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利用汊点水位预测-校正(junction-point water stage prediction and correction,JPWSPC)法处理缓流河网汊点处的回流效应,采用Preissmann格式离散Saint-Venant方程组,并采用Newton-Raphson方法求解非线性离散方程,构建了非恒定河网水动力模型.模型既无需特殊的河道编码,又避免了建立和求解总体矩阵.与常用的分级解法模型相比,保留了其既适用于树状又适用于环状河网的优点,同时克服了分级解法需要建立和求解河网总体矩阵的缺点,显著提高了稳定性和计算效率. 相似文献
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为克服基于"LINK-NODE"计算模式的排水管网模型不能细致模拟管道内部水流运动过程的缺陷,采用Preissmann窄缝理论开发完成了一套新的基于Godunov有限体积格式的一维排水管网水动力模型。模型采用HLL近似Riemann解计算单元界面处的数值通量,细致区分了管网节点水位对与其相连接管道的不同影响,并采用严格的质量守恒方程和特征线理论来更新管网节点水位。通过3个经典算例验证了模型能够很好地模拟有压瞬变流和瞬变混合流等复杂管网流态,具有良好的精度和稳定性。将模型应用于陕西省西咸新区天福和园小区实测场次降雨排水过程模拟,取得了理想的计算结果。新研发模型可提供所有计算单元中心和管网节点处的水力要素变化过程,为精细化城市洪涝过程模拟奠定基础。 相似文献
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在一维显式、二维隐式水动力联网数学模型的基础上,建立了一种一维、二维全隐河网海湾水动力联网数学模型。该一维河网模型采用Preissmann四点隐式格式,用节点水位控制法进行数值计算,二维海湾模型采用改进型双向隐式(DSI)法进行数值求解。在河口一维、二维连接处,水力因子通过接口断面法传递,无需重叠一个一维河段来传递水力因子,避免了口门处二维网格需取较小尺度的问题。模型在珠江三角洲河网及横门、洪奇沥口门海域做了检验,验证结果表明,建立的河网海湾水动力联网数学模型是可行的,可以用于河网、河口治理工程的数值研究。 相似文献
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以圣维南方程组、对流扩散方程以及未确知信息理论为基础,建立了环状河网一维水动力与未确知水质数学模型。采用Preissman四点隐格式法对圣维南方程组进行离散和采用显式差分对对流扩散方程进行离散,对河网水动力与水质分别进行了合理的编码,并考虑了泵闸等控制工程、降雨径流的影响,采用河网的三级解法编制河网非恒定流的计算程序求解各断面的水位Z和流量Q,实现了水动力和水质两模块之间的数据连接,且对微分形式的水质模型运用未确知数学理论进行了含有两个未确知参数的水质计算,从而不仅能获得污染物浓度区间值,还能得到相应的可信度。实例研究表明,建立的河网水动力模型和未确知信息的水质模型是可靠的,可以用于河网水质治理工程的数值模拟研究和水环境评估。 相似文献
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针对流域级闸控大型河网水环境日常管理的应用需求与实际特点,将资料适应性强的水文学方法与数据要求相对严苛的水动力-水质数值模型相融合,构建了一维与二维嵌套、分块组合的闸控大型河网水文-水动力-水质耦合数学模型DHQM（Hydrology, Hydrodynamics, and Water Quality Model for Impounded Rivers）。模型由河道径流模拟、闸坝调度过程模拟、河道水质模拟、区间入流及入河污染负荷估算和水质预警实时校正等5个模块组成。模型可服务于水环境实时预警和调度,也可为闸坝水文环境效应的量化提供基础工具。 相似文献
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通过对流域河网二维水流模拟问题的分析,提出了一个通用化的河网二维模拟概化模式,该模式将河网二维概化为"树状"河道计算单元、"环状"河道计算单元、"十字型"河道计算单元等河网二维基本单元,对这些河道计算单元的求解,构建流域型河网一二维耦合模式的求解模型,并由此建立了通用化的河网二维水流数学模型软件系统。通过"树状"河道二维计算单元求解模型的推导与实现,验证了概化模式的可行性,表明该思路可以应用于大型流域河网一、二维水流模拟,具有很好的应用推广价值。 相似文献
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平原河网区域来水组成原理 总被引：1，自引：0，他引：1
对于一般树状分布河网，上一级河道总是汇入至下一级河道，位于河道下游断面的流量总是由其上游汇集而至。但对于平原河网地区，特别是人工控制建筑物众多，又受潮汐影响的地区(如太湖流域)，河网错综复杂，水流方向不定，要跟踪某个断面的水流去向，或某个河段的水体、断面流量是从哪里汇集而来的，非常困难。但这样的问题在生产实践中往往对其很感兴趣。例如从常熟枢纽引长江水流进入望虞河后，流向何处?河网各断面流量中或各河段水体中常熟枢纽引江水量占多少比重?对这些问题的研究可以估计常熟枢纽引江的效果和影响范围。因此，平原河网区域来水组成方法在生产实践中具有重要意义。重点介绍了平原河网区域来水组成原理及其在太湖流域的应用。 相似文献
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Although pipe transport for storage of CO2 captured from combustion exhaust is most efficient under supercritical conditions, subcritical multi-phase transport might sometimes occur intentionally or unintentionally. To adequately assess the consequences of subcriticality, the fidelity of subcritical multi-phase turbulent transport modeling, including confinement and buoyancy effects, must be improved. For this reason, an extension of one-dimensional turbulence, a stochastic turbulence modeling strategy, for application to this regime is underway. As a step toward this extension, a turbulent liquid jet issuing from a planar channel is simulated and results are compared with liquid jet measurements and channel flow numerical simulations. A previously noted turbulence decay scaling is reproduced, suggesting that the scaling is more robust than might be supposed, given the complicating factors. This work provides a basis for extension to the primary breakup regime of liquid jets and hence to subcritical multi-phase turbulence more generally. 相似文献
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根据研究工程、工业废水及生活污水的水环境影响的需要,提出一个平面二维水流-水质有限体积法及黎曼近似解模型。在无结构网格上对偏微分方程进行有限体积的积分离散,把二维问题转化为一系列局部的一维问题进行求解,模型具备有限单元法及有限差分法两者的优点。由于模型采用黎曼近似解计算水量、动量及污染物输运等通量,不仅提高了数值模拟的精度,而且能模拟包括恒定、非恒定或急流、缓流等水流-水质状态。应用若干理想条件下的精确解对模型精度进行了检验,并结合汉江中下游的水质问题验证了模型的实际应用能力。模型计算结果与精确解拟合极好,与汉江中下游实测的污染分布带也相当吻合,为中线南水北调对汉江中下游水质的影响评价提供了依据。 相似文献
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Theoretical analysis and computational simulations have been carried out to investigate how medium and pore‐fluid compressibility affects the chemical‐dissolution front propagation, which is associated with a fully‐coupled nonlinear problem between porosity, pore‐fluid pressure, pore‐fluid density and reactive chemical‐species transport within a deformable and fluid‐saturated porous medium. When the fully‐coupled nonlinear system is in a subcritical state, some analytical solutions have been derived for a special case, in which the ratio of the equilibrium concentration to the solid molar density of the chemical species is approaching zero. To investigate the effect of either medium compressibility or pore‐fluid compressibility on the evolutions of chemical dissolution fronts in supercritical chemical dissolution systems, numerical algorithms and procedures have been also proposed. The related theoretical and numerical results have demonstrated that: (i) not only can pore‐fluid compressibility affect the propagating speeds of chemical dissolution fronts in both subcritical and supercritical systems, but also it can affect the growth and amplitudes of irregular chemical dissolution fronts in supercritical systems; (ii) medium compressibility may have a little influence on the propagating speeds of chemical dissolution fronts, but it can have significant effects on the growth and amplitudes of irregular chemical dissolution fronts in supercritical systems; and (iii) both medium and pore‐fluid compressibility may stabilize irregular chemical‐dissolution‐fronts in supercritical chemical dissolution systems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Matthieu J.B. Cartigny Dario Ventra George Postma Jan H. van Den Berg 《Sedimentology》2014,61(3):712-748
Supercritical‐flow phenomena are fairly common in modern sedimentary environments, yet their recognition and analysis remain difficult in the stratigraphic record. This fact is commonly ascribed to the poor preservation potential of deposits from high‐energy supercritical flows. However, the number of flume data sets on supercritical‐flow dynamics and sedimentary structures is very limited in comparison with available data for subcritical flows, which hampers the recognition and interpretation of such deposits. The results of systematic flume experiments spanning a broad range of supercritical‐flow bedforms (antidunes, chutes‐and‐pools and cyclic steps) developed in mobile sand beds of variable grain sizes are presented. Flow character and related bedform patterns are constrained through time‐series measurements of bed configurations, flow depths, flow velocities and Froude numbers. The results allow the refinement and extension of some widely used bedform stability diagrams in the supercritical‐flow domain, clarifying in particular the morphodynamic relations between antidunes and cyclic steps. The onset of antidunes is controlled by flows exceeding a threshold Froude number. The transition from antidunes to cyclic steps in fine to medium‐grained sand occurs at a threshold mobility parameter. Sedimentary structures associated with supercritical bedforms developed under variable aggradation rates are revealed by means of combining flume results and synthetic stratigraphy. The sedimentary structures are compared with examples from field and other flume studies. Aggradation rate is seen to exert an important control on the geometry of supercritical‐flow structures and should be considered when identifying supercritical bedforms in the sedimentary record. 相似文献
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高拱坝表孔宽尾墩收缩射流水舌的扩散特性与其出口流速分布密切相关,为了求得收缩射流的水力特性,应用RNGk ε双方程湍流模型对高拱坝表孔不同体型及过流量条件下可能出现的降水曲线流态、急流冲击波流态、水跃壅水流态、缓流流态4种流态进行了数值模拟计算,水流自由表面的模拟采用VOF法,得到了溢流水面及流速分布。结果表明,无论在何种流态下,计算所得的水面曲线均与物理模型试验值吻合良好,所得的出口流速分布结构也验证了高拱坝宽尾墩收缩射流水舌不同流态下分散的机理。 相似文献
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《Sedimentary Geology》2007,193(1-4):167-192
The coarse-grained, ice-contact, Porta Subaqueous Fan/Delta Complex was deposited in glacial Lake Rinteln at the margin of the Saalian ice sheet that advanced south of the Weser Chains, NW Germany. The ice-proximal depositional system was up to 15 km long and 10 km wide. The present study deals with ice-proximal subaqueous fan deposits, which are interpreted as products of a subcritical plane-wall outflow jet that periodically passed into a supercritical jet with hydraulic jump. The proximal facies assemblage consists of the coarse, clast-supported gravelly deposits of a hyperconcentrated (high-density) effluent and of related cohesionless debris flows attributed to the conduit or immediate proximal jet outflow zone of flow establishment. The intermediate facies assemblage, attributed to the outflow jet proximal zone of flow transition, is dominated by normally graded and cross-stratified gravels with scour structures at their bases; these gravels were deposited by a high-density effluent capable of forming mouthbar-like features. These deposits pass downcurrent into an assemblage of planar parallel-stratified and planar and trough cross-stratified sands and pebbly sands (partially interpreted as antidunes), with abundant scour structures and intercalated layers of fine sand/silt and silty mud, attributed to the jet distal zone of flow transition. The distal facies assemblage consists of trough cross-stratified sands and pebbly sands, and is attributed to the outflow jet proximal zone of established flow. The sedimentary succession as a whole has wedge-shape geometry, with a gentle fan-shaped inclination of the bedding from the southeast to the southwest. Repeated vertical alternations of supercritical and subcritical deposits and muddy interlayers can be attributed to temporary fluctuations in the meltwater outflow, whereas the overall upward fining of the succession indicates a net decline of meltwater discharges. 相似文献
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Flow-type landslides are an important hazard that can cause great destruction due to the rapid flow velocity and large disaster area. This paper presents a catastrophic flowslide that recently occurred at a landfill in Shenzhen, China. This disaster involved an area about 1100 m in length and 630 m in maximum width, and caused the death of 77 people and the destruction of 33 buildings. The precise reason for the landfill’s failure is still unknown, and therefore we try to contribute an increased understanding of the event for future prevention. In this study, the failure mechanism of the studied slope was analyzed and described under partially saturated condition. The solid–fluid transition during the flowslide occurrence was described using a unified constitutive model. The model was used to perform the hydro-elasto-plastic modeling in the pre-failure stage, the viscous modeling in the post-failure stage, and the second-order work criterion was introduced in between to model the solid–fluid transition. The consistent evolution of the flowslide, including initiation, propagation, and deposit stages, was simulated and analyzed using the finite element method with Lagrangian integration points after careful calibration of the viscous parameters. The numerical results were compared with the real case and used to explain the failure mechanism. 相似文献
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