布金汉方程一般解在测流变参数的应用

根据古典一元四次方程的解法,讨论了著名的布金汉方程,得出了布金汉方程的精确解,此解 可以应用在测宾汉体的流变参数极限应力和刚度系数中,从数学上解释了牛顿流体和非牛顿流体的区 别。并讨论了极限切应力为零时经典的非牛顿流体的泊谡叶方程。     

高浓度浑水的宾汉极限剪应力

高浓度浑水一般属宾汉体。由于试验条件及浑水流变特性的复杂,对浑水的宾汉极限剪应力的系统研究很少,现有试验成果很不统一,多数不能反映浑水中固体颗粒组成对宾汉极限剪应力的影响。本文通过应用毛细管粘度计对十一种混合沙作了流变试验,以反映颗粒级配特性的“极限浓度”及固体体积浓度为参数,求得浑水宾汉极限剪应力的统一表达式。文中并就极限浓度对非牛顿体形成条件及对非牛顿体由两相过渡到一相体的影响等向题,提出初步的经验关系。讨论了宾汉极限剪应力与固体体积浓度、颗粒级配特性及浑水流态之间的综合关系。     

确定毛细管粘度计α β值的方法

一、问题的提出 在研究高含沙水流运动规律时,其流变特性显得越来越重要.一般说来,高浓度泥浆呈非牛顿体特性,可近似地用宾汉模型来描述. 近几年,国内泥沙界普遍采用毛细管粘度计(见图1)测定流变参数.从目前各家所推荐的流变参数计算公式来看,计算的刚度系数值比较接近,相差不大;而计算的宾汉切应力相差很远,有的可差到3～5倍.鉴于宾汉切应力是一个非常重要的参数,就     

含沙水流的宾汉极限应力的计算公式

1922年美国学者宾汉(Bingham)提出了著名的流变方程——宾汉塑性流体流变方程(1)从而揭示了液体的一个重要流变特性。符合公式(1)的流体又称宾汉体,式中的τ_B称为宾汉极限应力(又称屈服应力),η称为刚性系数。宾汉体属于非牛顿流体。我国黄河的高含沙水流以及福建以北的淤泥质海岸、河口的浮泥运动大多属于宾汉体,或可以近似地看作宾汉体。因此,对于水利工作者来讲,研究水沙体系的流变特性具有重要的实际意义。极限应力τ_B是宾汉体中的重要特征值,在许多问题的研究中,都要涉及到它。而且,比起宾汉体的另一个特征值η来讲,τ_B的影响往往要大得很多。因此人们对此做了大量的试验研究工作。但由于影响流变特性的因素较多,也比较复杂,特别是对于水利工程中所遇到的高浓度水沙体系,其浓度范围广,粒径和级配变化大,各地水质和沙质又各不尽同,而这些基本因素对流变特性都会产生不同程度的影响。因此,泥沙浑水体系相对于极微     

毛细管流变仪测验流变参数的计算方法

根据毛细管粘度计试验资料,用简化的宾汉方程可求出流变参数.本文探讨了简化公式的误差和应用条件,提出了计算流变参数的方法.     

流变仪测定浆体流变参数的计算方法

本文介绍了在浆体流变试验中，根据浆体的实际受力情况，采用相应的虚流变方程，用数解法求得浆体的流变参数的方法。这种方法消除了以往采用图解法求解流变参数所引起的人为误差。使得所测定的流变参数值更接近于真实值。从而提高了流变参数的测验精度。     

稳定水泥浆流变性试验研究

对聚合物稳定剂水泥浆和膨润土稳定剂水泥浆进行了流变试验研究，按宾汉流变模型对其流变参数进行了理论计算；结果表明，聚合物稳定剂水泥浆动切应力较膨润土稳定剂水泥浆低，其可灌性和扩展半径要优于膨润土稳定剂水泥浆。     

黏性泥沙流变特性及其临界起动的研究

以天津大港淤泥质粉沙为研究对象,系统研究了其物理特性和临界起动性质。对密度范围在1.141~1.470g/cm3的黏性泥沙进行流变试验,确定其流变参数。结果表明:天津大港黏性泥沙有明显的屈服应力,适合用宾汉塑性体模型描述,且宾汉屈服应力和黏度系数均为泥沙密度的指数函数。长水槽中波浪作用下黏性泥沙起动试验以泥沙少量起动为标准,波浪底部临界切应力随黏性泥沙密度增大而增大,即不同于非黏性泥沙,黏性泥沙的起动主要与其密度有关,而非泥沙粒径。波浪作用下的黏性泥沙起动可以用延伸Shields曲线描述。根据实验结果拟合出临界起动切应力和宾汉屈服应力之间的关系式。     

单颗粒在宾汉体中沉降规律的试验研究

固体颗粒在液体中的沉降速度是一个十分重要的物理量.对于高含沙水流,由于浆体本身的物理性质由牛顿体转变成宾汉体,固体颗粒在这种宾汉体中沉降的受力条件与在清水中不同,其沉降特性亦不相伺.本文从宾汉体的物理特性入手,用力的平衡方程式导得宾汉体的阻力系数C'_D.由试验资料找出了C'_D与宾汉体中沉降的颗粒雷诺数Re_B之间的相关关系,与清水中基本相同,只是区分流区的雷诺数Re_B与清水不同.本文还提出了将任意形状的固体颗粒的C_D～Re_B相关关系转换成球体的计算方法,得出了各流区球体颗粒的阻力系数C'_D的表达式,并由力的平衡条件求得了宾汉体中最大不沉粒径d_max的表达式.     

压力式流变仪的设计原理和使用方法

近几年来,我国水利界许多科研和生产单位对北方地区、特别是对黄河流域的高含沙水流进行了多方面的研究和探讨,通过实践业已证明高含沙水流属于宾汉流体,本文所要介绍的是我们于1978年试制成功测量宾汉体流变特性参数的压力式流变仪。     

宾汉体水流中泥沙起动机理

本文分析了宾汉流体中宾汉极限剪切力τB对泥沙起动起阻碍作用的力学机制，得出均匀无粘性沙的起动拖曳力的一般表达式。并对结果定性分析得到：(1)存在粒径D*，对粒径小于0.1D*的泥沙，起动中重力因素可忽略不计；对粒径大于10D*的泥沙，宾汉极限剪切力因素可忽略不计。(2)宾汉流体中τc随颗粒粒径D的变化关系为马鞍状曲线。存在某个粒径Dmin，其所需τc最小。     

宾汉极限切应力的研究

本文对含沙高浓度流体的极限含沙浓度、刚度系数和宾汉极限切应力进行了理论和试验研究，得出了相应的计算式。各计算式均得到试验资料的验证，尤其是得到了轻质沙－电木粉试验资料的验证，且吻合良好。     

基于等幅周期荷载下软岩Bingham本构模型的研究

为建立一种描述等幅周期荷载下软岩应变特性的本构模型,将Bingham模型中的常值黏壶元件替换成与循环次数相关的变系数黏壶元件,常值弹性元件替换为随周期荷载循环次数的增大而衰减的非定值弹性元件,即可得到反映周期荷载下软岩各种应变规律的Bingham本构模型。当循环荷载应力上限值σmax大于岩石的临界强度σs时,模型为可反映软岩3个应变阶段的改进4参数Bingam模型;反之则为反映软岩前两个应变阶段的非常值2参数Hook模型。将周期荷载分解为一个定值荷载和一个平均应力值为零的周期荷载,基于流变力学理论给出了定值荷载作用下基于该模型的本构方程式,再根据黏弹性力学理论,给出了平均应力值为零的周期荷载下基于该模型的本构方程式,最后将已获得的本构方程式叠加即得到周期荷载下软岩本构方程式。结果表明:所建立的本构方程式可较好描述周期荷载下不同软岩各类应变特征,对各类软岩的应变曲线拟合的相关系数均在0.868以上,且同一种岩石模型中弹性元件系数初始值随周期荷载的动应力幅值的增大而减小,岩石加速应变速率参数随动应力幅值的增大而增大。     

浮泥的屈服应力确定方法

浮泥的流变特性对于研究浮泥的运动特性至关重要,其中屈服应力作为重要的流变参数,表征使浮泥产生流动状态的临界应力。针对目前大多数研究中浮泥屈服应力确定方法较为单一的情况,作者系统地介绍了浮泥屈服应力的直接确定方法和原理,包括流变学的方法、斜面平衡法、自由流动重力平衡法等。并通过实例,利用流变模型拟合法和自由流动重力平衡法确定连云港区浮泥样本的屈服应力,并对这2种方法得到的结果进行了比较和探讨。     

Application of binding theory for seepage of viscoelastic fluid in a variable diameter capillary

The polymer solution for polymer flooding is a viscoelastic fluid. There exist both shear flow and elongational flow when the polymer solution flows in a porous medium, where an additional dissipation is involved. The additional dissipation caused by elongational deformation is often ignored while studying the flow of the fluid in a porous medium. For a complex polymer solution, the generated elongational pressure drop cannot be ignored. In a capillary of fixed diameter, the polymer solution is only impacted by the shear force, and its rheological property is pseudoplastic. Therefore the variable diameter capillary and the converging-diverging flow model with different cross sections are required to describe the flow characteristics of the polymer solution in porous media more accurately. When the polymer solution flows through the port, we have the elongational flow and the polymer molecules undergo elongational deformation elastically. By using the mechanical energy balance principle and the minimum energy principle, a mathematical model of non-Newtonian fluid inlet flow was established by Binding. On the basis of the Binding theory, with the application of the theory of viscoelastic fluid flow in the circular capillary and the contraction-expansion tube, the relations between the viscoelastic fluid flow rate and the pressure drop are obtained.     

考虑损伤的软弱夹层剪切流变模型及程序实现

自然界中岩体破坏的主要形式是沿着滑面的剪切破坏,且主要表现为剪切流变损伤特征。根据软弱夹层不同剪切应力水平下的试验数据分析,引入可以表征其流变过程中参数损伤的变量D,提出了一个基于D的可以反映软弱夹层加速流变特性的黏弹塑性非线性流变模型,与伯格斯模型串联构成了一个能全面反映3个流变阶段的新的软弱夹层剪切流变损伤模型。基于FLAC3D使用C++语言对该流变损伤模型进行了二次开发,与室内流变试验进行了对比验证。结果表明:（1）每级剪应力下,其瞬时应变均较为接近,且经过相同时间的应力加载后,无论是稳定后的应变值还是加速阶段的应变值也均较为接近。（2）数值模拟试验中,当施加的剪切荷载未达到屈服应力时,其减速阶段历时较室内试验的历时短,即更快地达到稳定流变阶段;而当施加的剪切荷载超过屈服应力阈值时,其加速流变阶段位移变化速率大于室内试验的,且最终的位移比室内试验位移稍大。     

Electro-osmotic flow and heat transfer of a non-Newtonian fluid in a hydrophobic microchannel with Navier slip

In this paper, we investigate the implications of electro-osmosis on electrohydrodynamic transport of a non-Newtonian fluid on a hydrophobic micro-channel by developing a suitable analytical method. Velocity-slip and temperature-jump conditions are paid due attention. An attempt has been made to examine the effects of rheological and electro-osmotic parameters on the kinematics of the fluid. The nonlinear Poisson-Boltzmann equation governing the formation of the electrical double layer and the body force that is generated by the applied potential are accounted for in the study. Perturbation solutions are presented. In order to exhibit the applicability of the analysis, the problem of electro-osmotic flow and heat transfer of blood in an arteriole has been taken up as an illustrative example of a real-life problem. An intensive quantitative study has been made through numerical computation of the physical variables involved in the analysis, which are of special interest in the study. The computational results are presented graphically. The study reveals that the temperature of blood can be controlled by increasing/decreasing the Joule heating parameter.     

Evaluation of conditioning responses of thermophilic-mesophilic anaerobically and mesophilic aerobically digested biosolids using rheological properties.

One of the most crucial processes in biosolids management is stabilisation, which is typically accomplished using either anaerobic or aerobic digestion processes. Although there are many advantages to both of these methods--such as reduction of volatile organic matter, pathogen content, and offensive odours--one common disadvantage is that digested biosolids exhibit poor dewaterability characteristics. The deterioration in dewaterability of digested biosolids leads to increases in polymer requirements, connoting higher conditioning costs. Many studies have examined this phenomenon based on conventional filterability tests such as capillary suction time and specific resistance to filtration. However, these test methods are limited in their ability to predict full-scale dewatering behaviour (particularly in centrifugation), and do not regard handling properties as being important for sludge transport. For this purpose, new rheometric methods may assist in predicting sludge behaviour, potentially allowing optimisation of stabilisation and conditioning processes relative to the desired sludge properties. This paper investigates the possible utility of these methods. Classical methods for characterising biosolids, such as filtration tests, are compared with yield stress values and other rheological properties as determined using the steady-shear rate sweep test. The rheological behaviours are compared for different sludge types, including raw and polymer conditioned thermophilic anaerobically, mesophilic anaerobically, and mesophilic aerobically digested biosolids. The paper demonstrates the determination of specific energy values associated with breakdown of the flocculated matrix. Robust modelling approaches are employed to optimise the conditioning of the digested samples, and to shed light on commonly used rheological models such as Bingham, Herschel-Bulkley, and Ostwald equations.     

VIBRATION OF A SINGLE PROTEIN BUBBLE IN BINGHAM LIQUID

The vibration of a single protein bubble may take place under the action of high pressure difference. In this process, the bubble wall may experience a finite deformation. The equation describing the dynamics of the protein bubble with viscoelastic film in Bingham liquid is derived. A numerical solution to this equation is carried out to study the effect of liquid pressure, the characteristic parameters of Bingham liquid and the viscosity of the protein film on the finite deformation of the bubble. The results show that the vibration of the protein bubble wall is caused by the action of pressure difference, the elastic stress in finite deformation and the dissipation of viscosity of the protein film and Bingham liquid. The vibration is nonlinear. Decreasing the pressure difference between gas and Bingham liquid on both sides of the protein bubble will lead to a change of vibration performance. The frequency and amplitude are reduced, tegether with the speed of vibration damping. In addition, the deformation rate of the bubble is smaller when the amplitude of vibration is reduced, which means shorter time to reach a balance state. On the other side, the increase of the magnitude of viscosity of the protein film or the plastic viscosity of Bingham liquid can restrain the vibration of the protein bubble wall in the course of finite deformation, as a result, the load bearing capacity of bubble is enhanced.     

一类非牛顿流体非线性渗流的压力波解析求解方法及波形分析

一类非牛顿流体渗流的视粘度依赖于压力梯度,且在不同的压力梯度区间内变化规律不同。其具有既不同于牛顿流体渗流,也不同于幂律流体渗流和宾汉流体渗流的非线性渗流特征。建立了该流体在多孔介质内部渗流的数学模型并利用行波法推导出了压力波的解析解。通过一系列算例分析了渗流方程控制参数对压力波形的影响,对比了该类流体与牛顿流体渗流的压力波差异。