Thermocapillary instability of a deformable liquid film

The instability of a plane liquid film with a uniform transverse temperature gradient under conditions of weightlessness is considered. The surface tension is assumed to depend linearly on the temperature. On the basis of an exact solution of the neutral perturbation problem for a layer with deformable boundaries, the instability domains, the dispersion curves, and the shape of the perturbations are determined. It is shown that on the interval of low Prandtl numbers both thermocapillary waves with predominantly longitudinal flow and capillary waves, supported by the thermocapillary effect, with intense transverse liquid flow can develop on the film.Perm'. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 30–36, September–October, 1996.     

Helical flows with multiple circulation in channels of simple shape

A general solution is obtained for the problem of the helical motion of an incompressible liquid along a channel with a cross section in the shape of an annular sector or a triangle. The possible use of the solutions so obtained in order to describe secondary flows with repeated circulation in channels of simple shape (ring, circle, square, rhomb, rectangle, equilateral triangle) is demonstrated. The theory is in agreement with experiment. In one particular setting, problems as to the helical motion of an ideal incompressible liquid in channels of simple configuration were solved in [1, 2]. In this paper flows of a more general form with repeated circulation are considered, several vortices occurring inside the tube cross section.Deceased.Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 32–38, March–April, 1973.     

Effect of Thermocapillary Forces on the Initial Section of a Melt Film

The previous analysis of fields near the upper triple point of the floating–zone melting process is supplemented by the analysis of thermocapillary forces on the melt surface. It is shown that the effect of these forces is large in the general case, and a melt film with a macroscopic radius of curvature may be formed only if the temperature gradient over the melt surface and thermocapillary forces are small; in this case, the angular coordinates of the melt–film cross section are also small.     

Convective instability of a fluid in a vibration field under conditions of weightlessness

The problem of the convection and convective instability of a fluid in a high-frequency vibration field under conditions of weightlessness was formulated in an earlier paper of the authors [1]. In the present paper, the conditions of equilibrium are discussed and the boundaries of vibration instability are determined for some equilibrium states: a plane layer of fluid with transverse temperature gradient and arbitrary direction of the vibration, a cylindrical layer with radial gradient and longitudinal direction of the vibration, and an infinite circular cylinder with transverse and mutually perpendicular directions of the temperature gradient and the vibration axis.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 12–19, July–August, 1981.We thank G. I. Petrov for helpful discussions.     

Experimental investigation of flow in a trench

An experimental investigation was made of the flow of a viscous incompressible liquid in a trench of square transverse cross section, using a laser Doppler velocimeter. The investigation was made with two values of the Reynolds number Re, corresponding to laminar and turbulent flow conditions in the channel. The experimental data show that a core with a constant vorticity is formed in the trench, that a jet propagates near the walls of the trench, and that there are secondary eddies in the corners of the trench. The motion of a viscous liquid in a trench of rectangular cross section is part of a broad class of breakaway flows. Experimental data on the investigation of flow in trenches are extremely few. A majority of the existing information is limited to visual observations [1–4]. In [2, 5, 6] the question of the unstable character of flow in trenches was discussed. Quantitative measurements of stable eddy flows in trenches were made in [7–9] using a thermoanemometer, and in [7] measurements were made of the pressure at the bottom and walls of trenches; there are data on the distribution of the velocity in the middle sections of trenches. In [8] the mean velocity, the intensity of the turbulence, and the stress of the turbulent flow were obtained in several sections parallel to the side walls of the trench, In [9] a measurement was made of the velocities also in two cross sections of a trench in which one component of the velocity prevails. A brief analysis of the existing experimental results shows that these data are insufficient to form a detailed representation of the character of flow in a trench.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 76–86, March–April, 1976.     

On the possibility of enhancing the efficiency of tangential blowing of a slit jet from an airfoil surface

Experimental results are presented for a teardrop-shaped wing section with tangential slit jet blowing in the forward part of the section. It is shown that such airfoils can provide a lift significantly greater than the lift which can be achieved by blowing a tangential slit jet from a wing of ordinary shape with a flap.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 182–186, July–August, 1996.     

Natural convection from a thin heated wire situated on the surface of a liquid

The temperature and velocity fields associated with the free convection of a liquid near a thin heated wire situated close to the horizontal surface of the liquid were studied experimentally. The temperature field was analyzed by the shadow method using a Svil' 80 instrument, and the velocity field by observing the motion of light-scattering particles. Universal profiles of the horizontal velocity and vertical temperature gradient were derived by making scale transformations of the spatial profiles measured in various cross sections of the heated zone for several values of the power developed by the wire.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 139–142, November–December, 1970.     

Flow characteristics of two-phase dispersed annular streams in heated tubes

Patterns and characteristics of flow through heated tubes are investigated on the basis of concepts of two-phase dispersed annular flow patterns [1] within the framework of the three-velocity and single-temperature equilibrium model, with flowrates of the mixture not too close to critical. Conditions for onset of burnout of the second kind, i.e., deterioration in the transfer of heat leading to an abrupt rise in the temperature of the heating surface, and, as such, associated with desiccation of the thin film of liquid on the wall [2, 3], are investigated. Hydraulic drag, the flowrate of liquid in the film, and the true steam content by volume are among the factors discussed. Two-phase flow patterns in dispersed annular flow are characterized by the combined motion of the three components of the mixture: vapor, the liquid wall film, and droplets. The assumption entertained is that each component of the mixture acquires its own velocity, and that the temperature of the mixture is equal, in each cross section through the channel, to the saturation temperature at the pressure prevailing in the particular cross section.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 78–88, July–August, 1973.     

Nuclear magnetic resonance study of turbulent flow in a pipe

Results are given from an investigation of longitudinal turbulent diffusion by the nuclear magnetic tracer method, and a technique is described for determining the velocity distribution function of the fluid particles in the pipe cross section.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 105–110, November–December, 1971.     

The force produced by a liquid current on a thin curved body of circular cross section

In classical hydrodynamics the situation is examined in which a body moves in a liquid under the condition that at infinity the liquid is quiescent or in translation [1, 2]. In [3] the problem of flow around a cylinder by an arbitrary liquid current is solved, with consideration not only of flow velocities, but also of their variability over the coordinates. In the present study these earlier results will be generalized to the case of motion of a thin curved body of circular cross section in an arbitrary spatial potential flow of an ideal incompressible liquid.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 9–12, January–February, 1973.     

Stationary flow of a conducting liquid in a rectangular channel with two nonconducting walls and two walls having an arbitrary conductivity parallel to an external magnetic field

The flow of a conducting liquid in a channel of rectangular cross section with two walls (parallel to the external magnetic field) having an arbitrary conductivity, the other two being insulators, is considered. The solution of the problem is presented in the form of infinite series. The relationships obtained are used for numerical calculations of the velocity distribution and the distribution of the induced magnetic field over the cross section for several modes of flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkostt i Gaza, No. 5, pp. 46–52, September–October, 1970.     

Some exact solutions of the ferrohydrodynamics equations

The theoretical study of nonisothermal flows of magnetizable liquids presents serious matheical difficulties, which are intensified as compared to to the study of normal liquids by the necessity of simultaneous solution of both the hydrodynamics and Maxwell's equations, with corresponding boundary conditions for the magnetic field. Thus, in most cases problems of this type are solved by neglecting the effect of the liquid's nonisothermal state on the field distribution within the liquid, and also, as a rule, with use of an approximate solution for Maxwell's equations and fulfillment of the boundary conditions for the field [1–3]. The present study will present easily realizable practical formulations of the problem which permit exact one-dimensional solutions of the complete system of the equations of thermomechanic s of electrically nonconductive incompressible Newtonian magnetizable liquids with constant transfer coefficients. A common feature of the formulations is the presence of a longitudinal temperature gradient along the boundaries along which liquid motion is accomplished. Plane-parallel convective flows of this type in a conventional liquid and their stability were considered in [4–6].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 126–133, May–June, 1979.     

含双裂纹圆截面悬臂梁的损伤识别研究

裂纹的萌生和扩展直接影响构件的振动响应,对构件的安全可靠性具有重要影响．本文以圆截面悬臂梁为对象,结合转角模态振型和模态频率等高线,研究了一种双裂纹识别技术．首先,基于应力强度因子和卡氏定理推导了无裂纹梁单元和含裂纹梁单元的刚度矩阵;在此基础上,建立了含裂纹圆截面悬臂梁的有限元动力学方程;然后,结合裂纹对梁转角模态振型和模态频率的影响,提出了双裂纹识别策略．最后,通过算例讨论了双裂纹识别策略的可行性．结果表明,圆截面悬臂梁的模态转角在裂纹位置出现突变,裂纹深度越大转角突变值越大;将识别出的裂纹位置作为已知参数,通过模态频率等高线法,可以准确地识别出双裂纹的深度．     

Axisymmetric cavitation flow around a body in a tube

The problem of the axisymmetric flow around a body in a circular tube with arbitrary shape of the meridian section is reduced to the numerical solution of a system of two integral equations to determine the shape of the cavern and the intensity of the vortex rings arranged on the solid boundaries and the cavern boundary. Results of computations of the cavitation flow around a sphere, ellipsoid of revolution, and cone in a cylindrical tube, and also for a cone in converging and expanding tubes and in a hydrodynamic tunnel with the actual shape of the converging and working sections, are presented.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 50–55, July–August, 1976.     

Effect of high-frequency vibration on the development of secondary convective conditions

An investigation is made of the development of convective flows of a viscous incompressible liquid, subjected to high-frequency vibration. The nonlinear equations of convection are used in the Boussinesq approximation, averaged in time. The amplitude of the perturbations is assumed to be small, but finite. For a horizontal layer with solid walls the existence of both subcritical and supercritical stable secondary conditions is established. In a linear statement, the problem of stability in the presence of a modulation has been discussed in [1–3]. Articles [4–6] were devoted to investigation of the nonlinear problem. In [4], the method of grids was used to study secondary conditions in a cavity of square cross section. In the case of a horizontal layer with free boundaries [5, 6], the character of the branching is established by the method of a small parameter.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 90–96, March–April, 1976.The authors thank I. B. Simonenko for his useful evaluation of the work.     

Investigation of a compressible turbulent boundary layer and a region of separation at M=5 by a laser Doppler anemometer

Results are cited of an experimental investigation of the structure of a compressible turbulent boundary layer on a thermally insulated cylinder placed longitudinally in the flow. The experiments were conducted at M=5 and Re_x10⁷. In order to establish a longitudinal positive pressure gradient and a region of separation at the end of the cylinder, a tailpiece in the shape of an axisymmetric isentropic compression surface, or conical flaps with various half angles, were mounted. Profiles of the longitudinal velocity component were measured using p_o' and t_o probes, and also using a laser Doppler anemometer (LDA) with a Fabry-Perot interferometer. In the absence of a longitudinal pressure gradient the velocity profiles measured by the different methods were in satisfactory agreement among themselves and with the results of calculations. In the presence of a longitudinal positive pressure gradient, the velocity profiles become less filled and the static pressure, calculated according to the results of measurements of the velocity with the aid of the LDA and the pressure p_o', varied across the thickness of the boundary layer. In the separated region, the recirculating velocity of the flow was measured with the aid of the LDA.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 175–178, March–April, 1976.     

Pressure Waves in a Gas–Liquid Medium with a Stratified Liquid–Bubbly Mixture Structure

Evolution and decay of pressure waves of moderate amplitude in a vertical shock tube filled by a gas–liquid medium with a nonuniform (stepwise) distribution of bubbles over the tube cross section are studied experimentally. The gas–liquid layer has the form of a ring located near the tube wall or the form of a gas–liquid column located in the center of the tube. It is shown that the nonuniformity of bubble distribution over the tube cross section increases the attenuation rate of pressure waves.     

Mass transfer between bubbles and the continuous phase in a fluidized bed of variable cross section

A study is made of mass transfer in an inhomogeneous fluidized bed whose cross section varies over the height. The field of the liquid phase around a bubble is constructed, conditions are obtained for the existence of a region of closed circulation of the liquid phase, and the boundaries of this region are determined. A solution is given to the problem of convective diffusion of the substance to the region of closed circulation, and the mass-transfer coefficient between a bubble and the continuous phase is determined as a function of the flow parameters. By the same token, the results of [1] are generalized to a fluidized bed of variable cross section. It is shown that in this case the mass transfer is improved.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 20–29, November–December, 1974.     

Onset of convection regimes with double period in a periodic field of external forces

We investigate the onset of secondary convective flows in the Rayleigh problem (in a horizontal layer of a viscous incompressible liquid with free boundaries) in the presence of a parameter that varies with time and has a period T, namely the temperature gradient or the intensity of the gravitational field.Translated from Zhurnal Prikladnoi Mekhanlki i Tekhnicheskoi Fizlki, No. 6, pp. 65–70, November–December, 1972.     

Longitudinal dispersion associated with the motion of an adsorbed mixture in a column filled with porous granules

The effect of the radial nonuniformity of the linear flow velocity on the radial nonuniformity of the adsorbate concentration distribution over the cross section of a column and on the longitudinal dispersion is estimated for the diffusion model, and the legitimacy (for relatively small adsorber radii) of using a one-dimensional diffusion model for describing the interphase mass transfer in cylindrical adsorbers is thereby determined.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 93–101, July–August, 1987.