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1.
The instability of a free surface of aluminum after passage of two shocks that follow one after the other at a certain time
interval is studied numerically. The first shock is rather strong (the postshock pressure is about 75 GPa). It is shown that
if at the moment when the second shock arrives at the free surface, the perturbation evolution is nonlinear, then, in contrast
to the linear stage, the change in the growth rate of the amplitude depends weakly on the wavelength of the initial perturbation.
A formula is proposed which describes the effect of the second shock on the amplitude growth rate and in which the main structure
of Richtmyer's formula is preserved. It is demonstrated that the parameters of the second shock that ensure freezing of the
instability can be determined using only the growth rate of the amplitude.
Computing Center, Russian Academy of Sciences, Moscow 117967. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika,
Vol. 41, No. 1, pp. 28–37, January–February, 2000. 相似文献
2.
The development of the Richtmyer-Meshkov instability driven by a shock wave reflected from a rigid wall is investigated. It is shown that the perturbation amplitude growth rate depends on the nature of the shock wave refraction on the interface between gases of different density. In the case of regular-soft refraction the reduction in the growth rate of the Richtmyer-Meshkov instability associated with the continuous change in density on the interface is measured.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 52–58, September–October, 1996. 相似文献
3.
The direct numerical simulation method is adopted to study the non-linear characteristics of Rayleigh-Taylor instable perturbations at the ablation front of a 200 μm planar CH ablation target. In the simulation, the classical electrical thermal conductivity is included, and NND difference scheme is used. The linear growth rates obtained from the simulation agree with the Takabe formula. The ampli- tude distribution of the density perturbation at the ablation front is obtained for the linear growth case. The non-linear characteristics of Rayleigh-Taylor instable perturbations are analyzed and the numerical results show that the amplitude distributions of the compulsive harmonics are very different from that of the fundamental perturbation. The characteristics of the amplitude distributions of the harmonics and their fast growth explain why spikes occur at the ablation front. The numerical results also show that non-linear effects have relations with the phase differences of double mode initial perturbations, and different phase differences lead to varied spikes. 相似文献
4.
A. N. Kudryavtsev S. G. Mironov T. V. Poplavskaya I. S. Tsyryul’nikov 《Journal of Applied Mechanics and Technical Physics》2006,47(5):617-627
The evolution of disturbances in a hypersonic viscous shock layer on a flat plate excited by slow-mode acoustic waves is considered
numerically and experimentally. The parameters measured in the experiments performed with a free-stream Mach number M
∞ = 21 and Reynolds number Re
L = 1.44 · 105 are the transverse profiles of the mean density and Mach number, the spectra of density fluctuations, and growth rates of
natural disturbances. Direct numerical simulation of propagation of disturbances is performed by solving the Navier-Stokes
equations with a high-order shock-capturing scheme. The numerical and experimental data characterizing the mean flow field,
intensity of density fluctuations, and their growth rates are found to be in good agreement. Possible mechanisms of disturbance
generation and evolution in the shock layer at hypersonic velocities are discussed.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 3–15, September–October, 2006. 相似文献
5.
Thomas Boeck Jie Li Enrique López-Pagés Philip Yecko Stéphane Zaleski 《Theoretical and Computational Fluid Dynamics》2007,21(1):59-76
We perform numerical simulations of two-phase liquid–gas sheared layers, with the objective of studying atomization. The Navier–Stokes equations for two-dimensional incompressible flow are solved in a periodic domain. A volume-of-fluid method is used to track the interface. The density ratio is kept around 10. The calculations show good agreement with a fully viscous Orr–Sommerfeld linear theory over several orders of magnitude of interface growth. The nonlinear development shows the growth of finger-like structures, or ligaments, and the detachment of droplets. The effect of the Weber and Reynolds numbers, the boundary layer width and the initial perturbation amplitude are discussed through a number of typical cases. Inversion of the liquid boundary layer is shown to yield more readily ligaments bending upwards and is thus more likely to produce droplets. 相似文献
6.
The separated flow past a transverse barrier on a plate surface is modeled in a wind tunnel. The linear stability of the two-dimensional
laminar flow in the separation zone is investigated in the presence of a stationary disturbance imposed on the flow and concentrated
in a narrow spanwise region. It is experimentally shown that the local flow nonuniformity leads to a change in the flow stability
features, such as the frequencies of the growing oscillations, their growth rate, and the dispersion characteristics. As a
result, the transverse velocity gradients induced in the separation zone exert a strong destabilizing influence on the flow.
Novosibirsk. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 174–178, January–February,
2000.
The study was carried out with the support of the INTAS Foundation under grant No, 96-2225. 相似文献
7.
V. E. Dontsov V. E. Nakoryakov 《Journal of Applied Mechanics and Technical Physics》2000,41(5):845-854
The process of evolution and reflection of shock waves of moderate amplitude from a rigid boundary in a porous medium saturated
by a liquid with bubbles of a soluble gas is studied experimentally. Experimental values of the amplitude and velocity of
the reflected wave are compared with the calculated results obtained using mathematical models. The process of dissolution
of gas bubbles in the liquid behind the shock wave is studied.
Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 5, pp. 91–102, September–October, 2000. 相似文献
8.
9.
S. G. Mironov 《Journal of Applied Mechanics and Technical Physics》1999,40(6):1029-1035
The characteristics of travelling perturbations of density in a hypersonic shock layer on a flat plate for the Mach number
M∞=21 and unit Reynolds numberRe
1=6·105 m−1 were experimentally studied by the method of electron-beam fluorescence. The perturbations were generated by interaction
of the shock layer behind an oblique gas-dynamic whistle and the leading edge of the plate. The cases of unsteady and quasi-steady
interaction were considered. In both cases, vortex disturbances of finite amplitude were generated. The measurements were
performed at the fundamental frequency F=0.6·10−4 and at the harmonic; the streamwise phase velocities, the growth rates of the disturbances, and the angles of wave propagation
were obtained. The measurement results are compared with some experimental data for subsonic flows, some particular results
of the linear stability theory for compressible flows, and the results obtained on the basis of a simple model of the nonlinear
stage of disturbance evolution in a hypersonic boundary layer.
Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 41–47, November–December, 1999. 相似文献
10.
V. I. Bukreev 《Journal of Applied Mechanics and Technical Physics》2006,47(1):54-60
The effect of the nonmonotonic temperature dependence of water density on gravity current flow after removal of the shield
which separated warm and cold water was studied experimentally. If the temperature of water of maximum density was in the
interval between the initial temperatures on the different sides of the shield, Rayleigh-Taylor instability developed along
with shear instability under normal conditions.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 66–73, January–February, 2006. 相似文献
11.
W. D. Thacker S. Sarkar T. B. Gatski 《Theoretical and Computational Fluid Dynamics》2007,21(3):171-199
The influence of compressibility on the rapid pressure–strain rate tensor is investigated using the Green’s function for the
wave equation governing pressure fluctuations in compressible homogeneous shear flow. The solution for the Green’s function
is obtained as a combination of parabolic cylinder functions; it is oscillatory with monotonically increasing frequency and
decreasing amplitude at large times, and anisotropic in wave-vector space. The Green’s function depends explicitly on the
turbulent Mach number M
t
, given by the root mean square turbulent velocity fluctuations divided by the speed of sound, and the gradient Mach number
M
g
, which is the mean shear rate times the transverse integral scale of the turbulence divided by the speed of sound. Assuming
a form for the temporal decorrelation of velocity fluctuations brought about by the turbulence, the rapid pressure–strain
rate tensor is expressed exactly in terms of the energy (or Reynolds stress) spectrum tensor and the time integral of the
Green’s function times a decaying exponential. A model for the energy spectrum tensor linear in Reynolds stress anisotropies
and in mean shear is assumed for closure. The expression for the rapid pressure–strain correlation is evaluated using parameters
applicable to a mixing layer and a boundary layer. It is found that for the same range of M
t
there is a large reduction of the pressure–strain correlation in the mixing layer but not in the boundary layer. Implications
for compressible turbulence modeling are also explored.
相似文献
12.
V. E. Dontsov 《Journal of Applied Mechanics and Technical Physics》2005,46(3):346-354
Propagation of a stepwise shock wave in a liquid containing spherical gas-liquid clusters is experimentally studied. Measured
results are compared with available theoretical models. It is shown that resonant interaction of gas-liquid clusters in the
wave can increase the amplitude of oscillations in the shock wave.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 50–60, May–June, 2005. 相似文献
13.
Heat transfer characteristics to laminar pulsating pipe flow under different conditions of Reynolds number and pulsation
frequency were experimentally investigated. The tube wall of uniform heat flux condition was considered. Reynolds number was
varied from 780 to 1987 while the frequency of pulsation ranged from 1 to 29.5 Hz. The results showed that the relative mean
Nusselt number is strongly affected by pulsation frequency while it is slightly affected by Reynolds number. The results showed
enhancements in the relative mean Nusselt number. In the frequency range of 1–4 Hz, an enhancement up to 30% (at Reynolds
number of 1366 and pulsation frequency of 1.4 Hz) was obtained. In the frequency range of 17–25 Hz, an enhancement up to 9%
(at Reynolds number of 1366 and pulsation frequency of 17.5 Hz) was indicated. The rate of enhancement of the relative mean
Nusselt number decreased as pulsation frequency increased or as Reynolds number increased. A reduction in relative mean Nusselt
number occurred outside these ranges of pulsation frequencies. A reduction in relative mean Nusselt number up to 40% for pulsation
frequency range of 4.1–17 Hz and a reduction up to 20% for pulsation frequency range of 25–29.5 Hz for Reynolds numbers range
of 780–1987 were considered. This reduction is directly proportional to the pulsation frequency. Empirical dimensionless equations
have been developed for the relative mean Nusselt number that related to Reynolds number (750 < Re < 2000) and the dimensionless
frequency (3<Ω<18) with about 10% rms.
Received on 16 May 2000 / Published online: 29 November 2001 相似文献
14.
A. A. Lugovtsov 《Journal of Applied Mechanics and Technical Physics》2009,50(2):327-335
Equations describing the propagation of waves of small but finite amplitude in a liquid with gas bubbles are derived. The
bubble distribution density is a continuous function of bubble size and spatial coordinates. It is found that, for a uniform
bubble distribution, the obtained equations become the Korteweg-de Vries, Kadomtsev-Petviashvili and Khokhlov-Zabolotskaya
equations.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 188–197, March–April, 2009. 相似文献
15.
V. A. Ogorodnikov A. L. Mikhailov A. V. Romanov A. A. Sadovoi S. S. Sokolov O. A. Gorbenko 《Journal of Applied Mechanics and Technical Physics》2007,48(1):11-16
The problem of the incidence of a shock wave with a front-pressure amplitude of about 30 GPa at the profiled free surface
of an aluminum sample is studied. It is shown that in the case of large perturbations (amplitude 1 mm and wavelength 10 mm), jet flows occur on the free surface. The data obtained are described using a kinetic fracture model that takes into account
the damage initiation and growth in the material due to tensile stress and shear strain.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 16–23, January–February, 2007. 相似文献
16.
The investigation of codimension-2 bifurcations, in particular in systems with cylindric symmetry, enables us to deduce new
types of secondary regimes branching-off from the symmetric regimes. This investigation also allows us the unique possibility
of a rigorous treatment of chaotic solutions to Navier–Stokes and other nonlinear PDE’s. The central manifold approach combined
with the reduction to the normal form lead to the so-called amplitude systems. These ODE systems describe the nonlinear interaction
between the neutral modes, and always include several nonlinear terms due to so-called intrinsic resonances. However, sometimes
additional resonances appear. In this paper we present the complete list of all possible resonances in dynamic systems with
cylindric symmetry and the corresponding forms of the amplitude equations. Further, we present the results of extensive numerical
investigation of the resonant codimension-2 bifurcations in the Couette–Taylor problem, thus creating an intriguing subject
for further investigation. 相似文献
17.
The response of a magneto-rheological fluid (MRF) to a change of magnetic flux density is investigated by using a commercial
plate–plate magneto-rheometer MCR501 (Anton Paar GmbH) at constant shear rate. The instrument was modified to allow an online
determination of the transient flux density in the MRF. Both current and voltage imposition to the magneto-cell were applied
by using a power operational amplifier to drive the electromagnet. Assuming a Maxwell behavior with switching time λ and a linear increase in shear stress with flux density, analytic relations for the transient shear stress are derived for
sinusoidal and single exponential flux densities vs time. True switching times of a few milliseconds are only obtained if
the low pass filter in the original MCR501 torque signal is surpassed by a firmware allowing a sampling rate of 0.1 ms. For
a sinusoidal flux density, the switching time is derived from the modulation depth of the shear stress. An upper bound of
λ < 3 ms for a flux density of 0.8 T was found. For step coil current imposition of 1 T magnitude, switching times of 2.8 ms
(start-up) and 1.8 ms (shutdown) allowed to fit the transient torque signal more than 2/3 of the total change. Finally, the
effect of a sigmoidal characteristic on the switching time determination is addressed.
This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27-29, 2006. 相似文献
18.
The growth and coalescence of two microholes in copper foil were studied experimentally byin situ tensile tests under a scanning electronic microscope. Two microholes of 15–35 μm in diameter were arranged in different distances
and orientations. It was found that the mechanisms of microhole evolution were represented by slipping band creation, and
then crack initiation and propagation along the slipping bands in ligament. The process of microhole growth and coalescence
was influenced by the inter-center distance and orientation of microholes. The critical surface of microholes at coalescence
is about 2–2.5 times that of the initial one. The variation of both the inter-center distance and orientation depends on the
initial angle. 相似文献
19.
I.V. Erofeev V.V. Silberschmidt A.A. Kalin V.A. Moiseev I.V. Solomatin 《Shock Waves》1998,8(3):177-181
Effects of shock waves (generated by a nanosecond laser pulse in plates of Armco-iron) on structural changes are analysed.
Localisation of processes of martensitic transformation and twinning – for various values of laser pulse duration – is studied
both experimentally and numerically. A proposed model accounts for interaction of shock wave propagation and structure changes.
Realisation of martensitic transformation and twin formation influences wave front modification. A stress amplitude decrease
with increasing distance from a microcrater determines, together with the pulse duration, a character of spatial localisation
of structural changes. Numerical results are compared with experimental data and serve as a basis for additional interpretation
of phenomena.
Received 9 August 1994 / Accepted 30 June 1997 相似文献
20.
T. V. Bazhenova S. B. Bazarov T. A. Bormotova V. V. Golub A. M. Shulmeister 《Fluid Dynamics》1998,33(2):190-195
The nonstationary interaction between a supersonic pulse jet and a flat plate perpendicular to the jet axis is studied experimentally
and numerically. The time dependences of the pressure and heat flux at various points on the obstacle and the spatial distribution
of the density are obtained experimentally. The nonstationary flow is calculated numerically by the Godunov method. The experiments
and calculations reveal the effect of the reflected starting shock wave and the front part of the swirled gas outflow on the
distribution of the dynamic and thermal loads acting on the plate, in both time and space.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 45–51, March–April, 1998.
This research was carried out with partial financial support from the Russian Foundation for Fundamental Research (project
No. 96-02-16170). 相似文献