Analytical solution of specific energy and specific force equations: Trapezoidal and triangular channels     

Ali R. Vatankhah 《Advances in water resources》2010

The specific energy and specific force equations have many applications in open-channel flow problems. At present, these equations have analytical solution only for rectangular channels. Trial and error procedure also graphical solutions are the existing methods of solving these equations. No analytical solutions are available in the technical literature for these equations in trapezoidal and triangular channels because it is presumed that these equations are quintic equations. The inversion of such equations consists of finding the roots of quintic equations. In the current study for a given channel geometry and discharge, the subcritical (supercritical) depth is analytically found in terms of the other supercritical (subcritical) depth. For this purpose, by considering physically meaningful domains, a quintic equation has been reduced to a quartic equation. In the next step, this quartic equation has been converted to a resolvent cubic equation and two quadratic equations. This research shows these steps clearly to reach an acceptable physical analytic solution for water depth in trapezoidal and triangular channels.  相似文献   

国家级导航地理框架数据库建设     

刘丽芬  黄蔚  赵勇  王桂芝  王鹏 《测绘软科学研究》2010,(1):74-77

围绕基础地理信息如何真正在导航产业中发挥其社会基础平台的作用,本文首先提出了问题的解决方案是充分利用基础地理信息的资源,建设导航地理框架数据库,然后对导航地理框架数据的数据模型和内容进行了定义,最后提出了导航框架数据持续性发展在政策、运作模式等方面的关键技术以及建议。  相似文献   

The influence of roughness geometry and Shields parameter on flow resistance in gravel-bed channels     

Giorgio Baiamonte  Vito Ferro 《地球表面变化过程与地形》1997,22(8):759-772

The spatial variability of bed particles of a gravel-bed channel is analysed and treated experimentally in order to simulate the effects of the arrangement of coarse bed elements on the flow resistance law. For the studied bed patterns, characterized by the concentration Γ of coarser elements arranged on the bed layer, a particle arrangement parameter α is proposed. The α parameter is useful for estimating the intercept b₀ of the semi-logarithmic flow resistance law deduced by flume measurements carried out for the hydraulic condition of large-scale and transition roughness. The differences between the experimental friction factor parameter values and the ones calculated by the proposed semi-logarithmic relationship are explained by the ratio between the Shields parameter and its critical value. The analysis shows that estimates of the friction factor parameter are not improved by introducing the Froude number into the flow resistance law. © 1997 by John Wiley & Sons, Ltd.  相似文献   

The hydrochemistry of runoff from a ‘cold-based’ glacier in the High Arctic (Scott Turnerbreen,Svalbard)     

R. Hodgkins  M. Tranter  J. A. Dowdeswell 《水文研究》1998,12(1):87-103

There are still relatively few hydrochemical studies of glacial runoff and meltwater routing from the high latitudes, where non-temperate glacier ice is frequently encountered. Representative samples of glacier meltwater were obtained from Scott Turnerbreen, a ‘cold-based’ glacier at 78° N in the Norwegian high Arctic archipelago of Svalbard, during the 1993 melt season and analysed for major ion chemistry. Laboratory dissolution experiments were also conducted, using suspended sediment from the runoff. Significant concentrations of crustal weathering derived SO²⁻₄ are present in the runoff, which is characterized by high ratios of SO²⁻₄: (SO²⁻₄+HCO⁻₃) and high p(CO₂). Meltwater is not routed subglacially, but flows to the glacier terminus through subaerial, ice marginal channels, and partly flows through a proglacial icing, containing highly concentrated interstitial waters, immediately afront the terminus. The hydrochemistry of the runoff is controlled by: (1) seasonal variations in the input of solutes from snow- and icemelt; (2) proglacial solute acquisition from the icing; and (3) subaerial chemical weathering within saturated, ice-cored lateral moraine adjoining drainage channels at the glacier margins, sediment and concentrated pore water from which is entrained by flowing meltwater. Diurnal variations in solute concentration arise from the net effects of variable sediment pore water entrainment and dilution in the ice marginal streams. Explanation of the hydrochemistry of Scott Turnerbreen requires only one major subaerial flow path, the ice marginal channel system, in which seasonally varying inputs of concentrated snowmelt and dilute icemelt are modified by seepage or entrainment of concentrated pore waters from sediment in lateral moraine, and by concentrated interstitial waters from the proglacial icing, supplied by leaching, slow drainage at grain intersections or simple melting of the icing itself. The ice marginal channels are analogous neither to dilute supra/englacial nor to concentrated subglacial flow components. © 1998 John Wiley & Sons, Ltd.  相似文献   

持续性高藻输入河道温室气体时空排放特征及其影响因素     

张璐  荀凡  沈悦  柯凡  杜先  陈新芳  冯慕华 《湖泊科学》2022,34(3):752-765

淡水水生生态系统是大气中温室气体气体重要的"源",对于城市的动脉——城市河流(尤其是持续性高藻输入河道)温室气体的研究比较匮乏.太湖梅梁湖的高藻水排入地梁溪河是典型的高藻输入河道,月均藻密度为3.6×107 cells/L,夏季日均藻密度为1.2x108 cells/L.本文以梁溪河为研究对象,采用静态箱法测定了梁溪河...  相似文献   

初始孔压非均布下一维地基砂垫层优化研究     

蒙宇涵  陈征  冯健雪  李红坡  梅国雄 《岩土力学》2019,40(12):4793-4800

针对吹填土地基水平排水砂垫层铺设深度优化问题,建立了初始孔压非均布下含砂垫层地基的一维固结模型,利用有限Fourier正弦变换法得出了超静孔压和地基整体平均固结度的解答并通过退化验证了解答的正确性。采用二分法分析了砂垫层的最优铺设深度随时间的演化规律,给出了砂垫层最优铺设深度与时间的关系图。研究表明：在固结初期,砂垫层宜放置在土中初始超静孔压较大的位置;在固结后期,砂垫层的最优设置深度为土体厚度的2/3（单面排水）或者1/2（双面排水）的位置。以预压地基平均固结度达到90%所需时间最短为例,当初始孔压倒三角形、正三角形与梯形分布时,单面排水条件下,应分别在0.52、0.72、0.62倍地基土深度处设置砂垫层;双面排水条件下,应分别在0.42、0.58、0.46倍地基土深度处设置砂垫层。最后通过算例分析了当地基土中砂垫层采用最优铺设深度时,与在中间位置铺设砂垫层、不设砂垫层的情况分别进行对比,当时间因子取0.09时,地基土平均固结度分别提高6%和54%。  相似文献   

Multi‐scale analysis of a migrating submarine channel system in a tectonically‐confined basin: The Miocene Gorgoglione Flysch Formation,southern Italy     

Claudio I. Casciano  Marco Patacci  Sergio G. Longhitano  Marcello Tropeano  William D. McCaffrey  Claudio Di Celma 《Sedimentology》2019,66(1):205-240

The Miocene Gorgoglione Flysch Formation records the stratigraphic product of protracted sediment transfer and deposition through a long‐lived submarine channel system developed in a narrow and elongate thrust‐top basin of the Southern Apennines (Italy). Channel‐fill deposits are exposed in an outcrop belt approximately 500 m thick and 15 km long, oriented oblique to the palaeoflow, which was roughly south‐eastward. These exceptional exposures of channel‐fill strata allow the stacking architectures and the evolution of the channel system to be analyzed at multiple scales, enabling the effects of syn‐sedimentary thrust tectonics and basin confinement on the depositional system development to be deciphered. Two end‐member types of elementary channel architecture have been identified: high‐aspect‐ratio, weakly‐confined channels, and low‐aspect‐ratio, incisional channels. Their systematic stacking results in a complex pattern of seismic‐scale depositional architectures that determines the stratigraphic framework of the deep‐water system. From the base of the succession, two prominent channel complex sets have been recognized, namely CS1 and CS2, consisting of amalgamated incisional channel elements and weakly‐confined channel elements. These channelized units are overlain by isolated incisional channels, erosional into mud‐prone slope deposits. The juxtaposition of different channel architectures is interpreted to have been governed by regional thrust‐tectonics, in combination with a high subsidence rate that promoted significant aggradation. In this scenario, the alternating ‘in sequence’ and ‘out of sequence’ tectonic pulses of the basin‐bounding thrusts controlled the activation of coarse‐clastic inputs in the basin and the resulting stacking architectures of channelized units. The tectonically‐driven confinement of the depositional system limited the lateral offset in channel stacking, preventing large‐scale avulsions. This study represents an excellent opportunity to analyze the stratigraphic evolution of a submarine channel system in tectonically‐active settings from an outcrop perspective. It should find wide applicability in analogous depositional systems, whose stratigraphic architecture has been influenced by tectonically‐controlled lateral confinement and associated lateral tilting.  相似文献   

伶仃洋茅洲河口滩槽演变水沙模拟及治导线优化          下载免费PDF全文

陆永军  莫思平  王志力  季荣耀  顾继一 《水科学进展》2019,30(6):770-780

为适应伶仃洋茅洲河口治理开发条件,以保证行洪顺畅为泄洪纳潮的首要原则,同时顺应水沙运动和河势发展规律,对河口进行治导线比选和优化。该河口治导线方案分单、双通道,两类通道不同扩宽率下设计有围填、围填加开挖2种方案,开展水动力泥沙数学模拟计算和物理模型试验。结果表明:河口治导线各方案对伶仃洋涨、落潮流速的影响范围主要集中在交椅湾及其附近海域;方案实施后,周边海区冲淤变化较小,未对河势造成不利影响;根据对水动力、河口泄洪、河势稳定影响的综合分析,单双通道相比较而言,对洪水位、纳潮量、高低潮位、流速、河床冲淤的影响规律具有较好的一致性,相同扩宽率下各方案的影响程度均在同量级。  相似文献   

腹板开槽冷弯薄壁卷边槽钢抗火性能有限元分析模型     

马奇杰  王培军  郑英杰 《地震学刊》2012,(2):205-209

位于冷弯薄壁型钢构件腹板的槽孔,可延长构件两边的热量传递路线,减弱冷弯薄壁钢构件作为墙板龙骨引起的冷桥效应。常温下冷弯薄壁构件的屈曲破坏模态已非常复杂,包括整体屈曲、局部屈曲和畸变屈曲等,且不同的屈曲破坏模态可能会相互影响。火灾下冷弯薄壁构件的破坏机理将更为复杂,根据常规的稳定理论难以求解其火灾下的临界荷载。本文利用有限元方法对火灾下腹板开槽冷弯薄壁卷边槽钢的受力性能进行了模拟,研究了单元类型、材料模型、初始几何缺陷以及求解方法等因素对分析结果的影响,为同类构件抗火性能的有限元模拟分析提供了建模依据。  相似文献   

利用AIRS数据交叉辐射定标SVISSR分裂窗通道   总被引：1，自引：0，他引：1  

蒋耿明  延昊  马灵玲 《遥感学报》2009,13(5):797-807

利用高精度和稳定的AIRS/Aqua(Atmospheric InfraRed Sounder on board Aqua)数据对SVISSR/FY- 2C(Stretched Visible and Infrared Spin Scan Radiometer onboard FengYun 2C)的两个分裂窗通道IR1(InfraRed 1, 10.9 μm)和IR2(InfraRed 2, 11.9μm)进行交叉辐射定标的方法, 并利用赤道附近2006年12月和2007年12月的AIRS和SVISSR数据完成了交叉辐射定标, 结果表明, SVISSR数据与卷积得到的AIRS数据高度线性相关, SVISSR/FY-2C传感器的两个分裂窗通道不仅存在定标误差, 而且定标误差随时间的变化呈现增大的趋势。相对于AIRS/Aqua测量值, 当SVISSR的通道亮温从220 K变化到340 K时, 2006年12月IR1通道的温度调整量从5.8 K变化到-4.4 K, 而2007年12月IR1通道的温度调整量从6.9 K变化到-5.1 K; 2006年12月IR2通道的温度调整量从2.2 K变化到-1.5 K, 而2007年12月IR2通道的温度调整量从6.3 K变化到-6.1 K。  相似文献