Water quality model of the Danube in its Bulgarian part     

Ivan Diadovski  Veska Kazantzeva 《Aquatic Sciences - Research Across Boundaries》1996,58(3):269-279

Models for predicting river water quality could assist protection and utilization of water resources under alternative management strategies. The model of the water quality characteristics of the Danube is based on an ecosystem approach. Considered are all waste water discharges and inflow of tributaries among the catchment area. The identification of model parameters is realized according to the method of integral transformation. For the performance of the model a computer program was elaborated. It is applied in predicting the water quality of the Danube considering almost 20 indicators for the abiotic and biotic parameters of river ecosystem.  相似文献   

Trajectory Curvature As A Selection Criterion For valid Lagrangian Stochastic Dispersion Models     

John D. Wilson  Thomas K. Flesch 《Boundary-Layer Meteorology》1997,84(3):411-425

Among well-mixed multi-dimensional Lagrangian stochastic (LS) dispersion models, we observe that those in poorest agreement with observations produce spiralling trajectories, with an associated reduction in dispersion. We therefore investigate statistics of increments d ' to the orientation '= arctan(W'/U') of the Lagrangian velocity-fluctuation vector – as a possible means to distinguish the better LS models within the well-mixed class. Zero-spin models, having d' = 0, are found to provide best agreement with observations. It is not clear however, whether imposition of the zero-spin property selects (in conjunction with the well-mixed condition) a unique model.  相似文献   

Two sets of higher-order Boussinesq-type equations for water waves   总被引：1，自引：0，他引：1  

Z.B. Liu  Z.C. Sun 《Ocean Engineering》2005,32(11-12):1296-1310

Based on the classical Boussinesq model by Peregrine [Peregrine, D.H., 1967. Long waves on a beach. J. Fluid Mech. 27 (4), 815–827], two parameters are introduced to improve dispersion and linear shoaling characteristics. The higher order non-linear terms are added to the modified Boussinesq equations. The non-linearity of the Boussinesq model is analyzed. A parameter related to h/L₀ is used to improve the quadratic transfer function in relatively deep water. Since the dispersion characteristic of the modified Boussinesq equations with two parameters is only equal to the second-order Padé expansion of the linear dispersion relation, further improvement is done by introducing a new velocity vector to replace the depth-averaged one in the modified Boussinesq equations. The dispersion characteristic of the further modified Boussinesq equations is accurate to the fourth-order Padé approximation of the linear dispersion relation. Compared to the modified Boussinesq equations, the accuracy of quadratic transfer functions is improved and the shoaling characteristic of the equations has higher accuracy from shallow water to deep water.  相似文献   

Voigt粘弹性流体上的线性重力波   总被引：1，自引：0，他引：1  

赵子丹  张庆河 《海洋科学》1994,18(5):29-34

研究了半无限不可压缩Ｖｏｉｇｔ粘弹性体表面的线性重力波；通过引进无量纲粘弹性参数Ｈ、无量纲波数与无量纲表面张力解定解问题，导出了无量纲色散关系。由数值解给出了Ｈ的两个临界值ＨＡ＝０．６０７、ＨＢ＝２．３８０，并讨论了Ｈ对于色散关系的影响。  相似文献   

The estimation of dispersion behavior in discrete fractured networks of andesite in Lan-Yu Island,Taiwan     

Lee Cheng-Haw  Lee Chen-Chang  Lin Bih-Shan 《Environmental Geology》2007,52(7):1297-1306

This study was based on the discrete fracture model to investigate the influence of fracture parameters on the solute transport in the fractured rocks of andesite in Lan-Yu island, Taiwan. In the simulation cases, the centers of fractures, fracture lengths and apertures were assumed to have Poisson’s distribution, negative exponential distribution and lognormal distribution, respectively. With the above assumptions, constructing the discrete fracture model became practicable. Using the mass-balance equation with specified boundary conditions, the flow field in the rock was solved. Then particles were released under the flow field. Monte Carlo method was used assuming that the amount of particles was proportional to the flow rates to get the particle accumulated percentage breakthrough curve and to estimate the dispersion coefficient. On the basis of the discrete fracture model, it was possible to evaluate the property of dispersion behavior of andesite in Lan-Yu Island with flow and transport mechanism. Properties of the dispersion behavior such as the relation between distance and traveling-time (ln〈r ²〉 and ln 〈t〉), anisotropic behavior, and the overall dispersion coefficient in a fracture network were characterized: the slope value of ln〈r ²〉 and ln〈t〉 was 1.64 an indication of non-Fickian dispersion, the particles dispersion along the flow (D11) was bigger than that perpendicular to the flow (D22), and the dispersion coefficient by this study was 0.91 m comparing the value 1 m from Sauty’s method.  相似文献   

瞬态面波法在公路软基勘查中的应用研究          下载免费PDF全文

孙渊  丘斌煌  王赞文 《地震工程学报》2006,28(1):15-19

对公路建设中时常遇见的砂土类软弱路基问题,采用瞬态面波法并结合少量钻孔测试信息,建立面波速度和砂土力学参数的关系模型,可预测勘查区的砂土力学参数的纵横向展布特征和规律。经实践检验,预测结果与实际砂土介质的变化规律基本吻合,表明所建立的关系数学模型基本正确并具有较高的实用性。结果为公路砂土路基分类评价以及软弱路基的勘查提供了一个经济可行的思路和方法。  相似文献   

三维变量配置对惯性重力波频散性模拟的影响   总被引：1，自引：2，他引：1       下载免费PDF全文

朱红伟  刘宇迪 《应用气象学报》2003,14(5):533-541

在线性斜压原始方程组的基础上，从频率和群速方面讨论了由水平网格 (C、Z网格) 和垂直网格 (L、CP、LZ、LY网格) 组合而成的几种三维网格 (C/L、C/CP、Z/LZ、Z/LY) 的计算频散性并分析了各种网格出现偏差的原因，结果表明三维网格C/CP (水平网格为C网格垂直网格为Charney-Phillips网格) 与Z/LZ（水平网格为Z网格垂直网格为LZ网格）计算频散性能较好。从而为原始方程大气模式选取三维网格提供指导。  相似文献   

A Two-Dimensional Lagrangian Stochastic Dispersion Model for Convective Boundary Layers with Wind Shear     

A. M. Reynolds 《Boundary-Layer Meteorology》1998,86(2):345-352

Rotach, Gryning and Tassone constructed a two-dimensional Lagrangian stochastic model to describe the dispersion of passive tracers in turbulent boundary layers with stabilities ranging from ideally-neutral (w_* = 0) to fully-convective (u_* = 0). They found that the value of the Kolmogorov constant, C₀, as determined by optimizing model agreement with the measured spread of passive tracers, was dependent upon stability. Here, it is shown that the non-uniqueness, associated with satisfaction of the well-mixed condition, can be exploited to construct an alternative version of the model of Rotach et al. for which C₀ = 3 is universally applicable over the entire range of stabilities under consideration. This alternative model is shown to be in very close agreement with predictions, obtained in large-eddy simulations, for the dispersion of passive tracers in turbulent boundary layers with stabilities ranging from ideally-neutral to fully-convective.  相似文献   

中国城市机动车排放污染控制规划体系研究   总被引：6，自引：1，他引：6  

郝吉明  吴烨  傅立新  何东全  贺克斌 《应用气象学报》2002,13(Z1):195-203

建立城市机动车污染控制规划体系的目标在于揭示城市机动车排放特征以及由此形成的污染物的分布规律,并根据城市大气容量和环境质量的要求进行排放控制目标的选择和方案优化.该文吸收发达国家原有控制规划体系的主体思想,并对其进行了改造,使得新的规划控制体系能够更适合我国城市的特点.该体系结构的核心内容主要由机动车排放因子的确定、机动车污染物排放时空分布规律的确定、大气环境质量状况的模拟和分析、机动车排放优化模型的建立和综合控制实施影响评估四部分组成.通过建构上述四个核心模块的规划内容和方法,新的控制规划体系可以迅速、有效地为中国城市机动车污染控制管理和决策服务.  相似文献   

Analysis of macrodispersion through volume-averaging: Moment equations     

P. K. Kitanidis 《Stochastic Hydrology and Hydraulics》1992,6(1):5-25

Macrodispersion is spreading of a substance induced by spatial variations in local advective velocity at field scales. Consider the case that the steady-state seepage velocity and the local dispersion coefficients in a heterogeneous formation may be modeled as periodic in all directions in an unbounded domain. The equations satisfied by the first two spatial moments of the concentration are derived for the case of a conservative non-reacting solute. It is shown that the moments can be calculated from the solution of well-defined deterministic boundary value problems. Then, it is described how the rate of increase of the first two moments can be calculated at large times using a Taylor-Aris analysis as generalized by Brenner. It is demonstrated that the second-order tensor of macrodispersion (or effective dispersion) can be computed through the solution of steady-state boundary-value problems followed by the determination of volume averages. The analysis is based solely on volume averaging and is not limited by the assumption that the fluctuations are small. The large-time results are valid when the system is in a form of equilibrium in which a tagged particle samples all locations in an appropriately defined phase space with equal probability.  相似文献