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1.
Using the half-space moment method, the problem of the slip of a diatomic gas along a rigid spherical surface is solved within
the framework of a model kinetic equation previously proposed which takes into account the rotational degrees of freedom of
the gas. Second-order slip coefficients (correctionsC
m
′
, β
R
′
, and β
R
to the isothermal and thermal slip which are linear with respect to the Knudsen number Kn) are obtained. The gas macroparameter
jump coefficientsC
v andC
q, which are of the second order in the Knudsen number and characterize the discontinuity of the normal mass and heat fluxes
on the gas-rigid phase interface, are calculated. These coefficients are given as functions of the tangential momentum accommodation
coefficient, the translational and rotational energy accommodation coefficients, and the Prandtl number. The coefficients
are calculated for certain diatomic gases.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 163–173, January–February,
2000. 相似文献
2.
On the basis of a numerical solution of the unsteady Navier-Stokes equations, the flow past a finite plate with an upstream-moving
surface is investigated. For the Reynolds numbers Re =102−104, the flow past the plate is analyzed as a function of the relative plate surface velocity. On the basis of this analysis
a limiting mathematical model of the flow as Re → ∞ is proposed. 相似文献
3.
The flow and heat transfer in an inclined and horizontal rectangular duct with a heated plate longitudinally mounted in the
middle of cross section was experimentally investigated. The heated plate and rectangular duct were both made of highly conductive
materials, and the heated plate was subjected to a uniform heat flux. The heat transfer processes through the test section
were under various operating conditions: Pr ≈ 0.7, inclination angle ϕ = −60° to +60°, Reynolds number Re = 334–1,911, Grashof number Gr = 5.26 × 102–5.78 × 106. The experimental results showed that the average Nusselt number in the entrance region was 1.6–2 times as large as that
in the fully developed region. The average Nusselt numbers and pressure drops increased with the Reynolds number. The average
Nusselt numbers and pressure drops decreased with an increase in the inclination angle from −60° to +60° when the Reynolds
number was less than 1,500. But when the Reynolds number increased to over about 1,800, the heat transfer coefficients and
pressure drops were independent of inclination angles. 相似文献
4.
A. A. Vasil’ev V. N. Rychkov M. E. Topchiyan 《Journal of Applied Mechanics and Technical Physics》2007,48(3):361-367
The laminar-turbulent transition is experimentally studied in boundary-layer flows on cones with a rectangular axisymmetric
step in the base part of the cone and without the step. The experiments are performed in an A-1 two-step piston-driven gas-dynamic
facility with adiabatic compression of the working gas with Mach numbers at the nozzle exit M
∞ = 12–14 and pressures in the settling chamber P0 = 60–600 MPa. These values of parameters allow obtaining Reynolds numbers per meter near the cone surface equal to Re
1e = (53–200) · 106
m
−1. The transition occurs at Reynolds numbers Re
tr
= (2.3–5.7) · 106.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 76–83, May–June, 2007. 相似文献
5.
Understanding the radiation embrittlement of reactor pressure vessel (RPV) steels is required to be able to operate safely
a nuclear power plant or to extend its lifetime. The mechanical properties degradation is partly due to the clustering of
solute under irradiation. To gain knowledge about the clustering process, a Fe−1.1 Mn−0.7 Ni (at.%) alloy was irradiated in
a test reactor at two fluxes of 0.15 and 9 ×1017 n
E > 1MeV
.m − 2.s − 1 and at increasing doses from 0.18 to 1.3 ×1024 n
E > 1MeV
.m − 2 at 300°C. Atom probe tomography (APT) experiments revealed that the irradiation promotes the formation in the α iron matrix of Mn/Mn and/or Ni/Ni pair correlations at low dose and Mn–Ni enriched clusters at high dose. These clusters
dissolve partially after a thermal treatment at 400°C. Based on a comparison with thermodynamic calculations, we show that
the solute clustering under irradiation can just result from an induced mechanism. 相似文献
6.
The combined effect of a vertical AC electric field and the boundaries on the onset of Darcy–Brinkman convection in a dielectric
fluid saturated porous layer heated either from below or above is investigated using linear stability theory. The isothermal
bounding surfaces of the porous layer are considered to be either rigid or free. It is established that the principle of exchange
of stability is valid irrespective of the nature of velocity boundary conditions. The eigenvalue problem is solved exactly
for free–free (F/F) boundaries and numerically using the Galerkin technique for rigid–rigid (R/R) and lower-rigid and upper-free
(F/R) boundaries. It is observed that all the boundaries exhibit qualitatively similar results. The presence of electric field
is emphasized on the stability of the system and it is shown that increasing the AC electric Rayleigh number R
ea is to facilitate the transfer of heat more effectively and to hasten the onset of Darcy–Brinkman convection. Whereas, increase
in the ratio of viscosities Λ and the inverse Darcy number Da
−1 is to delay the onset of Darcy–Brinkman electroconvection. Besides, increasing R
ea and Da
−1 as well as decreasing Λ are to reduce the size of convection cells. 相似文献
7.
The problem of the self-similar boundary flow of a “Darcy-Boussinesq fluid” on a vertical plate with temperature distribution
T
w(x) = T
∞+A·x
λ and lateral mass flux v
w(x) = a·x
(λ−1)/2, embedded in a saturated porous medium is revisited. For the parameter values λ = 1,−1/3 and −1/2 exact analytic solutions
are written down and the characteristics of the corresponding boundary layers are discussed as functions of the suction/ injection
parameter in detail. The results are compared with the numerical findings of previous authors.
Received on 8 March 1999 相似文献
8.
N. I. Shishkin 《Journal of Applied Mechanics and Technical Physics》2007,48(2):145-152
The seismic energy transferred to an elastic half-space as a result of a contact explosion and a meteorite impact on a planet’s
surface is estimated. The seismic efficiency of the explosion and impact are evaluated as the ratio of the energy of the generated
seismic waves to the energy of explosion or the kinetic energy of the meteorite. In the case of contact explosions, this ratio
is in the range of 10−4–10−3. In the case of wide-scale impact effects, where the crater in the planet’s crust is produced in the gravitational regime,
a formula is derived that relates the seismic efficiency of an impact to its determining parameters.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 3–12, March–April, 2007. 相似文献
9.
Experiments were performed to study the strength of water under conditions of pulsed extension, which is typical of the interaction
between a triangular compression pulse and a free surface. The tests were performed in a wide (40–1000 MPa) range of rariation
in the amplitude of the compression pulse at deformation rates of 104−105 sec−1. It is found that as the compression-pulse amplitude increases from 150 to 1050 MPa, the strength of water decreases from
46 to 22 MPa. The deformation rate was found to have little effect on the strength. The possibility of using the model of
homogenous nucleation (formation of cavitation nuclei) to interpret the data obtained is discussed.
Institute of Chemical Physical, Russian Academy of Sciences, Chernogolovka 142432. Translated from Prikladmaya Mekhanika i
Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 198–205, July–August, 2000. 相似文献
10.
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
11.
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
12.
In order to evaluate characteristics of the liquid film flow and their influences on heat and mass transfer, measurements
of the instantaneous film thickness using a capacitance method and observation of film breakdown are performed. Experimental
results are reported in the paper. Experiments are carried out at Re = 250–10000, T
in = 20–50°C and three axial positions of vertically falling liquid films for film thickness measurements. Instantaneous surface
waveshapes are given by the interpretation of the test data using the cubic spline method. The correlation of the mean film
thickness versus the film Reynolds number is also given by fitting the test data. It is revealed that the surface wave has
nonlinear behavior. Observation of film breakdown is performed at Re = 1.40 × 103–1.75 × 104 and T
in = 85–95°C. From experimental results, the correlation of the film breakdown criterion can be obtained as follows: Bd = 1.567 × 10−6
Re
1.183 相似文献
13.
Leonid Brevdo 《Journal of Elasticity》1997,49(3):201-237
We solve the initial-boundary-value linear stability problem for small localised disturbances in a homogeneous elastic waveguide
formally by applying a combined Laplace – Fourier transform. An asymptotic evaluation of the solution, expressed as an inverse
Laplace – Fourier integral, is carried out by means of the mathematical formalism of absolute and convective instabilities.
Wave packets, triggered by perturbations localised in space and finite in time, as well as responses to sources localised
in space, with the time dependence satisfying e−iωt
+ O(e−ɛt
), for t → ∞, where Im ω0 = 0 and ω > 0 , that is, the signaling problem, are treated. For this purpose, we analyse the dispersion relation of the
problem analytically, and by solving numerically the eigenvalue stability problem. It is shown that due to double roots in
a wavenumber k of the dispersion relation function D(k, ω), for real frequencies ω, that satisfy a collision criterion, wave packets with an algebraic temporal decay and signaling
with an algebraic temporal growth, that is, temporal resonances, are present in a neutrally stable homogeneous waveguide.
Moreover, for any admissible combination of the physical parameters, a homogeneous waveguide possesses a countable set of
temporally resonant frequencies. Consequences of these results for modelling in seismology are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
Summary A boundary layer problem of a nonnewtonian fluid flow with fluid injection on a semi-infinite flat plate whose surface moves
with a constant velocity in the opposite direction to that of the uniform mainstream is analyzed. Concluding similarity equations
are solved numerically to show the dependence of the problem to the velocity ratio λ of the plate to uniform flow and to the
injection velocity parameter C. The critical values of λ and C for each nonnewtonian power-law index n are obtained, and their significance in drag reduction is discussed.
Received 26 August 1997; accepted for publication 21 October 1998 相似文献
15.
The unsteady natural convection boundary layer flow over a semi-infinite vertical cylinder is considered with combined buoyancy
force effects, for the situation in which the surface temperature T
′
w(x) and C
′
w(x) are subjected to the power-law surface heat and mass flux as K(T
′/r) = −ax
n
and D(C
′/r) = −bx
m
. The governing equations are solved by an implicit finite difference scheme of Crank-Nicolson method. Numerical results are
obtained for different values of Prandtl number, Schmidt number ‘n’ and ‘m’. The velocity, temperature and concentration profiles, local and average skin-friction, Nusselt and Sherwood numbers are
shown graphically. The local Nusselt and Sherwood number of the present study are compared with the available result and a
good agreement is found to exist.
Received on 7 July 1998 相似文献
16.
The passage of solid spheres through a liquid–liquid interface was experimentally investigated using a high-speed video and
PIV (particle image velocimetry) system. Experiments were conducted in a square Plexiglas column of 0.1 m. The Newtonian Emkarox
(HV45 50 and 65% wt) aqueous solutions were employed for the dense phase, while different silicone oils of different viscosity
ranging from 10 to 100 mPa s were used as light phase. Experimental results quantitatively reveal the effect of the sphere’s
size, interfacial tension and viscosity of both phases on the retaining time and the height of the liquid entrained behind
the sphere. These data were combined with our previous results concerning the passage of a rising bubble through a liquid–liquid
interface in order to propose a general relationship for the interface breakthrough for the wide range of Mo
1/Mo
2 ∈ [2 × 10−5–5 × 104] and Re
1/Re
2 ∈ [2 × 10−3–5 × 102]. 相似文献
17.
In this paper, an improved plate impact experimental technique is presented for studying dynamic fracture mechanism of materials,
under the conditions that the impacting loading is provided by a single pulse and the loading time is in the sub-microsecond
range. The impacting tests are carried out on the pressure-shear gas gun. The loading rate achieved is dK/dt∼108 MPa m1/2s−1. With the elimination of influence of the specimen boundary, the plane strain state of a semi-infinite crack in an infinite
elastic plate is used to simulate the deformation fields of crack tip. The single pulses are obtained by using the “momentum
trap” technique. Therefore, the one-time actions of the single pulse are achieved by eradicating the stress waves reflected
from the specimen boundary or diffracted from the crack surfaces. In the current study, some important phenomena have been
observed. The special loading of the single pulse can bring about material damage around crack tip, and affect the material
behavior, such as kinking and branching of the crack propagation. Failure mode transitions from mode I to mode II crack are
observed under asymmetrical impact conditions. The mechanisms of the dynamic crack propagation are consistent with the damage
failure model.
The project supported by the National Natural Science Foundation of China (No. 19672066 and 18981180-4) and the Key Project
of Chinese Academy of Sciences (No. KJ951-1-20) 相似文献
18.
Method for identification of the filled polymer material relaxation kernel in millisecond time range
The filled polymer materials exhibit viscoelastic properties in a wide time range including the millisecond range (∼10−2–10 ms) characteristic of different shock loadings of structures made of these materials. We propose a method for the identification
of the filled polymer material relaxation kernel in the millisecond time range; this method is based on a shock loading test
of a cylindrical sample made of this material. In this test, the disk indenter acceleration is measured by using a piezotransducer.
The test scheme does not impose any rigid constraints on the sample dimensions. In particular, it is possible to use samples
of typical dimensions of the order of 10 cm, for which the conditions that the sample material is representative of the structure
material are necessarily satisfied. The relaxation kernel parameters are identified by numerical minimization of the theoretically
predicted indenter velocity deviation from the velocity-time dependence obtained by integrating the acceleration transducer
readings. The minimization problem is solved by using a genetic algorithm. The problem of theoretical prediction of the indenter
velocity is solved numerically by using a reduced computational scheme whose parameters are chosen from the minimum condition
for the deviation from the prediction obtained in the framework of the detailed computational scheme. The use of the reduced
computational scheme permits decreasing the computational costs by 3–4 orders of magnitude compared with the detailed computational
scheme, which is a necessary condition for the practical applicability of the genetic algorithm in identification problems.
We present examples of relaxation kernel identification in the range of 0.1–10ms from the results of the test where the disk
indenter raised to the height of 1m falls on the sample end surface. 相似文献
19.
The characteristics of natural fluctuations of density in a laminar near wake behind a sharp cone in a hypersonic flow of
nitrogen at zero incidence are studied by the method of electronbeam fluorescence at Mach numberM=21 and unit Reynolds numberRe
1=6·105 m−1. The distributions of the mean density, integral fluctuations, and spectra of density fluctuations are obtained, the longitudinal
and azimuthal phase velocities of perturbations are determined, and the growth rates of perturbations in the wake are found.
The results are compared with the measurement data in the shock layer on a flat plate.
Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 3, pp. 111–117, May–June, 2000 相似文献
20.
V. M. Antonov É. L. Boyarintsev A. V. Melekhov V. G. Posukh A. G. Ponomarenko I. F. Shaikhislamov 《Journal of Applied Mechanics and Technical Physics》2009,50(3):389-395
The ion composition of a plasma flow obtained by intense irradiation of a solid target is determined by methods of probing
diagnostics and measuring the secondary emission rate. As the ions fly through a dense gas jet, C
5+
ions are found to recharge to C
4+
ions and then to C
3+
ions. The fraction of high-charge ions in the initial plasma flow and their concentration in the region of interaction with
the jet are calculated. The concentration of atoms in the gas jet is estimated on the basis of the integral change in the
charge value. Results necessary for analyzing the conditions of experiments on effective charge-transfer pumping and laser
generation in the far ultraviolet spectral range are obtained.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 36–43, May–June, 2009. 相似文献