Large Time Behavior of a Weak Solution for Non-Newtonian Flow

This paper concerns large time behavior of a regular weak solution for non-Newtonian flow equations. It is shown that the decay of the solution is of exponential type when the force term is equal to zero and the domain is bounded. Moreover, the ratio of the enstrophy over the energy has a limit as time tends to infinity, which is an eigenvaiue of the Stokes operator.

Analysis of one-dimensional consolidation of soft soils with non-Darcian flow caused by non-Newtonian liquid

Based on non-Darcian flow caused by non-Newtonian liquid, the theory of one-dimensional (1D) consolidation was modified to consider variation in the total vertical stress with depth and time. The finite difference method (FDM) was adopted to obtain numerical solutions for excess pore water pressure and average degree of consolidation. When non-Darcian flow is degenerated into Darcian flow, a comparison between numerical solutions and analytical solutions was made to verify reliability of finite difference solutions. Finally, taking into account the ramp time-dependent loading, consolidation behaviors with non-Darcian flow under various parameters were analyzed. Thus, a comprehensive analysis of 1D consolidation combined with non-Darcian flow caused by non-Newtonian liquid was conducted in this paper.

COMPUTATIONALINTELLECTUAL ANALYTICAL THEORYOF COMPUTATIONAL ANALYTICAL APPROACH TOROTATING FLOW OF NON_NEWTONIAN FLUID

A combination of the computational symbolic calculation, mathematical approach and physico-mechanical model lends to a computational intellectual analytical approach developed by the author. There is a principal difference between the computer proof and the computer derivation completed by the computer, also difference between the numerical and symbolic calculations. In this investigation the computational analytical approach is extended, and an unsteady flow of non-Newtonian fluid in the gap between two rotating coaxial cylinders is studied. The Oldroyd fluid B model is used by which the Weissenberg effects are explained in a good comparison with the experiments. The governing equations are reduced to a partial differential equation of 3 rd order for the dimensionless velocity. Using the computer software Macsyma and an improved variational approach the problem with the initial and boundary conditions is then reduced to a problem of an ordinary differential equation for different approximations. The analytical solutions are given for the 1 st, 2 nd and 3 rd approximations. The present investigation shows the ability of the computational symbolic manipulation in solving the problems of non-Newtonian fluid flows. There is a possibility of that to solve the problems in mathematics and mechanics. An important conclusion can be drawn from the results that the transition from a steady state to another steady state is non-unique.

Non-Newtonian steady shear flow characteristics of waxy crude oil

The experimental research on the non-Newtonian flow characteristic of a waxy crude oil was conducted through a rotational parallel-plates rheometer system.The test temperature is about 6.5 ℃ higher than its gel point.The shear stress and viscosity of the waxy crude oil show sophisticate non-Newtonian characteristics in the shear rate of 10-4-102 s-1,in which the shear stress can be divided into three parts qualitatively,i.e.stress-up region,leveling-off region,and stress-up region.This indicates that there is a yielding process in shearing for the waxy crude oil at the experimental temperature,which is similar to the yield phenomenon in thixotropy-loop test discussed by CHANG and BOGER.Furthermore,the steady shear experiment after the pre-shear process shows that the stress leveling-off region at low shear rate disappears for the waxy crude oil and the stress curve becomes a monotonic climbing one,which demonstrates that the internal structure property presenting through yielding stress at low shear rate can be changed by shearing.The experimental results also show that the internal structure of waxy crude oil presenting at low shear rate has no influence on the shear viscosity obtained at the shear rate higher than 0.1 s-1.The generalized Newtonian model is adopted to describe the shear-thinning viscosity property of the waxy crude oil at high shear rate.

Non-Newtonian Two-Phase Flow Characteristics across Sudden Expansion in Horizontal Rectangular Minichannel

In the present paper, in order to clarity the effects of non-Newtonian liquid properties on the flow, similar experiments have been conducted for that of 0.4 wt% polyacrylamide (PAM) aqueous solutions as the working liquid, and air as the working gas. Liquid single-phase and air-liquid two-phase flow experiments were conducted at room temperature using the horizontal rectangular mini-channel with a sudden expansion. The cross-sectional dimensions of the narrow channel upstream from the sudden expansion were 2.79 mm, 3.09 mm and 2.94 mm in the height (H), the width (W) and the hydraulic diameter (DH), while those for the wide channel were 2.95 mm, 5.98 mm and 3.95 mm. The pressure distributions in the channels upstream and downstream from the expansion were measured with calibrated pressure transducer to determine the pressure change due to the expansion. The flow pattern, the bubble velocity, the bubble length, and the void fraction were measured with a high-speed video camera. The flow pattern map is drawn from the observed flow pattern, i.e., bubble flow, slug flow and annular flow in both the wide and the narrow channels. The bubble length data were compared with the calculation by the scaling law proposed by Kanezaki et al. and Kawahara et al. The pressure change data at the expansion were compared with our previous data together with several correlations in literature. Results of such experiment and comparisons are reported in the present paper.

COMPUTER SIMULATION OF NON-NEWTONIAN FLOW AND MASS TRANSPORT THROUGH CORONARY ARTERIAL STENOSIS

A numerical analysis of Newtonian and non-Newtonian flow in an axi-symmetric tube with a local constriction simulating a stenosed artery under steady and pulsatile flow conditions war carried out. Bared on these results, the concentration fields of LDL ( (low-density lipoprotein) and Albumin were discussed. According to the results, in great details the macromolecule transport influences of wall shear stress, non-Newtonian fluid character and the scale of the molecule etc are given. The results of Newtonian fluid flow and non-Newtonian fluid flow, steady flow and pulsatile flow are compared. These investigations can provide much valuable information about the correlation between the flow properties, the macromolecule transport and the development of atherosclerosis.

THE NUMERICAL SIMULATION OF TURBULENT FLOWS OF NEWTONIAN AND A SORT OF NON-NEWTONIAN FLUID IN 180-DEGREE SQUARE SECTIONED BEND

Using k- model of turbulence and measured wall functions, turbulent flows of Newtonian (pure water) andasort of non-Newtonian fluid (dilute, drag-reduction solution of polymer) in a 180-degree curved bend were simulated numerically. The calculated results agreed well with the measured velocity profiles. On the basis of calculation and measurement, appropriateness of turbulence model to complicated flow in which the large-scale vortex exists was analyzed and discussed.

Jeffery-Hamel flow of non-Newtonian fluid with nonlinear viscosity and wall friction

A Jeffery-Hamel （J-H） flow model of the non-Newtonian fluid type inside a convergent wedge （inclined walls） with a wall friction is derived by a nonlinear ordinary differential equation with appropriate boundary conditions based on similarity relationships. Unlike the usual power law model, this paper develops nonlinear viscosity based only on a tangential coordinate function due to the radial geometry shape. Two kinds of solutions are developed, i.e., analytical and semi-analytical （numerical） solutions with suitable assumptions. As a result of the parametric examination, it has been found that the Newtonian normalized velocity gradually decreases with the tangential direction progress. Also, an increase in the friction coefficient leads to a decrease in the normalized Newtonian velocity profile values. However, an increase in the Reynolds number causes an increase in the normalized velocity function values. Additionally, for the small values of wedge semi-angle, the present solutions are in good agreement with the previous results in the literature.

Implementation of Non-Newtonian Fluid Properties for Compressible Multiphase Flows in OpenFOAM

The paper presents the implementation of non-Newtonian fluid properties for compressible multiphase solver in the open source framework OpenFOAM. The transport models for Power Law, Cross Power Law, Casson, Bird-Carreau and Herschel-Bulkley fluids were included in the thermophysical model library. Appropriate non-Newtonian liquids have been chosen from literature, and pressure driven test simulations are carried out. Therefore, the solver compressibleInterFoam is used to compute air-liquid mixture flows over a backward facing step. A validation of the novel models has been performed by means of a sample-based comparison of the strain rate viscosity relation. The theoretical rheological properties of the selected liquids agree well with the results of the simulated data.

ANALYTICAL SOLUTIONS OF THE HELICAL FLOW OF NONNEWTONIAN FLUID IN ECCENTRIC ANNULAR SPACE

Many problems in petroleum and chemical industry can be reduced to the solution of the helical flow of non-Newtonian fluid in eccentric annular space. The laminar helical flows of the power law fluid and Bingham fluid in eccentric annular space were studied. An approximate analytical solution was obtained by the infinite subdivision method, namely, the eccentric flow was replaced by the infinite concentric flows. Then, the expressions for apparent viscosity distribution, velocity distribution and the flow rate were derived for the power law fluid and the Bingham fluid respectively. In addition, the expressions for pressure drop and stability parameter were also given. It is concluded that this method is much easier to use and more accurate than the method which solves the equations directly. The results are useful for the drilling technology of oil industry, etc.

THE NONLINEAR STABILITY OF PLANE POISEUILLE FLOW FOR NON－NEWTONIAN POWER SERIES FLUID

Non-Newtonan fluid is a kind of fluid whose components of stresstensor aren’t theliear funtions of compoents of the strain rate tensor.Non-Newtonianfluid is beingprocessed in many kinds of modern industry,Stability of flows for Non- Newtonianfluid is of important applicatuib,In this article we calculate subcritical thrdshold of flow which oecurs in polymer-processing when the melting substance is driven throughtwo parallel fixed boundaries.

Free-surface Simulations of Newtonian and Non-Newtonian Fluids with the Lattice Boltzmann Method

This paper describes the application of a three-dimensional lattice Boltzmann method （LBM） to Newtonian and non-Newtonian （Bingham fluid in this work） flows with free surfaces. A mass tracking algorithm was incorporated to capture the free surface, whereas Papanastasiou＇s modified model was used for Bingham fluids. The lattice Boltzmann method was first validated using two benchmarks： Newtonian flow through a square cross-section tube and Bingham flow through a circular cross-section tube. Afterward, the dam-break problem for the Newtonian fluid and the slump test for Bingham fluid were simulated to validate the free-surface-capturing algorithm. The numerical results were in good agreement with analytical results, as well as other simulations, thereby proving the validity and correctness of the current method. The proposed method is a promising substitute for time-consuming and costly physical experiments to solve problems encountered in geotechnical and geological engineering, such as the surge and debris flow induced by a landslide or earthquake.

基于非牛顿微液滴的粒子封装及检测

微流控液滴封装技术可将单个或者多个颗粒物封装到微尺度液滴,具有细胞培养、药物可控释放和微量成分分析等重要生物医学应用,而这些应用往往涉及多相混合的复杂非牛顿流体.目前制备尺寸均匀的非牛顿微液滴并实现高效率单粒子封装仍较难实现.针对该问题,首先基于流动聚焦微通道和聚合物溶液开展非牛顿液滴生成实验,系统探究不同非牛顿性质对液滴生成模态的影响,指出兼具剪切稀化与弹性效应的聚合物溶液可在射流模态下实现高单分散性液滴的稳定生成.在此基础上,结合惯性-黏弹性粒子排序,实现了封装率超过58%的单粒子封装,突破了传统单粒子封装的泊松限制.最后,进一步构建了粒子封装率自动检测模型,验证了其在单液滴与多液滴场景下粒子封装率高精度检测的有效性.综上,研究结果不仅一定程度上拓展对于液滴微流控基础理论的认识,还充分验证了射流模态下非牛顿液滴稳定生成用于单粒子封装策略的可行性和优越性,可为优化基于非牛顿微液滴的粒子封装技术及开发一体化装置提供一定参考.

土体颗粒物流动物质点法模拟的弹塑性和非牛顿流体本构模型比较研究

土体颗粒物流动是一种典型的大变形破坏,具有非牛顿流体的流动特征。准确模拟土体颗粒物的流动及冲击过程,对滑坡和泥石流等地质灾害的防治具有重要意义。物质点法是一种无网格粒子类方法,已在各类大变形问题中得到了广泛应用。以往土体颗粒物流动的模拟,通常采用弹塑性本构模型,但缺乏对非牛顿本构模型的模拟分析。本文引入非牛顿本构模型的模拟分析,旨在为土体颗粒物流动模拟提供一种新的方法与思路。非牛顿本构模型的模拟分析是将非牛顿广义Cross模型引入三维物质点法,通过人工阻尼力模拟颗粒间的摩擦力,对土体颗粒物的坍塌、沿斜面滑动以及冲击障碍物等问题进行了动态模拟,研究了其运动全过程,并与弹塑性本构模型的模拟结果进行了对比验证。结果表明,基于非牛顿流体本构模型的物质点法可以较好地模拟土体颗粒物加速、减速到再次稳定的流动全过程及其对障碍物的冲击效应。

磷素对含沙水流流体变异特性影响

[目的]为探明磷素对含沙水流流体变异特性的影响。[方法]采用自制双竖管流变仪,研究了磷素对不同浓度含沙水流流体类型、流变参数及流体发生变异的临界阈值的影响。[结果](1)磷素浓度、泥沙浓度及泥沙理化性质是影响含沙水流发生流体变异的主要因素。在25℃下,过磷酸钙浓度每增加0.1 g/cm^(3),黏滞系数和宾汉极限剪切力分别增加0.48~1.47 mPa·s和3.49~6.84 N/m^(2)。(2)随着磷素和泥沙含量的增大,含磷素的含沙水流由牛顿流体变异为宾汉流体。构建并验证了磷-泥沙水流黏滞系数和宾汉极限剪切力等流变参数的计算模型。(3)给出了磷-泥沙水流流体变异的临界浓度阈值。当磷素浓度从0增加至0.45 g/cm^(3)时,含沙水流的流体变异临界浓度阈值降低49%,说明磷素的存在加速了含沙水流的流体变异。[结论]磷素的增加使得侵蚀水流更容易由牛顿流体变异为宾汉流体,从而影响侵蚀流内部的能量耗散过程,研究结果为深入认识侵蚀污染水流的输移机制提供了新的科学基础。

特高压换流站消防机器人长距离输送压缩空气泡沫有效性研究

为厘清压缩空气泡沫从产生装置运输至举高消防机器人过程中的可靠性,选用Fluent模拟软件对压缩空气泡沫在管道内的压降进行数值模拟研究。研究结果表明:在气液比6∶1~10∶1范围内,压缩空气泡沫在长距离运输过程中的压降随着气液比的增大而增大,硬管末端10∶1泡沫的压降可达到6∶1泡沫的1.7倍;在相同气液比混合比、供液流量条件下,硬管段中的压降与运输距离成正相关,运输至315 m处达到最大值166 kPa。接驳口前后存在较大的压降,其压降值大于硬管段输送150 m处的压降,是其1.18倍;软管段中的压降在运输过程中爬升阶段的下降尤为显著。气液比、运输距离、管径及高度变化是影响压缩空气泡沫运输过程中压降变化的主要因素,其中管径和高度的影响尤为显著。研究结果可为举高消防机器人在特高压换流站的应用提供一定的理论参考。

SQUEEZE FLOW OF A POWER-LAW FLUID BETWEEN TWO RIGID SPHERES WITH WALL SLIP

The effect of wall slip on the squeeze flow of a power-law fluid between two rigid spherical particles has been examined based on the Reynolds lubrication theory. It is shown that the viscous force arising from the squeeze flow with wall slip may be resolved to the no slip solution by introducing a slip correction coefficient. An expression for the slip correction coefficient of force is derived which is related to the slip parameter, the flow index and the upper limit of integration. Generally, wall slip results in a reduction in the viscous force. The reduction in the viscous force increases as the flow index increases, suggesting that wall slip has a more profound effect on shear thickening material. However, such reduction decreases as the upper limit of integration increases from finite liquid bridges to fully immersed systems. The reduction in the viscous force also increases as the slip parameter increases, which is the expected behaviour.

Nonlinear property of the visco-elastic-plastic material in the impact problem

In this paper a numerical investigation on the non-Newtonian flow problem is conducted, in order to shed further light on the mathematical and virtual test methods in the auto-crash safety analysis. The accurate mathematical prediction would supply ultimate research tool for the passive safety analysis in such a scale.

Time Dependent Pressure Gradient Effect on Unsteady MHD Couette Flow and Heat Transfer of a Casson Fluid

The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible non-Newto- nian Casson fluid bounded by two parallel non-conducting porous plates has been studied with heat transfer considering the Hall effect. The fluid is acted upon by a uniform and exponential decaying pressure gradient. An external uniform magnetic field is applied perpendicular to the plates and the fluid motion is subjected to a uniform suction and injection. The lower plate is stationary and the upper plate is suddenly set into mo- tion and simultaneously suddenly isothermally heated to a temperature other than the lower plate temperature. Numerical solutions are obtained for the governing momentum and energy equations taking the Joule and viscous dissipations into consideration. The effect of unsteady pressure gradient, the Hall term, the parameter describing the non-Newtonian behavior on both the velocities and temperature distributions have been stud- ied.

Experimental investigation on flow modes of electrospinning

Electrospinning experiments are performed by using a set of experimental apparatus, a stroboscopic system is adopted for capturing instantaneous images of the cone- jet configuration. The cone and the jet of aqueous solutions of polyethylene oxide （PEO） are formed from an orifice of a capillary tube under the electric field. The viscoelastic con- stitutive relationship of the PEO solution is measured and discussed. The phenomena owing to the jet instability are described, five flow modes and corresponding structures are obtained with variations of the fluid flow rate Q, the electric potential U and the distance h from the orifice of the cap- illary tube to the collector. The flow modes of the cone-jet configuration involves the steady bending mode, the rotat- ing bending mode, the swinging rotating mode, the blurring bending mode and the branching mode. Regimes in the Q-U plane of the flow modes are also obtained. These results may provide the fundamentals to predict the operating conditions expected in practical applications.