that the main root distribution zone moved upward under sprinkler and surface drip irrigation when compared to the traditional
border irrigation. Profile root distribution pattern changed with irrigation methods. Soil profile water uptake was correlated
to the root system and soil water dynamics. Due to the appropriate soil water and higher root density in the surface soil
layer under sprinkler and surface drip irrigation, the main water uptake zone was concentrated in the upper layer. Because
of the water deficit in the surface layer under border irrigation, water uptake in 50–100 cm depth was stimulated, which caused
the main uptake zone downward. The amount and pattern of root water uptake varied with irrigation methods. This may provide
valuable information on the aspect of agricultural management. 相似文献
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从师法自然出发,以静态接触角高达140°的箬叶下表面为仿生对象,使用2种模板法制备具有箬叶下表面微纳复合结构的聚合物仿生表面。采用扫描电镜观测聚合物仿生表面的微观形貌,借助接触角测量仪分析仿生表面的润湿性能。以箬叶下表面为模板,采用聚二甲基硅氧烷(PDMS)二次复形方法获得仿箬叶下表面,仅实现微乳突结构的部分复形,而大多数纳米片层结构缺失,其静态接触角与PDMS本征接触角相比只提高了7°左右。采用电铸与注射成型相结合的方法获得的仿箬叶聚丙烯(PP)表面,可基本实现微纳复合结构的复形,其静态接触角与PP本征接触角相比提高了50°以上,进一步采用低表面能的氟硅烷修饰注射成型仿箬叶PP表面,其静态接触角与PP本征接触角相比提高了70°左右,达到了133°±2°。但2种模板法成型的仿生聚合物表面均未能较好保留箬叶的动态润湿性能。实验结果表明,通过电铸-注射法构筑仿箬叶表面的微纳复合结构、在粗糙表面上修饰低表面能物质的双重途径可用于实现仿生疏水表面高效低成本的制备。 相似文献
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密集排水孔幕饱和-非饱和全精细 总被引：2，自引：0，他引：2
陈建余 《中国农村水利水电》2004,(11):53-56
对于有密集排水孔幕的工程渗流问题，只进行稳定饱和渗流分析往往是不够的，饱和-非饱和排水子结构分析方法正是解决了这一问题，同时为了全面精细地模拟排水子结构的实际渗流状态，首次提出了全精细数值模拟的理论和方法。在针对2类不同排水孔提出不同的完整水力学模型的基础上，详细讨论了不透水边界、已知结点水头边界、饱和逸出面边界、降雨入渗边界、非饱和蒸发入渗边界等有关子结构排水孔及其它表面可能存在的边界条件的分类处理方法，特别针对顶排型排水子结构排水孔内部水位提出了严密的数学处理方法。工程算例表明，本文提出的针对密集排水孔幕的全精细数值模拟方法是正确的，可以解决相关的工程渗流问题。 相似文献
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在逆向工程中出现了各种不同的参数曲面描述方法，但是在自由曲面设计过程中．最初的型线只是曲面截面的初步构想，而且轮廓也很粗糙。如何使二维平面的型线描述上升到三维物理空间的曲面构造，是需要解决的问题。为此，给出了用NURBS截面曲线构造自由曲面的放样法，重点研究了在放样法中截面曲线的生成方法．该方法适合于平面脊线同时有多条截面线的自由曲面生成。 相似文献
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Conjunctive use of canal and groundwater in Punjab,Pakistan: management and policy options 总被引：1，自引：0，他引：1
Data from 41 watercourses commands in Pakistan show that, as expected, farmers in head end reaches of canals receive more canal water than those in tail end reaches. Contrary to conventional wisdom, however, these head end farmers also use more groundwater than those at the tail end. Overall, groundwater plays a more important role in irrigation than surface water, ranging from 65% dependence on pumped water in head end areas to over 90% in tail end areas. This means that groundwater is no longer supplemental to canal water, but is an integral part of the irrigated agricultural environment. However, the cropping choices of farmers appear to reflect the amount of good quality canal water they receive: head end farmers are able to grow more high value basmati rice in the summer and more vegetables in the winter, leaving tail enders to rely on less valuable crops such as fodder and wheat.Tail end areas are not only deprived of their fair share of surface water: they have to pump proportionately more groundwater which shows decreasing quality towards the tail. Typically, head end areas have groundwater with EC values of less than 1.0 dS/m, rising to over 2.0 dS/m in tail end areas. When the quality of both surface and groundwater used by farmers is examined, only the top 40% of the distributary gets water of adequate quality, the next 40% get below average quality, while the tail 20% of farmers irrigate with water that is classified as saline.Because of higher dependence on more expensive groundwater tail enders use less water per unit area, thereby reducing the leaching requirement. The result is a clear increase in soil salinity from head to tail along distributary canals, and there is some evidence of land abandonment in tail end watercourses due to excess salinity.The implications of these results are far reaching. Government policy includes plans to divert significant quantities of fresh canal water to areas underlain by saline groundwater on the basis that farmers already have adapted to pumping fresh groundwater. The results reported suggest that if this policy were implemented, there is a risk that over-dependence on fresh groundwater could lead to an intensification of the rate of soil salinization and deterioration of quality in areas currently classified as fresh groundwater zones.At present, the location and utilization of privately owned shallow tubewells is not monitored, and thus it is not possible for government agencies to determine just how much water of different qualities is being used. Further, canal water deliveries, public deep well monitoring, watercourse monitoring programs, soil salinity measurements, and agricultural performance monitoring are all scattered among different agencies and organizations, making the task of effective conjunctive management of surface and groundwater even more difficult.Conventional wisdom: Groundwater in Pakistan ... where it exists within the canal system ... is used to supplement surface water supplies to meet peaks in demand. (WAPDA, 1990) 相似文献