Solution for the oscillation of a newtonian fluid in a co-axial viscometer

When one cup of a co-axial viscometer oscillates,the measured moment on theother(stationary)cup shows a phase lag,partly due to the inertial effect of the fluidwithin the gap between the cups.In this paper such an effect is illustrated by a newexact solution of the Navier-Stokes equation,which is derived herein by a scheme ofreducing it to a two-point boundary value problem for ODEs,Our numerical resultsindicate that,as the Womersley number a or the dimensionless gap widthδincreases,the fluid velocity profile within the gap gradually deviates from the linear one andtransits to that of the boundary layer type,with the result that the moment decreasesin the magnitude and lags behind in the phase.With the advantage of high accuracyand excellent stability,the scheme proposed herein can readily be extended to solveother linear periodic problems.     

Mixed compatible element and mixed hybrid incompatible element variational methods in dynamics of viscous barotropic fluids

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Effect of magnetic fields on viscous liquid column with finite length in a vertical straight tube

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用聚丙烯酰胺水溶液驱替油溶液的粘性指进现象的研究(Ⅰ)

流度比;驱油溶液;用聚丙烯酰胺水溶液驱替油溶液的粘性指进现象的研究(Ⅰ)     

Localization Phenomena in Liquid-Saturatedand Empty Porous Solids

Localization phenomena occur as a result of local concentrations of plastic deformations in small bands of finite width (shear bands). Porous materials, as, for instance, soil, rock, concrete and sinter materials as well as polymeric and metallic foams exhibit a strong tendency towards shear banding caused by plastic dilatation in the brittle deformation range. This kind of behaviour is of great practical importance in engineering design, for example in the study and computation of failure mechanisms in soil mechanics (base failure, slope failure, etc.). From the mathematical point of view, the computation of localization phenomena, for example within the framework of the finite element method (FEM), yields an ill-posed problem, since each mesh refinement leads to smaller shear bands until one obtains (ideally) a singular surface. Following this, regularization mechanisms should be introduced to obtain reliable and robust results.In the present article, two natural regularization mechanisms for liquid-saturated and empty granular porous materials are discussed. These mechanisms are (1) the inclusion of additional independent degrees of freedom in the sense of the Cosserat brothers for the granular porous solid and (2) the inclusion of pore-fluid viscosity in the saturated case.     

Mixed boundary elements for laminar flows

This paper presents a mixed boundary element formulation of the boundary domain integral method (BDIM) for solving diffusion–convective transport problems. The basic idea of mixed elements is the use of a continuous interpolation polynomial for conservative field function approximation and a discontinuous interpolation polynomial for its normal derivative along the boundary element. In this way, the advantages of continuous field function approximation are retained and its conservation is preserved while the normal flux values are approximated by interpolation nodal points with a uniquely defined normal direction. Due to the use of mixed boundary elements, the final discretized matrix system is overdetermined and a special solver based on the least squares method is applied. Driven cavity, natural and forced convection in a closed cavity are studied. Driven cavity results at Re=100, 400 and 1000 agree better with the benchmark solution than Finite Element Method or Finite Volume Method results for the same grid density with 21×21 degrees of freedom. The average Nusselt number values for natural convection 10³≤Ra≤10⁶ agree better than 0.1% with benchmark solutions for maximal calculated grid densities 61×61 degrees of freedom. Copyright © 1999 John Wiley & Sons, Ltd.     

Investigations of Viscous Dissipation in Stagnation Point Flow Past a Stretchable Riga Wall: Modern Analysis of Heat Transport

This article scrutinizes the features of viscous dissipation in the stagnation point flow past through a linearly stretched Riga wall by implementing Cattaneo-Christov heat flux model. Viscous dissipation is carried out in Cattaneo-Christov diffusion analysis for the first time in this letter. As a result of Cattaneo-Christov model, some extra terms of viscous dissipation are appeared in the energy equation. These extra terms of viscous dissipation are missing in the literature. On the utilization of suitable transformations, the equations governing the problem are reduced under the boundary layer approximation into the non-linear and dimensionless ordinary differential equations. Convergent approach is utilized to solve the dimensionless governing equations. The solution thus acquired is used to highlight the effects of emerging parameters on velocity distribution and fluid's temperature through the graphs. Features of the drag force (or skin friction co-efficient) are graphically interpreted. It is noticed that the presence of modified Hartman number helps to reduce the fluid's temperature but enhances the velocity profile. Further an enlargement in the value of thermal time relaxation parameter helps to decrease the temperature distribution.     

黏滞阻尼器在超高层结构体系中的效率研究

250m以上的超高层结构主要有框架-核心筒、框筒-核心筒和巨型框架-核心筒等三种结构体系．由于超高层结构的高宽比通常较大（5以上）,结构的侧向变形往往成为控制因素．随着消能减震技术的不断成熟,黏滞阻尼器越来越多的应用于建筑结构领域．本文分别将黏滞阻尼器均匀布置在上述三种超高层结构体系中,对比其消能减震效果并分析原因,最后建议了黏滞阻尼器在这些结构中的较优布置．     

黏性水波振荡型行波解的存在性

利用追赶法技巧,研究了倾度为常数的宽矩形通道中黏性水波振荡型行波解的存在性,证明了当黏性系数、摩擦系数、倾度和高度比满足一定关系时,存在唯一的振荡型行波解.由于解析求解的困难,通过数值计算,给出了部分结果,最后进一步讨论了可能存在的振荡型行波解的结构. 关键词： 追赶法 黏性水波 振荡型行波解     

Bianchi Type V Magnetized String Dust Bulk Viscous Fluid Cosmological Model with Variable Magnetic Permeability

Bianchi Type V magnetized string dust bulk viscous fluid cosmological model with variable magnetic permeability, is investigated. The magnetic field is due to an electric current produced along x-axis. Thus the magnetic fields is in yz-plane and F ₂₃ is the only non-vanishing component of electromagnetic field tensor F _ij . To get the deterministic model in terms of cosmic time t, we have also assumed the condition ζ θ=constant where ζ the coefficient of bulk viscosity and θ the expansion in the model. The behaviour of the model in presence and absence of magnetic field and bulk viscosity and singularities in the model are also discussed.