Electro-magneto-thermo-visco-elastic Plane Waves in Rotating Media with Thermal Relaxation

A study is made of the propagation of plane electro-magneto-thermo-visco-elastic harmonic waves in an unbounded isotropic conducting visco-elastic medium of Kelvin–Voigt type permeated by a primary uniform magnetic field when the entire medium rotates with a uniform angular velocity. The thermal relaxation time of heat conduction, the electric displacement current, the coupling between heat flow density and current density, and that between the temperature gradient and the electric current are included in the analysis. A more general dispersion relation is obtained to determine the effects of rotation, thermal relaxation time, visco-elastic parameters, and the external magnetic field on the phase velocity of the waves. Perturbation techniques are used to study the influence of small magneto-elastic and thermo-elastic couplings on the phase velocity of the waves. Cases of low and high frequencies are also analyzed to determine the effect of rotation, visco-elastic parameters, thermo elastic and magneto-elastic coupling, as well as thermal relaxation time of heat conduction on the waves.     

Temperature shock waves in a moving medium with allowance for the relaxation of the heat flux

The solution of the gasdynamic equation with allowance for the heat transfer in the relaxation of the heat flux is analyzed. The relations expressing the laws of conservation on the front of strong discontinuity of the quantities sought, including the discontinuity of the temperature and the heat-flux density, are discussed. The possibility of existence of two shock waves with fixed initial data is shown using the self-similar solution of the problem on gas motion ahead of the piston. The occurrence of two strong discontinuities is due to the presence of different velocities of propagation of gasdynamic and thermal disturbances — the velocity of sound and the finite rate of heat transfer at a nonzero time of relaxation of the heat flux. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 57–68, July–August, 2006.     

Discontinuous solutions of gas-dynamics equations taking into account the relaxation of a heat flow with a heat transfer

The gas-dynamics equations in Lagrangian mass coordinates for a heat flow with a relaxation and a hyperbolic heat transfer have been considered in the plane-symmetry approximation. The characteristics of the system of these equations were determined. Relations for the front of a strong discontinuity of its solution were obtained. With the theory of generalized solutions of quasi-linear equations, the stability of the discontinuities of gas-dynamic and heat quantities characteristic of the indicated flow was demonstrated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 350–357, March–April, 2009.     

Concerning the alternating-sign dissipation of energy in a fluid with relaxing viscous stresses

Total equations of motion of an incompressible fluid are investigated taking account of relaxation phenomena for viscous stresses and heat flux. In the K. I. Strakhovich class of solutions the fluid flows are considered that contain a strong hydrodynamic discontinuity. The conditions of motion are analyzed under which the dissipative function is negative. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 6, pp. 967–974, November–December, 1997.     

One-velocity model of a multicomponent heat-conducting medium

A model of a one-velocity heat-conducting heterogeneous medium with the Fourier relaxation law of heat transfer has been constructed. It is shown that the model’s equations are of hyperbolic type. The results of numerical experiments for a three-component mixture of ideal gases carried out with the use of the Courant–Isaacson–Rees scheme are presented.     

Determination of the kinetic curves of drying of blocks of adsorbents-dessicants with different cross sections of channels and of a granulated adsorbent on a change in the flow velocity

The kinetics of convective drying (regeneration) of different types of adsorbents-dessicants with different geometric parameters has been studied. It is shown that adsorbents of a “channel” (cellular) type have a long constant-rate stage of drying, whereas a granulated polydisperse adsorbent is mainly dried at a variable rate. Adsorbents having a maximum water yielding capacity have been revealed. It has been established that the velocity of a drying gas flow substantially influences the process of moisture extraction from all types of adsorbents. In order to describe the kinetic curves of the given phenomenon, a model of a relaxation kinetic equation that quite satisfactorily describes the kinetics of drying of the adsorbents studied was used. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 65–68, January–February, 2009.     

Influence of the concentration of a dispersed phase and of the magnetic field on the attenuation of ultrasonic waves in magnetic fluids

The regularities of the propagation of elastic waves of ultrasonic range in magnetic fluids have been experimentally established. The influence of relaxation processes — nonlocal heat exchange and viscous dissipation — on the coefficient of attenuation of sound has been revealed and a comparison to the existing theoretical data has been made. The dependences (anisotropic in form) of the attenuation of the wave’s amplitude on the value and direction of the magnetic field have been determined and an interpretation of the results obtained has been proposed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 133–140, September–October, 2007.     

Natural convection heat transfer of a viscous fluid in a vertical porous channel

Approximate analytic solutions to second-order nonlinear systems arising in natural convection flow and heat transfer in vertical porous channels are obtained via the Galerkin–Legendre Spectral Method. Furthermore, existence, uniqueness, and concavity results are established using Green’s functions and degree theory. We find that an increase in either the Darcy number or the quadratic density temperature variation results in an increase in the velocity and the temperature of a Newtonian fluid. Finally, parametric zones for the occurrence of reverse flow are considered, and the resulting influences on the obtained approximate solutions are analyzed.     

Modeling of Reduction in the Resistance of a Body of Revolution in a Viscous Fluid

The problem of flow past a body of revolution with modeling of a traveling wave on its surface has been solved. Parametric investigations of the qualitative and quantitative influence of the parameters of the traveling wave on control over the flow past the body of revolution have been carried out. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 193–195, May–June, 2005.     

Investigation of regimes of thermogravitational convection of a fluid between coaxial semicylinders with a heat-conducting shell in the presence of a local energy source

A numerical analysis has been made of the thermodynamic regimes of natural convection of a Newtonian fluid satisfying the Boussinesq approximation in the gap between coaxial semicylinders with finitely-thick walls in the presence of the heat-release source under the conditions of convective heat exchange with the environment. A mathematical model has been formulated in the dimensionless variables current function–velocity vorticity vector–temperature in polar coordinates. Streamlines and velocity and temperature fields reflecting the influence of the Prandtl number Pr = 0.7 and 7.0, the nonstationarity factor 0 < τ ≤ 300, the dimensions of the energy source, and of the relative thermal conductivity on the flow regimes and heat transfer have been obtained.     

Thermophysical and acoustic properties of aqueous solutions of the pluronic PE6400 copolymer

Experimental results of investigations of the specific heat and the velocity of sound in aqueous solutions of the Pluronic PE6400 copolymer have been presented. Phase transitions, phase states, and possible physical mechanisms of the effects have been discussed based on these results. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 158–163, May–June, 2006.     

Interfacial capillary–gravity waves due to a fundamental singularity in a system of two semi-infinite fluids

The interfacial capillary–gravity waves due to a transient fundamental singularity immersed in a system of two semi-infinite immiscible fluids of different densities are investigated analytically for two- and three- dimensional cases. The two-fluid system, which consists of an inviscid fluid overlying a viscous fluid, is assumed to be incompressible and initially quiescent. The two fluids are each homogeneous, and separated by a sharp and stable interface. The Laplace equation is taken as the governing equation for the inviscid flow, while the linearized unsteady Navier–Stokes equations are used for the viscous flow. With surface tension taken into consideration, the kinematic and dynamic conditions on the interface are linearized for small-amplitude waves. The singularity is modeled as a simple mass source when immersed in the inviscid fluid above the interface, or as a vertical point force when immersed in the viscous fluid beneath the interface. Based on the integral solutions for the interfacial waves, the asymptotic wave profiles are derived for large times with a fixed distance-to-time ratio by means of the generalized method of stationary phase. It is found that there exists a minimum group velocity, and the wave system observed will depend on the moving speed of the observer. Two schemes of expansion of the phase function are proposed for the two cases when the moving speed of an observer is larger than, or close to the minimum group velocity. Explicit analytical solutions are presented for the long gravity-dominant and the short capillary-dominant wave systems, incorporating the effects of density ratio, surface tension, viscosity and immersion depth of the singularity.     

Electro-magneto-thermo-elastic plane waves in rotating media with thermal relaxation

A study is made of the propagation of plane electro-magneto-thermo-elastic harmonic waves in an unbounded isotropic conducting medium permeated by a primary uniform magnetic field when the entire medium rotates with a uniform angular velocity. The thermal relaxation time of heat conduction, the electric displacement current, the coupling between heat flow density and current density and that between the temperature gradient and the electric current are included in the analysis. A more general dispersion relation is obtained to determine the effects of rotation, relaxation time and the external magnetic field on the phase velocity of the waves. Perturbation techniques are used to study the influence of small magneto-elastic and thermo-elastic couplings on the phase velocity of the waves. Cases of low and high frequencies are also studied to determine the effect of rotation, thermoelastic and magneto-elastic couplings on the waves.     

Nonlinear waves in an active-dissipative disperse medium

Nonlinear waves in a medium involving dissipation, dispersion, and enhancement described by the generalized Kuramoto-Sivashinsky equation are discussed. Analytical solutions of the equation are obtained in the form of solitary waves. For numerical modeling of the nonlinear waves a difference scheme is suggested. Interaction of nonlinear waves described by the Kuramoto-Sivashinsky model is considered. It is shown that for specified values of the problem parameters there is one solitary wave described by the initial model. The dependences of the velocity and amplitude of this wave on the problem parameters are determined. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 149–154, January–February, 1998.     

Acoustic study of nano-crystal embedded PbO-P2O5 glass

Nano-crystal embedded PbO-P₂O₅ glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region. The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature. A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination of the size of nano-crystals from the ultrasonic attenuation data.     

Deformation of a Viscous Heat Conducting Free Liquid Layer by the Thermocapillary Forces and Tangential Stresses: Analytical and Numerical Modeling

The coupled problem of a non stationary flow of a liquid layer with free boundaries and heat transfer in a layer is investigated under conditions of weightlessness. To describe the layer deformations caused by the inhomogeneous temperature distributions and additional tangential stresses a class of the solutions of the Navier–Stokes equations is used. The two-dimensional solutions are characterized by a linear dependence of the longitudinal component of velocity on the longitudinal coordinate. The results of the problem of the heat conducting liquid layer deformations allow to characterize a behavior of the free liquid films and to control the mechanisms of deformations.     

Toward calculation of free-convective motion of liquid over a linear heat source

The results of an analytical and numerical investigation of a laminar free-convective motion of liquid over a linear heat source are presented. The characteristic features of velocity and temperature field as functions of the density parameter and Prandtl number have been studied. A table of numerical solutions is given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 69–73, July–August, 2007.     

Gas flow through a porous heat-releasing medium with allowance for the temperature dependence of gas viscosity

The gas flow through a porous heat-releasing medium is considered. It has been noted that account for the temperature dependence of the gas viscosity strongly influences the solution: the gas flow rate markedly decreases and a stronger heating occurs. Analysis of the flow of a gas with a temperature-dependent viscosity by the Sutherland formula has revealed two steady-state cooling regimes — stable and unstable ones. It has been shown that the possibility of the steady-state regime is determined not only by the problem parameters but by the initial conditions as well. The transient process from the state of rest in the absence of heat release to the state of the regime of induced filtration upon instantaneous switching-on of heat input is described. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 35–40, January–February, 2006.     

Heat exchange in turbulent flow of an incompressible liquid in a rough tube with a constant wall temperature

Turbulent flow of an incompressible liquid in a tube is considered as flow of an oriented liquid whose symmetry is determined by the director. The velocity profile and the temperature field in steady-state flow in a straight circular tube with a rough wall are determined within the framework of the model. The solutions found coincide with analogous solutions for a smooth tube for roughness equal to zero. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 89–96, September–October, 2007.     

Flow of a gas out of the vessel to a medium with counterpressure under the conditions of intense heat supply

The basic regularities of the influence of heat supply on the parameters of the flow have been elucidated with the use of analytical and numerical solutions of the quasi-one-dimensional problem on flow, through a pipe, of the gas out of a vessel with prescribed pressure and stagnation temperature to a medium with a prescribed counterpressure. It has been shown that changeover from the stationary outflow to an unsteady self-oscillatory regime of outflow is possible with increase in the thermal action on the flow. The asymptotic dependences of the flow parameter in the case of an infinitely large supplied heat have been obtained; these dependences are used in finding the scale quantities and unified generalized dependences for the period-averaged parameters of nonstationary self-oscillatory flows. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 530–537, May–June, 2008.