Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
23
3&4
1996
Allowing for Terrain Irregularity in a Jet-Diffusion Model of Impurity Scattering
182-194
Ye. V.
Bruyatskiy
Fluid Mechanics Institute of the Ukrainian Academy of Sciences, Kiev, Ukraine
The feasibility of adapting the jet-diffusion model of scattering of an impurity from elevated sources in the atmosphere over an irregular terrain is explored. The cases of impurity scattering over single terrain irregularities, such as hills or some structures, and over a forest and over a city are analyzed in detail. Recommendations on calculating the distribution of concentrations in the ground layer of the air with allowance for the actual topography by appropriate correction of the dispersion values are presented. The method of utilizing potential flows and allowance for transformation of the wind-stream velocity for solving problems of atmospheric diffusion over an irregular terrain is analyzed separately.
Convective Stability and Spectrum of Perturbations of the Thermal Boundary Layer in Water
195-206
S. Ye.
Bruyatskaya
Fluid Mechanics Institute of the Ukrainian Academy of Sciences, Kiev, Ukraine
The convective stability of a horizontal, depthwise semi-infinite layer of liquid, with internal heat sources is investigated for the steady state, when the temperature distribution in the liquid is a function only of the vertical coordinate. The problem of stability is reduced to an eigenvalue problem for complex amplitudes of the perturbations, which is solved by the Bubnov-Galerkin method, combined with the method of collocations. The spectrum of decrements of small normal velocity and temperature perturbations is obtained, destabilization conditions are investigated. The dependence of critical Rayleigh and wave numbers on the governing parameters of the problem, associated with the strength of internal heat sources and the rate of evaporation from the free surface are obtained. The eigen-functions of the problem are determined.
The Axisymmetric Stokes Flow in a Finite Cylinder with Three Annular Disks
207-213
V. S.
Malyuga
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A. M.
Gomilko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The problem of steady-state axisymmetric Stokes flow in a finite cylinder with three rigid, thin coaxial disks is analyzed. The liquid flow is induced by a uniform axial motion of the lateral surface of the cylinder, simultaneous with rotation of the entire cylinder. The corresponding boundary-value problem for the Stokes system is reduced by means of the method of superposition and of the theory of hydrodynamic potentials to an infinite set of linear algebraic equations. The numerical analysis includes investigation of the kinematics and mixing of the liquid.
In-Situ Investigation of the Shore-Protection Devices in Crimea
214-220
S. F.
Yefremov
The Crimea Landslide-Prevention Administration Ukraine
Experience accumulated in monitoring shore-erosion prevention devices in the Crimea and the results of extended performance of these devices are correlated. Relationships between changes in the physical properties of the material of these devices and changes in their wave-breaking performance are derived.
Investigation of Transparent Inhomogeneities by the Toppler Method
221-235
V. I.
Nikishov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, 8/4, Zhelyabov St.,
Kyiv, 03057, Ukraine
V. N.
Il'chenko
Fluid Mechanics Institute of the Ukrainian Academy of Sciences, Kiev, Ukraine
Expressions describing the distribution of intensities of the light field in the plane of observation of the Toppler instrument are obtained in the linear approximation. Two classes of models of optically "soft" inhomogeneities of the distribution of the optical refraction index are analyzed. It is shown that the contribution of the nonlinear terms of the expansion of the function describing the change in phase of the light wave by inhomogeneities, with a continuously distributed refraction index, is small.
Modeling the Motion of Ground Water and the Migration of Radionuclides in the Soil
236-242
Ya. F.
Kayuk
The Timoshenko Institute of Mechanics, Ukrainian Academy of Sciences, Kiev, Ukraine
G. P.
Panasenko
The Timoshenko Institute of Mechanics, Ukrainian Academy of Sciences, Kiev, Ukraine
A. N.
Polevoy
The Lomonosov State Institute, Moscow, Russia
V. N.
Seredenko
Odessa Institute of Hydrometeorology, Odessa, Ukraine
A generalized formulation of a mathematical model of migration of dissolved substances in soils with allowance for their absorption by the plant root system is presented. An asymptotic solution of the general problem for the case when the ratio of the thickness of the water-bearing stratum is much smaller than the characteristic dimension in the plan is obtained. The equation of seepage of ground waters, equations of moisture transport in the unsaturated zone and migration of the dissolved substances are analyzed separately.
Heat Conduction Equations for Two-Phase Heterogeneous Media
243-249
S. I.
Kril'
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Averaged differential equations of heat conduction for two-phase media with allowance for discontinuities in the phase parameters at the phase interface are compiled. It is shown that the averaged heat flux contained in the right-hand side of these equations is the same for both phases, which is the cause of the novelty of the resulting equations.
Numerical Modeling of Eddy Diffusion of Pollutants over Irregular Terrain
250-255
V. G.
Kuz'menko
Fluid Mechanics Institute, Ukrainian Academy of Sciences Kiev, Ukraine
Eddy diffusion of pollutants over irregular terrain is modeled numerically. A numerical algorithm for solving a semiempirical three-dimensional differential equation of eddy diffusion with complex boundary conditions with allowance for the three-dimensional velocity distribution is worked out. Pollutant spreading for different mutual arrangements of the source and the hill is investigated numerically. The examples of calculations that are presented should be regarded as preliminary. The directions to be taken by further studies are discussed.
Two-Dimensional Vortical Gravity Waves near the Surface of a Deep Liquid
256-270
Yu. V.
Sedletskiy
Physics Institute, Ukrainian Academy of Sciences Kiev, Ukraine
V. P.
Lukomskiy
Physics Institute, Ukrainian Academy of Sciences Kiev, Ukraine
Potential and locally-swirled two-dimensional flows of an ideal ponderable fluid with a free surface are investigated within the framework of the slightly-nonlinear theory. A model nonlinear integro-differential equation is obtained for the limiting complex potential of an infinitely deep fluid. New types of steady-state locally-swirled flow with multipole structure of the velocity distribution near the free surface are found. The corresponding exact solutions of the model equations consist of free solitary gravity waves with vortex filaments oriented across the direction of motion and highly nonmonotone reduction of amplitude with length. Solutions describing solitary waves with peaked crests, the inception of which stems from the local swirl in the immediate proximity of the crest are analyzed in detail. A new model for explaining the manner of formation of various anomalous states of the sea surface is suggested.
Stability of a Tube of a Viscous Fluid in a Horizontal Rotating Cylinder
271-277
Yu. V.
Naumenko
Rivne State Humanitarian University, Ukraine
The stability conditions for two-dimensional steady-state viscous flow in the cavity of a cylinder rotating steadily about a horizontal axis are examined. Quantitative stability criteria, showing that increasing the viscosity reduces the angular velocity of the cylinder at which the tube breaks up are obtained.
Frequency Distortions Introduced by Contact Sensors in Single and Two-Channel Sensing of Respiration Noise
278-287
Valery
Oliynik
Institute of Hydromechanics of National Academy of Sciences of Ukraine
Aspects of designing multi-channel systems for electronic recording of respiration noise from the surface of the chest cavity are examined. The suggested mathematical model is employed for calculating the frequency curves of an output signal from single- and two-channel respiration-noise pickups. It is established that at frequencies below 500 Hz chestpiece pickups whose specific mechanical impedance exceeds the specific impedance of the chest-cavity surface (heavy chestpieces) markedly affect the vibrations of the contact spot as compared with a the pickup-free chest cavity. The interaction of contact pickups with the surface wave in two-chestpiece sensing of respiration noise is investigated. It is shown that signals from closely-spaced heavy chestpieces significantly affect one another. This distorts the frequency curve of the received signal as compared with the case of single-chestpiece sensing.
Intermittent Supply of Unlimited Nutrients to Isolated Roots
288-295
V. L.
Polyakov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
An approximate analytic solution of the problem of supply of nutrients to an isolated root is presented and validated. The contribution of different mechanisms of ion uptake by the root is estimated. Different methods of simplifying the original model that serve to broaden the range of application of the solution are analyzed.
The Helical Analog of Irrotational Potential Flow over a Circular Cylinder
296-301
P. A.
Shestopal
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
N. V.
Saltanov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Helical analogs of elementary helical flows: the homogeneous flow and the dipole, are obtained and utilized for writing the helical analog of potential irrotational flow of a circular cylinder. The effect of the helicity factor of helical flows on the streamline patterns and on the pressure coefficient is analyzed.
Computer Modeling of Pulsations of Ventilated Supercavities
302-312
V. N.
Semenenko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Nonlinear pulsations in a dynamic system with distributed lag, simulating a slender, gas-filled, axisymmetric supercavity in a liquid, are investigated numerically with visualization on a PC screen and analysis of the spectral composition of the pulsations.
Vorticity and Hysteresis Nonlinearities in Viscoelastic Flows
313-320
O. N.
Shablovskiy
P. O. Sukhoy Gomel State Engineering University, Byelarus
New properties of vorticity in viscoelastic flow onto a moving wall are obtained. Two examples of flow for which dynamic hysteresis takes place are presented.