Review of the uncertainty analysis of groundwater numerical simulation

Groundwater system is a complex and open system, which is affected by natural conditions and human activities. Natural hydrological processes is conceptualized through relatively simple flow governing equations in groundwater models. Moreover, observation data is always limited in field hydrogeological conditions. Therefore, the predictive results of groundwater simulation often deviate from true values, which is attribute to the uncertainty of groundwater numerical simulation. According to the process of system simulation, the uncertainty sources of groundwater numerical simulation can be divided into model parameters, conceptual model and observation data uncertainties. In addition, the uncertainty stemmed from boundary conditions is sometimes refered as scenario uncertainty. In this paper, the origination and category of groundwater modeling uncertainty are analyzed. The recent progresses on the methods of groundwater modeling uncertainty analysis are reivewed. Furthermore, the researches on the comprehensive analysis of uncertainty sources, and the predictive uncertainty of model outputs are discussed. Finally, several prospects on the deveolpment of groundwater modeling uncetainty analysis are proposed.     

Global analysis theory of climate system and its applications

The idea and main theoretical results of the global analysis theory of climate system are briefly summarized in this paper. A theorem on the global behavior of climate system is given, i.e. there exists a global attractor in the dynamical equations of climate, any state of climate system will be evolved into the global attractor as time increases,indicating the nonlinear adjustment process of climate system to external forcing. The different effects of external forcing, dissipation and nonlinearity on the long-term behavior of solutions are pointed out, and some main applications of the global analysis theory are also introduced. Especially, three applications, the adjustment and evolution processes of climate, the principle of numerical model design and the optimally numerical integration, are discussed.     

Constitutive modeling for unsaturated soils considering gas hardening effect

The influence of gases on unsaturated soils is discussed in the paper.First,the selection of stress state variables is discussed.It is shown that gas pressure as well as generalized effective stress and modified suction are required to construct a constitutive model of an unsaturated soil.The deformation mechanisms of solid,liquid and gas phases in soils are then investigated.It is realized that the deformation of gas phase interacts with the deformations of the other two phases in soils.Gas laws are used to describe the gas behavior.Similar to the other two phases in soil,the change of gas volume can be divided into an elastic part and a plastic part, and the latter part is then introduced to the soil hardening equation to reflect the impact of the gas on the soil.Then,a simple elasto-plastic model considering the gas effect for isotropic states is developed.Finally,the model predictions are given and compared with existing experimental data.A good agreement between them is found.Comparisons of the predictions between our model and Wheeler’s model are also performed.     

Implementation of transaction level AMBA bus models using systemC

This paper deals with how to implement AMBA bus transaction level modeling in SystemC.There are twom ain techniques used in the whole modeling process,which consist of starting the platform modeling at the transaction level and using the uniformed modeling language-System C.According to the concepts of interface,port and hierarchical channel introduced in SystemC 2.0,the system of master-channel (AMBA bus) slave is created as the architecture of the AMBA bus transaction level model,which can make it more extendable.The port and interface classes of the model that are prone to program are defined in accordance with the SoC hierarchical design methodology,In addition,method calls,not signal communication,are used between different modules in the model,so the higher-level abstraction is achieved and the simulation performance is improved.The AMBA bus transaction level model is analyzed and certified by simulation experiment,and proved to be completely compliant to the AMBA specification 2.0.     

Numerical modeling of Jinlong CJD burner copper flash smelting furnace

Fluid flow, heat transfer and combustion in Jinlong CJD concentrate burner flash smelting furnace have been investigated by numerical modeling and flow visualization. The modeling is based on the Eulerian approach for the gas flow equations and the Lagrangian approach for the particles. Interaction between the gas phase and particle phase, such as frictional forces, heat and mass transfer, are included by the addition of sources and sinks. The modeling results including the fluid flow field, temperature field, concentration field of gas phase and the trajectories of particles have been obtained. The predicted results are in good agreement with the data obtained from a series of experiments and tests in the Jinlong Copper Smelter and the temperature error is less than 20 K.     

Delayed drainage of aquitard in response to sudden change in groundwater level in adjacent confined aquifer: Analytical and experimental studies

The problem of the groundwater dynamics and water balance of a confined aquifer in the aquifer system has been solved in previous studies, whereas that in the aquitard adjacent to the confined aquifer has seldom been considered. In reality, the groundwater dynamics of the aquitard are closely related to the exploitation of groundwater resources, groundwater contamination, underground storage utilization and land subsidence. In this paper, an analytical solution is derived to describe the drawdown variation in the aquitard when the head in the adjacent confined aquifer declines by a constant value. The characteristics of groundwater dynamics and water balance of the aquitard are analyzed using a dimensionless analytical solution. There is obvious delayed behavior in the response of groundwater dynamics in the aquitard, which is characterized by the delay index t0. The delayed behavior in the response of groundwater dynamics is not only dependent on the properties of the aquitard, but also proportional to the square of the thickness of the aquitard. The law of the delayed release of water is described in terms of the ratio of the delayed release of water. A water balance equation for the aquitard is established. Three stages of the water balance and the corresponding characteristics are presented with the water balance curves of the aquitard. The analytical solution is given to analyze the flux per unit horizontal area of the aquitard. The hydrogeological parameters of the aquitard, namely the hydraulic conductivity, specific storativity and hydraulic diffusivity, are estimated according to type-curve fitting between the analytical solution and observed flux. The parameters are identified and validated in an experiment.     

A collaborative platform for complex product development based on multi-domain unified modeling and simulation

In order to intensify market competition,manufacturing enterprises must improve their product innovation capability.It is difficult to integrate the system modeling,simulation and collaborative process management in complex product development.A collaborative platform for complex product development based on multi-domain unified modeling and simulation is proposed in this paper.The architecture of the platform is firstly stated.The idea and realization of three key technologies,i.e.multi-domain modeling and simulation for complex product,knowledge management for product design and simulation,multi-domain collaborative mechanism,are emphasized.Finally,an industry case is given.The demonstration of the system shows that integration architecture is the effective infrastructure for multi-domain collaborative product development.     

Study on seal improvement and rotor thrust control of centrifugal compressor

Fluid pressure variations due to process fluctuations or balance drum seal degradation can result in rotor thrust increasing that may jeopardize thrust bearing and compressor’s reliability. Also, the leakage flow through balance drum seal can seriously affect the efficiency of compressor. A method that can improve both the efficiency and reliability of centrifugal compressor is presented. The method focused on rotor thrust control and balance drum seal upgrading. The low leakage feature of Dry-Gas-Seal（DGS）, high reliability of labyrinth, and the feasibility of upgrading existing structure are taken into account at the same time to design a combined labyrinth-dry gas seal system on the balancing drum. Based on the combined seal system, a Fault Self-Recovering（FSR） system for the fault of rotor shaft displacement is introduced to assure the safety and reliability of centrifugal compressor. The modern Computational Fluid Dynamics（CFD） is used to validate this envision. The numerical result and relevant information indicate that the combined sealing system could improve the efficiency of the centrifugal compressor by about 4%.     

Simulation for a New Real-time Ethernet MAC Protocol

A method for modeling broadcast protocols in OPNET is introduced by illustrating a simulation of a new real-time Ethemet MAC protocol. The details of network models in OPNET are given and the proce-dure in modeling is introduced. Simulation results verify that the protocol is correct and efficient.     

Influence of operation parameters on flash smelting furnace based on CFD

The influence of three important operation parameters in Jinlong flash smelting furnace, including the distributing blast speed, the oxygen enrichment rate of process air and the ratio of central oxygen to overall oxygen (O_c/O_o), has been investigated using a virtual simulation system on copper flash smelting furnace. The core of this virtual simulation system is a numerical simulation of CFD (computational fluid dynamics), and this system incorporates coupling momentum transport, heat transport, mass transport,reaction kinetics between gas and particles and chemical reactions between gas and gas. A set of numerical predicted data were obtained. The CFD simulation shows that there is a sensitive zone of the distributing blast speed, and the dust content ascends when the speed exceeds 180 m·s-1. Increasing the oxygen concentration of processing air benefits the efficient production of the flash smelting furnace.     

Capillary-Tube Model and Experiment of Multiphase Flow in Capillary Fringes

IntroductionUrbanization and industrial activities havesignificant potential to cause soil and groundwatercontamination through leakage,spill and disposalof industrial and household chemicals.Organicchemicals are used everywhere in the world andbecause most are very toxic to human beings anddo not easily degrade naturally[13] ,theircontamination of the soil and groundwater iscausing more and more problems worldwide.　Many contaminants are organic liquids with lowwater miscibility,which may mov…     

尾矿氰化物渗漏对地下水污染的动力学模型

通过分析尾矿氰化物渗漏在土壤中迁移机制的基础上,建立了污染物运移过程的耦合动力学模型，模拟了不同时间内氰化物在包气带土层中浓度分布。数值模拟结果表明。氰化物渗漏对地下水污染将产生一定的影响，当降雨量增大时，污染物质可穿过包气带而污染地下水。同时，微生物降解作用对浓度在包气带土层分布也产生很大的影响，这对于定量化评价氰化物类污染物渗漏对地下水污染的潜在性影响提供了可靠的理论根据。     

黏滞性对LNAPL 在非饱和多孔介质中优先流影响的试验研究

为探究轻非水相液体(LNAPL)在非饱和带通过裂隙快速通道产生的优先流对地下含水层造成污染的影响,选取大豆油和0号柴油2种不同黏滞性的LNAPL,通过室内试验,研究不同黏滞性的LNAPL在通过非饱和多孔介质中单裂隙快速通道产生的优先流迁移规律。试验结果表明:黏滞性小的LNAPL通过裂隙产生的优先流的运移速度快;LNAPL进入地下水毛细带后受毛细水的顶托力作用,垂向迁移速率减缓,横向扩散速度增大,LNAPL优先流锋面形态逐渐变缓;优先流不仅能通过裂隙非均质条件产生,而且可以在基质中以指流的形式存在,黏滞性大的LNAPL更容易产生多个狭长形的指流。     

水分及非保守性污染物在土壤中运移数值模拟

运用数值计算模型模拟计算水分及非保守性污染物在各种饱和度条件下的土壤中运移规律．采用有限差分离散水分方程和浓度方程，得到了适合于非保守性污染物运移的数值模型．利用试验资料验证了数值计算成果．验证结果表明，两者吻合良好，为研究和数值预报非保守性污染物运移问题提供了有效的手段．     

非饱和土力学行为的三维离散元分析

基于离散单元法颗粒流理论,土体颗粒单元间采用Hill接触模型来考虑非饱和土中吸力的作用,建立了非饱和土的颗粒流模型。根据室内试验结果对模型细观参数进行标定,开展了固结排水三轴剪切试验离散元数值模拟,揭示了在不同围压和吸力下,模型试样的应力-应变关系与强度特性等宏观力学性质以及细观信息平均配位数的变化规律。根据不同吸力下的莫尔-库伦破坏包线,建立了吸力与抗剪强度参数之间的关系。此外,通过标定室内试验结果中不同含水率下的应力-应变曲线,建立了Hill模型中吸力与含水率的关系。研究结果表明：Hill接触模型可以较好的模拟非饱和土的力学行为,可为非饱和土的离散元模拟提供参考。     

GMS在饱和—非饱和地下水流动及核素迁移模拟中的应用

为了研究某饱和——不饱和区域的地下水流动和核素迁移规律,采用GMS软件数值模拟的方法,介绍了应用GMS解决这类问题时的具体步骤,论述了初始条件、边界条件的设置技巧。模拟得到了该区域合理的地下水流场和不同时刻的核素质量浓度分布,与相关程序计算结果吻合较好。研究结果表明:GMS在饱和—非饱和地下水流动及核素迁移模拟中,具有较高的应用价值。     

降落漏斗区流场的灰色数值模拟方法研究

对地下水降落漏斗区流场进行灰色数值模拟时,应充分考虑漏斗区内水流的流向问题。由于流向的不同,所建立的方程也有差异。基于这一思想,在建立了地下水流基本灰色有限差分方程的基础上,探讨了降落漏斗区的灰色数值方程的求解方法;并对武安市东部水源地进行了模拟。模拟结果表明,所提出的解法具有很好的应用效果,从而验证了这种新的模拟方法的正确性。对开展地下水降落漏斗区的地下水资源评价和水环境保护具有积极的指导意义。     

FEFLOW在地下水流模拟方面的应用

介绍了基于有限元原理的FEFLOW软件，它的应用领域覆盖了水量、水质与温度的模拟，软件提供地理信息系统数据接口，能自动产生空间有限单元网格。FEFLOW程序包中配备了快速精确的数值算法来控制和优化求解过程，结果输出具有先进的图形视觉化效果，并能很好地处理相关的水文地质条件。举例说明了FEFLOW软件在建立黄河下游影响带三维地下水流模拟模型中的应用。     

考虑毛细滞后的未饱和多孔介质传热传质模型

本文从热湿迁移机理出发，通过在液相渗流中引入毛细滞后的影响，采用液相运动的最小梯度假设，建立了未饱和含湿多孔介质在考虑毛细滞后效应时传热传质的较普遍的模型理论．并对方程中的热湿迁移特性系数进行了分析，为进一步发展确定热湿迁移特性的有效实验方法提供了依据。