基于Poiseuille流动的汽车磁流变减振器分析与测试

利用牛顿流体模型和滨汉流体模型,对基于Poiseuile流动的汽车磁流变减振器进行了分析,设计制作了微型汽车磁流变减振器,并对此进行了测试,测试结果表明：所提出的分析方法是可行的,对设计汽车磁流变减振器有一定的指导意义。     

Associating fluids with four bonding sites against a hard wall: density functional theory

We present two new perturbation density functional theories to investigate non-uniform fluids of associating molecules. Each fluid molecule is modelled as a spherical hard core with four highly anisotropic square well sites placed in tetrahedral symmetry on the hard core surface. In one theory we apply the weighting from Tarazona's hard sphere density functional theory to Wertheim's bulk first-order perturbation theory. The other theory uses the inhomogeneous form of Wertheim's theory as a perturbation to Tarazona's hard-sphere density functional theory. Each theory approaches Tarazona's theory in the limit of zero association. We compare results from theory and simulation for density profiles, fraction of monomers, and adsorption of an associating fluid against a hard, smooth wall over a range of temperatures and densities. The non-uniform fluid theory which uses Tarazona's weighting of Wertheim's theory in the bulk is in good agreement with computer simulation results.     

Percus-Yevick theory and the Chandler-Weeks-Andersen reference fluid

Chandler, Weeks and Andersen have recently developed a successful perturbation theory of liquids. In their theory, the radial distribution function of the reference fluid is calculated from that of the hard-sphere fluid. In their published work, the Percus-Yevick theory is used to calculate the hard-sphere radial distribution function. In this paper, the Percus-Yevick theory is used to calculate directly the thermodynamic properties and radial distribution function of the reference fluid. If the Carnahan and Starling averaging procedure is used, the Percus-Yevick thermodynamic properties are excellent. However, the radial distribution function shows the same discrepancies as that of Chandler, Weeks and Andersen. Finally, recent calculations of Chandler, Weeks and Andersen, using the Monte Carlo estimates of the hardsphere radial distribution function are shown to give good results for the reference fluid distribution function. This indicates that the Percus-Yevick theory, rather than fundamental errors in the Chandler, Weeks and Andersen theory, is responsible for the discrepancies.     

Dynamics of finite-length tubular beams conveying fluid

The dynamics and stability of short tubes conveying fluid is re-examined by means of Timoshenko beam theory for the tube and a three-dimensional fluid-mechanical model for the fluid flow, rather than the plug-flow model utilized heretofore. The tubes considered are either clamped at both ends or cantilevered; in the latter case, special “outflow models” were introduced to describe the boundary conditions on the fluid exiting from the free end. By comparison with experiments, it is shown that this refined theory is necessary for describing adequately the dynamical behaviour of extremely short tubes, although Timoshenko beam theory together with a plug-flow model are quite satisfactory for relatively longer short tubes; for long tubes, Euler-Bernoulli beam theory and a plug-flow model are perfectly adequate.     

Statistical thermodynamics of bulk and surface properties of polymer mixtures

A generalized version of the lattice fluid theory of solutions is considered. Necessary and sufficient conditions for phase stability in a binary mixture are defined by a spinodal inequality. From the general properties of the spinodal, the necessary conditions for polymer/polymer miscibility and bimodal behavior of the spinodal are defined. A general theory of interfacial tension in phase separated multi-component mixtures is formulated. The interfacial tension theory can be combined with lattice fluid theory to obtain a unified theory of bulk and interfacial properties.     

改进的孔隙模型评价流体性质与裂缝孔隙度

随着勘探开发的不断深入,渤海油田面临越来越多的疑难储层,这类储层流体性质识别与裂缝孔隙度评价成为测井评价的难点。本文依据Biot理论,描述了存在裂隙条件下的含裂隙Biot理论,形成改进的孔隙介质模型。根据该模型利用阵列声波测井数据进行反演得到裂缝孔隙度,同时通过流体置换,得到不同流体对应的岩石体积模量,对其进行交会判别流体性质,实现了阵列声波测井裂缝孔隙度定量评价与流体性质识别综合应用。利用该模型对渤海油田十几口井进行计算,结果表明该方法对于常规砂泥岩和复杂岩性储层均能取得较好效果,本文提出的储层流体性质识别与裂缝孔隙度评价方法,有助于扩展阵列声声波测井的应用范围。     

Thermodynamic properties of inhomogeneous fluids

A general method, the method of variation under extension, is presented for expressing the thermodynamic properties of an inhomogeneous fluid as functionals of the local number density, when given a density functional for the total thermodynamic grand potential of the fluid. The method is demonstrated in detail for the van der Waals square-gradient density functional and for the nonlocal density functional which arises in the theory of fluids with long-ranged pair potentials or in the mean-field theory of penetrable-sphere models. As specific examples, we consider the planar and spherical interface between two fluid phases, the line of contact of three fluid phases, the contact line between two surface phases and the planar interface between a solid and fluid.     

The correlations in a star molecule fluid. Integral equation theory and Monte Carlo study

The structure of a starlike molecule (SLM) fluid with four arms of different length is studied by applying the associative Percus–Yevick integral equation (IE) theory and canonical Monte Carlo (MC) simulations. In the IE study the SLM fluid is modelled by a fluid of hard spheres with four associative sites on each sphere while the MC has been performed for a freely-joined tangent hard sphere fluid. The total radial distribution functions have been calculated in both approaches for different volume fraction regimes and different arm lengths. It is shown that the associative IE theory predicts the structure of SLM fluid best for relatively long arms and at high densities. Additionally, the dependence of the SLM centre–centre correlations on the functionality and fluid particle density has been analysed using the MC results.     

三层密度分层流体毛细重力波二阶Stokes波解

以小振幅波理论为基础,利用摄动方法研究了三层密度分层流体的毛细重力波,给出了三层成层状态下各层流体速度势的二阶渐近解及毛细重力波波面位移的二阶Stokes波解.结果表明:一阶解及二阶解除了依赖于各层流体的厚度及密度,与表面张力也有很重要的关系.     

On pore-fluid viscosity and the wave properties of saturated granular materials including marine sediments

The grain-shearing (GS) theory of wave propagation in a saturated granular material, such as a marine sediment, is extended to include the effects of the viscosity of the molecularly thin layer of pore fluid separating contiguous grains. An equivalent mechanical system consisting of a saturating, strain-hardening dashpot in series with a Hookean spring represents the intergranular interactions. Designated the VGS theory, the new model returns dispersion curves that differ mildly from those of the GS theory at lower frequencies, below 10 kHz, where effects due to the viscosity of the pore fluid may be non-negligible. At higher frequencies, the VGS dispersion curves approach those of the GS theory asymptotically. The VGS theory is shown to match the SAX99 dispersion curves reasonably well over the broad frequency band of the measurements, from 1 to 400 kHz. This includes the frequency regime between 1 and 10 kHz occupied by Schock's chirp sonar data, where the viscosity of the pore fluid appears to have a discernible effect on the dispersion curves.     

Diffusion within a near-critical nanopore fluid

Results are presented for grand canonical Monte Carlo (GCMC) and both equilibrium and non-equilibrium molecular dynamics simulations (EMD and NEMD) conducted over a range of densities and temperatures that span the two-phase coexistence and supercritical regions for a pure fluid adsorbed within a model crystalline nanopore. The GCMC simulations provided the low temperature coexistence points for the open pore fluid and were used to locate the capillary critical temperature for the system. The equilibrium configurational states obtained from these simulations were then used as input data for the EMD simulations in which the self-diffusion coefficients were computed using the Einstein equation. NEMD colour diffusion simulations were also conducted to validate the use of a system averaged Einstein analysis for this inhomogeneous fluid. In all cases excellent agreement was observed between the equilibrium (linear response theory) predictions for the diffusivities and non-equilibrium colour diffusivities. The simulation results are also compared with a recently published quasi-hydrodynamic theory of Pozhar and Gubbins (Pozhar, L. A., and Gubbins, K. E., 1993, J. Chem. Phys., 99, 8970; 1997, Phys. Rev. E, 56, 5367.). The model fluid and the nature of the fluid wall interactions employed conform to the decomposition of the particle–particle interaction potential explicitly used by Pozhar and Gubbins. The local self-diffusivity was calculated from the local fluid–fluid and fluid wall hard core collision frequencies. While this theory provides reasonable results at moderate pore fluid densities, poor agreement is observed in the low density limit.     

Theory of Brownian motion in a Jeffreys fluid

We have constructed a kinetic theory of Brownian motion in a rheologically complex medium—a Jeffreys fluid that is characterized by a combination of two viscosity mechanisms: ordinary and delayed. This model is shown to be much better suited for the interpretation of experiments on the microrheology of viscoelastic media than the standard Maxwell model. In particular, no oscillations of the mean-square particle displacement arise in a Jeffreys fluid, which is a nonremovable artifact of the theory of Brownian motion in a Maxwell fluid. The developed approach can to be used also consider the diffusion of particles in other complex fluids whose rheology is described by phenomenological schemes.     

DYNAMICS BEHAVIOR OF AXISYMMETRIC AND BEAM-LIKE ANISOTROPIC CYLINDRICAL SHELLS CONVEYING FLUID

The flow-induced vibration characteristics of anisotropic laminated cylindrical shells partially or completely filled with liquid or subjected to a flowing fluid are studied in this work for two cases of circumferential wave number, the axisymmetric, where n=0 and the beam-like, where n=1. The shear deformation effects are taken into account in this theory; therefore, the equations of motion are determined with displacements and transverse shear as independent variables. The present method is a combination of finite element analysis and refined shell theory in which the displacement functions are derived from the exact solution of refined shell equations based on orthogonal curvilinear co-ordinates. Mass and stiffness matrices are determined by precise analytical integration. A finite element is defined for the liquid in cases of potential flow that yields three forces (inertial, centrifugal and Coriolis) of moving fluid. The mass, stiffness and damping matrices due to the fluid effect are obtained by an analytical integration of the fluid pressure over the liquid element. The available solution based on Sanders' theory can also be obtained from the present theory in the limiting case of infinite stiffness in transverse shear. The natural frequencies of isotropic and anisotropic cylindrical shells that are empty, partially or completely filled with liquid as well as subjected to a flowing fluid, are given. When these results are compared with corresponding results obtained using existing theories, very good agreement is obtained.     

Gradient theory of fluid microstructures

The general gradient theory of fluid microstructures is outlined. This theory reduces the determination of fluid microstructures to a boundary value problem. The density and pressure tensor profiles and the tension of planar thin films and layered structures in one-component fluids are investigated. The boundary conditions determining these structures are given a geometric interpretation in the free energy-density diagram. Discussed are the implications of the theory for the validity of Antonov's rule, the duplex film hypothesis, and the asymptotic theory of disjoining pressure and of the origin of a characteristic length scale in spinodal decomposition.This work was supported financially by the U.S. Department of Energy and the National Science Foundation.     

Analysis of a compliantly suspended acoustic velocity sensor

The dynamics of a compliantly suspended acoustic velocity sensor having a spherical geometry are analyzed using theory and experiment. The analysis starts with a review of the motion associated with an unconstrained solid sphere when subjected to an acoustic plane wave in an unbounded inviscid fluid medium. The theory is then modified to account for the inclusion of an inertial sensor and an external suspension system. Accordingly, the open-circuit receiving response of a geophone-based and accelerometer-based device is derived. Density variations associated with the sphere and the surrounding fluid medium are assessed along with the effects fluid viscosity. Wave effects in the sphere and the suspension system are also analyzed.     

Generalized model of a fluid with spin

A generalized variational theory of a classical ideal fluid with spin is developed. Compared with the Weyssenhoff-Raabe model, the new theory takes into account interaction of the spin of the elements of the fluid with one another and with external fields.Translated from Izvestiya Vysshikh Uchebnykh, Zavedenii, Fizika, No. 2, pp. 98–101, February, 1991.