Lattice Boltzmann simulation of solute transport in a single rough fracture

In this study, the lattice Boltzmann method （LBM） was used to simulate the solute transport in a single rough fracture. The self-affine rough fracture wall was generated with the successive random addition method. The ability of the developed LBM to simulate the solute transport was validated by Taylor dispersion. The effect of fluid velocity on the solute transport in a single rough fracture was investigated using the LBM. The breakthrough curves （BTCs） for continuous injection sources in rough fractures were analyzed and discussed with different Reynolds numbers （Re）. The results show that the rough frac~＇e wall leads to a large fluid velocity gradient across the aperture. Consequently, there is a broad distribution of the immobile region along the rough fracture wall. This distribution of the immobile region is very sensitive to the Re and fracture geometry, and the immobile region is enlarged with the increase of Re and roughness. The concentration of the solute front in the mobile region increases with the Re. Furthermore, the Re and roughness have significant effects on BTCs, and the slow solute molecule exchange between the mobile and immobile regions results in a long breakthrough tail for the rough fracture. This study also demonstrates that the developed LBM can be effective in studying the solute transport in a rough fracture.

The effect of surface roughness on rarefied gas flows by lattice Boltzmann method

This paper studies the roughness effect combining with effects of rarefaction and compressibility by a lattice Boltzmann model for rarefied gas flows at high Knudsen numbers. By discussing the effect of the tangential momentum accommodation coefficient on the rough boundary condition, the lattice Boltzmann simulations of nitrogen and helium flows are performed in a two-dimensional microchannel with rough boundaries. The surface roughness effects in the microchannel on the velocity field, the mass flow rate and the friction coefficient are studied and analysed. Numerical results for the two gases in micro scale show different characteristics from macroscopic flows and demonstrate the feasibility of the lattice Boltzmann model in rarefied gas dynamics.

Modeling for Collapsing Cavitation Bubble near Rough Solid Wall by Mulit-Relaxation-Time Pseudopotential Lattice Boltzmann Model

Cavitation bubble collapse near rough solid wall is modeled by the multi-relaxation-time (MRT) pseudopotential lattice Boltzmann (LB) model. The modified forcing scheme, which can achieve LB model’s thermodynamic consistency by tuning a parameter related with the particle interaction range, is adopted to achieve desired stability and density ratio. The bubble collapse near rough solid wall was simulated by the improved MRT pseudopotential LB model. The mechanism of bubble collapse is studied by investigating the bubble profiles, pressure field and velocity field evolution. The eroding effects of collapsing bubble are analyzed in details. It is found that the process and the effect of the interaction between bubble collapse and rough solid wall are affected seriously by the geometry of solid boundary. At the same time, it demonstrates that the MRT pseudopotential LB model is a potential tool for the investigation of the interaction mechanism between the collapsing bubble and complex geometry boundary.

L-Fuzzy Rough Set Based on Complete Residuated Lattice

Residuated lattice is an important non-classical logic algebra, and L-fuzzy rough set based on residuated lattice can describe the information with incompleteness, fuzziness and uncomparativity in information systems. In this paper, the representation theorems of L-fuzzy rough sets based on residuated lattice are given. The properties and axiomatic definition of the lower and upper approximarion operators in L-fuzzy rough sets are discussed.

Special Lattice of Rough Algebras

This paper deals with the study of the special lattices of rough algebras. We discussed the basic properties such as the rough distributive lattice;the rough modular lattice and the rough semi-modular lattice etc., some results of lattice are generalized in this paper. The modular lattice of rough algebraic structure can provide academic base and proofs to analyze the coverage question and the reduction question in information system.

On Rough Intuitionistic Fuzzy Ideals（Filters） in Lattices

In this paper, we introduce a new algebraic structure, called a rough intuitionistic fuzzy ideal(filter) which is a generalized intuitionistic fuzzy ideal(filter) of a lattice and study some related properties of such ideals(filters).

The Effect of Cell Size and Surface Roughness on the Compressive Properties of ABS Lattice Structures Fabricated by Fused Deposition Modeling

Researchers looking to improve the surface roughness of acrylonitrile butadiene styrene(ABS)parts fabricated by fused deposition modeling(FDM)have determined that acetone smoothing not only achieves improved surface roughness but increases compressive strength as well.However,the sensitivity of ABS parts to acetone smoothing has not been explored.In this study we investigated FDM-fabricated ABS lattice structures of various cell sizes subjected to cold acetone vapor smoothing to determine the combined effect of cell size and acetone smoothing on the compressive properties of the lattice structures.The acetone-smoothed specimens performed better than the as-built specimens in both compression modulus and maximum load,and there was a decrease in those compressive properties with decreasing cell size.The difference between as-built and acetone-smoothed specimens was found to increase with decreasing cell size for the maximum load.

Rough Set Theory over Fuzzy Lattices

Rough set theory, proposed by Pawlak in 1982, is a tool for dealing with uncertainty and vagueness aspects of knowledge model. The main idea of rough sets corresponds to the lower and upper approximations based on equivalence relations. This paper studies the rough set and its extension. In our talk, we present a linear algebra approach to rough set and its extension, give an equivalent definition of the lower and upper approximations of rough set based on the characteristic function of sets, and then we explain the lower and upper approximations as the colinear map and linear map of sets, respectively. Finally, we define the rough sets over fuzzy lattices, which cover the rough set and fuzzy rough set,and the independent axiomatic systems are constructed to characterize the lower and upper approximations of rough set over fuzzy lattices,respectively,based on inner and outer products. The axiomatic systems unify the axiomization of Pawlak’s rough sets and fuzzy rough sets.

Rough Control Rule Mining Model Based on Decision Interval Concept Lattice and Its Application

Fusing the structure feature of interval concept lattice and the actual needs of rough control rules,we have constructed the decision interval concept lattice,further more,we also have built a rules mining model of rough control based on decision interval concept lattice,in order to achieve the optimality between rough control mining cost and control efficiency.Firstly,we have preprocessed the collected original data,so that we can transform it into Boolean formal context form,and then we have constructed the decision interval concept lattice in rough control;secondly,we have established the control rules mining algorithm based on decision interval concept lattice.By analyzing and judging redundant rules,we have formed the rough control association rule base in end.Analysis shows that under the premise of improving the reliability of rules,we have achieved the rough control optimization goal between cost and efficiency.Finally,the model of reservoir scheduling has verified its feasibility and efficiency.

剪切滑移裂缝中流体渗流的Lattice Boltzmann模拟研究

针对目前学界有关剪切滑移作用对裂缝中流体渗流研究较少的情况,分析现有研究方法的缺陷,改进现有的研究模型,以固定研究目标尺寸为基础,引入Lattice Boltzmann方法,研究流体在剪切滑移结构中的渗流,并考察非匹配性和接触面积对流体渗流的影响。结果表明:随机二维剖面线可拆分为V型、正弦和凹槽等基本单元体;在基本单元体、二维剖面线中,裂缝面的滑移造成渗流方向上开度分布的非均匀性,渗透率呈现数量级的减小;非匹配情况下的裂缝渗透率比匹配情况下的低,随滑移距离的增加,流体渗流能力均呈先下降后上升趋势;三维裂缝结构的渗透率随滑移距离的增加总体呈下降趋势,下降幅度比基本单元体和二维剖面线结构要低;裂缝面产生剪切滑移时,结构间的非匹配性造成流体渗流轨迹呈三维迂曲性;剪切滑移所造成的非匹配性及接触面积,均对渗流能力有负面作用,但非匹配性可以对裂缝结构起到一定的自支撑作用。

基于LBM的粗糙裂隙内两相驱替渗流特性模拟研究

岩体粗糙裂隙两相驱替渗流普遍存在于许多工程应用中,而裂隙开度分布特征与壁面润湿性是影响两相驱替特性的关键因素.基于分形理论生成三维粗糙裂隙面并分别构建开度分布一致的均质模型和不一致的非均质模型,通过LBM伪势模型模拟粗糙裂隙准静态排水过程,研究了裂隙开度分布特征与壁面润湿性对两相驱替渗流特性的影响规律及细观机制.研究结果表明:均质模型驱替前缘基本保持平稳推进,而非均质模型出现优先驱替阻力较小的大开度区域的优势驱替路径现象,润湿性增强可加剧该现象致使驱替前缘更快突破,对均质模型无明显作用;残余捕获可分为孤立的“圈闭”模式和吸附在裂隙壁面的“水膜”模式,非均质模型中圈闭捕获明显多于均质模型,强润湿性有利于水膜捕获增多;当驱替压力增大至进入压力后,非均质模型中部分小开度区域润湿相被逐步排驱,而均质模型大多数润湿相被快速驱替,因此非均质模型P_(c)-S_(w)曲线比均质模型更加平缓,润湿性增强使得两种裂隙模型驱替开始发生时的进入压力更大,施加相同驱替压力时驱替效率更低.

单裂隙端面复合形貌影响下流体渗流特征

自然储层裂隙端面在一定尺度下往往会表现出非匹配特征,由此产生的开度非均一分布对流体渗流行为具有重大影响。因此,厘清裂隙复合形貌特征对渗透性能的控制作用对于油气产能的准确评估至关重要。首先,结合岩石裂隙复合形貌特征,以解析推导方式确定了粗糙裂隙中阻碍流体运移的2种效应,分别是端面粗糙效应和开度粗糙效应;其次,在通过权重算法对粗糙裂隙端面间的非匹配行为进行二维表征的基础上,采用格子Boltzmann方法进行孔隙尺度模拟再现了非匹配粗糙裂隙中流体的运移过程,并据此系统分析了流体渗流的影响特征。结果表明:由于未考虑开度非均一分布的影响,导致了三重效应渗透率预测模型对渗透率的过高估计,且预测误差取决于端面非匹配程度;开度非均一分布在一定程度上阻碍了流体的有效运移,同时也间接削弱了裂隙的渗透性能,其削弱能力受控于开度相对粗糙度。

基于格子Boltzmann方法的单一粗糙裂隙渗流状态研究

岩体中普遍存在裂隙,基于格子Boltzmann方法以及D2G9离散模型在计算流体的渗流状态下具有边界条件易于设置、计算效率较高、计算结果可视化等优点,建立考虑不同粗糙度的单一裂隙渗流模型,模型的上下边界设置为无滑移的全反弹边界,左右边界则采用非平衡外推格式的分布函数边界,同时结合经典流体力学的Poiseuille流问题,对计算模型进行验证。最后,分析岩体裂隙表面粗糙程度对渗流状态的影响,计算结果表明:随壁面粗糙程度的增加,流体的流速、大小、方向均会发生不同程度的改变,并且在由粗糙度的改变而引起隙宽急剧变化的部位,局部伴随着流体旋涡的形成,导致流体内部摩擦阻力的增大,从而产生较大的局部能量损耗。

Numerical modeling of the effects of roughness on flow and eddy formation in fractures

The effect of roughness on flow in fractures was investigated using lattice Boltzmann method(LBM).Simulations were conducted for both statistically generated hypothetical fractures and a natural dolomite fracture. The effect of increasing roughness on effective hydraulic aperture, Izbash and Forchheimer parameters with increasing Reynolds number(Re) ranging from 0.01 to 500 was examined. The growth of complex flow features, such as eddies arising near the fracture surface, was directly associated with changes in surface roughness. Rapid eddy growth above Re values of 1, followed by less rapid growth at higher Re values, suggested a three-zone nonlinear model for flow in rough fractures. This three-zone model, relating effective hydraulic conductivity to Re, was also found to be appropriate for the simulation of water flow in the natural dolomite fracture. Increasing fracture roughness led to greater eddy volumes and lower effective hydraulic conductivities for the same Re values.

Numerical modeling investigation on turbulent oscillatory flow over a plane rough bed composed by randomly arrayed particles

A three-dimensional numerical model is established to simulate the turbulent oscillatory boundary layer over a fixed and rough bed composed by randomly arrayed solid spheres based on the lattice Boltzmann method and the large eddy simulation model.The equivalent roughness height,the location of the theoretical bed and the time variation of the friction velocity are investigated using the log-fit method.The time series of turbulent intensity and Reynolds stress are also investigated.The equivalent roughness height of cases with Reynolds numbers of 1×10^4–6×10^4 is approximately 2.81 d（grain size）.The time variation of the friction velocity in an oscillatory cycle exhibits sinusoidal-like behavior.The friction factor depends on the relative roughness in the rough turbulent regime,and the pattern of solid particles arrayed as the rough bed in the numerical simulations has no obvious effect on the friction factor.

完备格上的广义Rough集模型

基于way-below关系和弱way-below关系,在具有逆合对应的完备格上建立了广义Rough上下近似算子,研究了它们的基本性质,并说明本文提出的广义Rough集模型是Pawlak标准粗糙集的推广.同时,在De Morgan代数上建立了广义Rough上下近似算子,给出了相应的基本性质.

Realization of Rough Set Approximation Toplogical Operations Based on Formal Concept Analysis

There is an intimate correlation between rough set theory and formal concept analysis theory, so rough set approximations can be realized by means of formal concept analysis. For any given multiple valued information system, the realization of rough set approximation operation has two major steps, firstly convert the information system from multiple valued one to single valued formal context, secondly realize rough set approximation operations aided by concept lattice, which is equivalent to a query operation under some necessary conditions.

Role of Surface Roughness during Natural Convection

A computational study was performed in a two-dimensional square cavity in the presence of roughness using an algorithm based on mesoscopic method known as Lattice Boltzmann Method (LBM). A single relaxation time Bhatnagar-Gross-Krook (BGK) model of LBM was used to perform numerical study. Sinusoidal roughness elements of dimensionless amplitude of 0.1 were located on both the hot and cold walls of a square cavity. A Newtonian fluid of the Prandtl number (Pr) 1.0 was considered. The range of the Rayleigh (Ra) number explored was from 103 to 106 in a laminar region. Thermal and hydrodynamic behaviors of fluid were studied using sinusoidal roughness elements. Validation of computational algorithm was performed against previous benchmark studies, and a good agreement was found. Average Nu (Nusselt number) has been calculated to observe the effects of the surface roughness on the heat transfer. Results showed that sinusoidal roughness elements considerably affect the thermal and hydrodynamic behaviors of fluid in a square cavity. The maximum reduction in the average heat transfer in the presence of roughness was calculated to be 23.33%.

冲突分析的研究进展

冲突广泛存在于社会生活的各个方面,冲突分析受到越来越多的关注。由于冲突分析的研究仍然处于初始与发展阶段,为了促进冲突分析的研究与发展,本研究对冲突分析的理论与方法进行梳理和总结,并指出冲突分析研究中存在的若干问题,提出解决问题的初步研究设想,为冲突分析的后续研究提供有益的参考。

表面粗糙度对超薄电解铜箔性能的影响及机理研究

超薄电解铜箔为覆铜板、印制电路用铜箔,广泛应用于动力类锂电池、3C消费类锂电池及储能锂电池领域。针对原材料及轧辊导致成箔表面粗糙度较大差异的问题,研究了表面粗糙度对高品质超薄电解铜箔性能的影响规律并对机理进行了分析。采用同批次、同工艺、不同轧辊条件下所得铜箔为试样,研究了表面粗糙度对其耐蚀性、耐热性和力学性能的影响,并借助透射电子显微镜对其影响机理进行了分析。结果表明:在同批次、同工艺、不同轧辊条件下,粗糙度有较大差异;表面粗糙度大的铜箔表面易腐蚀,并且在表面粗糙度小的基体上,氯化亚铁会脱落,形成蚀坑,而在表面粗糙度大的基体上,氯化亚铁形成晶粒并镶嵌在基体中;表面粗糙度对耐热性也有影响,表面粗糙度越大,沿晶裂纹越明显,但不是决定因素;表面粗糙度对抗拉性能影响不大,但对其延伸率具有较大的影响;表面粗糙度对性能的影响主要是由于制造过程中铜的面心立方转变成了l=0的四方晶体。