Cellular Automata (CA) for Simulations of Complex Geothermal Reservoirs

The exploitation of geothermal power is a renewable energy source with great potential in future. But the exploration and development of deep geothermal energy is connected with high cost and risk. These require a reliable functionality of geological heat exchanger. However the geothermal reservoirs are really complicated as phenomena and concrete downhole data are not completely discovered at present. In order to simulate them, complex modelings combined with different time scale are necessary. Recently, the cellular automata (CA) method is being developed and widely used for solving many complex problems in different fields. Here we introduced CA method combined with Navier-Stoke equation and heat transfer; the domains of reservoirs are initially discretized into many lattice cells. The different cell type and their physical properties (e.g. water cell, porous cell, etc.) are introduced. Thermodynamically correct computation and computing fluid flow in different formations are performed. The paper will give some computational results, showing the efficiency and accuracy of this method, in order to complete the phenomena of complex geothermal problem. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stochastic Multi-Scale Methods for Turbulent Flow Simulations

The use of currently available methods for turbulent flow simulations is faced with significant problems: one has the choice between efficient methods with relatively low predictive power (which require evidence in each case) or relatively accurate but very expensive methods. The unification of these methods would be very helpful for a better understanding of the generality of modeling assumptions, and to make an optimal use of characteristic advantages of models. Previously, this problem was addressed on the basis of deterministic equations, which resulted in many different heuristic interpolation procedures. These problems can be solved by addressing the question considered at the more general level of stochastic equations: in this way it is possible to obtain consistent stochastic multi-scale methods which imply corresponding deterministic equations. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On a Double Porosity Model of Fractured-Porous Reservoirs Based on a Hybrid Flow Function

In this paper, a model of double porosity for a fractured porous medium using a combination of classical and gradient functions of mass transfer between the cracks and porous blocks in a weakly compressible single-phase fluid flow is considered. As compared to the wellknown models, the model with such a mass transfer function allows one to take into account the anisotropic properties of filtration in a more general form. The results of numerical tests for two- and three-dimensional model problems are presented. The computational algorithm is based on a finite element approximation with respect to space and a completely implicit approximation with respect to time.     

低渗透非均质油藏单相渗流敏感系数

建立了在单相低速非达西渗流条件下反求低渗透油藏参数的敏感系数公式,给出了各类非均质油藏条件下压力关于渗透率和孔隙度的数值计算结果。认识到井底压力对井底附近的渗透率更敏感,启动压力梯度的存在,使生产井附近区域敏感系数变大。观测井敏感系数在两井连线区域受启动压力梯度影响很大。     

Parameterized Scalar Profile Mixing Model for Turbulent Combustion Simulations

The composition fields in turbulent reacting flows are affected by turbulent transport (macromixing), molecular diffusion (micromixing), and chemical reactions. In the joint velocity-composition probability density function transport equation the highly non-linear macromixing and chemical reaction terms appear in closed form. This is a considerable advantage over moment closure methods. Micromixing on the other hand requires modeling and especially for turbulent combustion accurate mixing models are crucial. Our approach to model the mixing of scalars, e.g. species mass fractions or temperature, is based on considering one-dimensional parameterized scalar profiles (PSP). Here, an extension of the PSP mixing model to inhomogeneous flows is presented. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

低渗透非均质油藏油水两相渗流敏感系数理论模型

本文研究了低渗透油藏低速非达西油水两相渗流的反问题，建立了基于动态信息的油藏敏感系数计算模型，给出了井底压力和水油比关于渗透率和孔隙度的敏感系数的有效算法，为油藏数值模自动拟合和油藏精细描述算法提供了理论基础。     

湍流度对翼型绕流影响的数值模拟及与实验的对比

研究了NACA0012翼型在低Reynolds数不同湍流度下的空气动力学特性．既运用了有限谱法和QUICK格式相结合的数值计算方法,又通过实验手段,研究了湍流度对流场的影响,并得到了计算与实验相符的结果．计算结果说明了有限谱法的高精度及与其他格式结合后应用的灵活性．对翼型受力和流场的结果分析显示:低湍流度下无明显的失速特征,高湍流度下失速特征明显;湍流度还对边界层后的剪切层有很大影响,高湍流度的受力特征和流场结果与高Reynolds数下的情形相似．     

非饱和水流问题的迎风差分法及其数值模拟

本文考察了非饱和水流问题模型方程的守恒型迎风差分法.我们基于有限体积方法建立的非饱和流动的守恒形式,分别提出了一阶和二阶迎风差分格式,并对差分格式进行了误差估计,给出了收敛性定理.最后,数值模拟验证了计算格式的有效性.     

Model Equations for Turbulent Shear Flow

A set of model equations for the calculation of turbulent shear flows is presented. It is shown how the equations can be modified to allow for the inclusion of viscosity, compressibility and density variations. Some results of numerical computations are given. The constant in the law of the wall is predicted to within 10% for flow over a perfectly smooth wall, and a dependence on wall roughness is obtained. The empirical law of the wall for compressible flow is also shown to be a consequence of the equations.     

Optimally controlled hydrodynamics for tidal power in the Severn Estuary

A representation of the hydrodynamics of a wedge-shaped tidal estuary, involving the integration of a set of ordinary differential equations, is developed and applied to the Severn Estuary, with an energy-extracting barrage present on a line from Brean Down to Lavernnock Point. Within the hydrodynamic model, the barrage is controlled so as to maximize energy output over one tidal cycle, using ebb generation only; dynamic programming is used to find the optimal control. Numerically accurate machinery characteristics are used.     

A Variational Finite Element Model for Large-Eddy Simulations of Turbulent Flows

The authors introduce a new Large Eddy Simulation model in a channel,based on the projection on finite element spaces as filtering operation in its variational form,for a given triangulation{Th}h>0.The eddy viscosity is expressed in terms of the friction velocity in the boundary layer due to the wall,and is of a standard sub grid-model form outside the boundary layer.The mixing length scale is locally equal to the grid size.The computational domain is the channel without the linear sub-layer of the boundary layer.The no-slip boundary condition(or BC for short)is replaced by a Navier(BC)at the computational wall.Considering the steady state case,the authors show that the variational finite element model they have introduced,has a solution(vh,ph)h>0that converges to a solution of the steady state Navier-Stokes equation with Navier BC.     

随钻电磁波测井中的数学模型

随钻电磁波测井是当前一种较为先进的测井方式,论文通过构建均匀介质、层状各向同性介质和层状各向异性介质等3种地层模型,详细推导出了随钻电磁波测井正演数学模型,并给出了相应的数值模拟结果。     

A Chemotactic Model for Interaction of Antagonistic Microflora Colonies: Front Asymptotics and Numerical Simulations

This paper studies a two‐dimensional chemotactic model for two species in which one of them produces a chemo‐repellent for the other. It is shown asymptotically and numerically how the chemical inhibits the invasion of a moving front for the second species and how stable steady states, which depend on the chemical concentration, can be reached. The results qualitatively explain experimental observations by Swain and Ray [ 1 ] showing that colonies of bacteria produce metabolite agents which prevent the invasion of fungi.     

二维无界自由衰减流的数值研究

无界区域上的流体运动是流体力学中的热点和难点问题.采用传统的扩大计算区域算法和新发展的基于无界区域的Hermite基函数算法对二维无界区域的自由衰减流动进行研究. 结果发现,对于只存在相同符号涡的初始流场而言,两种方法都可以得出正确的结果;而对于正负涡都存在的初始流场,传统方法即便利用非常大的计算区域也无法进行正确的长时间模拟,但是新方法却能高效求解.对算例的Hermite算法数值模拟验证了理论解Oseen涡的存在.     

A Multi-Mechanism Model for Cutting Simulations Combining Visco-plastic Asymmetry and Phase Transformation

We develop a multi-mechanism model for strainrate- and temperature-dependent asymmetric plastic material behavior accompanied by phase transformations, which are important phenomena in steel production processes. To this end the well-known Johnson-Cook model is extended by the concept of weighting functions, and it is combined with a model of tranformation-induced plasticity (TRIP) based on Leblond's approach. The bulk model is formulated within a thermodynamic framework at large strains, and it will be specialized and applied to cutting processes in steel production. In the examples parameters are identified for the material DIN 100Cr6, and we illustrate the characteristic effects of our multimechanism model, such as strain softening due to temperature, rate dependence and temperature dependence as well as the SD-effect. A finite-element simulation illustrates the different mechanisms for a cutting process. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimally Conditions for Pareto Nonsmooth Nonconvex Programming in Banach Spaces

In this paper, we consider a vector optimization problem where all functions involved are defined on Banach spaces. We obtain necessary and sufficient criteria for optimality in the form of Karush–Kuhn–Tucker conditions. We also introduce a nonsmooth dual problem and provide duality theorems.     

裂缝孔隙介质中二相驱动问题的交替方向有限元方法及理论分析

考虑裂缝孔隙介质中二相驱动问题的数值方法及理论分析。对压力方程采用混合有限元方法,对裂缝和岩块系统上的饱和度方程采用交替方向有限元方法,证明了交替方向有限元格式具有最优Ｌ２模和Ｈ１模误差估计。     

控压钻井井底气侵停止与否实时判别方法研究

实时判别井底气侵停止与否是控压钻井井控方法的关键,直接关系到基于立压控制法循环排气或常规关井等后续作业的选取.综合考虑气体运移膨胀和气体溶解的因素,指出出入口流量一致并不等同于井底气侵停止,两者存在时间先后关系.基于快速施加井口回压控制方法,建立了控压钻井井筒与地层耦合的多相变质量流动模型,采用有限差分法迭代求解,模型计算值与实验测量值吻合较好.模拟结果表明,出口流量有无明显拐点是区分出入口流量一致和井底气侵停止时间先后的标志.一旦井底气侵停止,立管压力的二阶导数会迅速降至0点附近且趋于稳定.根据上述参数变化特征,提出了基于出入口流量和立管压力实时监测的井底气侵停止与否实时判别方法.该研究对于完善控压钻井井控理论具有重要的指导意义.     

模糊置换流水车间调度的多目标模型

为了求解同时考虑模糊加工时间和模糊交货期的多目标置换流水车间调度问题,提出一种模糊多目标调度模型。针对目标之一的最大化满意度,考虑决策者偏好,建立基于悲观准则的偏好满意度模型,并在此基础上,兼顾考虑可信度,对满意度模型进行改进;针对Pareto最优解的选取,引入模糊集理论和概率论,运用面积补偿法将最大模糊完工时间去模糊化,便于可行解之间进行比较。最后,采用随机系列算例以及典型算例进行优化计算,计算结果验证了模型的有效性。     

Fluid Flow Model for Energy-Aware Server Performance Evaluation

Methodology and Computing in Applied Probability - We use a fluid flow model with reactive bounds to analyze a data processing center with energy-aware servers. The servers switch between four...