Research on the behavior of fiber orientation probability distribution function in the planar flows

INTRODUCTION The orientation of fibers plays an important rolein determining the rheological properties of fibersuspensions and the behaviors of composite materialsproduced by various forming operations. A fiber canbe treated as a rigid cylinder with length l and di-ameter d. It is convenient to define three regimes ofconcentration: dilute, semi-concentrated and concen-trated. Dilute regime is defined when c<(d/l)2, wherec is the volume fraction of fibers. In this regime fibersare …     

Science Letters： Research on 3D fiber orientation distribution in arbitrary planar flows

A non-stretchable fiber rotation in planar flows has been solved. The fiber will rotate periodically or run to the asymptotical direction decided by a discriminant defined in the paper involving the fiber aspect ratio and the flow characteristics. Subsequently the fiber orientation distribution is derived directly without the bother of solving the Fokker-Planck equation. The research clearly indicates the overall configuration of a fiber rotation movement in planar flows.     

On the structural features of fiber suspensions in converging channel flow

The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective viscosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of the rate-of-strain tensor and the fiber orientation state; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local streamlines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of effective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds number but on the converging channel angle. Projects (No. 19925210) supported by the National Natural Science Foundation of China     

On the structural features of fiber suspensions in converging channel flow

INTRODUCTIONModelingfiber fiberinteractionsinnon di lutefibersuspensionsanddescribinghowtheseinteractionsaffecttherheologicalpropertiesofthesuspensionsintheflowsarefundamentalandimportantinmulti phaseflowsresearch .Ulti matelywewouldliketobeabletodesignan…     

Motion and orientation of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio

Lattice Boltzmann method was used to numerically investigate the motion and orientation distribution of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio. The transient impulse model of 3D collisions between particles and between particle and wall is proposed. The numerical results are qualitatively in agreement with and quantitatively comparable to the experiment data. The results show that the increases of both the cylindrical particle to pipe size ratio and the particle aspect ratio decrease the rotation about all axes. All rotations of cubic particles decrease with increasing the particle concentration. The cubic particles, rotating more drastically in the flow with large Reynolds number, rotate faster than the cylindrical particles with the same size. The cylindrical particles align with the flow direction more obviously with decreasing Reynolds numbers. However, the orientations of cubic particles are spread all over the range with no significant difference in magnitude, and the Reynolds numbers have no obvious effect on the orientations of cubic particles.     

Two-dimensional pipe leakage through a line crack in water distribution systems

In water distribution systems, water leakage from cracked water pipes is a major concern for water providers. Generally, the relationship between the leakage rate and the water pressure can be modeled by a power function developed from the orifice equation. This paper presents an approximate solution for the computation of the steady-state leakage rate through a longitudinal line crack of a water distribution pipe considering the surrounding soil properties. The derived solution agrees well with results of numerical simulations. Compared with the traditional models, the new solution allows assessment of all the parameters that related with leakage including the pressure head inside the pipe, hydraulic conductivity, crack size and its position, and pipe size and its depth.     

Low frequency oscillatory flow in a rotating curved pipe

INTRODUCTIONThemotionoftheflowinarotatingcurvedpipeisafundamentalproblem ,whosesolutionhaspotentialapplicationsingasturbines ,elec tricgenerators ,electricmotorsandsomeequip mentsusedinseparationprocesses.Itisimpor tanttoknowtheflowstructurecharacteristic…     

Low frequency oscillatory flow in a rotating curved pipe

The low frequency oscillatory flow in a rotating curved pipe was studied by using the method of biparameter perturbation. Perturbation solutions up to the second order were obtained and the effects of rotation on the low frequency oscillatory flow were examined in detail. The results indicated that there exists evident difference between the low frequency oscillatory flow in a rotating curved pipe and in a curved pipe without rotation. During a period, four secondary vortexes may exist on the circular cross-section and the distribution of axial velocity and wall shear stress are related to the ratio of the Coriolis force to centrifugal force and the axial pressure gradient. Project (No: 10272096) supported by the National Natural Science Fundation of China     

Non-axisymmetric instability in the Taylor-Couette flow of fiber suspension

An analysis of the instability in the Taylor-Couette flow of fiber suspensions with respect to the non-axisymmetric disturbances was performed. The constitutive model proposed by Ericksen was used to represent the role of fiber additives on the stress tensor. The generalized eigenvalue equation governing the hydrodynamic stability of the system was solved using a direct numerical procedure. The results showed that the fiber additives can suppress the instability of the flow. At the same time, the non-axisymmetric disturbance is the preferred mode that makes the fiber suspensions unstable when the ratio of the angular velocity of the outer cylinder to that of the inner cylinder is a large negative number.     

矩形管道内充分发展热流动的可视化计算

推导了求解矩形管道内充分发展流体流动和热交换的有限差分方程,编写了相应的计算机程序,借此求得了管道横截面内速度和温度的结点值,然后利用计算机图形显示算法自动生成相应的速度和温度等值线图形．最后,对管道内充分发展热流动的特性进行了讨论．     

Design optimization on the front wheel orientation parameters of a vehicle

1. Introduction In order to improve the driving operation performance, the front suspension of a vehicle is generally of McPherson independent style, which can simplify the structure, lighten the unsprung mass, and conveniently arrange the engine and steering system. Moreover, it can adapt to many types of springs and is of advantage to adjust the height of the vehicle. In such a system, the axis of the kingpin is the line between the upper damper end and the intersection of the transverse ar…     

Prediction of wall deposition behaviour in a pilot-scale spray dryer using deposition correlations for pipe flows

INTRODUCTION Abbott (1990) reported that wall deposition inspray dryers may pose a potential fire risk and com-promise hygiene requirements, and reduce productquality and yield. Spray dryer hazards include igni-tion of explosible dust clouds, dust deposits, bulkpowder deposits and flammable vapour. Kieviet(1997) noted that wall deposition affected the resi-dence time distribution of particles, and particularlythat an important factor in determining residencetimes with high wall deposition…     

圆截面正交旋转直管流动的Galerkin解

根据在直角坐标系下建立的旋转直管内的流体流动方程,采用Galerkin 方法编写了相应的数值计算程序,然后对不同Re数和Ro数条件下的管内层流流动进行了求解,从而基于Galerkin 方法的特点获得了问题的高阶半解析解,有效地克服了摄动解的小参数局限.最后,研究了对圆截面正交旋转直管内的二次流动特性.     

基于ANSYS软件三通管应力分布特性分析

应用有限元分析软件ANSYS10.0,对三通管应力进行计算分析,获得了内压作用下三通管的应力分布特性,在工程上,可以解决设备开孔部位是否需要加强的问题。     

N-E-V分布的实用性研究

本文推导了统计热力学中粒子数N、能量E、体积V和熵S在第八种分布(N-E-V分布)情况下的计算公式,并以单原子理想气体和量子气体为例说明了N-E-V分布具有其实用性.     

Modeling of D-STATCOM in distribution systems load flow

This paper presents modeling of Distribution STATCOM (D-STATCOM) in load flow calculations for the steady- state voltage compensation. An accurate model for D-STATCOM is derived to use in load flow calculations. The rating of this device as well as the direction of required reactive power injection for voltage compensation in the desired value (1 p.u.) is de- rived and discussed analytically and mathematically by the phasor diagram method. Furthermore, an efficient method for node and line identification used in load flow calculations is presented. The validity of the proposed model is examined by using two standard distribution systems consisting of 33 and 69 nodes, respectively. The best location of D-STATCOM for under voltage problem mitigation approach in the distribution networks is determined. The results validate the proposed model for D- STATCOM in large distribution systems.     

交通量分布模型应用探讨

交通量预测是决定公路运输网络规划成败的基础工作。笔者根据系数增长法的原理 ,在区域不大的公路运输网络规划中 ,采用佛尼斯模型预测交通量 ,能得到较为符合实际的科学预测结果 ,为交通规划决策提供依据。     

冷凝管内冷却水流动方向的解析

1 问题的提出 在室温下,有些反应速率很小或难于进行.为了使反应顺利地进行,常常需要使反应物质较长时间保持沸腾.这种情况就需要使用回流冷凝装置,使蒸气不断地在冷凝管内冷凝而返回反应器中,以防止反应瓶中的物质逃逸损失[1].     

课程实施的价值取向研究

课程实施是课程改革的关键性环节，课程实施的价值取向是课程改革成功的先决条件。长期以来人们关注的三种课程实施价值取向虽然各有千秋，但也都有其致命的弱点。梳理这三种课程实施的价值取向，意识到我国的课程改革只有走自动催化的课程价值取向之路，才能取得预期的效果。     

概率论中的二项分布的应用研究

独立重复试验是研究随机现象的重要途径之一,很多概率模型的建立都以独立重复试验为背景,二项分布就是来自于独立重复试验的一个概率模型。我们知道,二项分布的概率公式为简简单单的一个公式,却有着千变万化的应用。下面将对概率论中二项分布的研究做一个仔细的阐述。