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1.
2.
V. M. Sadovskii 《Journal of Applied Mechanics and Technical Physics》2009,50(3):519-524
An exact solution that describes the fields of displacements and stresses in an expanding spherical layer is constructed within
the framework of the theory of small strains of a granular medium with rigid particles. For finite strains, the problem reduces
to a nonlinear system of ordinary differential equations, which is solved by numerical methods. Similar solutions are found
in the problem for a cylindrical layer. Based on these solutions, the effect of the dilatancy of the granular medium on the
stress-strain state near expanding cavities is found.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 190–196, May–June, 2009. 相似文献
3.
Yu. A. Berezin L. A. Spodareva 《Journal of Applied Mechanics and Technical Physics》1998,39(2):261-264
The shape of the free surface of a layer of granular material moving on an inclined plane is studied on the basis of a model
of a non-Newtonian fluid with a nonlinear relation between the stress tensor and the shear rate of the flow. For small but
finite elevations of the free surface, the governing equations are reduced to a quasilinear Burgers equation. Results of a
numerical solution are presented for the case of arbitrary elevations.
Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 2, pp. 117–120, March–April, 1998. 相似文献
4.
G. Sh. Boltachev N. B. Volkov V. V. Ivanov S. N. Paranin 《Journal of Applied Mechanics and Technical Physics》2008,49(2):336-339
A model for dynamic compaction of granular medium is proposed for the case in which the external action far exceeds the yield
strength of the material. A radial axisymmetric compaction problem is solved for a granular medium with nanosize structure
in the presence of a rigid rod at the symmetry axis. Simulated data are compared with experimental data on magnetic pulsed
compaction of oxide nanopowders.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 211–215, March–April, 2008. 相似文献
5.
A thermodynamically consistent continuum theory for single-phase, single-constituent cohesionless granular materials is presented. The theory is motivated by dimensional inconsistencies of the original Goodman-Cowin theory [1–3]; it is constructed by removing these inconsistencies through the introduction of an internal length ℓ. Four constitutive models are proposed and discussed in which ℓ is (i) a material constant (Model I), (ii) an independent constitutive variable (Model II), (iii) an independent dynamic field quantity (Model III) and (iv) an independent kinematic field quantity (Model IV). Expressions of the constitutive variables emerging in the systems of the balance equations in these four models in thermodynamic equilibrium are deduced by use of a thermodynamic analysis based on the Müller-Liu entropy principle. Comments on the validity of these four models are given and discussed; the results presented in the current study show a more general formulation for the constitutive quantities and can be used as a basis for further continuum-based theoretical investigations on the behaviour of flowing granular materials. Numerical results regarding simple plane shear flows will be discussed and compared in Part II of this work. 相似文献
6.
The dynamics of a granular medium in a cavity filled with incompressible viscous fluid under harmonic vertical vibration are
studied experimentally. The sand is fluidized in a relatively thin sublayer of the granular layer near the interface between
the media. The fluidization is of the threshold type and is accompanied by intense parametric oscillations of the interface.
For viscous fluids, the transition of the sand from a quasi-solid to a fluidized state and the reverse transition associated
with a decrease in the oscillation rate occur with hysteresis. The nondimensional governing parameters determining the sand
dynamics are established. The analysis is focused on the case of low nondimensional frequencies.
Perm’, Paris. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 113–122, May–June,
2000. 相似文献
7.
Certain aspects of wave propagation and the dynamic reaction of a granular material when subjected to a long-duration impulse
load are studied. In the majority of studies published on this subject the unsteady pressure behavior at the end-wall covered
by a layer of granular material was observed and documented. However, up to now little attention was given to explaining the
physical mechanism of this process.
Experimental results, obtained in the course of this study, regarding the pressure fields inside granular layers of different
materials, clearly show that the compaction effect strongly depends on the characteristics of the medium. This phenomenon
manifests itself by changing the gas-particle interaction in the course of the gas filtration, and by variation in the contribution
of the different forces and effective stress, σ, to the energy exchange between the gas, the particles and the shock-tube
wall.
The material permeability, f, the relative density, ν, and the particle response time, τ
p
, are the most important parameters affecting the stress formation at the end-wall covered by the granular layer. In addition
to the effect of the material parameters, the effective stress, σ, was found to strongly depend on the granular layer height,
h.
Based on detailed pressure measurements a qualitative analysis regarding the role of the particle rearrangement in the formation
of the unsteady peak at the end-wall was performed. The phenomenology of the particle–particle interaction includes rotation
and consolidation of the granules and movement or sliding of particle planes within the layer over each other. Most of these
processes are frictional in their nature. They are related to the energy losses and affect the profile and magnitude of the
compressive stress as measured at the shock-tube end-wall covered by the granular layer.
Received: 10 June 1996/Accepted: 15 October 1996 相似文献
8.
K. R. Jayaprakash Yuli Starosvetsky Alexander F. Vakakis Maxime Peeters Gaetan Kerschen 《Nonlinear dynamics》2011,63(3):359-385
We study standing waves (nonlinear normal modes—NNMs) and band zones in finite granular chains composed of spherical granular
beads in Hertzian contact, with fixed boundary conditions. Although these are homogeneous dynamical systems in the notation
of Rosenberg (Adv. Appl. Mech. 9:155–242, 1966), we show that the discontinuous nature of the dynamics leads to interesting effects such as separation between beads, NNMs
that appear as traveling waves (these are characterized as pseudo-waves), and localization phenomena. In the limit of infinite
extent, we study band zones, i.e., pass and stop bands in the frequency–energy plane of these dynamical systems, and classify
the essentially nonlinear responses that occur in these bands. Moreover, we show how the topologies of these bands significantly
affect the forced dynamics of these granular media subject to narrowband excitations. This work provides a classification
of the coherent (regular) intrinsic dynamics of one-dimensional homogeneous granular chains with no pre-compression, and provides
a rigorous theoretical foundation for further systematic study of the dynamics of granular systems, e.g., the effects of disorders
or clearances, discrete breathers, nonlinear localized modes, and high-frequency scattering by local disorders. Moreover,
it contributes toward the design of granular media as shock protectors, and in the passive mitigation of transmission of unwanted
disturbances. 相似文献
9.
Chung Fang 《Continuum Mechanics and Thermodynamics》2010,22(2):121-136
A selection of models for the variation in porosity in dry granular flows is investigated and compared on the basis of thermodynamic
consistency to illustrate their performance and limitations in equilibrium situations. To this end, the thermodynamic analysis,
based on the Müller–Liu entropy principle, is employed to deduce the ultimate constitutive equations at equilibrium. Results
show that while all the models deliver appropriate equilibrium expressions of the Cauchy stress tensor for compressible grains,
the model in which the variation in porosity is treated kinematically yields a spherical stress tensor for incompressible
grains. Only the model in which the variation in porosity is modeled by a dynamic equation can give rise to a non-spherical
stress tensor at equilibrium. The present study illuminates the validity and thermodynamic justification of the two modeling
approaches for the porosity variation in dry granular matter. 相似文献
10.
By the discrete element method (DEM), we perform numerical simulations of shock-induced load transfer processes in granular
layers composed of spherical particles packed in vertical channels. In order to isolate the load transfer through the grains’
contact points from the complicated load transfer processes, we simulate the shock wave interactions with granular layers
having no permeability for gas. The shock loading is achieved by applying a downward step force on the top of the granular
layers. Complex, three-dimensional load transfer processes in the granular media, which are extremely difficult to understand
from experiments, are visualized based on the results from the present DEM simulation. The numerical results show that highly
concentrated load transfer paths, through which shock loads are transferred mainly, exist in the granular media, and that
the dimensions of the container of the granular media considerably affect the shock-induced load transfer processes. From
a coarse-grained representation of intergranular stress, wave-like load transfer processes are clearly observed. For relatively
deep granular layers, however, the wave fronts became unclear as they propagated. 相似文献
11.
L. A. Spodareva 《Journal of Applied Mechanics and Technical Physics》1999,40(6):1111-1115
An inertial flow of a granular material can be described by the laws of conservation of mass, momentum, and energy of random
motion of solid particles by invoking some closing relations. In this work, these closing relations are inferred from the
dimensional theory. The system of equations obtained is used to determine characteristics of a steady flow of a bed of a granular
material down an inclined surface with a microrelief for various Richardson numbers and finite contact times of the particles
during their collisions.
Novosibirsk Military Institute, Novosibirsk 630103. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40,
No. 6, pp. 128–132, November–December, 1999. 相似文献
12.
Yu. A. Berezin L. A. Spodareva 《Journal of Applied Mechanics and Technical Physics》1998,39(6):918-921
The stability of a layer of a granular medium on an inclined plane has been studied within the framework of the model of a
non-Newtonian fluid with an index of 2, which ensures the experimentally found quadratic dependence of the shear stress on
the shear rate. It is shown analytically and numerically that these flows are stable or unstable depending on the value of
the generalized Reynolds number relative to the critical value equal to5 cot α.
Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 113–117, November–December, 1998. 相似文献
13.
G. Sh. Boltachev N. B. Volkov 《Journal of Applied Mechanics and Technical Physics》2008,49(6):1040-1046
The previously developed continual approximation is used to analyze the radial axisymmetric compaction of a granular medium
in the presence of a rigid undeformable rod on the symmetry axis. It is shown that, during pulsed loading, high densities
close to those corresponding to the nonporous state can be attained due to inertia effects. The influence of the initial radial
dimensions of the rod-powder-medium system on the compaction process is analyzed. The problem is found to be scale invariant
under various constraints imposed on the ratio of the characteristic dimensions.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 181–189, November–December, 2008 相似文献
14.
PIV for granular flows 总被引:4,自引:0,他引:4
Particle image velocimetry (PIV) has been adapted for use in measuring particle displacement and velocity fields in granular
flows. “Seeding” is achieved by using light and dark particles. The granular flow adjacent to a clear bounding wall is illuminated
with a strobe, and the recorded images are analyzed using standard PIV techniques. The application is demonstrated by measuring
convection rolls in a granular bed undergoing vertical oscillations. The PIV measured displacement is consistent with displacement
of a marked layer of particles.
Received: 29 January 1998/Accepted: 8 April 1999 相似文献
15.
Filtration in a Porous Granular Medium: 1. Simulation of Pore-Scale Particle Deposition and Clogging
This paper presents a numerical model for simulating the pore-scale transport and infiltration of dilute suspensions of particles
in a granular porous medium under the action of hydrodynamic and gravitational forces. The formulation solves the Stokes’
flow equations for an incompressible fluid using a fixed grid, multigrid finite difference method and an embedded boundary
technique for modeling particle–fluid coupling. The analyses simulate a constant flux of the fluid suspension through a cylindrical
model pore. Randomly generated particles are collected within the model pore, initially through contact and attachment at
the grain surface (pore wall) and later through mounding close to the pore inlet. Simple correlations have been derived from
extensive numerical simulations in order to estimate the volume of filtered particles that accumulate in the pore and the
differential pressure needed to maintain a constant flux through the pore. The results show that particle collection efficiency
is correlated with the Stokes’ settling velocity and indirectly through the attachment probability with the particle–grain
surface roughness. The differential pressure is correlated directly with the maximum mound height and indirectly with particle
size and settling velocity that affect mound packing density. Simple modification factors are introduced to account for pore
length and dip angle. These parameters are used to characterize pore-scale infiltration processes within larger scale network
models of particle transport in granular porous media in a companion paper.
Articlenote: Currently at GZA GeoEnvironmental Inc., 1 Edgewater Drive, Norwood, MA 02062, U.S.A. 相似文献
16.
Aristeidis Nikolopoulos Nikos Nikolopoulos Nikos Varveris Sotirios Karellas Panagiotis Grammelis Emmanuel Kakaras 《Particuology》2012,10(6):699-709
The aim of this paper is the development of new models and/or the improvement of existing numerical models, used for simulating granular flow in CFB (circulating fluidized bed) recirculation systems. Most recent models follow the TFM (two-fluid model) methodology, but they cannot effectively simulate the inter-particle friction forces in the recirculation system, because the respective stress tensor does not incorporate compressibility of flow due to change of effective particle density. As a consequence, the induced normal and shear stresses are not modeled appropriately during the flow of the granular phase in the CFB recirculation system. The failure of conventional models, such as that of von Mises/Coulomb, is mainly caused by false approximation of the yield criterion which is not applicable to the CFB recirculation system. The present work adopts an alternative yield function, used for the first time in TFM Eulerian modeling. The proposed model is based on the Pitman–Schaeffer–Gray–Stiles yield criterion. Both the temporal deformation of the solid granular phase and the repose angle that the granular phase forms are more accurately simulated by this model. The numerical results of the proposed model agree well with experimental data, implying that frictional forces are efficiently simulated by the new model. 相似文献
17.
密集颗粒物质由大量颗粒组成的多体相互作用体系,在一定条件下,颗粒互相连接,形成相对稳定的介观尺度结构,其几何和动力学性质较大程度上决定了颗粒体系的宏观物理和力学性质,因此开展颗粒的介观结构研究具有重要的理论价值,是科学的前沿之一.自然界的堆石坝、堰塞体和碎屑流,以及工程中的高温气冷堆堆芯颗粒流和先进核裂变能系统(ADS嬗变)的颗粒散裂靶等都是典型的颗粒体系,研究颗粒体系宏观力学性质是灾害预测和调控技术的关键.本文首先介绍颗粒接触力理论和简化模型的研究进展,接着介绍介观尺度结构分析方法与测量技术,颗粒体系Jamming转变、软点和颗粒微位移测量技术等,最后列举了几个关键的科学问题.颗粒介质中很多基本力学问题的解决需要借鉴物理和数学等学科的最新成果,建立新的概念和范式,从新的角度、思路、理念去认识颗粒介质的基本问题.同时,颗粒介质的基础研究还要紧密结合工程应用领域的大量相关的核心技术,与工程领域专家共同合作,使得颗粒介质的研究有的放矢,更具生命力. 相似文献
18.
Modeling granular media on the computer 总被引:4,自引:0,他引:4
19.
密集颗粒物质的介观结构 总被引:2,自引:0,他引:2
密集颗粒物质由大量颗粒组成的多体相互作用体系,在一定条件下,颗粒互相连接,形成相对稳定的介观尺度结构,其几何和动力学性质较大程度上决定了颗粒体系的宏观物理和力学性质,因此开展颗粒的介观结构研究具有重要的理论价值,是科学的前沿之一.自然界的堆石坝、堰塞体和碎屑流,以及工程中的高温气冷堆堆芯颗粒流和先进核裂变能系统(ADS嬗变)的颗粒散裂靶等都是典型的颗粒体系,研究颗粒体系宏观力学性质是灾害预测和调控技术的关键.本文首先介绍颗粒接触力理论和简化模型的研究进展,接着介绍介观尺度结构分析方法与测量技术,颗粒体系Jamming转变、软点和颗粒微位移测量技术等,最后列举了几个关键的科学问题.颗粒介质中很多基本力学问题的解决需要借鉴物理和数学等学科的最新成果,建立新的概念和范式,从新的角度、思路、理念去认识颗粒介质的基本问题.同时,颗粒介质的基础研究还要紧密结合工程应用领域的大量相关的核心技术,与工程领域专家共同合作,使得颗粒介质的研究有的放矢,更具生命力. 相似文献
20.
Pattern formation in granular avalanches 总被引:2,自引:0,他引:2
Three new experiments are described which exhibit strong pattern formation in the deposits left by successive granular avalanches.
At low flow rates continuous deposition, erosion or rotation gives rise to intermittent avalanche release. Once in motion
kinetic sieving of a bi-disperse granular mixture creates a two-layer shear band in which the larger particles overlie the
smaller particles. When this is brought abruptly to rest by the upslope propagation of a shock wave a pair of str
ipes is “frozen” into the deposited material. Successive releases create a large scale pattern, which strongly reflects the
history of the granular flow. At faster deposition, erosion and rotation rates a new flow regime is entered in which intermittency
and shock formation ceases, and the associated patterns change.
Received Aug. 25, 1997 相似文献