An electron fluid model for the lattice dynamics of metals

An electron fluid model is proposed for the lattice dynamics of metals which satisfies the requirement of translational invariance and the lattice is in equilibrium without recourse to external forces. The model is applied to calculate the phonon dispersion of sodium in the symmetry directions.     

An efficient flexible-order model for 3D nonlinear water waves

The flexible-order, finite difference based fully nonlinear potential flow model described in [H.B. Bingham, H. Zhang, On the accuracy of finite difference solutions for nonlinear water waves, J. Eng. Math. 58 (2007) 211–228] is extended to three dimensions (3D). In order to obtain an optimal scaling of the solution effort multigrid is employed to precondition a GMRES iterative solution of the discretized Laplace problem. A robust multigrid method based on Gauss–Seidel smoothing is found to require special treatment of the boundary conditions along solid boundaries, and in particular on the sea bottom. A new discretization scheme using one layer of grid points outside the fluid domain is presented and shown to provide convergent solutions over the full physical and discrete parameter space of interest. Linear analysis of the fundamental properties of the scheme with respect to accuracy, robustness and energy conservation are presented together with demonstrations of grid independent iteration count and optimal scaling of the solution effort. Calculations are made for 3D nonlinear wave problems for steep nonlinear waves and a shoaling problem which show good agreement with experimental measurements and other calculations from the literature.     

An anisotropic magnetized viscous fluid cosmological model in general relativity

We investigate the behavior of a magnetic field in a viscous fluid cosmological model where the free gravitational field is of Petrov type D and the coefficient of shear viscosity is proportional to the rate of expansion in the model. Also discussed are the behavior of the model when the magnetic field tends to zero and some other physical properties.     

An eight-mode lorenz model of travelling waves in binary fluid convection

An eight-mode truncation of a model of binary fluid convection, allowing travelling wave solutions, is introduced. Qualitatively new dynamics is found, in much closer correspondence with recent experiment than a previous five-mode truncation that is restricted to standing waves.     

A hard sphere fluid model for superionic conductors

We develop a theory for the mobile constituent of a superionic conductor using the Ornstein-Zernike integral equation for the pair correlation function of an inhomogeneous fluid. We solve this equation in the Percus-Yevick approximation using a simple decoupling procedure and hard core potentials. Comparison is made with molecular dynamics calculations on α-AgI.     

An integral model for simulating the environmental effects of water vapour releases from cooling towers

Summary This study presents an integral model for the simulation of the environmental effects produced by wet plumes released by cooling towers associated to large power plants. The environmental impact is evaluated in terms of the increase in the relative humidity at ground level and of the reduction of solar radiation due to the shade projected onto the ground by the visible plume. The paper discusses the parametrization of the model and its application to simulate the consequences of the introduction of a cooling tower in an area characterized by a regime of weak winds. Results are presented in terms of statistics of the plume behaviour over a period of four years. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, Rome, June 19–22, 1984.     

An adaptive GRP scheme for compressible fluid flows

This paper presents a second-order accurate adaptive generalized Riemann problem (GRP) scheme for one and two dimensional compressible fluid flows. The current scheme consists of two independent parts: Mesh redistribution and PDE evolution. The first part is an iterative procedure. In each iteration, mesh points are first redistributed, and then a conservative interpolation formula is used to calculate the cell-averages and the slopes of conservative variables on the resulting new mesh. The second part is to evolve the compressible fluid flows on a fixed nonuniform mesh with the Eulerian GRP scheme, which is directly extended to two-dimensional arbitrary quadrilateral meshes. Several numerical examples show that the current adaptive GRP scheme does not only improve the resolution as well as accuracy of numerical solutions with a few mesh points, but also reduces possible errors or oscillations effectively.     

Variable thickness model for fluid films under large displacement

We propose dynamic nonlinear equations for free thin fluid films. The obtained numerical solutions display a number of features consistent with recent experiments with fluid films under large deformations. In particular, we observe dynamic thickening. Our analysis is based on a two-dimensional model. The film's thickness is represented by the two-dimensional density ρ. We show that a broad range of effects can be captured by a proper internal energy function e(ρ).     

Static aspects of a model for metastable fluid states

A mean field-theory originally presented by Brout is used to obtain the limit of (meta-) stability for a Lennard-Jones system. Certain aspects of the theory are discussed in relation to recent results for liquid-solid phase transitions.     

Time-delayed map as a model for open fluid flow

It is shown that a time-delayed map for just one (chaotic) element whose feedback is periodically interrupted can be exactly mapped to a coupled map lattice model for open fluid flow.     

An oscillator model for hadronization

This article brings together a comparison of the predictions of a model of long standing with experimental data. The model is based on a parallel between quark bound states and a diatom, with the quarks as the atoms and the mesons as the photons. The results are partially already published and partially new. The motivation for this full compilation is the compelling nature of the many phenomena covered correctly by the model’s predictions. Only one parameter is necessary for a complete specification of the model; it is related to the constant relating string length to excitation energy.     

An oscillator model for hadronization

This article brings together a comparison of the predictions of a model of long standing with experimental data. The model is based on a parallel between quark bound states and a diatom, with the quarks as the atoms and the mesons as the photons. The results are partially already published and partially new. The motivation for this full compilation is the compelling nature of the many phenomena covered correctly by the model??s predictions. Only one parameter is necessary for a complete specification of the model; it is related to the constant relating string length to excitation energy.     

A model dipolar ellipsoidal fluid

A theoretical method previously introduced in order to study the structure and thermodynamics of a charged ellipsoidal fluid is here applied to the study of a dipolar ellipsoidal fluid. To enable the strong-coupling (large dipole) form of the direct correlation function to be written analytically, the model employs ellipsoids with charges distributed over their surfaces. This implies that the electric field at a large distance from one molecule results from many multipoles although the dipole is the dominant one. A geometric ansatz for the direct correlation function containing a small number of parameters is then constructed and the parameters determined through the means of a variational principle based upon the mean spherical approximation. From the resultant direct correlation function it is possible to determine thermodynamic properties, including the relative permittivity of the fluid and the electrostatic energy. Within the model no ferroelectric transition is observed. Further the resultant direct correlation function is in a suitable analytic form for applications to the structure of an inhomogeneous fluid. The model is applied to fluids of ellipsoids with elongations ranging between 1/5 (oblate) and 5 (prolate). The range of dipole moments and densities allows relative permitivities up to approximately 80. The results are consistent with other studies of hard dipolar fluids although the model is not precisely the same except in the special case of hard spheres.     

Cosmological mesonic viscous fluid model

A class of exact nonstatic solutions is obtained for Einstein field equations in a closed elliptic Robertson-Walker spacetime filled with viscous perfect fluid in the presence of attractive scalar fields. The solutions characterize strong interaction of elementary particles. It is also shown that the massive graviton possesses zero spin.     

Acoustic force model for the fluid flow under standing waves

An acoustic Strouhal number is introduced to demonstrate that the viscosity of fluid can be ignored in the process of sound propagation and acoustic streaming is independent on the frequency of the acoustic wave. Furthermore, acoustic force based on the periodic velocity fluctuation caused by standing acoustic wave is introduced into Navier–Stokes equation in order to describe the fluid flow in the acoustic boundary layer. The numerical results show that the predicted results are consistent with the analytic solution. And the effect of the nonlinear terms cannot be ignored so the analytic solution derived by boundary-velocity condition is only an approximation for acoustic streaming.     

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。     

地层静温预测的非牛顿流体数学模型

根据热力学参数、泥浆参数及井筒结构参数等，先选定一个地层温度梯度进行计算，得出泥浆出口温度.将此计算值与实测温度值比较，按照比较结果再修正所选的地层温度梯度.如此反复，直到得出合理的地层温度梯度.在此基础上，从热力学及流体力学等有关方程出发， 经过推演得到井壁上温度随深度变化以及地层温度分布的数学模型.由于钻井过程中泥浆、 岩石及其温度场间是相互作用、相互影响的，这为研究热 流 固耦合渗流过程的理论与应 用提供了一种新的方法. 关键词： 温度梯度 非牛顿流体 数学模型