共查询到20条相似文献,搜索用时 15 毫秒
1.
A numerical study has been undertaken to examine the behaviour of a gas liquid interface in a vertical cylindrical vessel subjected to a sinusoidal vertical motion. The computational method used is based on the simplified marker‐and‐cell method and includes a continuum surface model for the incorporation of surface tension. The numerical results indicate that the surface tension has very little effect on the period and amplitude of oscillations of the interfacial waves. The stability of the interfacial waves has been found to depend on the initial pressure pulse disturbance, and exponential growth of the interfacial wave has been observed in some cases. The influence of the amplitude and frequency of the forcing oscillations has also been investigated. The results are in good agreement with available experimental and analytical solutions. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
N. Afgan 《Journal of Applied Mechanics and Technical Physics》1973,14(5):654-659
One of the basic parameters defining the intensity of heat transfer on the boundary separating liquid and vapor phases is the superheating of the liquid during boiling. In a two-phase boundary layer superheating constitutes a variable (fluctuating) quantity, which depends on several parameters of the system and is of a statistical nature. This paper is devoted to a study of the statistical nature of the fluctuations in the superheating of a liquid. Starting from experimental data, obtained in measuring temperature fluctuations in a two-phase boundary layer during the boiling of water in contact with a heated surface, we carry out a statistical analysis of the amplitude of the fluctuations. Based on this analysis, we determine the average and the maximum superheating as a function of the distance to the heated wall. To determine the microstructure of the temperature fluctuations and to study their origin, we took high-speed pictures of the head of a thermocouple in contact with the two-phase medium. We established that the presence of various size amplitudes is associated, in the main, with two effects: the existence of a superheated layer on a bubble in the course of its growth and the convection of the liquid close to the bubble.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 62–69, September–October, 1973. 相似文献
3.
Some of the main progress on the investigation of the mechanism of the wave formation in explosive welding at the Institute
of Mechanics is summarized and others' previous works are reviewed. Our systematic experiments and analysis do not substantiate
the theory of wave formation based on Karman vortex-street analogy or Helmholtz instability. On the contrary, they show that
material strength insensitive to strain rate plays an important role. A simple hydro-plastic model is presented to explain
the main features regarding the interfacial wave formation and to estimate the magnitude of wave length. The result is in
broad agreement with experiment. 相似文献
4.
I. N. Soldatov 《Journal of Applied Mechanics and Technical Physics》2008,49(2):167-171
The dispersion characteristics of gyroscopic waves in an incompressible liquid layer in a cavity of a rapidly rotating cylinder
are studied. It is shown that in a viscous incompressible liquid layer, an inertial wave can be represented as the sum of
six helical harmonics. The effects of the liquid viscosity and the ratio of the wave frequency to the angular velocity of
rotation of the cylinder on the real and imaginary parts of the wavenumber are studied.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 15–20, March–April, 2008. 相似文献
5.
The paper presents a contribution to modelling the problem of vapour–liquid interface receding into dried body and stresses
induced by drying of capillary-porous bodies. A complex algorithm comprising the specific mechanisms of drying in the first
and second periods of drying is constructed. It enables calculation and drawing of the body temperature and drying curves
for the whole drying process and identification of the vapour–liquid interface receding into the body. The drying induced
stresses caused by the receding vapour–liquid interface and the non-uniform distribution of moisture content and/or temperature
are analyzed. Numerical calculations of the temperature and drying curves and the drying induced stresses are carried out
for the example of a finite dimensional kaolin cylinder dried convectively. 相似文献
6.
S. D. R. Wilson 《Rheologica Acta》1995,34(6):601-605
The problem of thermocapillary (Marangoni) convection in a layer of viscoelastic liquid is considered. The stability boundary for this problem has been previously calculated in various cases by a number of authors. Here attention is fixed on the magnitude of the growth rate in the parameter regime corresponding to instability. Two noteworthy features are pointed out. First, there are anomalously large values of the growth rate at or near the limiting special case of a Maxwell fluid. Second, the complex values of the growth rate (corresponding to overstability, or the onset of instability via oscillatory motion) coalesce into real (positive) values at moderately supercritical values of the Marangoni number, suggesting that overstability might be elusive to observation. 相似文献
7.
8.
According to the classical elastic theory, there is always a discontinuity of rotation angle on the interface between different
materials. This illogic result can be overcome by the strain gradient plasticity theory. In the light of this theory, there
is a group of boundary layer solutions near the interface, which have made important adjustment of the classical results.
This project is supported by National Natural Science Foundation of China (19891180). 相似文献
9.
A. A. Korobkin 《Journal of Applied Mechanics and Technical Physics》2006,47(5):643-653
The two-dimensional unsteady problem of the impact of a vertical wall on a layer of a liquid which is mixed with air near
the wall and does not contain air bubbles away from the wall is solved in a linear approximation. The gas-liquid mixture is
modeled by a homogeneous, ideal, and weakly compressible medium with a reduced sound velocity dependent on the air concentration
in the gas-liquid mixture. Outside the gas-liquid layer, the liquid is considered ideal and incompressible. During the initial
stage of the impact, the liquid flow and the hydrodynamic pressure are determined using the linear theory of the potential
motion of an inhomogeneous liquid. The dependence of the amplitude of the impact pressure along the wall on the air concentration
in the gas-liquid layer and on the thickness of this layer is investigated. For a small relative thickness of the layer, the
thin-layer approximation is used. It is shown that the solution of the original problem tends to the approximate solution
as the thickness of the layer decreases. It is shown that the presence of the gas-liquid layer leads to wall pressure oscillations.
Estimates are obtained for the pressure amplitude and the oscillation period.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 34–46, September–October, 2006. 相似文献
10.
Helmut F. Bauer 《Applied Scientific Research》1992,49(3):283-305
A cylindrical annular liquid layer between two plates and around a rigid center-core consisting of incompressible and viscous liquid is subjected to different axial excitations, such as one-sided, counter-directional and double-sided unequal excitations. The response of the free liquid surface, the velocity- and pressure-distribution has been determined.
List of symbols a radius of liquid layer - b radius of inner cylindrical core - (a–b) thickness of layer - e r , e , k unit vectors in the radial, angular and axial direction resp. - h length of layer - I m , K m modified Bessel functions of first and second kind and order m - diameter ratio - p pressure - q 2na/h - q* na/h - r, , z cylindrical coordinates - complex frequency - S sa 2/ - t time - u, w velocity components in the radial- and axial direction - 0 excitation amplitude - abbreviation - surface tension parameter - surface tension - dynamic viscosity - kinematic viscosity - density of liquid - free liquid surface elevation - dimensionless time - rz shear stress - reduced forcing frequency - forcing frequency - stream function - mn natural frequency of non-viscous liquid 相似文献
Zusammenfassung Eine zylindrische Flüssigkeitsschicht bestehend aus inkompressibler und viskoser Flüssigkeit wurde verschiedenen harmonischen Anregungsformen ausgesetzt. Dabei wurden die Fälle einseitiger, doppelseitiger entgegengesetzter und ungleicher doppelseitiger Anregung mit Phase behandelt. Die Vergrößerungsfunktionen für die freie Flüssigkeitsoberfläche, für die Geschwindigkeits- und Druckverteilung wurden bestimmt.
List of symbols a radius of liquid layer - b radius of inner cylindrical core - (a–b) thickness of layer - e r , e , k unit vectors in the radial, angular and axial direction resp. - h length of layer - I m , K m modified Bessel functions of first and second kind and order m - diameter ratio - p pressure - q 2na/h - q* na/h - r, , z cylindrical coordinates - complex frequency - S sa 2/ - t time - u, w velocity components in the radial- and axial direction - 0 excitation amplitude - abbreviation - surface tension parameter - surface tension - dynamic viscosity - kinematic viscosity - density of liquid - free liquid surface elevation - dimensionless time - rz shear stress - reduced forcing frequency - forcing frequency - stream function - mn natural frequency of non-viscous liquid 相似文献
11.
V. K. Andreev 《Journal of Applied Mechanics and Technical Physics》2008,49(4):598-609
A study is made of an invariant solution of the equations of a viscous heat-conducting fluid, which is treated as unidirectional
motion of two such fluids in a plane layer with a common boundary under the action of an unsteady pressure gradient. A priori
estimates of the velocity and temperature are obtained. The steady state is determined, and it is shown (under some conditions
on the pressure gradient) that, at larger times, this state is the limiting one. For semiinfinite layers, a solution in closed
form is obtained using the Laplace transform.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 4, pp. 94–107, July–August, 2008. 相似文献
12.
13.
The transient flow in the Ekman layer of an elastico-viscous liquid near a flat plate is discussed. Initially the fluid and the plate were rotating together and the plate then suddently starts moving with a uniform velocity in its own plane relative to the rotating frame of reference. It is shown that the ultimate steady state is reached through decay of inertial oscillations whose frequency decreases with increase in the elastic parameter. 相似文献
14.
The linear stability of a viscoelastic liquid saturated horizontal anisotropic porous layer heated from below and cooled from
above is investigated by considering the Oldroyd type liquid. A generalized Darcy model, which takes into account the viscoelastic
properties, the mechanical and thermal anisotropy is employed as momentum equation. The critical Rayleigh number, wavenumber,
for stationary and oscillatory states and frequency of oscillation are determined analytically. It is shown that oscillatory
instabilities can set in before stationary modes are exhibited. The effect of the viscoelastic parameter, the mechanical and
thermal anisotropy parameters and specific heat ratio on the linear stability of the system is analyzed and presented graphically. 相似文献
15.
Yu. V. Sanochkin 《Fluid Dynamics》1984,19(6):986-992
The article considers stationary thermocapillary convection in a thin horizontal layer of fluid with Prandtl number Pr < 1 when it is being locally heated from above in conditions in which the curvature of the free surface is small. It is shown that the motion has a cellular structure. The size of the convective cell is determined from the solution to the spectral problem to which the integration of the free convection system of equations reduces. If the Maragoni (Péclet) number is sufficiently high, the length of the convective cell turns out to be large in comparison with the thickness of the layer. The convection picture is considered and an expression obtained for the velocity of the developing flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 146–152, November–December, 1984. 相似文献
16.
V. E. Zakhvataev 《Journal of Applied Mechanics and Technical Physics》1995,36(2):177-182
Research performed with financial support from the Krasnoyarsk Scientific Fund (Project Code 2F0059). 相似文献
17.
18.
研究了二个半平面的反平面运动,二个半平面都是剪切弹性模量与材料密度为梯度的非均匀介质,它们之间的界面是具有Coulomb摩擦的单侧界面. 当介质的梯度参数按二次幂规律变化时,求得了这一问题的解析解,给出了界面上粘着区与滑移区以及相应的界面剪应力与相对滑移量的分布. 通过抛物线脉冲入射下的数值计算发现:界面上的剪应力呈反双峰形分布,正、反滑移区出现在峰值点附近,其范围随界面上施加的外压力σ=fsp∞/μ0的增加而减小,当外压力达到某一数值时,滑移区消失,整个界面将完全粘着在一起. 相似文献
19.
The effect of fillers on the flow curves of polymeric liquid crystals is investigated. Suspensions of polystyrene particles
in liquid crystalline solutions of hydroxypropylcellulose (HPC) in water are used. By reducing the HPC concentration an isotropic
solution can be prepared. It serves as a reference to isolate the effect of the isotropic/anisotropic structure of the suspending
medium on the rheological behaviour. Suspensions in the isotropic solution behave as expected for filled viscoelastic matrices
in general. In the anisotropic medium the shear rate rather than the shear stress seems to govern the changes in the relative
viscosity. This behaviour is clearly different from isotropic viscoelastic media. The most dramatic effect however is that
even small amounts of particles eliminate or drastically shift the region of negative normal stress differences. As far as
the structure is concerned, microscopic observations show that particles align in anisotropic as well as in isotropic media.
At rest or at relatively low shear stresses the liquid crystalline structure is, in the present case, hardly affected by the
presence of the particles. If anything, it becomes more homogeneous.
Received: 28 April 1998 Accepted: 28 July 1998 相似文献
20.
E. A. Demekhin 《Fluid Dynamics》1983,18(5):687-694
Traveling waves in a viscous liquid flowing down an inclined plane can be described at small and moderate Reynolds numbers by an ordinary differential equation in the thickness of the layer [1, 2]. As the Reynolds number tends to zero, this equation goes over into an equation of third order with quadratic nonlinearity [3]. Periodic solutions of this last equation bifurcating from the plane-parallel solution have been investigated by Nepomnyashchii and Tsvelodub [3–6]. In the present paper, a study is made of the bifurcation of periodic solutions from periodic solutions, namely, an investigation is made of the values of the wave number for which a periodic solution is not unique; a bifurcation equation is derived, the number of bifurcating solutions is found, and their behavior near a bifurcation point is considered; and the bifurcating solutions are continued numerically with respect to a parameter (the wave number) from the neighborhoods of the bifurcation points. 相似文献