Izvestiâ Akademii nauk. Rossijskaâ akademiâ nauk. Mehanika židkosti i gaza
Fluid Dynamics is the English version of the leading Russian journal Izvestia RAN, Mekhanika Zhidkosti i Gaza. It publishes original articles in the field of classical fluid and plasma dynamics, biomechanics of continuous media, flow in electro-magnetic fields, dynamics of multiphase and chemically reactive flow, including flow in porous media.
The journal publishes theoretical and experimental investigations. Numerical research should focus on new mechanical results with a short description of the numerical method itself.
The manuscripts are peer reviewed by two experts. In accordance with the "Statute of Scientific Journals of the Russian Academy of Sciences", the Editorial Board has the exclusive right to accept or reject manuscripts. According to the rules of our journal, authors will not be informed of the reasons for rejection. Papers are published free of charge to the authors and no fee is paid to them.
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No 6 (2023)
Articles
ВЗАИМОДЕЙСТВИЕ АКУСТИЧЕСКИХ ВОЗМУЩЕНИЙ СО СВЕРХЗВУКОВЫМ ПОГРАНИЧНЫМ СЛОЕМ НА ПЛОСКОЙ ПЛАСТИНЕ
Abstract
В рамках полных уравнений Навье–Стокса проведено численное моделирование восприимчивости сверхзвукового пограничного слоя на плоской заостренной пластине к модельным акустическим возмущениям, которые распространяются в набегающем потоке (число Маха 5) и характерны для фонового шума ударных аэродинамических труб. Проведен спектральный анализ возмущений, индуцированных в пограничном слое. Обсуждается способ восстановления амплитуды акустического возмущения в набегающем потоке с помощью измерения пульсаций давления на поверхности пластины.
3-13
Numerical Estimates of the Influence of Ion Diffusion on Injection-Type Electroconvection in the Plane Layer of a Low-Conductivity Fluid
Abstract
The influence of diffusion on isothermal electroconvective flow of a low- conductivity fluid under unipolar injection in the constant electric field in a plane-parallel electrode system is studied. The dependences of the space charge density and flow fields on the diffusion intensity are obtained. The diffusion coefficient of injected ions is numerically estimated for TO + I2. The results obtained are based on comparison of the numerical experiment with the available experimental data.
14-21
ДИНАМИКА ВЯЗКОГО ГАЗА В ЗАКРЫТОЙ УЗКОЙ ТРУБЕ ПРИ ГАРМОНИЧЕСКИХ КОЛЕБАНИЯХ ПОРШНЯ
Abstract
В результате решения линеаризованных двумерных уравнений Навье–Стокса в цилиндрической системе координат получено периодическое решение задачи о динамике газа в закрытой трубе при колебаниях поршня по гармоническому закону. Представлены зависимости резонансных частот от диаметра трубы. Исследован вопрос о максимальной амплитуде продольной скорости колебаний вязкого политропного газа на первой резонансной частоте. Полученные зависимости сравнены с известными результатами для плоского резонатора. Показано, что максимальная продольная скорость примерно в два раза больше в плоском резонаторе, чем в трубе с диаметром, равным ширине плоского резонатора.
22-31
Modeling of Main Parameters for Near Wake from Pair of Side-by-Side not too Close Cylinders
Abstract
A one-dimensional model of the near wake produced by a pair of not-too-close cylinders in a viscous incompressible fluid is developed on the basis of the Stuart–Landau model and perturbation theory. The whole wake is considered as two interacting partial von Kàrmàn vortex streets or two coupled Stuart–Landau oscillators, when the nonlinear nature of the interaction of these streets is taken into account. The observable spectrum of the global modes of the wake is obtained, the calculated and experimental eigenfrequencies of the oscillation modes being in agreement with respect to the modes.
32-37
The Effect of Boundary Conditions on the Modeling of Anomalous Intensification of Turbulent Heat Transfer in an Inclined Groove in the Wall of a Narrow Channel
Abstract
The effect of the boundary conditions of the first and second kind on the predicted characteristics of anomalous heat transfer intensification in the case of turbulent low-velocity air flow over an inclined groove in the hot wall of a narrow channel is numerically investigated. It is shown that the isothermality conditions lead to a considerable underestimation of the thermal efficiency of a surface structured with narrow grooves, compared with the conditions of heat flux constancy.
38-47
Self-Similar Solution to the Problem of Unsteady Film Condensation on a Vertical Semi-Infinite Plate
Abstract
Changes in the regimes of condensate film flow along the underlying surface in the presence of a body force are considered within the framework of a simplified physical and mathematical model of hydrodynamic and thermal processes occurring under unsteady film condensation on a vertical semi-infinite plate. The model is used to determine the applicability conditions of the zero-gravity approximation when considering film condensation. It is found that the validity of using the zero-gravity approximation to calculate the film thickness growth rate on any plate section depends not only on the magnitude of the body force, but also on time and distance between this section and the leading edge of the plate.
48-58
Deformations and Wave Forces in the Motion of a Load on an Ice Cover in the Presence of a Current with Velocity Shear
Abstract
The deformations of an ice cover on the surface of an ideal incompressible fluid of finite depth under the action of a pressure domain that moves rectilinearly at a constant velocity in the presence of a current with velocity shift, as well as the wave forces exerted on a moving body, are studied. Fluid flow is not potential. The ice cover is modeled by a thin elastic plate with account for uniform compression. The motion of the load can occur at an arbitrary angle to the direction of current. It is assumed that the ice deflection is steady in the coordinate system moving with the load. The Fourier transform method is used within the framework of the linear wave theory. The maximum deformations of ice cover and the wave forces are studied depending on the current velocity gradient, the direction of motion, and the compression ratio.
59-66
Laminar Swirling Wall Jets
Abstract
The problem of determining the characteristics of a laminar swirling wall jet of an incompressible fluid is considered. Numerical solutions of the Navier–Stokes equations are obtained in the stationary and non-statitonary formulations. It is shown that the jet characteristics obey a self-similar law at large distances from the jet source, as in the case of a three-dimensional laminar non-swirling jet, but in our case the jet propagates at a certain angle to the initial direction of jet blowing. With a large swirling of flow in the jet, regions of recirculation flow appear and the jet flow becomes unsteady.
67-74
Wall Pressure Fluctuations on the Surface of a Fairing in the Shape of a Semi-Ellipsoid and in its Vicinity
Abstract
The wall pressure fluctuation fields on fairing surfaces and in the surrounding turbulent boundary layer are experimentally investigated. The fairings were in the shape of semi-ellipsoids and were mounted on the wall of a subsonic low-noise wind tunnel. Their heights amounted to 25% of the oncoming boundary layer thickness. The main physical features of the flows under consideration are determined by means of the surface oil-flow visualization. The fluctuating wall pressure field is compared with the flow pattern. It is shown that the greatest pressure fluctuation levels are recorded in the nose region of the fairing surface. It is established that lengthening the model leads to a considerable reduction of the pressure fluctuation strength in the region of flow separation from the fairing surface.
75-85
Effect of a Conical Extension on Aerosol Sedimentation in the Case of Acoustic Small-Amplitude Oscillations in a Tube
Abstract
The effect of acoustic low-intensity oscillations in a homogeneous tube and in a tube with a conical extension is experimentally investigated for the same resonator volumes. The resonator shape is shown to have an effect on the oscillation spectrum and intensity and the pressure wave shape at constant values of the resonance frequency and the piston displacement amplitude. An increase in the resonator Q-factor is observable, when the resonator has a conical extension. An accelerated aerosol sedimentation in tubes is revealed in the case of acoustic oscillation with the resonance frequency. In the presence of a conical extension the aerosol drop concentration is reduced by a factor of 1.2 more rapidly than in the case of a uniform tube and three times more rapidly as compared with natural sedimentation. The results obtained can be used for increasing the efficiency of acoustic methods of gas purification from the disperse phase
86-94
Regimes of Fluid Displacement from an Anisotropic Formation in the Gravity Field
Abstract
The problem of two-phase flow of incompressible fluids through anisotropic porous media in the gravity field is considered. Similarity criteria characterizing the flow directions of the displacing and displaced fluids are determined. The regimes of displacement from an anisotropic formation are classified within the framework of study of numerical solutions to the profile problem of flow through an anisotropic porous medium. It is shown that there are four regimes corresponding to qualitatively different flows. Their effectiveness is compared in terms of the coefficient of fluid extraction from the formation and the displacement sweep factor. The influence of the capillary pressure on the displacement efficiency in various flow regimes is studied. It is shown that in some cases increase in the influence of the capillary pressure leads to increase in the displacement coefficient, while in other regimes, on the contrary, to its decrease.
95-109
Trajectories of Liquid Particles in a Dark Soliton Field in a Fluid Beneath an Ice Cover
Abstract
A fluid layer of finite depth described by Euler equations is considered. The ice cover is modeled by a geometrically non-linear elastic Kirchhoff–Love plate. The trajectories of liquid particles under the ice cover are found in the field of a nonlinear surface traveling wave tending to a periodic wave at infinity: the so-called “dark soliton” (which is a nonlinear product of a step-wave and a periodic wave) of small but finite amplitude. The presence of dark solitons in the system is an indicator of the modulation stability of the carrier periodic wave (defocusing). The analysis uses explicit asymptotic expressions for solutions describing wave structures on the water–ice interface such as dark solitons, as well as asymptotic solutions for the velocity field in the liquid column generated by these waves.
110-120
ОСОБЕННОСТИ ТРАНСФОРМАЦИИ НЕЛИНЕЙНЫХ ВНУТРЕННИХ ВОЛН НА ШЕЛЬФЕ И В ГЛУБОКОМ ОЗЕРЕ
Abstract
Характерной особенностью стратифицированных течений в больших водоемах является генерация интенсивных короткопериодных внутренних волн на фронте длинноволновых возмущений. Наиболее выражены нелинейные процессы при распространении придонных и приповерхностных возмущений. Эффективным инструментом исследования волновых процессов в океане является теория многослойной мелкой воды с учетом эффектов нелинейности и дисперсии. Показано, что разработанные математические модели пригодны для описания трансформации нелинейных внутренних волн как в шельфовой зоне моря, так и в глубоких пресноводных водоемах. В частности, проведено сравнение структуры придонных внутренних волн в шельфовой зоне Японского моря и недавно обнаруженных приповерхностных внутренних волн в Телецком озере. Обсуждается механизм генерации интенсивных внутренних волн при возбуждении сейшевых колебаний в узких водоемах. Построены бегущие волны в многослойной жидкости и найдены численные решения нестационарной проблемы генерации внутренних волн. Проведено сравнение с лабораторными экспериментами по генерации пакета короткопериодных внутренних волн при сейшевых колебаниях двухслойной жидкости в длинном канале, а также с зарегистрированной приповерхностной внутренней уединенной волной в Телецком озере.
121-131
Turbulent Schmidt and Prandtl Numbers in the Boundary Layer on a Wall with Film Cooling when a Foreign Gas is Injected through a Porous Insert
Abstract
Variations in the turbulent Schmidt and Prandtl numbers in the boundary layer on a wall with film cooling when helium is injected into xenon flow through a porous insert is investigated numerically using the three-parameter RANS turbulence model supplemented with transport equations for turbulent heat and mass transfer. The results obtained are compared with calculated data for constant turbulent Schmidt and Prandtl numbers.
132-143
Supersonic Flow past a Sharp Plate with Surface Anomalous Glow Discharge in a Magnetic Field
Abstract
The electrodynamic structure of an anomalous glow discharge between two plane electrodes located on the surface of a sharp plate in supersonic flow of molecular nitrogen is studied numerically in a wide range of Mach numbers using a modified ambipolar model of quasi-neutral electric-discharge plasma. The ambipolar diffusion coefficient and the effective ionization rate are modified while taking into account the external magnetic field. The problem is solved in the two-dimensional x–y formulation, when the external magnetic field strength is directed in the positive or negative direction of the z axis. The parameters of anomalous glow discharge are numerically studied in the pressure range p = 0.14–5 Torr and the voltage drops on the quasineutral current column of discharge plasma V = 30–320 V. The main problem parameters which make it possible to obtain a reasonable agreement with the available experimental data are determined.
144-167
ИССЛЕДОВАНИЯ АВТОКОЛЕБАТЕЛЬНЫХ ПРОЦЕССОВ МЕЖДУ ВОЗВРАЩАЕМЫМ АППАРАТОМ И ДВИГАТЕЛЬНЫМ ОТСЕКОМ ПИЛОТИРУЕМОГО КОСМИЧЕСКОГО КОРАБЛЯ ПРИ ИХ РАЗДЕЛЕНИИ В СЛУЧАЕ АВАРИИ
Abstract
Представлены результаты анализа исследований течения в зазоре между возвращаемым аппаратом пилотируемого космического корабля и расположенным за ним двигательным отсеком при их разделении в случае аварии ракеты на активном участке траектории. Особое внимание уделено автоколебательным процессам различной природы, возникающим при определенных расстояниях разделения на трансзвуковых режимах полета. Предложен подход к оценке режимов существования и частот автоколебаний на основе геометрии задачи и условий обтекания.
168-182
Kinetic Theory of Expansion of Two-Component Plasma in a Plane Vacuum Diode
Abstract
The results of study of the initial stage of expansion of a collisionless plasma with the electric current into a plane vacuum gap on the basis of kinetic equations for electrons and ions and the Poisson equation for the electric field are given. Self-consistent dynamics of a two-component plasma and electric field are theoretically modeled and the fundamental mechanism for establishing superthermal velocities of charged particles is described in detail. The parameters of anode-directed flows of positive ions in the cathode plume plasma are calculated. The expansion velocities of the cathode plume plasma observed in vacuum arcs at the level of (1−5) × 106 cm/s can be explained within the framework of the proposed collisionless mechanism.
183-191
ЧИСЛЕННОЕ ИССЛЕДОВАНИЕ ИЗЛУЧЕНИЯ В УДАРНО-НАГРЕТОЙ СМЕСИ CO2 И N2 МЕТОДОМ ПРЯМОГО СТАТИСТИЧЕСКОГО МОДЕЛИРОВАНИЯ
Abstract
Предложена модель для численного исследования излучения за фронтом сильной ударной волны в газовой смеси CO2–N2. Модель основана на методе прямого статистического моделирования Монте-Карло и учитывает физико-химические свойства атомов и молекул, поступательно-вращательный и поступательно-колебательный обмен энергией, кинетику химических реакций, возбуждение электронных уровней атомов и молекул, а также процессы переноса радиационной энергии. Проведена серия расчетов спектральных характеристик ударно нагретой смеси. Полученные результаты сравниваются с имеющимися экспериментальными данными.
192-204