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Propagation of SH waves in an irregular monoclinic crustal layer 总被引:2,自引:0,他引:2
A. Chattopadhyay S. Gupta V. K. Sharma Pato Kumari 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(12):989-999
The present paper discusses the dispersion equation for SH waves in a monoclinic layer over a semi-infinite elastic medium
with an irregularity. In the absence of the irregularity, the dispersion equation reduces to standard dispersion equation
for SH waves in a monoclinic layer over an isotropic semi-infinite medium. The dispersion curves for different size of the
irregularity are computed and compared for the half-space without any irregularity. It can be seen that the phase velocity
is strongly influenced by the wave number and the depth of the irregularity. 相似文献
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压路机高铁路基在建设过程中产生低频振动的振动波,在周边砂土层的传播扰动对周边房屋造成损伤.本文采用DA&P-B01型数据采集分析系统和配套的891-2拾振器,在不同距离处布置测试点进行振动试验,得到各测试点的时程变化曲线并加以分析,运用符合率结合前人研究成果验证本次实验的正确性.结果表明:低频振动波在砂土层中的峰值频率相同,振动速度、加速度、能量同距离的递减曲线为指数函数与幂函数的共同作用,且衰减速率与距离呈递减关系.本试验得到的结论可为同一地质条件的施工以及振动影响范围预测提供理论参考,为日后深入研究奠定基础. 相似文献
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《Particuology》2018
Granular material discharge from a flat-bottomed silo has been simulated by using continuum modeling and a three-dimensional discrete-element method (DEM). The predictive abilities of three commonly used frictional viscosity models (Schaeffer, S–S, and μ(I)) were evaluated by comparing them with the DEM data. The funnel-flow pattern (type C) and the semi-mass-flow pattern (type B) that was predicted by DEM simulations can be represented when the Schaeffer or μ(I) model is used, whereas the S–S model gives a consistent type-B flow pattern. All three models over-estimate the discharge rate compared with the DEM. The profiles of the solids volume fraction and the vertical velocity above the outlet show that the larger discharge rates given by the Schaeffer and μ(I) model result from an over-estimation of volume fraction, whereas the deviation in the S–S model stems from the failure to predict a solid vertical velocity and a volume fraction. 相似文献
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Gill and Sankarasubramanian's analysis of the dispersion of Newtonian fluids in laminar flow between two parallel walls are extended to the flow of non-Newtonian viscoelastic fluid (known as third-grade fluid) using a generalized dispersion model which is valid for all times after the solute injection. The exact expression is obtained for longitudinal convective coefficient K1(Γ), which shows the effect of the added viscosity coefficient Γ on the convective coefficient. It is seen that the value of the K1(Γ) for Γ≠0 is always smaller than the corresponding value for a Newtonian fluid. Also, the effect of the added viscosity coefficient on the K2(t,Γ) (which is a measure of the longitudinal dispersion coefficient of the solute) is explored numerically. Finally, the axial distribution of the average concentration Cm of the solute over the channel cross-section is determined at a fixed instant after the solute injection for several values of the added viscosity coefficient. 相似文献
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The acoustic emission (AE) features in rock fracture are simulated numerically with discrete element model (DEM). The specimen is constructed by using spherical particles bonded via the parallel bond model. As a result of the heterogeneity in rock specimen, the failure criterion of bonded particle is coupled by the shear and tensile strengths, which follow a normal probability distribution. The Kaiser effect is simulated in the fracture process, for a cubic rock specimen under uniaxial compression with a constant rate. The AE number is estimated with breakages of bonded particles using a pair of parameters, in the temporal and spatial scale, respectively. It is found that the AE numbers and the elastic energy release curves coincide. The range for the Kaiser effect from the AE number and the elastic energy release are the same. Furthermore, the frequency-magnitude relation of the AE number shows that the value of B determined with DEM is consistent with the experimental data. 相似文献
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《Particuology》2017
A classical Euler–Lagrangian model for gas–solid flows was extended with gas component mass conservation equations and used to obtain fundamental insights into bubble-to-emulsion phase mass transfer in bubbling gas–solid fluidized beds. Simulations of injected single rising bubbles under incipient fluidization conditions were carried out, using Geldart-A and -B particles. Phenomena observed in the simulations and those of various theoretical models used to derive phenomenological models were compared to challenge the assumptions underlying the phenomenological models. The bubble-to-emulsion phase mass transfer coefficients calculated for the simulations using Geldart-B particles were in a good agreement with predictions made using the Davidson and Harrison (1963) model. The bubble-to-emulsion phase mass transfer coefficients for Geldart-A particles were, however, much smaller than the predictions obtained from theoretical models (e.g. Chiba and Kobayashi (1970)). The newly developed model allows a detailed analysis of various hydrodynamic aspects and their effects on the mass transfer characteristics in and around rising bubbles in fluidized beds. 相似文献
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L. V. Baev 《Journal of Applied Mechanics and Technical Physics》2009,50(4):691-697
A problem of propagation of longitudinal and transverse waves in a multimodulus elastic isotropic medium is considered. In
the model used, the medium is described by a potential depending on three invariants of strains, which allows the influence
of preliminary deformation of the medium on the longitudinal and transverse velocities to be taken into account.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 176–182, July–August, 2009. 相似文献
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Equations for studying the axisymmetric deformation of a cylindrical shell are derived on the basis of Timoshenko shell theory. A dispersion equation is set up to study natural harmonic waves in a cylindrical isotropic shell. A numerical approach to plotting dispersion diagrams is proposed. The wave velocities obtained coincide with analytical solutions 相似文献
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A new subgrid-scale (SGS) model based on partially integrated transport method (PITM) is applied to the case of a turbulent
spectral non-equilibrium flow created by the mixing of two turbulence fields of differing scales: the shearless mixing layer.
The method can be viewed as a continuous hybrid RANS/LES approach. In this model the SGS length scale is no longer given by
the size of the discretization step, but is dynamically estimated using an additional transport equation for the dissipation
rate. The results are compared to those corresponding to the classical model of Smagorinsky and to the experimental data of
Veeravalli and Warhaft. A method for creating an anisotropic analytical pseudo-random field for inflow conditions is also
proposed. This approach based on subgrid-scale transport modelling combined with anisotropic inlet conditions gives better
results for the prediction of the shearless mixing layer. 相似文献
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In this paper we develop a multiple scattering model for elastic waves in random anisotropic media. It relies on a kinetic approach of wave propagation phenomena pertaining to the situation whereby the wavelength is comparable to the correlation length of the weak random inhomogeneities—the so-called weak coupling limit. The waves are described in terms of their associated energy densities in the phase space position × wave vector. They satisfy radiative transfer equations in this scaling, characterized by collision operators depending on the correlation structure of the heterogeneities. The derivation is based on a multi-scale asymptotic analysis using spatio-temporal Wigner transforms and their interpretation in terms of semiclassical operators, along the same lines as Bal (2005). The model accounts for all possible polarizations of waves in anisotropic elastic media and their interactions, as well as for the degeneracy directions of propagation when two phase speeds possibly coincide. Thus it embodies isotropic elasticity which was considered in several previous publications. Some particular anisotropic cases of engineering interest are derived in detail. 相似文献
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The exact solutions of the equations of motion derived under refined theories of shells and ribs based on the Timoshenko model
are used to plot dispersion curves for harmonic waves propagating along a cylindrical shell reinforced with discrete longitudinal
ribs
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Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 37–41, May 2006. 相似文献
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The continuum equations for a dilute particle distribution in inhomogeneous turbulence are tested against results from a Langevin particle tracking simulation. Reeks’ version of the kinetic theory is used to generate the mass, momentum and kinetic stress equations for the particle distribution. The particle tracking data are used to directly evaluate the dispersion tensors λ and μ which serve as closure relations for the continuum equations. These exact forms are compared to approximate, local forms. Even for low Stokes numbers (corresponding to low particle inertia defined by τ/τp ? 1), the tensor λ is strongly affected by the inhomogeneity and depends on turbulence parameters in the volume corresponding to the particle path dispersion over the particle Lagrangian integral timescale τ. In contrast, the locally homogeneous form of the velocity dispersion tensor μ is a sufficient approximation, since it depends on the dispersion volume over the much smaller particle relaxation time τp. It is demonstrated that the body force due to the dispersion vector γ cannot be neglected. In the limit of passive tracers (zero stopping distance), γ is equal to the gradient of λ, if the physical setting is such that we can invoke constant tracer density in this limit. 相似文献
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H. R. Kess S. Sundararaman C. D. Shah D. E. Adams S. M. Walsh C. Pergantis M. Triplett 《Experimental Mechanics》2007,47(4):497-509
The future United States military arsenal is transitioning from homogeneous metallic materials to stronger and lighter heterogeneous
composite materials. Although these composites offer numerous advantages such as the ability to tune strength to weight ratios
for each particular application, composites are susceptible to numerous damage mechanisms and environmental factors. Accidental
in-field impacts resulting from mishandling or transportation loads have been identified by the U.S. Army as the primary cause
of damage in composite weapon systems. This paper presents a hybrid approach to detect, locate, and quantify damage in filament
wound canisters using a complementary set of vibration-based (transmissibility and embedded sensitivity) and wave propagation-based
(phased array beamforming) methods. It is shown that this hybrid approach accurately detects, locates, and quantifies the
damage imposed by 1.36 and 6.78 N-m impact energies. By measuring the static stiffness of the baseline canister at the mid-point,
it was determined that the 1.36 N-m impact resulted in an overall 6% reduction of the tubes bending stiffness, while the 6.78 N-m
impact resulted in a 28% reduction. 相似文献