Waves on a viscous-fluid film flowing down a vibrating vertical plate

A thin film of a viscous fluid flowing down a vertical plane in a gravitational field is considered. The plane executes harmonic oscillations in the direction normal to itself. An equation that describes the evolution of surface disturbances at small fluid flow rates is obtained. Some solutions of this equation are found. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 4, pp. 90–98, July–August, 1999.     

Nonlinear development of two-dimensional hydroelastic instability in a turbulent boundary layer on an elastic coating

Nonlinear evolution of hydroelastic instability arising in the flow past a coating of a rubber-type material by a turbulent boundary layer of an incompressible fluid is studied. A nonlinear dispersion equation for two-dimensional, quasi-monochromatic, low-amplitude waves is derived. The Prandtl equations for the mean (over the waviness period) boundary-layer flow are solved in the approximation of local similarity and by direct numerical integration. Evolution of unstable waves in time is studied on the basis of the Landau equation, which is derived separately for the instability of fast waves (flutter) and the quasi-static instability (divergence). The calculation results are compared with available experimental data. Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod 603600. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 69–80, July–August, 2000.     

EFFECT OF LASER IMPACT PARAMETERS ON THE FORMATION OF A POOL OF THE MOLTEN B4C — Ti–6Al–4V CERMET MIXTURE

Journal of Applied Mechanics and Technical Physics - Results of a series of experiments aimed at studying laser cladding of individual tracks with the use of the B4C–Ti–6Al–4V...     

Heat transfer in a horizontal fluid layer heated from below upon rotation of one of the boundaries

The mixed convection in a horizontal fluid layer which is generated by uniform heating from below and by rotation of one of the boundaries of the layer was studied experimentally. The region occupied by the fluid is a cylinder of radius320 mm and height45 mm. Either the upper or the lower boundary together with the side wall rotates. For Rayleigh numbersRa≃2·10 ⁷, in a broad range of Reynolds numbers, based on experimental data we constructed mean-temperature profiles along the normal to the upper boundary and with a uniform step over the radius. In addition, we obtained data on the radial thermal stratification of the fluid, the integral flow through the fluid layer, and information on temperature fluctuations. The complicated character of the dependence of the heat transfer on the Reynolds number was shown. The obtained dependences of the heat transfer and temperature inhomogeneity on Reynolds numbers was explained qualitatively. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 126–133, May–June, 1998.     

Some characteristics of heat and mass transfer in a turbulent air flow over a surface

It is shown that, for a certain proportion between the rib height (2–15 mm) installed at the test-section entrance and the turbulence level of the main flow (1–26%), there are extrema of parameters that describe mass transfer on the surface of an evaporating liquid fuel. In tests with and without combustion, discrete changes in the rates of heat and mass transfer are observed. Conditions for their manifestation are analyzed. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskava Fizika, Vol. 41, No.4, pp. 124–130, July–August, 2000.     

Specification and evolution of local (periodic) perturbations in experimental studies of the rayleigh-taylor instability in strong media

Various techniques for specifying the initial local or periodic perturbations on the boundaries of strong solids are discussed. The evolution of a local perturbation is studied experimentally. It is shown that the “mass inhomogeneity” of the perturbation zone and the geometrical dimensions of an insert play an important role in the perturbation transformation. Institute of Experimental Physics, Sarov 607190. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 171–176, March–April, 2000.     

Effect of heating on the spall fracture of a composite based on SKTN rubber

Russian Research Institute of Experimental Physics, Arzamas-16. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 36, No. 3, pp 167–169, May–June, 1995.     

Convective mass transfer across fluid interfaces in straight angular pores

Steady convective mass transfer to or from fluid interfaces in pores of angular cross-section is theoretically investigated. This situation is relevant to a variety of mass transport process in porous media, including the fate of residual non-aqueous phase liquid ganglia and gas bubbles. The model incorporates the essential physics of capillarity and solute mass transfer by convection and diffusion in corner fluid filaments. The geometry of the corner filaments, characterized by the fluid–fluid contact angle, the corner half-angle and the interface meniscus curvature, is accounted for. Boundary conditions of zero surface shear (‘perfect-slip’) and infinite surface shear (‘no-slip’) at the fluid–fluid interface are considered. The governing equations for laminar flow within the corner filament and convective diffusion to or from the fluid–fluid interface are solved using finite-element methods. Flow computations are verified by comparing the dimensionless resistance factor and hydraulic conductance of corner filaments against recent numerical solutions by Patzek and Kristensen (J. Colloid Interface Sci 236, 305–317 2001). Novel results are obtained for the average effluent concentration as a function of flow geometry and pore-scale Peclet number. These results are correlated to a characteristic corner length and local pore-scale Peclet number using empirical equations appropriate for implementation in pore network models. Finally, a previously published “2D-slit” approximation to the problem at hand is checked and found to be in considerable error.     

Energetic criteria of artificial magnetosphere formation

Institute of Laser Physics, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 36, No. 4, pp. 3–7, July–August, 1995.     

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.     

Effect of absorption in time-resolved optoacoustic tomography

The reconstructive problem of time-resolved optoacoustic tomography is solved taking into account the absorption of initiating (laser) and secondary (acoustic) radiations. Numerical results that confirm theoretical data are presented. A relatively simple relation between the unknown and the experimental functions of spatial distribution of the absorption coefficient is obtained. Institute of Physics, Dagestan Scientific Center, Russian Academy of Sciences, Makhachkala 367003. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 216–219, July–August, 2000.     

Explicit Rate–Time Solutions for Modeling Matrix–Fracture Flow of Single Phase Gas in Dual-Porosity Media

One of the widely used methods for modeling matrix–fracture fluid exchange in naturally fractured reservoirs is dual porosity approach. In this type of modeling, matrix blocks are regarded as sources/sinks in the fracture network medium. The rate of fluid transfer from matrix blocks into fracture medium may be modeled using shape factor concept (Warren and Root, SPEJ 3:245–255, 1963); or the rate–time solution is directly derived for the specific matrix geometry (de Swaan, SPEJ 16:117–122, 1976). Numerous works have been conducted to study matrix–fracture fluid exchange for slightly compressible fluids (e.g. oil). However, little attention has been taken to systems containing gas (compressible fluid). The objective of this work is to develop explicit rate–time solutions for matrix–fracture fluid transfer in systems containing single phase gas. For this purpose, the governing equation describing flow of gas from matrix block into fracture system is linearized using pseudopressure and pseudotime functions. Then, the governing equation is solved under specific boundary conditions to obtain an implicit relation between rate and time. Since rate calculations using such an implicit relation need iterations, which may be computationally inconvenient, an explicit rate–time relation is developed with the aid of material balance equation and several specific assumptions. Also, expressions are derived for average pseudopressure in matrix block. Furthermore, simplified solutions (originated from the complex general solutions) are introduced applicable in infinite and finite acting flow periods in matrix. Based on the derived solutions, expressions are developed for shape factor. An important observation is that the shape factor for gas systems is the same as that of oil bearing matrix blocks. Subsequently, a multiplier is introduced which relates rate to matrix pressure instead of matrix pseudopressure. Finally, the introduced equations are verified using a numerical simulator.     

Invariant Measures for Dissipative Systems and Generalised Banach Limits

Inspired by a theory due to Foias and coworkers (see, for example, Foias et al. Navier–Stokes equations and turbulence, Cambridge University Press, Cambridge, 2001) and recent work of Wang (Disc Cont Dyn Sys 23:521–540, 2009), we show that the generalised Banach limit can be used to construct invariant measures for continuous dynamical systems on metric spaces that have compact attracting sets, taking limits evaluated along individual trajectories. We also show that if the space is a reflexive separable Banach space, or if the dynamical system has a compact absorbing set, then rather than taking limits evaluated along individual trajectories, we can take an ensemble of initial conditions: the generalised Banach limit can be used to construct an invariant measure based on an arbitrary initial probability measure, and any invariant measure can be obtained in this way. We thus propose an alternative to the classical Krylov–Bogoliubov construction, which we show is also applicable in this situation.     

Heat transfer in condensation on a vertical tube in a granular bed

S. S. Kutateladze Institute of Heat Physics, Siberian Branch of the Russian Academy of Sciences. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 36, No. 6, pp. 102–107, November–December, 1995.     

Formation of thermal localized structures in a weld in pulse-arc welding by a nonmelting electrode

The technological regimes of welding that promote uniform distribution of the properties over the length of a welded joint are studied by numerically modeling the formation of a weld seam by a nonmelting electrode. Institute of Physics of Strength and Materials Science, Siberian Division, Russian Academy of Sciences, Tomsk 634021. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 172–177, November–December, 1998.     

Nanoscale Poiseuille flow and effects of modified Lennard–Jones potential function

Numerical simulation of Poiseuille flow of liquid Argon in a nanochannel using the non-equilibrium molecular dynamics simulation (NEMD) is performed. The nanochannel is a three-dimensional rectangular prism geometry where the concerned numbers of Argon atoms are 2,700, 2,550 and 2,400 at 102, 108 and 120 K. Poiseuille flow is simulated by embedding the fluid particles in a uniform force field. An external driving force, ranging from 1 to 11 PN (Pico Newton), is applied along the flow direction to inlet fluid particles during the simulation. To obtain a more uniform temperature distribution across the channel, local thermostating near the wall are used. Also, the effect of other mixing rules (Lorenthz–Berthelot and Waldman–Kugler rules) on the interface structure are examined by comparing the density profiles near the liquid/solid interfaces for wall temperatures 108 and 133 K for an external force of 7 PN. Using Kong and Waldman–Kugler rules, the molecules near the solid walls were more randomly distributed compared to Lorenthz–Berthelot rule. These mean that the attraction between solid–fluid atoms was weakened by using Kong rule and Waldman–Kugler rule rather than the Lorenthz–Berthelot rule. Also, results show that the mean axial velocity has symmetrical distribution near the channel centerline and an increase in external driving force can increase maximum and average velocity values of fluid. Furthermore, the slip length and slip velocity are functions of the driving forces and they show an arising trend with an increase in inlet driving force and no slip boundary condition is satisfied at very low external force (<1 PN).     

Viscoelastic properties of fractal media

Temporal fractal sets for analysis of viscoelastic properties of nonhomogeneous media are considered. A fractional derivative directly related to fractal dimension is constructed. The relationship between the diffusion of the relaxation spectrum and the fractal dimension is established. Odessa State Polytechnical University, Odessa 270044, Ukraine. Institute of Molecular Physics, Polish Academy of Sciences, Poznan, Poland. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 162–172, January–February, 2000.     

Strength and fracture of plutonium and its alloy with gallium under impact loading

Results are presented from a theoretical analysis of the conditions of cleavage fracture of plutonium and its alloy with 1.6 wt. % gallium under shock loading. Experimental data obtained earlier are used to determine the critical tensile stresses corresponding to the initial stage of macroscopic cleavage fracture of specimens. The elastoplastic properties of the materials and polymorphic transformations that occur in the alloy at normal and high (315°C) temperatures were taken into account in the calculations. Institute of Experimental Physics, Sarov 607190. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 4, pp. 135–140, July–August, 1998.     

Shape of the vapor bubble upon explosive boiling

A relation for the shape of a vapor bubble forming during propagation of a vaporization front is proposed. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 122–123, March–April, 2000.     

Boundaries of the plasma-free regime of electroexplosion of a foil

Results of the experimental studies of the commutation characteristics of an electroexplosive breaker upon heating of a copper foil by a current pulse of duration τ≈1msec are given. The dependences of the electric-field strength and the specific power of the circuit breaker during an electroexplosion of the foil on the specific power of the source P_s are found and it is shown that the transition of the plasma-free regime of electroexplosion of the foil to a plasma regime occurs for P_s=30–40GW/g. Institute of Experimental Physics, Sarov 607190. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 14–20, January–February, 2000.