Oscillations of a body filled with a viscous fluid

The oscillations of a physical pendulum containing a spherical cavity filled with an incompressible viscous liquid were discussed in [1]. In this paper we consider the mote general problem of the motion of an axially symmetric solid with a spherical cavity filled with an incompressible viscous fluid and moving about a fixed point. It is assumed that the center of the cavity and the fixed point lie on the axis of symmetry of the body.     

Oscillations of an ideal stratified fluid in a fixed vessel

Oscillations of a stratified fluid with a continuous distribution of the density that completely or partly fills a fixed vessel are investigated. Small oscillations of a stratified fluid with discrete distribution of the density have been investigated by Kopachevskii [1, 2]. Individual examples of the analysis of oscillations of a fluid consisting of layers of different densities have been given by Gontkevich and Ganichev et al. [3, 4].     

Flow of a viscous fluid in a cylindrical vessel with a rotating cover

The problem considered arises in solving various technical problems associated with flows of a viscous fluid in a closed space near rotating plane surfaces, turbomachine disks, thrust bearings, rotational viscosimeters, etc. The approximate solution of the problem on the basis of a simplified flow scheme was first obtained by Schultz-Grunow [1], The most complete investigation has been made recently by Grohne [2], who outlined a program for solving the problem by joining several partial solutions on the basis of definite hypotheses concerning the flow core.With the development of electronic digital computers and the necessary numerical methods, the most effective means of solving the considered problem is the use of the grid methods for solving partial differential equations. The present paper is devoted to presenting the results of the solution of the problem using the grid method on a digital computer.     

Oscillations of a viscous fluid in a thin layer between two coaxial disks rotating together

A study is made of the problem of the motion of an incompressible viscous fluid in the space between two coaxial disks rotating together with constant angular velocity under the assumption that the pressure changes in time in accordance with a harmonic law. The problem is solved using the equations of unsteady motion of an incompressible viscous fluid in a thin layer. It is shown that the velocity field in this case is a superposition on a steady field of damped oscillations with cyclic frequency equal to twice the angular velocity of the disks and forced oscillations with cyclic frequency equal to the cyclic frequency of the oscillations of the pressure field. It is shown that the amplitude of the forced oscillations of the velocity field depends strongly on the ratio of the cyclic frequency of the oscillations of the pressure field to the angular velocity of the disks. It is shown that there is a certain value of the ratio at which the amplitude of the forced oscillations has a maximal value (resonance). It is shown that even for very small amplitudes of the pressure oscillations the amplitude of the oscillations of the relative velocity at resonance may reach values comparable with the mean velocity of the main flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 166–169, January–February, 1984.     

Nonaxisymmetric waves in an orthotropic timoshenko shell containing a viscous fluid

Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 26, No. 12, pp. 22–28, December, 1990.     

Axisymmetric motion of a viscous fluid in the finite annular cavity of a rotating cylindrical vessel

The method of nets is used to investigate unsteady axisymmetric viscous flow in a cylindrical gap of finite height. This situation is characterized by vortex motion in a plane passing through the axis of the coaxial cylinders. These flows have previously been studied in relation to the case of stepwise variation of the angular velocity of the cylinders [1]. In the present case the angular velocity is varied linearly in the acceleration stage and the acceleration interval is a parameter of the problem. After acceleration the rotation rate is determined from the ordinary differential equation describing the process of deceleration of the system as a whole.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 37–42, March–April, 1988.The authors are grateful to E. M. Zhukhovitskii for his interest and valuable comments.     

Radiation of nonstationary waves by a thin-walled piezoceramic cylinder containing a viscous compressible fluid

The transient operation conditions of a thin-walled piezoradiator containing a viscous compressible fluid and immersed into an acoustic medium are considered. The problem is solved using the integral Laplace time transformation. Originals of the general solution of the linearized Navier-Stokes equations are constructed for the interior of the domain. These originals are used to find the unknowns from a system of integral Volterra equations. Numerical examples are presented. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 35, No. 12, pp. 63–71, December, 1999.     

Motion of two viscous fluids in a precessing vessel

An approximate solution of the problem of the motion of two viscous fluids in a cylindrical vessel executing slow regular precession with an arbitrary angle of nutation is constructed. The axial component of the moment of the forces exerted by the fluid on the lateral surface of the vessel is determined.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 27–34, September–October, 1995.     

Flow of a viscous fluid down a slope

A thin layer of viscous fluid flowing down a slope under gravity is considered. The stability of this flow is studied in the framework of a shallow water model. A number of equations of shallow water motion are derived with consideration of the viscous friction. The corresponding Cauchy problem is solved analytically. It is shown that the uniform flow may be unstable with respect to small initial perturbations. A criterion of instability is proposed.     

Unsteady jet flow of a viscous fluid

A solution is obtained, within the framework of the boundary layer theory, to the problem of the unsteady flow created by a two-dimensional jet source for a given momentum flux variation with time. In particular, aperiodic and periodic momentum variations are examined, and a qualitative analog with turbulent flow is noted for the latter.     

Oscillations of cylinders in a linearly stratified fluid

The paper studies theoretically and experimentally hydrodynamic loads that act on horizontally placed cylinders of rhombic and square cross sections, oscillating harmonically in a linearly stratified fluid. An analytical solution is found with the use of affine similitude. Hydrodynamic force coefficients were evaluated experimentally from Fourier transforms of records of damped oscillations in a time—frequency region. It is shown that for polygonal contours, hydrodynamic loads change abruptly if the slope of the polygon sides coincides with the slope of the internalwave group velocity vector.     

Optimization of suction-blowing in a viscous fluid

The problem of drag minimization in a viscous fluid by means of controlled suction (blowing) is considered. In the low Reynolds number approximation matched asymptotic expansions are used to construct the second approximation and analytic solutions of the optimization problem are found for a sphere and a circular cylinder. Transition from unseparated to separated flow is accompanied by a qualitative restructuring of the optimal solution.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 27–32, May–June, 1989.     

Rising vortex ring in a viscous fluid

Most theoretical results for thermals, whose motion is determined by the complex interaction between dynamics and buoyancy, have been obtained numerically [1–4]. The analytic solutions for a convection element have been limited to consideration of the self-similar regime [5]. At the same time, the preself-similar stage of development of a vortex ring of dynamic origin has been described analytically [6]. This approach is now extended to a rising vortex ring. In this case a modification of the traditional formulation of the problem makes it possible to obtain an analytic solution of the problem of a weak thermal in the form of unsteady temperature, vorticity and stream function fields that tend in the limit to the self-similar regime. The rate of ascent of the convective vortex ring is found. A solution is obtained for the two-dimensional analog of the problem.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 42–48, May–June, 1989.     

Oscillations of liquid in a vessel in the form of a rectangular parallelepiped

We consider the forced and the free oscillations of a liquid partially filling a cavity in the form of a rectangular parallelepiped. The characteristics of these oscillations are studied for small deformations of the free surface. It is shown that for definite frequencies and amplitudes of two-dimensional translational motions of the parallelepiped the fundamental of the liquid oscillations is excited in the plane perpendicular to the plane of motion of the vessel. The effect of small linear damping of the liquid oscillations on the shape of the boundaries of the principal region of instability of the liquid oscillations is evaluated. Fairly large oscillations of a liquid in a cylinder were considered in [1]. The same problem for a cavity of arbitrary configuration was studied in [2]. We note also that the conclusions of the study presented here are in qualitative agreement with the basic results obtained by a somewhat different method in [3] for a cavity in the form of a right circular cylinder.     

Point vortex in a viscous incompressible fluid

A plane steady problem of a point vortex in a domain filled by a viscous incompressible fluid and bounded by a solid wall is considered. The existence of the solution of Navier-Stokes equations, which describe such a flow, is proved in the case where the vortex circulation Θ and viscosity ν satisfy the condition |Θ| < 2πν. The velocity field of the resultant solution has an infinite Dirichlet integral. It is shown that this solution can be approximated by the solution of the problem of rotation of a disk of radius Γ with an angular velocity ω under the condition 2πγ ² ω → Γ as γ → 0 and ω→∞.     

Oscillations of a cylinder piercing a linearly stratified fluid layer

The plane problem of the small steady-state oscillations of a horizontal cylinder arbitrarily located in a three-layer fluid whose upper and lower layers are homogeneous and whose middle layer is linearly stratified is considered in the linear formulation using the Boussinesq approximation. The fluid is assumed to be ideal and incompressible. The method of mass sources distributed along the body contour is used in the internal wave generation regime and an integral equation for the fluid pressure is derived in the non-wave regime. The hydrodynamic load acting on the body is calculated as a function of the oscillation frequency of the cylinder and its location. The results are compared with experimental data.