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1.
The flow of a non-Newtonian fluid through a porous media in between two parallel plates at different temperatures is considered.
The governing momentum equation of third-grade fluid with modified Darcy’s law and energy equation have been derived. Approximate
analytical solutions of momentum and energy equations are obtained by using perturbation techniques. Constant viscosity, Reynold’s
model viscosity, and Vogel’s model viscosity cases are treated separately. The criteria for validity of approximate solutions
are derived. A numerical residual error analysis is performed for the solutions. Within the validity range, analytical and
numerical solutions are in good agreement. 相似文献
2.
3.
A. B. Gorshkov 《Fluid Dynamics》2009,44(5):785-795
The axisymmetric laminar flowfield and heat transfer characteristics of the RAM-C experimental spacecraft moving in the Earth’s
atmosphere at an altitude of 61 km and a velocity of 7.65 km/s are investigated on the basis of a numerical solution of the
Navier-Stokes equations. In studying the effect of the physical and chemical nonequilibrium processes on the flow parameters
two approximations are employed for describing the gas properties, namely, that of a perfect gas with a constant adiabatic
exponent and a model of dissociating and vibrationally-relaxing air. Emphasis is placed on the study of the spacecraft’s near-wake
parameters. The results obtained are compared with experimental data on the electron concentration in the shock layer on the
lateral surface and the calculated results of other authors. 相似文献
4.
Bo Zhao·Ji-Ping Cui·Jing Fan Key Laboratory of High Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences Beijing China 《Acta Mechanica Sinica》2010,26(3):365-370
We have calculated the Hugoniot properties of shocked nitromethane based on the improved Tsien's equa- tion of state (EOS) that optimized by "exact" numerical molecular dynamic data at high temperatures and pressures. Comparison of the calculated results of the improved Tsien's EOS with the existed experimental data and the direct simu- lations show that the behavior of the improved Tsien's EOS is very good in many aspects. Because of its simple analytical form, the improved Tsien's EOS can be prospectively used to study the condensed explosive detonation coupling with chemical reaction. 相似文献
5.
This paper has reformulated the mathematical model and boundary conditions in the semi-physical plan (x,ψ)by using W.H.Hui’s method and suggested two new ways of numerical calculation for the coefficients of Stokes harmonic waves of high order. By transforming the perturbation parameter? into a new one we we rejind Cokelet’s results (1977) of phase speed and semi-waveheight expressions. 相似文献
6.
Quanquan Yang Cun-Fa Gao Wentao Chen 《Archive of Applied Mechanics (Ingenieur Archiv)》2010,80(8):895-907
This paper is to study the two-dimensional stress distribution of a functional graded material plate (FGMP) with a circular
hole under arbitrary constant loads. With using the method of piece-wise homogeneous layers, the stress distribution of the
functional graded material plate having radial arbitrary elastic properties is derived based on the theory of the complex
variable functions. As examples, numerical results are presented for the FGMPs having given radial Young’s modulus or Poisson’s
ratio. It is shown that the stress is greatly reduced as the radial Young’s modulus increased, but it is less influenced by
the variation of the Poisson’s ratio. Moreover, it is also found that the stress level varies when the radial Young’s modulus
increased in different ways. Thus, it can be concluded that the stress around the circular hole in the FGMP can be effectively
reduced by choosing the proper change ways of the radial elastic properties. 相似文献
7.
The quasi-Green’s function method is used to solve the free vibration problem of clamped thin plates on the Winkler foundation.
Quasi-Green’s function is established by the fundamental solution and the boundary equation of the problem. The function satisfies
the homogeneous boundary condition of the problem. The mode-shape differential equation of the free vibration problem of clamped
thin plates on the Winkler foundation is reduced to the Fredholm integral equation of the second kind by Green’s formula.
The irregularity of the kernel of the integral equation is overcome by choosing a suitable form of the normalized boundary
equation. The numerical results show the high accuracy of the proposed method. 相似文献
8.
A semi-analytical solution is obtained for a rotating stress-free edge disk of constant thickness and density. In the plastic
range, the Hill’s quadratic orthotropic yield criterion is adopted. In the elastic range, the Hooke’s law holds with thermal
effects included. The analysis of singularities performed may be used for correct implementation of numerical codes and preliminary
engineering design. 相似文献
9.
Lidiya Nazarenko Leonid Khoroshun Wolfgang H. Müller Ralf Wille 《Continuum Mechanics and Thermodynamics》2009,20(7):429-458
In the present paper, we will illustrate the application of the method of conditional moments by constructing the algorithm
for determination of the effective elastic properties of composites from the given elastic constants of the components and
geometrical parameters of inclusions. A special case of two-component matrix composite with randomly distributed unidirectional
spheroidal inclusions is considered. To this end it is assumed that the components of the composite show transversally isotropic
symmetry of thermoelastic properties and that the axes of symmetry of the thermoelastic properties of the matrix and inclusions
coincide with the coordinate axis x
3. As a numerical example a composite based on carbon inclusions and epoxide matrix is investigated. The dependencies of Young’s
moduli, Poisson’s ratios and shear modulus from the concentration of inclusions and for certain values which characterize
the shape of inclusions are analyzed. The results are compared and discussed in context with other theoretical predictions
and experimental data.
相似文献
10.
Study of effective behavior of heterogeneous materials, starting from the properties of the microstructure, represents a critical
step in the design and modeling of new materials. Within this framework, the aim of this work is to introduce a general internal
variables approach for scale transition problem in linear viscoelastic case. A new integral formulation is established, based
on the complete taking into account of field equations and differential constitutive laws of the heterogeneous problem, in
which the effects of elasticity and viscosity interact in a representative volume element. Thanks to Green’s techniques applied
to space convolution’s term, a new concentration relation is obtained. The step of homogenization is then carried out according
to the self-consistent approximation. The results of the present model are illustrated and compared with those provided by
Hashin’s and Rougier’s ones, considered as references, and by internal variables models such as those of Weng and translated
fields. 相似文献
11.
The need of accurate and efficient numerical schemes to solve Richards’ equation is well recognized. This study is carried
out to examine the numerical performances of the nonlinear multigrid method for numerical solving of the two-dimensional Richards’
equation modeling water flow in variably saturated porous media. The numerical approach is based on an implicit, second-order
accurate time discretization combined with a vertex centered finite volume method for spatial discretization. The test problems
simulate infiltration of water in 2D saturated–unsaturated soils with hydraulic properties described by van Genuchten–Mualem
models. The numerical results obtained are compared with those provided by the modified Picard–preconditioned conjugated gradient
(Krylov subspace) approach. 相似文献
12.
Bending analysis of thin functionally graded plates using generalized differential quadrature method
A. Fereidoon M. Asghardokht seyedmahalle A. Mohyeddin 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(11):1523-1539
In this paper, the differential quadrature (DQ) method is presented for easy and effective analysis of isotropic functionally
graded (FG) and functionally graded coated (FGC) thin plates with constant Poisson’s ratio and varying Young’s modulus in
the thickness direction. The bending of FG and FGC plates under transverse loading has been studied using the polynomial differential
quadrature (PDQ) and the harmonic differential quadrature (HDQ) methods. A three-dimensional elasticity solution for a moderately
thick FG plate with exponential Young’s modulus is used as the benchmark. Two examples, including a thin FG rectangular plate
and a thin FGC rectangular plate with sigmoidal Young’s modulus, are investigated. The numerical results of PDQ and HDQ methods
reveal good agreement with other solutions. Also, it is shown that the formulations for thin FG plates and homogeneous plates
are similar, except that the plane strain components of the middle surface in FG plates are not zero. 相似文献
13.
The stress state of an elastic orthotropic medium with an arbitrarily oriented triaxial ellipsoidal inclusion is analyzed.
A solution is obtained using the triple Fourier transform and the Fourier-transformed Green’s function for an infinite anisotropic
medium. The high efficiency of the approach is demonstrated by solving the problem for a transversely isotropic material with
a spheroidal cavity for which the exact solution is known. A numerical analysis is conducted to study the stress distribution
over the surface of the inclusion with different orientations in the orthotropic space. It is revealed that in some cases
the orientation of the inclusion has a strong effect on the stress concentration
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 4, pp. 55–61, April 2007. 相似文献
14.
In this paper we deal with the control of chaotic systems. Knowing that a chaotic attractor contains a myriad of unstable
periodic orbits (UPO’s), the aim of our work is to stabilize some of the UPO’s embedded in the chaotic attractor and which
have interesting characteristics. First, using the input-to-state linearization method in conjunction with a time-delayed
state feedback, we design a control signal that can achieve stabilization. Next, an adaptive time-delayed state feedback is
proposed which shows at once efficiency and simplicity and circumvents the construction complexity of the first controller.
Finally, we propose a reduced order sliding mode observer to estimate the necessary states for the design of an adaptive time
delayed state feedback controller. This last controller has one main advantage, it in fact achieves UPO stabilization without
using the system model. The efficacy of the proposed methods is illustrated by numerical simulations onto Chua’s system. 相似文献
15.
Jean-Louis Auriault 《Transport in Porous Media》2009,79(2):215-223
An increasing number of articles are adopting Brinkman’s equation in place of Darcy’s law for describing flow in porous media.
That poses the question of the respective domains of validity of both laws, as well as the question of the value of the effective
viscosity μ
e
which is present in Brinkman’s equation. These two topics are addressed in this article, mainly by a priori estimates and
by recalling existing analyses. Three main classes of porous media can be distinguished: “classical” porous media with a connected
solid structure where the pore surface S
p
is a function of the characteristic pore size l
p
(such as for cylindrical pores), swarms of low concentration fixed particles where the pore surface is a function of the
characteristic particle size l
s
, and fiber-made porous media at low solid concentration where the pore surface is a function of the fiber diameter. If Brinkman’s
3D flow equation is valid to describe the flow of a Newtonian fluid through a swarm of fixed particles or fibrous media at
low concentration under very precise conditions (Lévy 1983), then we show that it cannot apply to the flow of such a fluid
through classical porous media. 相似文献
16.
M. I. Gritsevich 《Moscow University Mechanics Bulletin》2010,65(4):94-95
The general equation describing the motion of a meteoroid in the Earth’s atmosphere is considered. It is shown that, in this
case, the momentum variation of the system consisting of the meteoroid and its separating mass is due to the velocity variation
of the meteoroid. The projection of Newton’s equation onto the tangent to the meteoroid trajectory is analyzed. It is also
shown that, because of large geocentric velocities (between 11 and 72 km/s), the dominant force is the drag force proportional
to the square of the incident air flow velocity. Some numerical results obtained for the Bene>sov bolide registered by the
European Fireball Network (May 7, 1991) are given as an illustrative example. 相似文献
17.
Based on the driver’s individual difference of the driver’s perception ability, we in this paper develop a new fundamental
diagram with the driver’s perceived error and speed deviation difference. The analytical and numerical results show that the
speed-density and flow-density data are divided into three prominent regions. In the first region, the speed-density and flow-density
data are scattered around the equilibrium speed-density and flow-density curves of the classical fundamental diagram theory,
where the widths of these scattered data are very narrow and slightly increase with the real density (i.e., the scattered
data appear as two thicker lines); the running speed is approximately equal to the free flow speed and the real flow approximately
linearly increases with the real density. In the second region, the speed-density and flow-density data are scattered widely
in a two-dimensional region, but the shapes of these widely scattered data are related to the properties of the driver’s perceived
error and speed deviation difference. In the third region, the scattered speed-density and flow-density data appear but these
scattered data will quickly degenerate into the equilibrium speed-density and flow-density curves with the increase of the
real density. Finally, the numerical results illustrate that the new fundamental diagram theory also produces the F-line,
U-line, and L-line. The shapes of the scattered data, F-line, U-line, and L-line are relevant to the properties of the driver’s
perceived error and speed deviation difference. These results are qualitatively accordant with the real traffic, which shows
that the new fundamental diagram theory can better describe some complex traffic phenomena in the real traffic system. In
addition, the above results can help us to further explain why the widely scattered speed-density and flow-density data appear
in the real traffic system and better understand the effects of the driver’s individual difference on traffic flow. 相似文献
18.
Waverider configurations derived from general conical flowfields 总被引:1,自引:0,他引:1
A method based on the computational fluid dynamics (CFD) is presented for a flexible waverider’s design. The generating bodies
of this method could be any cones. In addition, either the leading edge or the profile of the scramjet’s inlet is used as
the waverider’s definition curve, parameterized by the quadric function, the sigmoid function or the B-spline function. Furthermore,
several numerical examples are carried out to validate the method and the relevant codes. The CFD results of the configurations
show that all the designs are successful. Moreover, primary suggestions are proposed for practical design by comparing the
geometrical and aerodynamic performances of the cone-derived waveriders at Mach 6.
The project supported by the National Natural Science Foundation of China (10502053, 10372106 and 10402043), K. C. Wong Education
Foundation of Hong Kong, the Key Laboratory of High Temperature Gas Dynamics of Chinese Academy of Sciences and the State
Key Laboratory of Structural Analysis for Industrial Equipment of Dalian University of Technology. 相似文献
19.
20.
We consider three dimensional finite element computations of thermoelastic damping ratios of arbitrary bodies using Zener’s
approach. In our small-damping formulation, unlike existing fully coupled formulations, the calculation is split into three
smaller parts. Of these, the first sub-calculation involves routine undamped modal analysis using ANSYS. The second sub-calculation
takes the mode shape, and solves on the same mesh a periodic heat conduction problem. Finally, the damping coefficient is
a volume integral, evaluated elementwise. In the only other decoupled three dimensional computation of thermoelastic damping
reported in the literature, the heat conduction problem is solved much less efficiently, using a modal expansion. We provide
numerical examples using some beam-like geometries, for which Zener’s and similar formulas are valid. Among these we examine
tapered beams, including the limiting case of a sharp tip. The latter’s higher-mode damping ratios dramatically exceed those
of a comparable uniform beam. 相似文献