The flow in a planar-radial vortex chamber. 1. An experimental study of the velocity field in transient and steady flows

Two methods for determining the flow velocity in a vortex chamber of planar-radial geometry under transient and steady-state conditions are proposed. Local flow velocities throughout the entire volume of the chamber are measured, and the flow is found to be rotational. The effect of accumulation of particles heavier than air in the butt-end boundary layer is revealed. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 112–121, November–December, 1999.     

Excitation of subharmonic oscillations in an axisymmetric flow with coherent structures in the regime of aeroacoustic resonance

Conditions of origination of aeroacoustic resonance phenomena near an axisymmetric body in the form of a thick-walled tube in an air flow in a rectangular channel are studied experimentally. Dependences of the eigenfrequency of acoustic oscillations on the model length are determined. By studying the mechanism of origination of oscillations in the wake flow, it is shown that the process of generation of annular coherent structures in resonant regimes is characterized by evolution of nonlinearities including a subharmonic packet. Possible methods of flow control are discussed. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i, Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 59–68, July–August, 2000.     

The flow in a planar-radial vortex chamber. 2. Vortex structure of the flow

A vortex structure of an air flow with a characteristic size of vortices comparable with the primary vortex size was observed in a vortex chamber of planar-radial geometry for the first time. The vortex component of the flow velocity along the chamber radius and its axis was calculated. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 41–49, January–February, 2000.     

Inertial steady flow of a bed of granular material down a surface with microrelief with allowance for finite time of intergranular contacting

An inertial flow of a granular material can be described by the laws of conservation of mass, momentum, and energy of random motion of solid particles by invoking some closing relations. In this work, these closing relations are inferred from the dimensional theory. The system of equations obtained is used to determine characteristics of a steady flow of a bed of a granular material down an inclined surface with a microrelief for various Richardson numbers and finite contact times of the particles during their collisions. Novosibirsk Military Institute, Novosibirsk 630103. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 128–132, November–December, 1999.     

Velocity of ions of a plasma jet from an arc source at various potentials on the plasma boundary

The effect of the potential of a conical electrode near the anode of an ion source on the speed of ions of the plasma jet ejected from the anode orifice is studied. An original method for measuring the velocity is used. Qualitative diffferences in the effect of the electrode on ions in the anode region and on the periphery of the plasma flow are discussed. Institute of Chemical Kinetics and Combustion, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 3–7, November–December, 1998.     

Experimental and numerical study of the stability of a pre-separated flow on an airfoil

The problem of the origin and evolution of two-dimensional waves of unstable disturbances in the boundary layer on an airfoil in the region of adverse pressure gradient in the preseparation flow region is solved numerically. The stability of the experimental velocity profiles, including the inflected profiles, is studied. As a result of the calculations, the boundaries of the instability region and the parameters of the maximally unstable disturbances (frequency, growth rate, wavelength, and propagation velocity) are determined for each velocity profile. The characteristics obtained in the present work are in good agreement with the real experimental parameters of instability waves. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 1, pp. 126–132, January–February, 1999.     

Kinetics of charge-exchange interaction of dense flows

The nonlinear problem of charge exchange between an ion flow and neutral particles is considered. An exact solution of the equations of charge-exchange interaction in plane geometry is found. Parameters determining the effectiveness of interpenetration of dense flows and the structure of the layer of intense interaction are obtained. Institute of Laser Physics, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 11–19, March–April, 2000.     

Experimental study of deformation and attachment of microparticles to an obstacle upon high-rate impact

Results of an experimental study of the high-rate (400–1200 m/sec) interaction of spherical aluminum particles with a surface are given. Particle deformation was studied by means of a microscope. The mean values of the degree of particle strain were determined by statistical processing for specimens with different hardness (hardened and unhardened steel and copper) and produced in different spraying regimes (the pressure and temperature of a gas in a plenum chamber and a working gas). A relation between the degree of particle strain and the impact velocity was obtained by using the design particle velocities for the corresponding parameters. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 47–52, March–April, 2000.     

Optical response of a layer of a nematic liquid crystal to an air flow

A liquid crystal coating is used to measure the surface friction created when a flat plate is subjected to an air flow. Surface friction is determined from the optical response of the nematic liquid crystal coating to the flow. The proposed method does not require precise monitoring of the thickness of the coating or the angles of illumination and observation. This makes it possible to eventually progress to panoramic measurements of surface aerodynamic characteristics. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 4, pp. 102–109, July–August, 1998.     

Appearance of a “cold” layer upon explosive compacting of powders

Explosive compacting of powders is numerically simulated in the two-dimensional formulation. Different flow regimes depending on the detonation velocity are considered. Based on the calculations, the nature of the appearance of a “cold” layer upon explosive compacting of powders is revealed. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 192–197. January–February, 2000.     

Aerosol aspiration into a tube from a calm medium

The problem of aerosol aspiration into a thin-walled tube from a calm medium is solved. The dependence of the aspiration coefficient on the Stokes number and the steady-state settling velocity is investigated. The results obtained are compared with the calculations [1, 2] and the experimental formula [3]. Kazan’. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 104–109, March–April, 2000. The work received financial support from the Russian Foundation for Basic Research (project No. 96-01-00111).     

Changes of a porous structure in flow of a monodisperse medium

The motion of fluids with suspended particles in porous media is considered. A mathematical model for the interaction of a monodisperse suspension with a porous structure is proposed. Changes in the parameters of the medium and the flow are studied for equilibrium regimes. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 113–121, March–April, 2000.     

A mixing layer in a homogeneous fluid

A mathematical model for the evolution of a mixing layer in shear flows is constructed. The problem of a mixing layer with pressure gradient is solved: in particular, the distributions of the velocity and basic characteristics of turbulent flow in the mixing layer are obtained. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 81–92, July–August, 2000.     

Numerical simulation of an obliquely incident solitary wave

Calculations using the finite-difference method with dynamically adaptive grids were performed within the framework of the Zheleznyak-Pelinovskii nonlinear-dispersion model and the three-dimensional potential flow model. The results are compared with calculations by other authors. Institute of Computational Technologies, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 17–25, November–December, 1999.     

Thermocapillary flow near a “cold corner”

The velocity field in a neighborhood of the point of contact between the free and solid boundaries is studied numerically for the problem of noncrucible zone melting in a two-dimensional model formulation. A distinct Prandtl boundary layer on the solid boundary and a Marangoni boundary layer on the free boundary and high gradients of the longitudinal velocity along the free boundary in the immediate vicinity of the “cold corner” are observed. It is found for the first time that with distance from the solid boundary, the velocity curve has a maximum, which is not typical of the ordinary flow near the solid boundary. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 141–148, May–June, 1998.     

Calculation of dynamic stall on an oscillating airfoil

A mathematical model of an unsteady separated flow around an oscillating airfoil is considered. This model is based on a viscid-inviscid approach. The points of separation and the intensity of vorticity displaced into the external flow are determined using boundary-layer equations in an integral form. Dynamic stall on an oscillating airfoil is studied. The mechanism and nature of antidamping are discovered. Novosibirsk State Technical University, Novosibirsk 630092. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 3, pp. 81–85, May–June, 2000.     

Rheological properties of materials from the point of view of physical kinetics

Zhurkov and Kauzmann rheological bodies, reflecting the physical regularities of plastic deformation of materials, are studied. Solutions of differential equations of flow for composite rheological bodies are obtained. Examples of using structural models of materials that consist of new rheological bodies and describe the inelastic behavior of alloys for various types of temperature-force loading are given. The obtained solutions of the differential equations are used for analysis of the creep of a structurally unstable alloy. Chaplygin Siberian Aviation Research Institute, Novosibirsk 630051. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 1, pp. 119–128, January–February, 1998.     

Nonstationary hydrodynamic characteristics of a double grid of profiles

The flow about a double grid of solid profiles of arbitrary shape which vibrate in a stream of an ideal incompressible fluid is considered. Behind the grid profiles, the nonstationary vortex traces simulated by the lines of contact velocity discontinuity are taken into account. The problem is reduced to the solution of a system of two integral equations relative to the fluid velocity on the initial profiles of the double grid under the assumption that the vibration amplitudes are small. Formulas for calculating the nonstationary forces and moments are derived. The dependences of these forces on the shape, mutual positions, and laws of vibration of the grid profiles are studied. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 4, pp. 150–155, July–August, 1999.     

Slow motion of a granular layer on an inclined plane

The shape of the free surface of a layer of granular material moving on an inclined plane is studied on the basis of a model of a non-Newtonian fluid with a nonlinear relation between the stress tensor and the shear rate of the flow. For small but finite elevations of the free surface, the governing equations are reduced to a quasilinear Burgers equation. Results of a numerical solution are presented for the case of arbitrary elevations. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 2, pp. 117–120, March–April, 1998.     

Thermodynamic instability of disperse media isolated from external actions

The evolution of the structure of a medium containing disperse elements (the drops in a weakly viscous fluid, rigid spheres in glycerin, and air pores in a gel) is studied experimentally in the case where the gradient temperature and the concentration fields are absent in the system, and the medium is isolated from the influence of an external force field (including gravity forces). It is shown that these systems are nonequilibrium: if the initial distance between disperse particles is of the order of their sizes, the particles approach until they come in contact (coagulation) irrespective of the scale of the system. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 3, pp. 53–58, May–June, 1999.