Two Approaches of Substance Flow Analysis—An Inspiration from Fluid Mechanics

That flow is the common feature of substance flow and fluid flow is the viewpoint emphasized in the paper. Some notes on fluid mechanics, including the two approaches of fluid flow description, were given. The concepts of the chain and the chain group of product life cycles, which are essential for understanding the specific features of substance flow, were advanced. Taking the specific feature of substance flow into consideration, on the analogy of the two approaches in fluid mechanics, two approaches of substance flow analysis, i.e. L method and E model, were formulated. Illustrative models of steady and unsteady substance flow were sketched by both methods, and comparison between them was made in general.

FINITE ELEMENT GALERKIN APPROACH FOR A COMPUTATIONAL STUDY OF ARTERIAL FLOW

A finite element solution for the Navier_Stokes equations for steady flow through a double branched two dimensional section of three dimensional model of canine aorta is obtained. The numerical technique involves transformation of the physical coordinates to a curvilinear boundary fitted coordinate system. The shear stress at the wall is calculated for Reynolds number of 1000 with branch to main aortic flow rate ratio as a parameter. The results are compared with earlier works involving experimental data and it is observed that the results are very close to their solutions. This work in fact is an improvement of the work of Sharma and Kapoor (1995) in the sense that computations scheme is economic and Reynolds number is large.

Numerical study of equilibrium solutions for axisymmetric plasmas with toroidal flow obtained using Solovev approach

Solovev approach of finding equilibrium solutions,which was extended to include the vacuum solutions provided by Zheng,Wooton,and Solano,was found extremely useful for the purpose of shaping studies.Its extension to toroidal equilibria with a general plasma flow was examined theoretically in a companion paper by Chu,Hu and Guo.The only meaningful extension was found for plasmas with a pure toroidal rotation and with a constant Mach number.A set of functions{SOLOVEV_ZWSm}was obtained which fixed location of the magnetic axis for equilibria with quasi-constant current density profile,with toroidal flow at constant Mach number and with specific heat capacity 1.The set{Solovev_ZWSm}should have complete shaping capability for plasma shapes with positive curvature at the boundary;but not for plasmas with negative curvature boundary points,i.e.the doublets or bean shaped tokamaks.We report here extensive numerical studies showing the shaping capability of{Solovev_ZWSm}for plasmas with pure toroidal rotations,including the change in topology of the solution when the rotation mach number changes.Included plasma topology are the sphere(spheromaks);and the tokamaks(including the doublets).

A VARIATIONAL ANALYTICAL APPROACH TO TIME DEPENDENT FLOW OF OLDROYD B FLUID IN CIRCULAR TUBE

In the present investigation the time dependent flow of an Oldroyd fluid B in ahorizontal eylindrical pipe is stuided by the variational analytical approach developedby author. The tome dependent problem is mathematically reduced to a partialdifferential equation of third order. Using the improved variational approach due toKantorovich the partial differential equation can be reduced to a system of ordinarydifferential equations for different approximations. The ordinary differential equationsare solved by the method of the Laplace transform which is led to an analytical formof the solutions.

Turbulence modulation model for gas–particle flow based on probability density function approach

he paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function（PDF） approach. By means of the PDF method, a general statistical moment turbulence modulation model without considering the trajectory difference between two phases is derived from the Navier–Stokes equations. A new turbulence production term induced by the dispersed-phase is analyzed and considered. Furthermore, the trajectory difference between two media is taken into account. Subsequently, a new k–ε turbulence modulation model in dilute particle-laden flow is successfully set up. Then, the changes to several terms, including the turbulence production, dissipation, and diffusion terms, are well described consequently. The promoted model provides a more probable explanation for the modification of particles on the turbulence. Finally, we applied the model to simulate a gas–particle turbulence flow case in a wall jet, and found that the simulation results agree well with the experimental data.

A LIMITING VISCOSITY APPROACH TO THE RIEMANN PROBLEM FOR TRANSONIC FLOW

In this paper we have obtained the existence of weak solutions of the small disturbance equations of steady two-dimension flow [GRAPHICS] with Riemann date [GRAPHICS] where v+ greater-than-or-equal-to 0, v- greater-than-or-equal-to 0 and u- less-than-or-equal-to u+ by introducing 'artificial' viscosity terms and employing Helley's theorem. The setting under our consideration is a nonstrictly hyperbolic system. our analysis in this article is quite fundamental.

A Simple Weighted Integration Method for Calculating Surface Tension Force to Suppress Parasitic Flow in the Level Set Approach

Parasitic flows may occur in the numerical simulation of incompressible multiphase flow due to errors in the calculation of surface tension terms, specifically for the curvature and unit normal vector. An improved method for calculating the surface tension based on the level set approach is proposed, in which the contribution of not only the center node but also the rest area of a control volume to the calculation of surface tension is considered in a balanced manner. The weighted integration method (WIM) is more consistent with the concept of a banded in- terface in the level set method. It is applied to the temporal evolution of a two-dimensional neutrally buoyant liquid drop and a buoyancy driven deformable bubble in an immiscible fluid for the validation of WIM. The results show that the parasitic flows are evidently suppressed by the weighted integration method. The weight factors for WIM in 3-D cases are also suggested.

抚河疏山水利枢纽船闸通航水流条件研究

为满足水运需求,解决船闸引航道口门区受河段地形和涉河建筑物影响而导致的通航条件困难等问题,保障船舶安全通行,以抚河疏山水利枢纽船闸工程为例,采用数值模拟方法,对枢纽船闸上游引航道口门区通航条件进行计算分析,针对不良流态问题提出优化方案措施,并对方案前后枢纽通航条件进行对比分析。研究表明,调整船闸平面布置等措施对改善设计阶段的枢纽船闸上引航道口门区通航条件是有效的。研究成果可为抚河疏山水利枢纽船闸工程通航及其他类似河段工程提供技术支持。

求解 Flow Shop 排序问题的模拟进化法

为ＦｌｏｗＳｈｏｐ排序问题的求解构造了一类模拟进化寻优方法——基于启发式规则的有序遗传算法，并对不同规模的实例进行了计算机模拟。

Application of Stochastic Fracture Network with Numerical Fluid Flow Simulations to Groundwater Flow Modeling in Fractured Rocks

The continuum approach in fluid flow modeling is generally applied to porous geological media, but has limited applicability to fractured rocks. With the presence of a discrete fracture network relatively sparsely distributed in the matrix, it may be difficult or erroneous to use a porous medium fluid flow model with continuum assumptions to describe the fluid flow in fractured rocks at small or even large field scales. A discrete fracture fluid flow approach incorporating a stochastic fracture network with numerical fluid flow simulations could have the capability of capturing fluid flow behaviors such as inhomogeneity and anisotropy while reflecting the changes of hydraulic features at different scales. Moreover, this approach can be implemented to estimate the size of the representative elementary volume (REV) in order to find out the scales at which a porous medium flow model could be applied, and then to determine the hydraulic conductivity tensor for fractured rocks. The following topics are focused on in this study: (a) conceptual discrete fracture fluid flow modeling incorporating a stochastic fracture network with numerical flow simulations; (b) estimation of REV and hydraulic conductivity tensor for fractured rocks utilizing a stochastic fracture network with numerical fluid flow simulations; (c) investigation of the effect of fracture orientation and density on the hydraulic conductivity and REV by implementing a stochastic fracture network with numerical fluid flow simulations, and (d) fluid flow conceptual models accounting for major and minor fractures in the 2 D or 3 D flow fields incorporating a stochastic fracture network with numerical fluid flow simulations.

面向江豚生境需求的长江干流(铜陵段)生态流量过程研究

长江江豚是长江水生态系统健康的重要指示物种,满足其生境需求的生态流量过程是长江干流生态需水研究的关键。为科学明确保障长江江豚适宜生境的流量需求,采用水文改变指标法和变化范围法评价长江干流(铜陵段)水文情势变化。以水深、流速为限制因子,通过栖息地模拟法获得适宜江豚栖息的生态流量范围,耦合水文学法结果,推荐月尺度的生态流量方案;结合流量组分特征进行高流量脉冲设计,综合确定生态流量过程。结果表明:1)长江干流(铜陵段)水文情势改变度达49.74%,为中度改变,且流量事件主要以枯水流量和高流量脉冲为主,环境流量事件趋向单一化;2)长江江豚栖息地适宜流量范围为19000~31100 m^(3)/s,最佳适宜流量范围为22500~28500 m^(3)/s;丰水期适宜范围为27000~31000 m^(3)/s、35000~45000 m^(3)/s、60000~62000 m^(3)/s;高流量脉冲事件为流量值高于39100 m^(3)/s时,其持续时间至少在3 d以上,并以高流量脉冲峰值上限48000 m^(3)/s作为小洪水发生的初始值。本研究成果可为长江干流江豚生境保护和生态调度提供科学数据支撑,为切实推进长江大保护提供技术支撑。

不同雷诺数下4∶1圆角矩形柱气动力特性及流场数值模拟研究

圆角化处理的矩形柱绕流具有复杂的气动力和流场特性。为深入了解圆角矩形柱的雷诺数(Reynolds number, Re)效应,采用基于计算流体力学(Computational fluid dynamics, CFD)的大涡模拟(Large eddy simulation,LES)方法,开展了不同Re下宽高比4∶1圆角矩形柱绕流数值模拟,研究了不同Re下圆角矩形柱的气动力系数、斯特劳哈尔数(Strouhal number, St)、风压系数和流场等变化规律。结果表明:表面风压和时均流场在Re≤4×10^(3)时,Re效应显著,但当Re>4×10^(3)时,Re效应较弱。当Re≤4×10^(3)时,升力系数均方根和平均阻力系数随着Re先增大后减小,在Re=1×10^(3)时达到最大;而St先增大后减小再增大,分别在Re=2×10^(3)时达到最大,在Re=4×10^(3)时达到最小。回流长度随着Re先减小后增大,尾流旋涡中心逐渐后移。

基于改进遗传算法的柔性流水车间调度研究

针对最小化最大完工时间的柔性流水车间调度问题,文章提出了多目标选择的改进的遗传算法(MTGA),设计了针对该问题的一维的编码与解码方法,采用对立的方法进行种群的初始化。针对遗传算法,交叉操作进行整个工序的交叉向最优解靠拢加快了算法的收敛速度,变异操作中对所有的工序操作顺序进行整体变异,选择操作将种群分成多份做到向多个较优解靠拢,扩大了算法的搜索范围,降低了陷入局部最优的概率,并应用了两套交叉和变异概率增加算法灵活性。通过多个已有算法进行对比验证了算法的有效性。

船闸引航道隔流墙物理模型试验优化研究

引航道通航水流条件是航运安全的关键,为研究不同形式隔流墙整流效果,依托浯溪枢纽二线船闸工程,建立定床物理模型通过测量表面流速分布评价船闸通航水流条件,系统地对比研究全实体形式隔流墙、实体与多型透空隔流墙组合、排桩整流等方案的整流效果,并提出排桩与桩基插板隔流墙组合方案。结果表明:延长隔流墙长度可以降低横、纵向流速,有效改善引航道水流条件;合理布置浮式隔流结构可以满足引航道水流条件,整流效果优于全实体隔流墙;排桩方案的整流效果较佳;排桩与桩基插板隔流墙组合方案综合浮式隔流结构、排桩整流技术的优势,在保障整流效果的同时降低了工程造价。

An Improved Level Set Approach to the Simulation of Drop and Bubble Motion

An improved level set approach for computing the incompressible two-phase flow with significantly deformed free interface in presented.The control volume formulation with the semi-implicit method for pressure-linked equations consistent(SIMPLEC)algorithm incroporated is used to solve the governing equations on a staggered grid.Several improvements concerning the convergence and numerical stability.The motion of a bubble or drop in a liquid with large density ratio,viscosity ratio and surface tension in numerically simulated.The computational results are in good agreement with the reported experimental data.

难治性青光眼患者内路直视睫状体光凝手术前后脉络膜厚度、血流密度变化及其与视力改善相关性

目的探究难治性青光眼患者内路直视睫状体光凝手术前后脉络膜厚度、血流密度变化及其与视力改善相关性。方法选取2021年1月—2023年1月拟行内路直视睫状体光凝手术的130例难治性青光眼(130只患眼),将130只患眼作为研究组,130只对侧正常眼作为对照组。比较2组术前眼球中心凹颞侧2500μm处(T2.5)和从眼球中心凹处往鼻侧(N0.5~N2.5)及研究组术前、术后6个月T2.5黄斑区脉络膜厚度和血流密度,不同视力改善情况难治性青光眼患者患眼术前、术后6个月T2.5黄斑区脉络膜厚度、血流密度及其手术前后变化值绝对值。分析研究组术前T2.5、N0.5~N2.5黄斑区脉络膜厚度与血流密度的相关性,T2.5黄斑区脉络膜厚度和血流密度手术前后变化值绝对值与难治性青光眼患者患眼视力改善情况相关性,探讨T2.5黄斑区脉络膜厚度和血流密度手术前后变化值绝对值评估难治性青光眼患者患眼内路直视睫状体光凝手术后视力改善价值。结果研究组术前T2.5和N0.5~N2.5黄斑区脉络膜厚度和血流密度薄于或低于对照组,研究组术前T2.5和N0.5~N2.5黄斑区脉络膜厚度与血流密度呈正相关(P<0.01)。研究组术后6个月T2.5黄斑区脉络膜厚度和血流密度均大于术前(P<0.01)。视力改善难治性青光眼患者患眼术后6个月T2.5黄斑区脉络膜厚度、血流密度及其手术前后变化值绝对值大于视力不变和视力降低患者,视力不变患者大于视力降低患者(P<0.05)。T2.5黄斑区脉络膜厚度、血流密度手术前后变化值绝对值与难治性青光眼患者患眼视力改善情况呈正相关(P<0.05)。受试者工作特征曲线结果显示,T2.5黄斑区脉络膜厚度和血流密度手术前后变化值绝对值联合评估难治性青光眼患者患眼内路直视睫状体光凝手术后视力改善价值的曲线下面积为0.911,高于单独评估的0.760和0.829(P<0.05)。结论难治性青光眼患者患眼T2.5和N0.5~N2.5黄斑区脉络膜厚度和血流密度明显变薄或降低,二者呈正相关关系,且内路直视睫状体光凝术后患眼T2.5黄斑区脉络膜厚度和血流密度明显增大,手术前后T2.5脉络膜厚度和血流密度变化值绝对值与视力改善情况密切相关。

Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows

The dynamic and thermal performance of particle-laden turbulent flow is investigated via direction numerical simulation combined with the Lagrangian point-particle tracking under the condition of two-way coupling, with a focus on the contributions of particle feedback effect to momentum and heat transfer of turbulence. We take into account the effects of particles on flow drag and Nusselt number and explore the possibility of drag reduction in conjunction with heat transfer enhancement in particle-laden turbulent flows. The effects of particles on momentum and heat transfer are analyzed, and the possibility of drag reduction in conjunction with heat transfer enhancement for the prototypical case of particle-laden turbulent channel flows is addressed. We present results of turbulence modification and heat transfer in turbulent particle-laden channel flow, which shows the heat transfer reduction when large inertial particles with low specific heat capacity are added to the flow. However, we also found an enhancement of the heat transfer and a small reduction of the flow drag when particles with high specific heat capacity are involved. The present results show that particles, which are active agents, interact not only with the velocity field, but also the temperature field and can cause a dissimilarity in momentum and heat transport. This demonstrates that the possibility to increase heat transfer and suppress friction drag can be achieved with addition of particles with different thermal properties.

Mechanisms for Particle Clustering in Upward Gas-Solid Flows

Two-dimensional unsteady cocurrent upward gas-solid flows in the vertical channel are simulated and the mechanisms of particles accumulation are analyzed according to the simulation results. The gaseous turbulent flow is simulated using the large eddy simulation (LES) method and the solid phase is treated using the Lagrangian approach, and the motion of the gas and particles are coupled. The formation of clusters and the accumulation of particles near the wall in dense gas-solid flows are demonstrated even if the particle-particle collisions were ignored. It is found that a cluster grows up by capturing the particles in the dilute phase due to its lower vertical velocity. By this way the small size clusters can evolve to large-scale clusters. Due to the interaction of gas and particles, the large-scale vortices appear in the channel and the boundary layer separates from the wall, which results in very high particle concentration in the near wall region and a very large-scale cluster formed near the separation point.

Pseudo-dynamic analysis of seismic stability of reinforced slopes considering non-associated flow rule

The required reinforcement force to prevent instability and the yield acceleration of reinforced slopes are computed under seismic loading by applying the kinematic approach of limit analysis in conjunction with the pseudo-dynamic method for a wide range of soil cohesion, friction angle, dilation angle and horizontal and vertical seismic coefficients. Each parameter threatening the stability of the slope enhances the magnitude of the required reinforcement force and vice versa. Moreover, the yield acceleration increases with the increase in soil shear strength parameters but decreases with the increase in the slope angle. The comparison of the present work with some of the available solutions in the literatures shows a reasonable agreement.