青藏高原地壳的伸缩及其力学性质

根据青藏高原地壳厚度，采用平衡剖面法对地壳伸缩量进行了粗略的计算，表明其水平缩短约 １４００ｋｍ ， 垂直方向伸张约 ３０ｋｍ 或２５ｋｍ 。如此巨大的地壳伸缩量证明了青藏高原地壳为弹粘性体， 绝非所谓的刚性板块。

Modeling and analysis of azimuthal AVO responses from a viscoelastic anisotropic reflector

We propose a method for mOdeling azimuthal AVO responses from a fractured i reflector. The method calculates the integrated reflected wavetrains, and the wavetrains contain elastodynamic information including the contrast in impedance and anelasticity i across interfaces, the intemal anisotropic propagation, the dispersion and attenuation along i the wave path, and tuning and interference. The results suggest that for large angles of incidence, the velocity dispersion and attenuation increase the amplitudes of PP waves from the top and decrease those from the bottom. For azimuthal responses at specific angles of incidence, the reflected wavetrains of PP waves tend to have longer duration with increasing azimuth. In contrast, model-converted PSV and PSH reflections show stable azimuthal features and are less affected by the reflector thickness. The amplitudes of PSV reflections increase with increasing azimuth; moreover, the waves have no reflection energy at 0° and 90° azimuth and maximum amplitude at 45° azimuth.

Theoretical Study on the Temporary Cavity Caused by a High Speed Projectile When Wounding Living Organisms

Analyzes and calculates the process of development of a temporary cavity in the muscle directly after a projectile wounds organisms at a high speed. The muscle is taken as a non compressible Voigt Kelvin viscoelastic fluid model, on the assumption of moving in a radial direction and on spherical symmetry, a theoretical model proposed using the basic equations of the non Newtonian fluid mechanics. The model can well describe the pulsation process of the temporary cavity and changes of pressure in the cavity. The calculated results are in correspondence with the experimental results. The model can be applied in the quantitative analysis of a temporary cavity.

Slip flow and variable properties of viscoelastic fluid past a stretching surface embedded in a porous medium with heat generation

This study examines theoretically and computationally the non-Newtonian boundary layer flow and heat transfer for a viscoelastic fluid over a stretching continuous sheet embedded in a porous medium with variable fluid properties, slip velocity, and internal heat generation/absorption. The flow in boundary layer is considered to be generated solely by the stretching of the sheet adjacent to porous medium with boundary wall slip condition. Highly nonlinear momentum and thermal boundary layer equations governing the flow and heat transfer are reduced to set of nonlinear ordinary differential equations by appropriate transformation. The resulting ODEs are successfully solved numerically with the help of shooting method. Graphical results are shown for non-dimensional velocities and temperature. The effects of heat generation/absorption parameter, the porous parameter, the viscoelastic parameter, velocity slip parameter, variable thermal conductivity and the Prandtl number on the flow and temperature profiles are presented. Moreover, the local skin-friction coefficient and Nusselt number are presented. Comparison of numerical results is made with the earlier published results under limiting cases.

Existence and uniqueness theorem for flow and heat transfer of a non-Newtonian fluid over a stretching sheet

Analysis is carried out to study the existence, uniqueness and behavior of exact solutions of the fourth order nonlinear coupled ordinary differential equations arising in the flow and heat transfer of a viscoelastic, electrically conducting fluid past a continuously stretching sheet. The ranges of the parametric values are obtained for which the system has a unique pair of solutions, a double pair of solutions and infinitely many solutions.

Non-Newtionian Effects on Chaotic Mixing Between Eccentric Cylinders

Effect of fluid elasticity and shear-thinning viscosity on the chaotic mixing between two alternately rotating cylinders has been studied. The h-p finite element method is used to obtain high accurate solutions of the steady flow. The unsteady, periodic flow is simulated using the piecewise-steady approximation. Characteristics of the chaotic mixing are analyzed by examining the asymptotic coverage of a passive tracer and the lineal stretching of the fluid elements in the annulus. For the viscoelastic fluids modeled by the upper-convected Maxwell constitutive equation (UCM), our computation predicts little effect of the fluid elasticity on the mixing patterns. On the other hand, the shear-thinning viscosity, modeled by the Carreau equation, has a large impact on the advection of a passive tracer and the distribution of lineal stretching. We find that the zones of the lowest stretching match remarkably well with the regular zones in the tracer-coverage plotting. Our study reveals the vital importance of reducing the discretization errors of the velocity field in the numerical simulation of chaotic flews.

MHD three dimensional flow of viscoelastic fluid with thermal radiation and variable thermal conductivity

The objective of the present work is to model the magnetohydrodynamic(MHD) three dimensional flow of viscoelastic fluid passing a stretching surface. Heat transfer analysis is carried out in the presence of variable thermal conductivity and thermal radiation. Arising nonlinear analysis for velocity and temperature is computed. Discussion to importantly involved parameters through plots is presented. Comparison between present and previous limiting solutions is shown. Numerical values of local Nusselt number are computed and analyzed. It can be observed that the effects of viscoelastic parameter and Hartman number on the temperature profile are similar in a qualitative way. The variations in temperature are more pronounced for viscoelastic parameter K in comparison to the Hartman number M. The parameters N and ε give rise to the temperature. It is interesting to note that values of local Nusselt number are smaller for the larger values of ε.

A triaxial creep model for coal containing gas and its stability analysis

Triaxial creep tests on CCG specimens were systematically performed using aself-made creep seepage experimental apparatus for determining the creep law of CCG.An improved triaxial creep model of CCG was established on the basis of a Nishiharamodel and another visco-elasto-plastic model,parameters of which were fitted on test data.Furthermore,the creep model is validated according to the result of triaxial creep experiments,and the outcome shows that the proposed triaxial creep model can properly characterizethe properties of various creep deformation phases of CCG,especially the acceleratingcreep phase.At the same time,the instability conditions of CCG were presentedbased on the discussion of the improved model's stability in terms of stability theories ofdifferential equation solution.

Nonlinear dynamic characteristics of magneto-rheological visco-elastomers

The smart magneto-rheological visco-elastomer (MRVE) has a promising application to vibration control.Its dynamic characteristics are described by complex moduli which are applicable to linear dynamics.However,experimental results show remarkable nonlinear relations between force and deformation for certain large deformations,and the nonlinear dynamic modeling needs to be developed.The present study focuses on the nonlinear dynamic characteristics of MRVE.The MRVE was fabricated and specimens were tested to show nonlinear mechanical properties and dynamic behaviors.The nonlinear effect induced by applied magnetic fields was investigated.A phenomenological model for the dynamic behaviors of MRVE was proposed to describe the nonlinear elasticity,linear damping and hysteretic effect,and the corresponding equivalent linear model in the frequency domain was also given for small deformations.The proposed model is applicable to the dynamics and control analysis of composite structures with MRVE.

Analysis of heat transfer performance for turbulent viscoelastic fluid-based nanofluid using field synergy principle

In this paper,the field synergy principle is firstly performed on the viscoelastic fluid-based nanofluid and other relevant fluid in channel at turbulent flow state to scrutinize their heat transfer performance based on our direct numerical simulation database.The cosine values of intersection angle between velocity vector and temperature gradient vector are calculated for different simulated cases with varying nanoparticle volume fraction,nanoparticle diameter,Reynolds number and Weissenberg number.It is found that the filed synergy effect is enhanced when the nanoparticle volume fraction is increased,nanoparticle diameter is decreased and Weissenberg number is decreased,i.e.the heat transfer is also enhanced.However,the filed synergy effect is weakened with the increase of Reynolds number which may be the possible reason for the power function relationship in empirical correlation of heat transfer between heat transfer performance and Reynolds number with the constant power exponent lower than 1.Finally,it is also observed that the field synergy principle can be used to analyze the heat transfer process of viscoelastic fluid-based nanofluid at the turbulent flow state even if some negative cosine values of intersection angle exist in the flow field.

Time Periodic Electroosmotic Flow of The Generalized Maxwell Fluids in a Semicircular Microchannel

Analytical solutions are presented using method of separation of variables for the time periodic electroosmotic flow (EOF) of linear viscoelastic fluids in semicircular microchannel. The linear viscoelastic fluids used here are described by the general Maxwell model. The solution involves analytically solving the linearized Poisson-Boltzmann (P -B) equation, together with the Cauchy momentum equation and the general Maxwell constitutive equation. By numerical computations, the influences of electric oscillating Reynolds number Re and Deborah number De on velocity amplitude are presented. For small Re, results show that the larger velocity amplitude is confined to the region near the charged wall when De is small. With the increase of the Deborah number De, the velocity far away the charged wall becomes larger for large Deborah number De. However, for larger Re, the oscillating characteristic of the velocity amplitude occurs and becomes significant with the increase of De, especially for larger Deborah number.

Micro-macro models for viscoelastic fluids： modelling, mathematics and numerics Dedicated to the NSFC-CNRS Chinese-French summer institute on fluid mechanics in 2010

This paper is an introduction to the modelling of viscoelastic fluids, with an emphasis on micromacro （or multiscale） models. Some elements of mathematical and numerical analysis are provided. These notes closely follow the lectures delivered by the second author at the Chinese Academy of Science during the Workshop ＂Stress Tensor Effects on Fluid Mechanics＂ in January 2010.

Heat transfer analysis of viscoelastic fluid flow due to metachronal wave of cilia

This study describes ciliary motion on the transport of fluids in human body with heat transfer. The mathematical model of the flow of a Jeffrey fluid in a tube of finite length is considered due to metachronal wave of cilia motion. Flow equations have been modeled and simplified using similarity variables. Exact solutions of the formulated problem have been obtained for velocity, temperature and pressure gradient and graphs for velocity, pressure rise pressure gradient and temperature profile have been plotted and studied for different values of specific physical parameters. Trapping phenomena and isotherms are presented at the end of the paper.

Mixed Convective Viscoelastic Nanofluid Flow Past a Porous Media with Soret–Dufour Effects

The present study is carried out to see the thermal-diffusion(Dufour) and diffusion-thermo(Soret) effects on the mixed convection boundary layer flow of viscoelastic nanofluid flow over a vertical stretching surface in a porous medium. Optimal homotopy analysis method(OHAM) is best candidate to handle highly nonlinear system of differential equations obtained from boundary layer partial differential equations via appropriate transformations. Graphical illustrations depicting different physical arising parameters against velocity, temperature and concentration distributions with required discussion have also been added. Numerically calculated values of skin friction coefficient, local Nusselt and Sherwood numbers are given in the form of table and well argued. It is found that nanofluid velocity increases with increase in mixed convective and viscoelastic parameters but it decreases with the increasing values of porosity parameter. Also, it is observed that Dufour number has opposite behavior on temperature and concentration profiles.

Experimental Study for Pressure Drop of Viscoelastic Fluids through Periodically Sudden Converging－Diverging Tube

The purpose of this work is to investigate experimentally the pressure drop of drag-reducing polymer solutions in the fully developed flow region in a periodically sudden converging-diverging tube as well as in a straight tube.Testing fluids were aqueous polyacrylamide solutions with concentration ranged from 200 to 1400 w.p.p.m.,and the Reynolds number ranged from 5 x 103 to 7 x 104.Drag-reducing phenomenon is found to exist in the straight tube flow with the viscoelastic fluid,while in the periodically sudden converging-diverging tube the friction factor is insensitive to the concentration of solution

Prediction of fish body's passive visco-elastic properties and related muscle mechanical performance in vivo during steady swimming

For attaining the optimized locomotory performance of swimming fishes,both the passive visco-elastic properties of the fish body and the mechanical behavior of the active muscles should coordinate with the fish body’s undulatory motion pattern.However,it is difficult to directly measure the visco-elastic constitutive relation and the muscular mechanical performance in vivo.In the present paper,a new approach based on the continuous beam model for steady swimming fish is proposed to predict the fish body’s visco-elastic properties and the related muscle mechanical behavior in vivo.Given the lateral travelling-wave-like movement as the input condition,the required muscle force and the energy consumption are functions of the fish body’s visco-elastic parameters,i.e.the Young’s modulus E and the viscosity coefficient in the Kelvin model.After investigating the variations of the propagating speed of the required muscle force with the fish body’s visco-elastic parameters,we analyze the impacts of the visco-elastic properties on the energy efficiencies,including the energy utilization ratios of each element of the kinematic chain in fish swimming and the overall efficiency.Under the constraints of reasonable wave speed of muscle activation and the physiological feasibility,the optimal design of the passive visco-elastic properties can be predicted aiming at maximizing the overall efficiency.The analysis is based on the small-amplitude steady swimming of the carangiform swimmer,with typical Reynolds number varying from 2.5×104to 2.5×105,and the present results show that the non-dimensional Young’s modulus is 112±34,and the non-dimensional viscosity coefficient is 13 approximately.In the present estimated ranges,the overall efficiency of the swimming fish is insensitive to the viscosity,and its magnitude is about 0.11±0.02,in the predicted range given by previous study.

On the some issues of particle motion in the flow of viscoelastic fluids

Particle motion in confined shear flow of viscoelastic fluids is very common in nature and has a wide range of applications.Understanding and mastering the motion characteristics of particles in viscoelastic fluids has important academic value and practical significance.In this paper,we first introduce the related equations and characteristic parameter,and then emphasize the following issues:the lateral equilibrium position of particle;interaction and aggregation of multiple particles;the chain structure formed by multiple particles;and the motion of non-spherical particle.Finally,some unresolved issues,challenges,and future research directions are highlighted.

Effects of mass layer imperfect bonding on the electrical impedance of a quartz crystal microbalance

We study electrically forced vibrations of a crystal plate of AT-cut quartz carrying a thin mass layer operating as a quartz crystal microbalance for mass sensing.The mass layer is imperfectly bonded to the crystal plate with their interface described by the so-called interface-slip model which allows a discontinuity of the tangential interface displacement.Mindlin’s equations for piezoelectric plates are used.An analytical solution is obtained.The electrical impedance is calculated.The effects of an elastic interface and a viscoelastic interface are examined.

Model for mucus transport in the airways due to air motion： Effect of slipperiness

In this paper, a circular three-layer flow model is proposed to study mucus transport in the airways due to air motion caused by mild forced expiration or mild coughing. Mucus is represented by four-parameter viscoelastic fluid, a combination of Maxwell and Voigt elements, whereas air and serous fluid are taken as Newtonian fluids （incompressible）. The pressure gradient generated in the fluid layers is assumed to be given by a time- dependent function representing mild forced expiration or mild cough in the airways causing laminar flow. The effect of slip velocity at the mucus-serous interface caused by the presence of surfactant and at the top surface caused by immotile cilia are Mso taken into account. The roles of rheological properties of mucus on its transport are studied. The effect of serous fluid and its viscosity on mucus transport is also considered.

Particle size polydispersity of the rheological properties in magnetorheological fluids

Dispersion of metal particles in fluids can be used to manufacture magnetorheologic fluids(MRF).Properties of these dispersion systems are mainly determined by the arrangements and contacts among particles.In this paper,particles with smaller sizes than those in the target dispersion system are added using iron particles dispersed in silicon oil as a model to control the arrangements and contacts.The result suggests that these small-sized particles have a significant effect on the viscoelastic properties of the dispersion.The maximum packing density and the fluid viscosity depend mainly on the adhesion of small particles,which is directly related to the fraction of small particles in the model dispersion system.Under a magnetic field,the yield stress of the dispersion system is proportional to the concentration of iron particles,suggesting that the yield stress relies directly on the presence of small particles.These small particles in the fluid determine the difference in stress of the magnetorheological fluid(MRF) with or without a magnetic field.