Oleg Troshkin

• Doctor of Sciences
• Researcher at Russian Academy of Sciences

A scheme for deriving conditions for the nonlinear stability of an ideal or viscous incom-pressible steady flow in a two-dimensional channel that is periodic in one direction is described. A lower bound for the main factor ensuring the stability of the Reynolds–Kolmogorov sinusoidal flow with no-slip conditions (short wavelength stability) is impro...

It's about fluid strains and stresses and related stability. Mechanically, a stability of such a kind means that even being far from such exotic and supposed to be very first states of matter as strongly symmetry and quark–gluon plasma where all the conceivable mechanical conversations are generally possible, if any, an ordinary steadily flowing w...

It turns out that the turbulence of the upper layer of windblown water leading to the Langmuir circulation manifests itself in its own way. First, it creates special boundary conditions called further the contact inversion that transforms any fluid shock falling on the layer from bellow into the boundary inflow vorticity, as in the water hammer exp...

Stiff extrusion helps effectively agglomerate a full range of finely dispersed natural and anthropogenic materials in ferrous metallurgy with a capacity exceeding 100 t of raw briquettes per hour. Obtaining analytical dependences of the influence of the geometric parameters of the auger on the capacity of the extruder is an urgent task. Analytical...

The dynamics of a continuous medium in a pipe is not exhausted by spontaneous unsteady turbulence vortices (first seen in flashes of light and generated at high Reynolds numbers), which permanently level the parabolic velocity profile in the pipe. The ambient space also includes steady swirls and curls, which are usually approximated by analytical...

On the Movement of Briquetted Mass in Extruder A. M. Bizhanov J.C. Steele & Sons, Inc. Statesville, USA O. V. Troshkin Scientific Research Institute for System Research, Russian Academy of Sciences, Russia Corresponding author: A. M. Bizhanov E-mail: bizhanov@briket-brex.ru Keywords: stiff extrusion, briquetting, viscous medium, Navier-Stokes equa...

It turns out that the turbulence of the upper layer of windblown water leading to the Langmuir circulation manifests itself in its own way. First, it creates special boundary conditions called further the contact inversion that transforms any fluid shock falling on the layer from bellow into the boundary inflow vorticity, as in the water hammer exp...

This book covers a new approach to analyzing hydrodynamic stability.With the use of standard remedies of functional analysis, theory of boundary value problems and infinitesimal Lie algebras, it is shown in the book that large vortex mushrooms of an ideal incompressible fluid in a vertical strip behind a water hammer proves to be 2D (plane-parallel...

The dynamics of a continuous medium in a pipe is not exhausted by spontaneous unsteady turbulence vortices (first seen in flashes of light and generated at high Reynolds numbers), which permanently level the parabolic velocity profile in the pipe. The ambient space also includes steady swirls and curls, which are usually approximated by analytical...

The dynamics of a continuous medium in a pipe is not exhausted by spontaneous unsteady turbulence vortices (first seen in flashes of light and generated at high Reynolds numbers), which permanently level the parabolic velocity profile in the pipe. The ambient space also includes steady swirls and curls, which are usually approximated by analytical...

Origional text.

Излагается схема получения условий нелинейной устойчивости стационарного течения идеальной или вязкой несжимаемой жидкости в плоском канале, периодическом в одном из ортогональных направлений. Уточняется нижняя граница главного фактора, обеспечивающая устойчивость синуса Рейнольдса–Колмогорова при наличии условий прилипания (коротковолновая устойчи...

Numerical simulation is presented, which models the evolution of the initial perturbation in axisymmetric subsonic flow of an ideal gas. The undisturbed flow is an axial flow perturbed by an azimuthal velocity, or a twist of the flow around the axis of symmetry. The twist leads to the establishment in the flow of an annular or ball vortex with incr...

It is well known that the steady-state plane-parallel or spatial axisymmetric flow of an ideal incompressible fluid in a finite-length plane channel or pipe that can be decomposed in powers of spatial coordinates (i.e., is an analytical and, hence, exactly computable flow) is uniquely determined by the inflow vorticity. Under the same boundary cond...

In this article, we describe a new mathematical model (bifurcational turbulence model) and justify its suitability for the prediction of laminar and turbulent boundary layer characteristics. The main specific feature of the model is the laminar-turbulent transition, arising as a new solution of the equation for Reynolds stresses, closing the system...

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08.11.2018 г. Переработанный вариант 08.11.2018 г. Принята к публикации 10.06.2019 г. Известно, что установившееся во времени и разложимое в степенной ряд по пространствен-ным координатам, т.е. аналитическое, а значит, точно вычисляемое стационарное плоскопа-раллельное или осесимметричное течение идеальной несжимаемой жидкости на конечном отрезке д...

Описан процесс построения новой модели (бифуркационной модели турбулентности), описывающей течение сплошной среды как в ламинарном, так и турбулентном режимах. Главной ее особенностью является ламинарно-турбулентный переход, возникающий как новое решение уравнения для напряжений Рейнольдса, замыкающего систему RANS (Reynolds-averaged Navier-Stokes)...

It is well known that a steady plane-parallel or axisymmetric ideal incompressible flow in a finite-length plane channel or pipe that can be decomposed in powers of spatial coordinates (i.e., is an analytical and, hence, exactly computable flow) is uniquely determined by the inflow vorticity. Under the same boundary conditions, an infinite number o...

The paper presents the results of numerical simulation of the development of hydrodynamic instabilities of Richtmyer-Meshkov and Rayleigh-Taylor encountered in experiments [1-3]. For the numerical solution used the TPS software package (Turbulence Problem Solver) that implements a generalized approach to constructing computer programs for a wide ra...

The suggested constructions are related closely to fluid motion and devoted mainly to get affirmative answers for the known astronomy questions originated in the first half of the last century. As observations continue to evidence, the light, or visible part of universe is not in the void, but is submerged in the invisible dark matter that compleme...

The suggested constructions are related closely to fluid motion and devoted mainly to get affirmative answers for the known astronomy questions originated in the first half of the last century. As observations continue to evidence, the light, or visible part of universe is not in the void, but is submerged in the invisible dark matter that compleme...

The suggested constructions are related closely to fluid motion and devoted mainly to get affirmative answers for the known astronomy questions originated in the first half of the last century. As observations continue to evidence, the light, or visible part of universe is not in the void, but is submerged in the invisible dark matter that compleme...

The nonlinear stability of vortex zones of reverse flows in a plane-parallel ideal incompress-ible flow is proved. The zones originate at large values of a dimensionless parameter taken in the inflow part of the boundary, the so-called vorticity level. Positive or negative values of this parameter lead to a left-or right-hand oriented vortex, respe...

By means of single-, double-, and three-dimensional simulation, the dynamic processes occurring at a high speed impact of two metal plates of different densities are investigated. It is shown that in the process of collision, the Rayleigh-Taylor instability is developed on the boundary of the metals, which leads to the formation of three-dimensiona...

In the case of a variable period (wavelength) of a perturbed interface, the instability and stability of Richtmyer–Meshkov vortices in perfect gas and incompressible perfect fluid, respectively, are investigated numerically and analytically. Taking into account available experiments, the instability of the interface between the argon and xenon in t...

2D-flows of an ideal incompressible fluid are treated in a rectangular. If analytical (resolved in series of powers of coordinates), the stationary flows are uniquely determined with the inflow vorticity. When excluded vortices of a spectral origin, such flows prove to be stable.

2D-flows of an ideal incompressible fluid are treated in a rectangular. If analytical (resolved in series of powers of coordinates), the stationary flows are uniquely determined with the inflow vorticity. When excluded vortices of a spectral origin, such flows prove to be stable.

The evolution of an initial perturbation in an axisymmetric subsonic normal inviscid gas flow through a pipe is directly simulated. The basic (unperturbed) flow has a zero radial velocity component, while its axial velocity component (along the axis of symmetry) increases or decreases linearly with the radius. The perturbation is specified as a swi...

An inviscid or viscous incompressible flow with a general parabolic velocity profile in an infinite plane periodic channel with parallel walls that can move is considered with the impermeability conditions (for the Euler equations) or the no-slip conditions (for the Navier-Stokes equations). The nonlinear (for the original equations) and nonlocal (...

The idea hydrodynamic stability, like a pair of fraternal twins of stable and unstable flows, it has been born in 1883, from particular cause of Reynolds [1883Rey] concerning two problems and on either conservation or collapse of parabolic and sinusoidal velocity profiles in Fig.0.1, Fig.0.1. Parabolic (P) and sinusoidal (S) velocity profiles of...

The stability of the Couette flow with a linear velocity profile and the instability of the Poiseuille flow with a parabolic profile for a viscous incompressible fluid in a plane channel had been proved at restricted three-dimensional and indefinitely small two-dimensional perturbations of the velocity field, respectively. They were already useful...

Vortex cascades of instabilities forming a core are studied. Large-scale linear waves in a fluctuating medium are described. Keywordsshear instabilities–vortex cascades–large-scale turbulent waves

The countercurrent flow in a gas centrifuge is simulated. Mechanical and thermal methods for its excitation are discussed; thermal restructuring, the thermal control of the velocity field, and a shift in the inversion point are analyzed; and the formation of overtone flows in the rarefaction zone is studied. Keywordscountercurrent gas centrifuge–s...

A new exact solution of the Navier–Stokes equations is derived for a rotating gas tube. The solution improves the well-known rigid-like rotation at a constant temperature. The new temperature is shown to be variable. It increases from the boundary to the center of rotation due to the torsion strain produced by the swirl in the gas tube.

An exact solution of the Navier-Stokes equations for a normal state viscous heat conduct ing gas (with constant viscosity and heat conductivity) is obtained in the form of a stationary plane-parallel flow in a cylinder; the gas is heated by self-rotation at the angular velocity that monotonically increases (or decreases) along the central axis. Na...

The stability of the laminar flow between two rotating cylinders (Taylor-Couette flow) is numerically studied. The simulation is based on the equations of motion of an inviscid fluid (Euler equations). The influence exerted on the flow stability by physical parameters of the problem (such as the gap width between the cylinders, the initial perturba...

A viscous incompressible fluid is taken in a space layer (a channel) periodic in two directions and supplied with either third periodic direction or two parrallel rigid walls with no-slip conditions. The fluid in motion is treated as a mechanical system with a series of its own modes being produced by restrictions imposed during the state of rest....

Constructively, the analysis of the phenomenon of turbulence must and can be performed through direct numerical simulations of mechanics supposed to be inherent to secondary flows. This one reveals itself through such instances as large vortices, structural instabilities, vortex cascades and principal modes discussed in this paper. Like fragments o...

Four coupled relations are obtained for a Newtonian incompressible fluid in a space layer periodic in two directions. The system uses two Fourier averages (horizontal velocity components) and two Fourier pulsations (vertical velocity and vorticity) taken on a plane periodic grid. On first sight, it resembles a turbulent closure scheme. In fact, it...

The equations of motion for incompressible fluid in periodic layer is discussed, concerning channel flows, shear instability, and structure analysis of turbulence. The flows are bounded by a smooth vector field in a layer of constant height and it is assumed that the vector field is periodic along the layer and possibly depends on time. The hydroac...

A conceptual error in the formally closed but physically incomplete Kim-Moin-Moser form of equations for viscous incompressible fluid in a horizontal periodic layer is corrected. This form, which has lately become popular, assumes that the vertical projections of the rotor and the second rotor of the field of accelerations vanish. This assumption c...

Nonstationary equation for the stream function ψ for plane-parallel flow of viscous incompressible fluid in the channel with rigid walls is considered, with a given period in longitudinal direction x and non-passing and sticking boundary conditions. Substitution of the boundary conditions by periodicity condition in orthogonal direction leads to th...

Small perturbations of the solutions of a system of Reynolds equations which is closed on iterated averaging moments are considered. In the region of the turbulence centre, long-wave linear oscillations of coupled fields of average velocity and Reynolds stresses, identical in structure to electromagnetic waves are identified. A bound for the scale...

The transition from laminar to turbulent flow is studied on the basis of an exact equation for the averaged velocity and an approximate nonlinear equation for the Reynolds stress τ. The stationary state can be determined from the condition of minimum of a functional that is analogous to the Landau functional in the theory of phase transitions. The...

The exact solution of the two-dimensional equations of a viscous liquid is given which describes the evolution of an isolated vortex with finite lifetime.

The problem of the propagation of small disturbances of the averaged field of velocities, Reynolds stresses and the pressure in an incompressible turbulent medium, with negligible molecular and turbulent diffusions, is considered. The availability of a limit velocity of such a propagation and the existence of a characteristic cone similar to the Ma...

A boundary value problem for plane and spatial axially symmetric flows of an ideal (inviscid and incompressible) fluid in a bounded domain is considered. Bibliography: 35 titles.

In this paper we consider the two-dimensional stationary flows of an ideal (inviscid and incompressible) fluid in a bounded region.

CONTENTS § 0. Introduction § 1. Extended version of some Morse constructions § 2. Potential flows § 3. Superposition of a vortex on a simple passage § 4. Superposition of a vortex on a reverse flow § 5. Analytic uniqueness theorem References Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts:...

The main goal is to present a number of features of mathematical models for incompressible fluids. Three basic systems of hydrodynamical equations are considered, namely, the system of stationary Euler equations for flows of ideal (nonviscous) fluid, stationary Navier-Stokes equations for flows of a viscous fluid, and Reynolds equations for the mea...