共查询到20条相似文献,搜索用时 62 毫秒
1.
A computational thermo-metallographic and thermoelastoplastic model for the analysis of the quenching process is developed
and validated. The diffusive transfor-mations are modeled according to the Johnson–Mehl–Avrami–Kolmogorov model and the Scheil’s
additivity rule. Two different models are investigated for the non-diffusive transformation—the Koistinen–Marburger model
and the Yu model. A large displacement formulation is assumed for the deformation analysis, modeling the plastic behavior
of the material according to the Prandtl–Reuss model. Two different bilinear hardening models—the isotropic and the kinematic
hardening model—are used and compared. The model allows to evaluate the transient stress and strain distributions during the
quenching process, the final phases and hardness distributions, and to predict the residual stress and the final deformation
of the processed part. A good agreement between computational results and reference data is found 相似文献
2.
S. A. Nazarov 《Journal of Applied Mechanics and Technical Physics》2007,48(6):861-870
Explicit presentations for the initial terms of the asymptotic solution of the spectral problem of the elasticity theory in
a plane region with a rapidly oscillating boundary are obtained. Based on asymptotic formulas, two methods for problem modeling
are proposed: with the use of Wenzel’s boundary conditions and with the use of the principle of a smooth image of a singularly
perturbed boundary. Various approaches to justification of asymptotic presentations are discussed.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 103–114, November–December, 2007. 相似文献
3.
Mohammadhossein Heidari Sureshjani Shahab Gerami Mohammad Ali Emadi 《Transport in Porous Media》2012,93(1):147-169
One of the widely used methods for modeling matrix–fracture fluid exchange in naturally fractured reservoirs is dual porosity
approach. In this type of modeling, matrix blocks are regarded as sources/sinks in the fracture network medium. The rate of
fluid transfer from matrix blocks into fracture medium may be modeled using shape factor concept (Warren and Root, SPEJ 3:245–255,
1963); or the rate–time solution is directly derived for the specific matrix geometry (de Swaan, SPEJ 16:117–122, 1976). Numerous works have been conducted to study matrix–fracture fluid exchange for slightly compressible fluids (e.g. oil).
However, little attention has been taken to systems containing gas (compressible fluid). The objective of this work is to
develop explicit rate–time solutions for matrix–fracture fluid transfer in systems containing single phase gas. For this purpose,
the governing equation describing flow of gas from matrix block into fracture system is linearized using pseudopressure and
pseudotime functions. Then, the governing equation is solved under specific boundary conditions to obtain an implicit relation
between rate and time. Since rate calculations using such an implicit relation need iterations, which may be computationally
inconvenient, an explicit rate–time relation is developed with the aid of material balance equation and several specific assumptions.
Also, expressions are derived for average pseudopressure in matrix block. Furthermore, simplified solutions (originated from
the complex general solutions) are introduced applicable in infinite and finite acting flow periods in matrix. Based on the
derived solutions, expressions are developed for shape factor. An important observation is that the shape factor for gas systems
is the same as that of oil bearing matrix blocks. Subsequently, a multiplier is introduced which relates rate to matrix pressure
instead of matrix pseudopressure. Finally, the introduced equations are verified using a numerical simulator. 相似文献
4.
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
5.
A version of Hill's lemma for Cosserat continuum 总被引:4,自引:0,他引:4
On the basis of Hill's lemma for classical Cauchy continuum, a version of Hill's lemma for micro-macro homogenization modeling of heterogeneous Cosserat continuum is presented in the flame of average-field theory. The admissible boundary conditions required to prescribe on the representative volume element for the modeling are extracted and discussed to ensure the satisfaction of Hill-Mandel energy condition and the first-order average field theory. 相似文献
6.
Shock tube study of n-decane ignition at low pressures 总被引:1,自引:0,他引:1
Xiao-Fei Nie Ping Li Chang-Hua Zhang Wei Xie Cong-Shan Li Xiang-Yuan Li 《Acta Mechanica Sinica》2012,28(1):79-82
Ignition delay times for n-decane/O 2 /Ar mixtures were measured behind reflected shock waves using endwall pressure and CH* emission measurements in a heated shock tube. The initial postshock conditions cover pressures of 0.09-0.26 MPa, temperatures of 1 227-1 536 K, and oxygen mole fractions of 3.9%-20.7% with an equivalence ratio of 1.0. The correlation formula of ignition delay dependence on pressure, temperature, and oxygen mole fraction was obtained. The current data are in good agreement with available low-pressure experimental data, and they are then compared with the prediction of a kinetic mechanism. The current measurements extend the kinetic modeling targets for the n-decane combustion at low pressures. 相似文献
7.
Supersonic (M∞ = 2−5) turbulent flows in the vicinity of a two-dimensional backward-facing step with an inclined leeward side are considered
by methods of mathematical modeling. The wave structure of the flow with a varied angle of inclination of the leeward side
of the step and a varied free-stream Mach number is considered.
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Translated From Prikladnaya Mekhanika I Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 48–58, November–December, 2006. 相似文献
8.
Large Eddy Simulations Using the Subgrid-Scale Estimation Model and Truncated Navier–Stokes Dynamics
J. Andrzej Domaradzki Kuo Chieh Loh Patrick P. Yee 《Theoretical and Computational Fluid Dynamics》2002,15(6):421-450
We describe a procedure for large eddy simulations of turbulence which uses the subgrid-scale estimation model and truncated
Navier–Stokes dynamics. In the procedure the large eddy simulation equations are advanced in time with the subgrid-scale stress
tensor calculated from the parallel solution of the truncated Navier–Stokes equations on a mesh two times smaller in each
Cartesian direction than the mesh employed for a discretization of the resolved quantities. The truncated Navier–Stokes equations
are solved through a sequence of runs, each initialized using the subgrid-scale estimation model. The modeling procedure is
evaluated by comparing results of large eddy simulations for isotropic turbulence and turbulent channel flow with the corresponding
results of experiments, theory, direct numerical simulations, and other large eddy simulations. Subsequently, simplifications
of the general procedure are discussed and evaluated. In particular, it is possible to formulate the procedure entirely in
terms of the truncated Navier–Stokes equation and a periodic processing of the small-scale component of its solution.
Received 27 April 2001 and accepted 16 December 2001 相似文献
9.
M. G. Khazhoyan G. S. Khakimzyanov 《Journal of Applied Mechanics and Technical Physics》2006,47(6):785-789
Results of calculations of fluid flow over a step located on a channel bottom are given. Numerical modeling is performed for
the model of free-boundary potential flows of an ideal incompressible fluid using a finite-difference method with dynamically
adaptive grids. The behavior of the free surface in the neighborhood of the step is studied as a function of the incident-flow
velocity. The results are compared with experimental data.
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Translated from PrikladnayaMekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 17–22, November–December, 2006. 相似文献
10.
Fujihiro Hamba 《Theoretical and Computational Fluid Dynamics》2001,14(5):323-336
Large eddy simulation (LES) is combined with the Reynolds-averaged Navier–Stokes (RANS) equation in a turbulent channel-flow
calculation. A one-equation subgrid-scale model is solved in a three-dimensional grid in the near-wall region whereas the
standard k–ε model is solved in a one-dimensional grid in the outer region away from the wall. The two grid systems are overlapped to
connect the two models smoothly. A turbulent channel flow is calculated at Reynolds numbers higher than typical LES and several
statistical quantities are examined. The mean velocity profile is in good agreement with the logarithmic law. The profile
of the turbulent kinetic energy in the near-wall region is smoothly connected with that of the turbulent energy for the k–ε model in the outer region. Turbulence statistics show that the solution in the near-wall region is as accurate as a usual
LES. The present approach is different from wall modeling in LES that uses a RANS model near the wall. The former is not as
efficient as the latter for calculating high-Reynolds-number flows. Nevertheless, the present method of combining the two
models is expected to pave the way for constructing a unified turbulence model that is useful for many purposes including
wall modeling.
Received 11 June 1999 and accepted 15 December 2000 相似文献
11.
C.G. Speziale 《Theoretical and Computational Fluid Dynamics》1999,13(3):161-166
A resent extension of the nonlinear K–ε model is critically discussed from a basic theoretical standpoint. While it was said in the paper that this model was formulated
to incorporate relaxation effects, it will be shown that the model is incapable of describing one of the most basic such turbulent
flows as is obvious but is described for clarity. It will be shown in detail that this generalized nonlinear K–ε model yields erroneous results for the Reynolds stress tensor when the mean strains are set to zero in a turbulent flow
– the return-to-isotropy problem which is one of the most elementary relaxational turbulent flows. It is clear that K–ε type models cannot describe relaxation effects. While their general formalism can describe relaxation effects, the nonlinear
K–ε model – which the paper is centered on – cannot. The deviatoric part of the Reynolds stress tensor is predicted to be zero
when it actually only gradually relaxes to zero. Since this model was formulated by using the extended thermodynamics, it
too will be critically assessed. It will be argued that there is an unsubstantial physical basis for the use of extended thermodynamics
in turbulence. The role of Material Frame-Indifference and the implications for future research in turbulence modeling are
also discussed.
Received 19 February 1998 and accepted 23 October 1998 相似文献
12.
V. V. Borovikov A. V. Bystrov 《Journal of Applied Mechanics and Technical Physics》1999,40(3):531-534
A new gas-dynamic method for decreasing the resistance of ground to the penetration of a solid body is developed. The physical
essence of the process is considered. Theoretical fundamentals of scaled modeling are given. Results of experimental studies
are presented, and the range of parameter for which the method is effective is determined.
Mozhaiskii Military Space-Engineering Academy, St. Petersburg 197082. Translated from Prikladnaya Mekhanika i Tekhnicheskaya
Fizika, Vol. 40, No. 3, pp. 196–199, May–June, 1999. 相似文献
13.
N. N. Belov O. V. Kabantsev A. A. Konyaev D. G. Kopanitsa V. F. Tolkachev A. A. Yugov N. T. Yugov 《Journal of Applied Mechanics and Technical Physics》2006,47(6):911-917
A mathematical model is proposed to describe deformation and fracture of reinforced concrete under impact loading within the
framework of mechanics of continuous media. The problem of the impact of steel cylindrical projectiles on rectangular slabs
made of reinforced concrete is solved. The results of mathematical modeling are in good agreement with experimental data.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 165–173, November–December, 2006. 相似文献
14.
A. A. Kashevarov 《Journal of Applied Mechanics and Technical Physics》2008,49(2):253-260
A stationary mathematical model describing the time-integrated effect on an oil-saturated reservoir during drilling is considered.
Calculated results are compared with the solution of the problem in an exact nonstationary formulation. The formation of an
invaded zone in straight borehole drilling in water-and oil-saturated reservoirs is studied by numerical modeling.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 113–122, March–April, 2008. 相似文献
15.
V. B. Kurzin 《Journal of Applied Mechanics and Technical Physics》2008,49(1):84-92
A number of important properties of vibrations of linear systems (the quality of stability of the systems, their conditionality
with respect to the eigenvalues of the matrices, and the possibility of modeling systems with a large number of degrees of
freedom by their subsystems with a smaller number of degrees of freedom), which can be determined by a new mathematical tool
called “One-dimensional spectral portraits of matrices” developed under the guidance of S. K. Godunov, are considered. An
example is given on constructing one-dimensional spectral portraits for matrices that describe aeroelastic vibrations of hydrodynamic
cascades.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 1, pp. 104–113, January–February, 2008. 相似文献
16.
Yu. M. Volchkov L. A. Dergileva 《Journal of Applied Mechanics and Technical Physics》1999,40(2):354-359
The edge effects in the stress state of an interlayer in stretching and shearing by rigid slabs are studied. On the basis
of the equations of momentless and moment elastic layers, we solve problems modeling qualitatively the stress-strain state
in the “soft” layer between two “rigid” layers.
Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 2, pp. 189–195, March–April, 1999. 相似文献
17.
The general Hoyle–Youngdahl and Love solutions in the three-dimensional theory of inhomogeneous linear elastic materials are
proposed. Following a brief historical outline of various general solutions existing in the classical linear elasticity of
homogeneous isotropic media, key steps of the derivation of the Hoyle–Youngdahl and Love solutions are presented. The procedure
is then generalized to the case of inhomogeneous elastic materials with elastic constants depending on the z-coordinate. The significance of the solutions and their relevance to modeling of functionally graded materials is discussed
in brief 相似文献
18.
Mahmoud Rajabian Charles Dubois Miroslav Grmela Pierre J. Carreau 《Rheologica Acta》2008,47(7):701-717
Rheological properties of suspensions of fibers in polymeric fluids are influenced by fiber–polymer interactions. In this
paper, we investigate this influence from both experimental and modeling standpoints. In the experimental part of this investigation,
we have changed the fiber–polymer interactions by treating the surface of the fibers. The resulting effects are observed using
scanning electron microscopy and dynamic mechanical analysis techniques and quantified from the measurements of the viscosity
in the start-up of shear flows and dynamic tests in the linear viscoelastic range region. The results are interpreted with
the help of a mesoscopic rheological model developed for suspensions of fibers in viscoelastic fluids. 相似文献
19.
H. H. Liakos E. P. Keramida M. A. Founti N. C. Markatos 《Heat and Mass Transfer》2002,38(4-5):425-432
Impinging jet combusting flows on granite plates are studied. A mathematical model for calculating heat release in turbulent
impinging premixed flames is developed. The combustion including radiative heat transfer and local extinction effects, and
flow characteristics are modeled using a finite volume computational approach. Two different eddy viscosity turbulence models,
namely the standard k–ɛ and the RNG k–ɛ model with and without radiation (discrete transfer model) are assessed. The heat released predictions are compared with
experimental data and the agreement is satisfactory only when both radiative heat transfer and local extinction modeling are
taken into account. The results indicate that the main effect of radiation is the decrease of temperature values near the
jet stagnation point and along the plate surface. Radiation increases temperature gradients and affects predicted turbulence
levels independently of the closure model used. Also, the RNG k–ɛ predicts higher temperatures close the solid plate, with and without radiative heat transfer.
Received on 13 November 2000 / Published online: 29 November 2001 相似文献
20.
In recent years two nonlinear dispersive partial differential equations have attracted much attention due to their integrable
structure. We prove that both equations arise in the modeling of the propagation of shallow water waves over a flat bed. The
equations capture stronger nonlinear effects than the classical nonlinear dispersive Benjamin–Bona–Mahoney and Korteweg–de
Vries equations. In particular, they accommodate wave breaking phenomena. 相似文献