多相非牛顿流体驱替过程的格子Boltzmann模拟

将非牛顿流体模型引入多相格子Boltzmann方法（LBM）,研究多相非牛顿流体的驱替过程.首先以牛顿流体驱替过程作对照,比较非牛顿流体的驱替特性.然后基于简单结构模型,分析不同界面张力下,非牛顿流体的驱替能力和驱替过程中被驱替相的形态变化规律,揭示界面张力的影响机理.结果表明：界面张力在驱替过程中起阻碍作用,其它参数相同情况下,界面张力越低,流体的驱替能力越强.最后,结合四参数随机生长（QSGS）结构生成方法,模拟不同压差、不同界面张力以及不同润湿性条件下多孔复杂结构内的非牛顿多相驱替过程,分析这些参数对过程的影响.     

五维地震油气识别方法*

五维地震流体识别,即利用五维地震资料对复杂储层含流体特征进行识别和描述,为业内研究的前沿和重要难题。该文首先从岩石物理机制出发,研究了含流体各向异性储层参数与物性参数的关系,构建了高敏感参数的各向异性因子f^ani,并验证了该流体因子的合理性以及实用性。其次,利用各向异性反演算法尽可能地挖掘五维地震数据中丰富的方位各向异性信息,反演得到用来表征地下流体的各向异性因子,实了现五维地震流体识别。实际应用结果表明,基于新的各向异性因子及各向异性反演算法能够稳定可靠地从五维地震数据中获取储层流体特征,为五维地震流体识别提供了一套新的理论方法。     

Conformal Killing vectors and FRW spacetimes

Fluid space-times which admit a conformal Killing vector (CKV) are studied. It is shown that even in a perfect fluid space-time a conformal motion will not, in general, map the fluid flow lines onto fluid flow lines; consequently, perfect fluid space-times and, in particular, the simplest perfect fluid space-times known to admit a CKV, namely the Friedmann-Robertson-Walker (FRW) space-times, are studied. A direct proof that there do not exist any special CKV in FRW space-times will be given, thereby motivating the study of the physically more relevant proper CKV. Indeed, one of the principal motivations of the present work is the study of the symmetry inheritance problem for proper CKV. Since the FRW metric can, in general, satisfy the Einstein field equations for a non-comoving imperfect fluid, the relationship between the FRW models (and in particular the standard comoving perfect fluid models) and the conditions under which conformal motions (and in addition homothetic motions) map fluid flow lines onto fluid flow lines are investigated. Finally, further properties of fluid space-times which admit a proper CKV, and in particular space-times in which the CKV is parallel to the fluid four-velocity, are discussed.     

Heat capacities of the dipolar Yukawa model polar fluid

The Stockmayer fluid is often used to describe a polar fluid. The dipolar Yukawa (DY) fluid is also a useful model for such fluids and is convenient for theoretical applications. Here we use the mean spherical approximation (MSA) and perturbation theory (PT) to study the heat capacities of the DY fluid model of a polar fluid and compare these results with Monte Carlo simulations for this model polar fluid. We find that the DY fluid shows the same features as the Stockmayer fluid does; demonstrating the utility of the DY fluid and further finding that the MSA and PT approaches give reasonably accurate results for the heat capacity.     

The Compressible Viscous Surface-Internal Wave Problem: Stability and Vanishing Surface Tension Limit

This paper concerns the dynamics of two layers of compressible, barotropic, viscous fluid lying atop one another. The lower fluid is bounded below by a rigid bottom, and the upper fluid is bounded above by a trivial fluid of constant pressure. This is a free boundary problem: the interfaces between the fluids and above the upper fluid are free to move. The fluids are acted on by gravity in the bulk, and at the free interfaces we consider both the case of surface tension and the case of no surface forces. We establish a sharp nonlinear global-in-time stability criterion and give the explicit decay rates to the equilibrium. When the upper fluid is heavier than the lower fluid along the equilibrium interface, we characterize the set of surface tension values in which the equilibrium is nonlinearly stable. Remarkably, this set is non-empty, i.e., sufficiently large surface tension can prevent the onset of the Rayleigh-Taylor instability. When the lower fluid is heavier than the upper fluid, we show that the equilibrium is stable for all non-negative surface tensions and we establish the zero surface tension limit.     

Exact Solutions for the Flow of Fractional Maxwell Fluid in Pipe-Like Domains

This paper presents an analysis of unsteady flow of incompressible fractional Maxwell fluid filled in the annular region between two infinite coaxial circular cylinders. The fluid motion is created by the inner cylinder that applies a longitudinal time-dependent shear stress and the outer cylinder that is moving at a constant velocity. The velocity field and shear stress are determined using the Laplace and finite Hankel transforms. Obtained solutions are presented in terms of the generalized G and R functions. We also obtain the solutions for ordinary Maxwell fluid and Newtonian fluid as special cases of generalized solutions. The influence of different parameters on the velocity field and shear stress is also presented using graphical illustration. Finally, a comparison is drawn between motions of fractional Maxwell fluid, ordinary Maxwell fluid and Newtonian fluid.     

两个非磁性颗粒在磁流体中的沉降现象研究

在磁场作用下,在磁流体里添加非磁性颗粒(non-magnetic particles,NPs),可以使得NPs形成不同的结构,操控NPs的运动从而影响磁流体的特性,这种应用逐渐受到了研究者的关注.为了更好地操控磁流体里NPs的运动,本文采用一种多物理模型研究在外加磁场作用下,磁流体中两个NPs沉降的运动过程.其中,用格子玻尔兹曼方法模拟磁流体的运动,外加磁场对磁流体的影响用一种自修正方法求解泊松方程,这个自修正方法可以使欧姆定律满足守恒定律.NPs之间的偶极干扰力采用偶极力模型,同时采用一种相对过渡平滑的共轭边界条件处理NPs与磁流体交界面的流固干扰以避免磁场密度过渡的突变.本文主要探究两个NPs在磁流体中的沉降,揭示磁场作用下NPs的相互干扰原理;同时,对控制NPs运动时的参数进行调节,得到NPs不同的运动轨迹,达到操控颗粒运动的目的.本研究可对NPs在磁流体中的应用提供定量的分析结果,对NPs在工业上的应用提供有力的理论支撑.     

Streamer radius model and its assessment using two-dimensionalmodels

The variable radius method is proposed to approximate the radius of the ionization channel in the one and a half-dimensional (1.5-D) fluid models for studying streamer development, in which the unreasonable constant radius in the traditional 1.5-D fluid models is corrected. The streamer development and propagation between the 1.5-D fluid model with the variable radius method and the two-dimensional (2-D) fluid model using the same initial and external conditions are compared. The radius in each stage of streamer development from the 1.5-D fluid model with the variable radius method shows agreement to a certain degree with that of the 2-D fluid model. The purpose of this paper is not to negate the role of the 2-D fluid models, but to explore the potential of the 1.5-D fluid models and make them more useful and accurate as well as to understand the evolution of streamer radius. The streamer development from the 1.5-D fluid model with the variable radius method not only maintains simplicity of the 1.5-D fluid models, but also presents agreement with the 2-D fluid models for streamers     

非对称纳米通道内流体流动与传热的分子动力学

采用分子动力学方法研究了流体在非对称浸润性粗糙纳米通道内的流动与传热过程,分析了两侧壁面浸润性不对称对流体速度滑移和温度阶跃的影响,以及非对称浸润性组合对流体内部热量传递的影响.研究结果表明,纳米通道主流区域的流体速度在外力作用下呈抛物线分布,但是纳米通道上下壁面浸润性不对称导致速度分布不呈中心对称,同时通道壁面的纳米结构也会限制流体的流动.流体在流动过程中产生黏性耗散,使流体温度升高.增强冷壁面的疏水性对近热壁面区域的流体速度几乎没有影响,滑移速度和滑移长度基本不变,始终为锁定边界,但是会导致近冷壁面区域的流体速度逐渐增大,对应的滑移速度和滑移长度随之增大.此时,近冷壁面区域的流体温度逐渐超过近热壁面区域的流体温度,流体出现反转温度分布,流体内部热流逆向传递.随着两侧壁面浸润性不对称程度增加,流体反转温度分布更加明显.     

Fallopian tube analysis of the peristaltic-ciliary flow of third grade fluid in a finite narrow tube

The present prospective theoretical investigation deals with analysis of the peristaltic-ciliary transport of a developing embryo within the fallopian tubal fluid in the human fallopian tube. A mathematical model of peristalsis-cilia induced flow of viscoelastic fluid characterized by the third grade fluid model within the fallopian tubal fluid in a finite two dimensional narrow tube is developed. Non-linear partial differential equation resulting from the modelling of the proposed model is solved using perturbation method. Flow variables like axial and radial velocities, appropriate residue time over tube length, pressure difference over wavelength and stream function are analyzed for embedded parameters and constants. Salient features of the pumping characteristics and trapping phenomenon are discussed in detail. The analysis showed that embedded parameters and constants have opposite effects on axial velocity and appropriate residue time over tube length. Moreover, a comparison of the peristaltic flow with the peristaltic-ciliary flow and the third grade fluid with the linearly viscous fluid is made as a special case. The relevance of the current results to the transport of a developing embryo within the fallopian tubal fluid is also explored. It reveals that, third grade fluid instead of the linearly viscous fluid and the inclusion of cilia along with peristalsis help to complete the required mitotic divisions while transporting the developing embryo within the fallopian tubal fluid in the human fallopian tube.     

Hydrodynamic fluctuation forces

We consider the fluctuating hydrodynamics of Landau and Lifshitz for a fluid confined by hard walls at finite distance. By considering the non-linearity of the stochastic fluid equations of motion, we show that there can be an inhomogeneous average stress set up throughout the fluid. The average stress corresponds to a force density on the fluid which is expressed in terms of the Green's function for the fluid in the linearized theory. For simple geometries we obtain the average stress explicitly as a long range pressure field. The effect can be interpreted as a long range effective force acting between the fluid boundaries. In this sense it might have observable consequences in thin films or in suspensions of hard colloid particles. The effect is strongest in incompressible fluids. It is greatly weakened by compressibility but relaxation of the fluid viscosity prevents the effect vanishing.     

Perfect fluid and scalar field in the Reissner-Nordström metric

We describe the spherically symmetric steady-state accretion of perfect fluid in the Reissner-Nordström metric. We present analytic solutions for accretion of a fluid with linear equations of state and of the Chaplygin gas. We also show that under reasonable physical conditions, there is no steady-state accretion of a perfect fluid onto a Reissner-Nordström naked singularity. Instead, a static atmosphere of fluid is formed. We discuss a possibility of violation of the third law of black hole thermodynamics for a phantom fluid accretion.     

Experimental simulation of a liquid-metal heat-transfer fluid flow in a T-shaped mixer

The structure of the temperature field in a liquid-metal heat-transfer fluid flowing through a T-shaped mixer is studied experimentally. The experiments are carried out using Rose’s alloy as a working fluid. To find the temperature distribution over the wall of a working section, IR thermography is applied. It is shown that the wall temperature distribution in the zone where fluid flows with different temperatures mix is heavily nonuniform. The temperature distribution substantially depends on the ratio between the hot and cold fluid flow rates. The results can be used to verify the thermal hydraulic computational codes for fluid metal flows.     

Plane waves in noncommutative fluids

We study the dynamics of the noncommutative fluid in the Snyder space perturbatively at the first order in powers of the noncommutative parameter. The linearized noncommutative fluid dynamics is described by a system of coupled linear partial differential equations in which the variables are the fluid density and the fluid potentials. We show that these equations admit a set of solutions that are monochromatic plane waves for the fluid density and two of the potentials and a linear function for the third potential. The energy–momentum tensor of the plane waves is calculated.     

Electrohydrodynamic wave-packet collapse and soliton instability for dielectric fluids in (2 + 1)-dimensions

In this paper we introduce a modified lattice Boltzmann model (LBM) with the capability of mimicking a fluid system with dynamic heterogeneities. The physical system is modeled as a one-dimensional fluid, interacting with finite-lifetime moving obstacles. Fluid motion is described by a lattice Boltzmann equation and obstacles are randomly distributed semi-permeable barriers which constrain the motion of the fluid particles. After a lifetime delay, obstacles move to new random positions. It is found that the non-linearly coupled dynamics of the fluid and obstacles produces heterogeneous patterns in fluid density and non-exponential relaxation of two-time autocorrelation function.Received: 19 March 2004, Published online: 29 June 2004PACS: 47.11. + j Computational methods in fluid dynamics - 05.70.Ln Nonequilibrium and irreversible thermodynamics     

复合液腔高灵敏度水听器

探索新的换能器结构是提高换能器性能的主要途径之一。设计了一种利用液腔结构提高接收灵敏度的水听器,称为复合液腔水听器。该水听器用压电陶瓷圆管作为敏感材料,并将其放在一个底部开孔的金属圆桶内。在流体中,开孔圆桶形成两个频率不同的液腔谐振模态,并与压电陶瓷圆管的径向谐振模态衔接在一起,形成具有一定带宽的高接收灵敏度频段。采用有限元方法对水听器进行了优化设计并研制了水听器样机。水池测试结果表明,该水听器样机在1.5 k Hz～11.5 k Hz频率范围内灵敏度保持在-185 d B以上,比传统的压电陶瓷圆管水听器结构具有显著优势。     

Experimental analysis on MR fluid channel flow dynamics with complex fluid-wall interactions

MR fluid plugging performance by aggregation of magnetized particles in MR fluid is recently expected to be one of the most promising applications in medical or safety devices, such as blood flow control, steam issuing shut-down valve and fuel supply control for automobile. In this study, dynamic response of MR fluid plugging and its breakdown in a pressure mode with complex fluid-wall interactions was experimentally investigated, considering the effects of magnetic flux density, wall surface structure, wall permeability and wall elasticity of tube. Higher endurance pressure is obtained for wall surface groove structure and for steel wall due to a strong anchoring effect by rigid cluster formation in a concave region and strong MR fluid column formation in a channel core region, respectively. Furthermore, MR fluid plugging performance and the fluid storage characteristic of PVA tube as a bio-material was clarified. Because of the large radial expansion of the tube at the applied magnetic region in a pressure mode, PVA tube shows unique characteristics, such as storing MR fluid under magnetic field and MR fluid jet issuing under releasing magnetic field.     

井下核磁共振流体分析实验室及其应用

井下流体分析在储层实时评价有十分重要的应用. 该文介绍了NMR流体分析实验室的发展,并以哈里伯顿的井下NMR流体分析实验室为例, 详细讨论了其关键技术,包括探头结构、磁体结构和电路结构,探讨了获取流体核磁共振特性参数的测量方法. NMR流体分析实验室可以获取流体的多种重要参数,结合NMR测井能够进行综合解释,其实时评价性能实现NMR测量的优势.     

General symmetries of a string fluid space-time

It is shown that a string fluid is the simplest anisotropic fluid with vanishing heat flux. Furthermore it has the property that the Ricci tensor is obtained from the energy momentum tensor, and vice versa, if one interchanges the fluid variables. We use previous works on the collineations of anisotropic fluids, which include the string fluid as a particular case, to compute the kinematic and the dynamic effects of certain collineations of a string fluid. It is found that the possible spacetimes, which can carry a string fluid, are severely restricted and the possible string fluids in spacetimes, which can admit them are more or less fixed. We recover previous results on the effect of symmetries in string fluid spacetimes and get many new ones, for example the matter inheritance collineations. The study and the results are presented in a systematic manner, which allows the comprehension and the comparison of the restrictions imposed by each collineation. Finally one can use the same method of work for a systematic study of similar problems.     

Heuristic optimality criterion algorithm for shape design of fluid flow

This paper presents a heuristic optimality criterion algorithm for shape design of fluid flow. In this algorithm, the lattice Boltzmann method (LBM) is utilized to calculate the flow field of a fluid domain which is divided into elemental cells. A heuristic optimality criterion is applied for cells at the solid–fluid interface, i.e. the dynamic pressure for fluid cells and the viscous stress on their neighboring solid cells. An automatic program is processed step by step to exchange the positions of solid and fluid cells identified by the optimality criterion, with the objective of decreasing the flow resistance at the constraint of constant fluid volume. To illustrate the procedure of this algorithm for shape design of fluid flow, two simple examples are presented: one with fluid flowing through a right angle elbow and the other through a converging T-junction. Numerical results show that this algorithm can successfully reduce the total pressure drop of the system, demonstrating its potential applications in engineering optimal design.