共查询到20条相似文献,搜索用时 15 毫秒
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Analytical solutions for the time evolution of a capillary-gravitational wave in a charged layer of a viscous conducting liquid
on a solid support are found. It is shown that the velocity field eddy component of the wave-induced liquid flow arises not
only near the free surface of the liquid, but also at the solid bottom. The ratio between the amplitudes of these eddy components
depends on the relationship between the thickness of the layer and the wavelength. If the wavelength far exceeds the thickness,
the eddy flow amplitude near the bottom exceeds that near the free surface and the eddy flow occupies the whole volume of
the liquid. 相似文献
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The dispersion relation for the spectrum of capillary waves of a spherical layer of a viscous liquid coating a solid spherical
core with a layer of finite thickness is introduced and analyzed. It is shown that the existence of two mechanisms for the
viscous dissipation of the energy of the capillary-wave motions of the liquid, viz., damping in the bulk of the layer and
on the solid core, leads to restriction of the spectrum of the realizable capillary waves of the liquid on both the high-and
low-mode sides. At a fixed value of the system charge which is supercritical for the first several capillary modes, the maximum
growth rates in the case of a small solid core are possessed by modes from the middle of the band of unstable modes, while
in thin liquid layers the highest of the unstable modes have the largest growth rates. This points out differences in the
realization of the instability of the charged surface of the spherical layer for small and large relative sizes of the solid
core.
Zh. Tekh. Fiz. 67, 8–13 (September 1997) 相似文献
4.
《Journal of sound and vibration》1987,115(2):339-349
Parametric instabilities of a horizontal liquid layer with a finite depth covered by a thin elastic plate under a vertical periodic motion are investigated with account taken of the viscosity of the liquid layer. The primary regions and the secondary ones of dynamic instabilities are determined by using the equation of a thin elastic plate including the normal component of the viscous stress, but not the tangential component of it. The critical amplitude of the imposed oscillation, beyond which a parametric instability occurs (that is, the neutral stability curves) is found in the space of the frequency and amplitude of the imposed vertical oscillation. These results are confirmed by experimental ones for a liquid layer of glycerine covered with a thin rubber plate. 相似文献
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In this paper we study the interaction of a viscous fluid with an elastic solid. Of particular interest are the eigenmodes of the coupled system. Starting from the Navier-Stokes equations for the fluid and the linear elasticity equations for the solid, we derive the linear equations governing the motion of the system. It is shown how a variational formulation of the problem may be obtained by re-scaling the displacement unknowns. The finite-element technique is then used to discretize the equations. The resulting quadratic eigenvalue problem is solved by means of an inverse iteration procedure. 相似文献
7.
The theory of a boundary layer near the periodically oscillating free surface of a spherical viscous liquid layer over a solid
core (bottom) is modified. Two boundary layers are considered to adequately describe a liquid viscous flow in the system:
one at the free surface of the liquid and the other at the solid bottom. The thicknesses of the boundary layers are estimated,
which provide any given discrepancy between an exact solution to the model problem and a solution obtained in the small viscosity
approximation. Taking into account the boundary layer near the solid bottom is shown to be significant only for lower oscillation
modes. For higher modes, the flow near the core can be considered potential. In the case of lower modes and shallow liquid,
the surface and bottom boundary layers overlap and an eddy flow occupies the entire volume of the liquid. 相似文献
8.
Experimental results are presented on the Si damage induced by a copper-vapor laser beam under a layer of chemically neutral liquid (H2O, DMFA, DMSO). The lateral dimensions of the damaged area coincide with those of laser beam, while the depth of the damaged area increases with time. The rate of hole formation may be as high as 75 m/s. The qualitative interpretation of the results is given on the basis of laser generation of vacancies, and their combination and redistribution in the field of the inhomogeneous mechanical strains due to multiple heating/cooling cycles of the surface of the semiconductor. 相似文献
9.
We report results of computer simulations of the deformation and failure behavior of a thin crystalline strip of "hard disks" in two dimensions confined within a quasi-one-dimensional "hard-wall" channel of fixed width corresponding to a few disk diameters. Starting from a commensurate triangular solid, stretching the strip along its length introduces a rectangular distortion. This, beyond a critical strain, leads to failure of the solid by "phase separation" into alternating bands of solid and smectic-like phases. The critical strain is inversely proportional to the channel width, i.e., thinner strips are stronger. The large plastic deformation which precedes failure is observed to be reversible. 相似文献
10.
H.?N.?Yoshikawa C.?Mathis P.?Ma?ssa G.?Rousseaux S.?Douady 《The European physical journal. E, Soft matter》2010,33(1):11-18
Patterns formed by centimeter scale bubbles on the free surface of a viscous liquid are investigated in a cylindrical container.
These bubbles emerge periodically at the surface and interact with each other in the central zone. Their radial emission,
due to interaction and radial surface flow, leads to the formation of a variety of patterns. Different star-like and spiral
patterns appear spontaneously by increasing the bubble emergence frequency. It is found that these patterns are due to a constant
angular shift in the bubble emission direction. Measurements of this angular shift show a supercritical bifurcation accompanied
by a transition from a pattern of two opposed straight arms to spiral patterns. By applying the tools and concepts from the
study of leaf arrangement in botany (phyllotaxis), the recognized patterns and the mechanism of the pattern formation are
discussed. Close similarities to the leaf arrangement are found in the behavior of the angular shift and the patterns. These
findings suggest that the observed patterns are formed by a packing mechanism of successively appearing elements (bubbles),
which is similar to that of the leaves at the earliest stage of phyllotaxis. 相似文献
11.
Walker WF 《The Journal of the Acoustical Society of America》1999,105(4):2508-2518
Tissue elasticity estimation is a growing area of ultrasound research. One proposed approach would apply acoustic radiation force to displace tissue and use ultrasonic motion tracking techniques to measure the resultant displacement. Such a technique might allow noninvasive imaging of tissue elastic properties. The potential of this method will be limited by the magnitude of displacements which can be generated at reasonable acoustic intensity levels. This paper presents methods for estimating the internal displacements induced in an elastic solid by acoustic radiation force. These methods predict displacements on the order of 400 microns in the human vitreous body, 0.008 micron in human breast, and 0.020 micron in human liver at an acoustic intensity of 1.0 W/cm2 (in water) and an operating frequency of 10 MHz. While the displacement generated in the vitreous should be readily detectable using ultrasonic methods, the displacements generated in the breast and liver will be much more difficult to detect. Methods are also developed for predicting the time dependent temperature increases associated with attenuated acoustic fields in the absence of perfusion. These results indicate promise for radiation force imaging in the vitreous, but potential difficulties in applying these techniques in other parts of the body. 相似文献
12.
I. V. Marchuk 《Journal of Engineering Thermophysics》2009,18(3):227-237
In this paper, steady thermocapillary flow in a thin horizontal layer of a viscous incompressible liquid with a free surface
is considered. An axially symmetric steady problem with a localized thermal action on a horizontal liquid layer with a deformable
free surface is solved in a thin-layer approximation. In addition to the thermocapillary effect, the model takes into account
the capillary pressure caused by the free surface variable curvature and the convective mechanism of heat transfer in the
liquid. Analytical expressions for the velocity vector components as functions of the liquid layer thickness and surface temperature
are obtained. The free surface and velocity profiles caused by various kinds of heating are calculated. The influence of convective
heat transfer on the flow pattern is analyzed. 相似文献
13.
The present paper attempts to investigate the effect of sandiness, corrugated boundary surfaces, heterogeneity, and gravity on phase velocity and attenuation of SH-wave propagating in a viscous sandy layer with corrugated upper and lower boundary surfaces sandwiched between an upper heterogeneous elastic half-space and lower viscoelastic half-space under gravity. Heterogeneity associated with the upper half-space is due to exponentially varying density which is a function of depth; but the rigidity is constant. The closed form of dispersion relation is established and found to be in complex form. Real part and imaginary part of the dispersion relation correspond to dispersion curve and attenuation curve, respectively. One of the salient points of present study is the use of DEBYE asymptotic expansion to establish that the obtained dispersion relation is in well-agreement with the classical Love wave equation in isotropic case. The effect of presence and absence of corrugated boundary surfaces, measured by initial flatness parameter, on dispersion and attenuation curves have been meticulously examined. Moreover, the substantial effect of heterogeneity, sandiness, internal friction, and Biot’s gravity parameter on phase velocity and attenuation coefficient of SH-wave has been studied and demonstrated by means of graphical illustration and numerical computations. 相似文献
14.
Efficient electroluminescence (EL) was obtained from quinacridone (QA) sub-monolayer inserted in a tris(8-quinolinolato) aluminum (ALQ) layer which was confined by a blocking layer 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The thickness of the confined ALQ layer was optimized and the highest EL current efficiency of 7.2 cd/A was obtained by inserting a 0.02 nm-thick QA layer in the 10-nm thick ALQ layer, we attribute it to the narrow exciton formation zone, in which both electron and hole carriers were confined and resulted in efficient collision capture in the exciton formation process. In addition, exciton confinement led to improved energy transfer from ALQ to QA and weaken the emission from the ALQ itself. The two factors are simultaneously operating in efficiency enhancement. 相似文献
15.
Viscous liquid layer motion between a probe with a tip shaped as a paraboloid of revolution and a surface is considered for semicontact-mode operation of a scanning probe microscope. The presence of a viscous liquid layer leads to energy dissipation and is one of the factors responsible for the decrease in the probe oscillation amplitude. The Reynolds equation for viscous liquid motion is used to obtain an analytic solution to the problem. The formula derived for the loss is compared with experimental data obtained for probes and layers with various curvature radii and viscosities. 相似文献
16.
We suggest a scalar model for deformation and flow of an amorphous material such as a foam or an emulsion. To describe elastic,
plastic and viscous behaviours, we use three scalar variables: elastic deformation, plastic deformation rate and total deformation
rate; and three material-specific parameters: shear modulus, yield deformation and viscosity. We obtain equations valid for
different types of deformations and flows slower than the relaxation rate towards mechanical equilibrium. In particular, they
are valid both in transient or steady flow regimes, even at large elastic deformation. We discuss why viscosity can be relevant
even in this slow shear (often called “quasi-static”) limit. Predictions of the storage and loss moduli agree with the experimental
literature, and explain with simple arguments the non-linear large amplitude trends. 相似文献
17.
It is found theoretically that the critical conditions under which a charged liquid surface becomes unstable against the electric charge relax as a result of interaction between capillary-gravitational and convective flows in the liquid. As the surface charge density approaches a value critical in terms of development of Tonks-Frenkel instability, convection in the liquid arises at a temperature gradient however small, this effect depending on the liquid layer thickness. 相似文献
18.
It is shown that the analytical estimator for the boundary layer thickness that contains the wave frequency in the denominator and is proposed for approximate calculation of the wave motion on the free surface of a viscous liquid cannot be formally applied to the wave motion on the uniformly charged liquid surface. The fact is that, when the surface charge density attains a value critical in terms for the Tonks-Frenkel instability, the wave frequency tends to zero. From the analysis of liquid motions near the electric charge critical density, a technique is proposed for calculating the thickness of a boundary layer attributed to flows of various kinds. It is found that the thickness of the boundary layer due to aperiodic flows with amplitudes exponentially growing with time (such flows take place at the stage of instability against the surface charge) does not exceed a few tenths of the wavelength, whereas the thickness of the boundary layer due to exponentially decaying liquid flows is roughly equal to the wavelength. 相似文献
19.
The existing concepts of the boundary layer arising near the free surface of a viscous liquid, which is related to its periodic motion, are revised with the aim to calculate finite-amplitude linear oscillations of a viscous liquid charged drop. Equations complementing the boundary layer theory are derived for the vicinity of the oscillating free spherical surface of the drop. An analytical solution to these equations is found, comparison with an exact solution is made, and an estimate of the boundary layer thickness is obtained. The domain of applicability of the modified theory is defined. 相似文献