共查询到17条相似文献，搜索用时 250 毫秒
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建立了湖泊三维风生流的隐格式差分模型，通过对该模型计算稳定性的分析发现，它的时间步长的取值具有较大的灵活性，该模型被用于武汉市墨水湖的风生流模拟，实例计算表明该模型计算结果合理，能较好地反映湖泊风生流的流态特征。 相似文献
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太湖风生流的三维数值模拟 总被引：30，自引：14，他引：16
建立了太湖三维风生流数值模型,并用差分法求解;垂直方向上采用了坐标变换技术,把任一节点的水深转换成无量纲水深,从而有效地消除了因风力作用造成的自由水面波动和湖底不规则的影响;水平面上采用锯齿网格处理,对于四周以闭边界为主的湖泊水域,显得比较合理。计算结果表明,湖泊风生流沿垂直、水平方向都有较大变化,流向上下、水平也并不一致,这是湖泊水流区别于其它水域水流之所在。计算模拟显示所建模型的有效性和可操作性。 相似文献
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深入认识大型湖泊在不同风速、风向和水位下三维风生流结构特征对于湖泊污染控制、生态恢复及资源的开发利用具有重要意义.本文在构建笛卡尔坐标系下洪泽湖三维水动力模型的基础上,利用2次全湖30个点位流场监测数据验证了模型精度.基于1975-2020年长系列风场观测数据,确定了洪泽湖典型风速风向.在此基础上,模拟了16种不同风向,13种不同风速和20种不同水位工况条件下洪泽湖三维风生流结构.结果表明：水动力模型可以较好地刻画洪泽湖三维湖流变化特征.洪泽湖风生流结构随风向变化呈现出较大空间差异.风生流流速随着风速的升高呈加速上升趋势,其中表层水体流速上升幅度远高于其他水层.在2.4 m/s东风驱动下,溧河洼、成子湖和南部湖区垂向平均流速随着水位上升呈先升高后降低的趋势,3个湖区分别在12.7、12.4和12.2 m水位下流速达到最大值. 相似文献
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蒙新高原湖泊高等水生植物和大型底栖无脊椎动物调查 总被引：2，自引：2，他引：0
2008年7月和9月调查了我国蒙新高原12个湖泊的高等水生植物和大型底栖无脊椎动物,除阜康天池外皆采集到了水生植物和底栖动物.水生植物共有8科12种,优势种为芦苇和蓖齿眼子菜.底栖动物共鉴定出4门8纲26科64种(属),优势类群为摇蚊和水丝蚓.乌梁素海的水生植物和底栖动物种类最丰富,分别为9种和35种(属).乌梁素海和哈素海全湖都有水生植物分布,但其它湖泊仅分布在个别湖湾.不同湖泊间的底栖动物群落相似性很低.将蒙新地区湖泊湖区分为敞水区、沿岸带水生植物区和强劲湖流区.底栖动物在沿岸带水生植物区的多样性比敞水区高,优势集中性比敞水区低,而强劲湖流区无底栖动物.沿岸带水生植物区不同类型生境中的底栖动物群落相似性分析表明沉水植物密布、风生湖流微弱生境中的底栖动物最丰富,风生湖流强劲生境中无底栖动物.总体上,蒙新高原湖泊水生植物和底栖动物群落相似性较低,要保护湖泊生物多样性,建议对每个湖泊进行适当保护,重点保护风生湖流较弱的沉水植物区. 相似文献
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A new up-winding finite element numerical model, which is two-dimensional and suitable for modeling lake current and the distribution of total phosphorus(TP) in shallow lakes, is derived. Moreover, it is used in the study of wind-driven current in Taihu Lake, and the impact of lake current field on the distribution of TP is also discussed. 相似文献
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Alan M. Davies 《Continental Shelf Research》1982,2(4):275-300
A numerical formulation is developed to solve the three-dimensional hydrodynamic equations which describe flow in a stratified sea.Arbitrary continuous physically realistic variations of density and eddy viscosity can be included in the model, which is sufficiently flexible to be applicable to sea areas of any horizontal extent and depth. A continuous current profile from sea surface to sea bed, is computed with the model. A method for expanding computed current profiles in terms of vertical modes is proposed and the contribution of these modes to the current profiles is considered.The time variation of the wind-induced circulation of a stratified lake in response to a suddenly imposed and maintained wind stress is examined. Calculations show that the wind-driven surface current is modulated by the internal seiche motion of the lake. 相似文献
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从麦克斯韦旋度方程出发可以直接导出瞬变电磁场扩散方程,然而扩散方程不含电场对时间的一阶导数,不能构成显式的时域有限差分方程,借鉴du Fort-Frankel有限差分离散方法引入虚拟位移电流项构建显式时域有限差分方程.对Wang和Hohmann的经典时域算法进行了两点改进:第一,通过将矩形回线源电流密度加入麦克斯韦方程组的安培环路定理方程,实现回线源瞬变电磁激发源加入;第二,在计算中考虑关断时间.第一点改进使时域有限差分方程考虑了一次场的计算,并且源的计算不再依赖均匀半空间模型响应作为初始条件,使算法能够适应表层电阻率不均匀时的三维复杂模型.由于实际观测中不可能出现阶跃电流的关断形式,第二点改进可以方便设置发射电流下降沿.采用改进的三维时域有限差分正演算法对均匀半空间模型、四类三层模型、均匀半空间中含有低阻块体模型进行了计算并分别与解析解、线性数字滤波解、积分方程解和Wang的三维时域有限差分解进行了对比验证.以H模型为例,采用建立的三维时域有限差分正演算法计算了不同关断时间的斜阶跃脉冲回线源瞬变电磁中心点感应电动势衰减曲线.以实际地质资料为基础,构建包含两层采空区的三维复杂模型,以1 μs的极短关断时间进行了复杂模型定回线源瞬变电磁响应计算,并计算了该复杂模型的视电阻率曲线. 相似文献
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大气-水耦合模式下三维太湖湖流场研究 总被引：6，自引：1，他引：6
利用太湖区域的大气边界层三维数值模式和三维水动力学数值模式,采用气-水耦合方法,对太湖的风生流特征进行了深入研究。结果表明,太湖区域大气边界层风场具有明显的时空变化特征,与均匀定常风作用下的太湖流场相比,大气-水耦合模式下太湖流场变化较大,形成稳定湖流场所需的时间也较长。三维模式计算出的流速值明显比二维模式大(表层约大一倍,整层平均约大50％),且与实际观测值符合较好。故即使对于像太湖这样的浅水湖泊,三维水动力学模式的应用仍然是很必要的。模拟结果中还发现湖流的上下流矢有时出现非常大的切变,甚至达到了180°。由于浅水湖中仍存在两个边界层(水-气和水-土),故浅水湖中存在流矢的巨大切变是可能的。 相似文献
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Dam-break flows usually propagate along rivers and floodplains, where the processes of fluid flow, sediment transport and bed evolution are closely linked. However, the majority of existing two-dimensional (2D) models used to simulate dam-break flows are only applicable to fixed beds. Details are given in this paper of the development of a 2D morphodynamic model for predicting dam-break flows over mobile beds. In this model, the common 2D shallow water equations are modified, so that the effects of sediment concentrations and bed evolution on the flood wave propagation can be considered. These equations are used together with the non-equilibrium transport equations for graded sediments and the equation of bed evolution. The governing equations are solved using a matrix method, thus the hydrodynamic, sediment transport and morphological processes can be jointly solved. The model employs an unstructured finite volume algorithm, with an approximate Riemann solver, based on the Roe-MUSCL scheme. A predictor–corrector scheme is used in time stepping, leading to a second-order accurate solution in both time and space. In addition, the model considers the adjustment process of bed material composition during the morphological evolution process. The model was first verified against results from existing numerical models and laboratory experiments. It was then used to simulate dam-break flows over a fixed bed and a mobile bed to examine the differences in the predicted flood wave speed and depth. The effects of bed material size distributions on the flood flow and bed evolution were also investigated. The results indicate that there is a great difference between the dam-break flow predictions made over a fixed bed and a mobile bed. At the initial stage of a dam-break flow, the rate of bed evolution could be comparable to that of water depth change. Therefore, it is often necessary to employ the turbid water governing equations using a coupled approach for simulating dam-break flows. 相似文献
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A finite difference implicit scheme is presented in this paper for solution of the shallow water equations in one dimensional (1D) form. The present model has many advantages like, handling of discontinuous and complex bed topography, satisfying C-property (preservation of motionless water surface over a wet or dry bed) and capability of handling large value of temporal step etc. Another very important feature of the present model is that, no special treatment of the source vector of the governing equations is required here to deal with very less water depth. To investigate the performance of the present model in diverse situations, it is used to replicate four different problems of known analytical solution, and the model is found to be quite capable for varied situations. 相似文献
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A shallow flow generally features complex hydrodynamics induced by complicated domain topography and geometry. A numerical scheme with well-balanced flux and source term gradients is therefore essential before a shallow flow model can be applied to simulate real-world problems. The issue of source term balancing has been exhaustively investigated in grid-based numerical approaches, e.g. discontinuous Galerkin finite element methods and finite volume Godunov-type methods. In recent years, a relatively new computational method, smooth particle hydrodynamics (SPH), has started to gain popularity in solving the shallow water equations (SWEs). However, the well-balanced problem has not been fully investigated and resolved in the context of SPH. This work aims to discuss the well-balanced problem caused by a standard SPH discretization to the SWEs with slope source terms and derive a corrected SPH algorithm that is able to preserve the solution of lake at rest. In order to enhance the shock capturing capability of the resulting SPH model, the Monotone Upwind-centered Scheme for Conservation Laws (MUSCL) is also explored and applied to enable Riemann solver based artificial viscosity. The new SPH model is validated against several idealized benchmark tests and a real-world dam-break case and promising results are obtained. 相似文献