Filtration in a porous medium with a fluctuating permeability

Based on the T-matrix method, filtration in a porous medium with a fluctuating permeability is investigated. A closed system of equations for the T-matrix and the pressure is obtained. A fluctuation correction to the output is calculated. Cases of correlation functions of the first and second kinds are analyzed. Institute for Problems of Geometry, Makhachkala, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 2, pp. 238–242, March–April, 1996.     

Numerical investigation of the radiation characteristics of a perforated cylinder in a circular chamber filled with an absorbing medium

A problem on radiant heat exchange in a circular chamber filled with an absorbing medium and containing a perforated cylinder is solved.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 6, pp. 995–998, June, 1985.     

The theory of the thermohydrodynamic gas lens

We find an analytical solution for the equation of the beam trajectory for arbitrary lens-like media of the type n=n(y). We examine the optical properties of certain specific lens-type media.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 1, pp. 145–149, July, 1969.     

On the thermohydrodynamic analysis of a Bingham fluid in slider bearings

Summary A theoretical analysis of finite slider bearings with the Bingham rheological model is presented which includes a full consideration for thermal effects. Full thermohydrodynamic (THD) as well as simplified ISOADI solutions are presented for a wide range of operating conditions. Results are authenticated with a number of published one-dimensional isoviscous solutions. An extensive set of parametric studies of the Bingham model together with an illustrative example is presented.Notation a Clearance ratio - B Pad length in the direction of motion (m) - c _o Lubricant specific heat (J/Kg K) - f Friction coefficient - F Frictional force (Pa) - H _b Thickness of the stationary component (m) - h Film thickness (m) - h ₁,h ₂ Maximum and minimum film thickness (m) - h _a,h _b Height of the lower and upper boundary of core (m) - h _L,h _H Height of the lower and upper boundary of fluid film (m) - h _conv Convective heat transfer coefficient (W/m² K) - K _f Bearing characteristic number - k _o Thermal conductivity of the lubricant (W/m K) - L Bearing length in the axial direction (m) - m Slope of the slider bearing - P Pressure (Pa) - P _a Ambient pressure (Pa) - P _L Average unit load (Pa) - P _max Maximum pressure (Pa) - P _s Supply pressure (Pa) - Q _in Inlet flow rate (m³/sec) - Q _leakage Leakage flow rate (m³/sec) - S _h Difference between the maximum and minimum film thickness (m) - T Temperature (^oC) - T _a Ambient temperature (^oC) - T _b Stationary component temperature (^oC) - T _max Maximum temperature (^oC) - T _mean Mean temperature (^oC) - T _s Lubricant temperature supplied (^oC) - T _exit Exit temperature (^oC) - U ₁,U ₂ Velocity of the lower and upper surface along the film (m/sec) - U _L,U _H Velocity of the lower and upper boundary of fluid film along the film (m/sec) - U _c,W _c Velocity of core along the film and in the axial direction (m/sec) - u, v, w Velocity component along, across the film and in the axial direction (m/sec) - W Bearing load-carrying capacity (N) - W _L,W _H Velocity of the lower and upper boundary of fluid film in the axial direction (m/sec) - x, y, z Coordinate system (m) - x _b,y _b Coordinate system used in the stationary component (m) - Temperature-viscosity coefficient (1/K) - Yield stress-temperature coefficient (1/K) - Shear rate (1/sec) - Non-Newtonian viscosity (Pa·sec) - ₁, ₂ Temperature-rise parameters - _s Aspect ratio of the slider bearing - Viscosity (Pa·sec) - _i Inlet viscosity (Pa·sec) - _eff Effective viscosity (Pa·sec) - _o Density of the lubricant (Kg/m³) - Shear stress (Pa) - ₀ Critical shear stress (Pa)     

Effective electrical characteristics of a three-dimensional composite medium

The electrical characteristics of a three-dimensional composite consisting of components with strongly different conductivities, σ₁ and σ₂, are theoretically described. The quadratic field and current correlators at the percolation threshold are determined, and the distribution of the energy dissipated in the composite between the components is found. The lower limit of the critical index of the nonlinear effective conductivity is estimated.     

Numerical investigation of convective flows of a highly inhomogeneous gaseous medium

Equations of convection in a gas are analyzed and a computational algorithm that is efficient when the condition gh/RT1 is satisfied for an arbitrary (fairly large) temperature drop is proposed. Calculations of convection occurring in steady nonuniform heating of walls are performed for axisymmetric argoncontaining volumes of different shape. Results of these calculations demonstrate the establishment of steady and periodic motions of the gas.Academic Scientific Complex A. V. Luikov Institute of Heat and Mass Transfer of the Academy of Sciences of Belarus, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 6, pp. 983–990, 1995.     

Peculiarities of the current-voltage characteristics of a Josephson medium in a YBCO high-temperature superconductor

The influence of a weak magnetic field (H < 150 Oe) on the current-voltage (I-U) characteristic of a YBa₂Cu₃O_{7 ? x} (YBCO) high-temperature superconductor (HTSC) near the superconducting transition temperature has been studied. It is established that there exist narrow (<0.2 K) temperature regions where the I-U curve exhibits sharp bending for H < 30 Oe and the ohmic behavior changes to a quadratic dependence of the voltage on current in a region of several milliamperes. At higher temperatures, the I-U curve bending exhibits smearing. This behavior is observed at a temperature below that corresponding to a zero critical current. Above a certain current, the temperature and magnetic field exhibit equivalent effects on the I-U curve of YBCO. Experimental results are explained by a sharp decrease in the critical currents of intergranular Josephson junctions under the action of magnetic field and by the current-induced formation of uncoupled (with respect to the order parameter) superconducting grains. Characteristic currents for the transition of the intergranular Josephson medium into an incoherent state are determined and the first critical fields in YBCO are evaluated.     

Theoretical and experimental investigation of the characteristics of a rotary-pulsatory apparatus

Experimental-theoretical investigation of the characteristics of a rotary-pulsatory apparatus with an impeller and controlled flow rate, which is intended to intensify the processes of extraction of substances from a vegetable raw material in the pharmaceutical industry, has been carried out. A semiempirical physicomathematical hydrodynamic model has been proposed; expressions for the characteristics of the averaged flow have been determined. Agreement between the calculated and experimental data on the head and the power consumption as functions of the flow-rate of the medium and the rotational velocity of the motor has been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 817–825, September–October, 2008.     

Service characteristics of steel after grinding in a polymer-containing medium

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 5, pp. 101–103, September–October, 1989.     

On the microscopic derivation of the two-fluid thermohydrodynamic equations for4He II

The equivalence of the set of hydrodynamic equations for the macroscopic quantities associated with the ⁴ He II condensate and noncondensate—the natural parameters which occur in an O.D.L.R.O.-based microscopic theory—to the phenomenological equations for the super and normal fluids of the thermodynamic two-fluid model is uniquely established. This is achieved by defining the velocity of the normal fluid operationally as the velocity of entropy transport, from which follows a relationship between the condensate and superfluid densities. Consideration of boundary conditions together with this relation between the condensate and superfluid densities shows that the presence of the condensate allows the rest (majority) of the fluid to slip relative to a stationary boundary. The amount of slip is temperature dependent and, in particular, at absolute zero total slip occurs, i.e., the whole system is superfluid. Finally, the density relation is used to estimate the temperature dependence of the condensate density, and it is suggested that the dramatic change at about 0.5K, predicted on the basis of this relation, be investigated via measurement of the temperature dependence of the liquid structure factor.     

Propagation characteristics of plane waves of defects in a viscoplastic medium

It is shown that dispersion is not observed in the propagation of a weakly damped wave, and dissipation is frequency-dependent. For strongly damped waves, dispersion and dissipation are observed. However, a wave in a viscoplastic medium decays over very short distances and the penetration depth of strongly damped waves of defects is bounded by the skinlayer thickness. Pis’ma Zh. Tekh. Fiz. 25, 91–94 (September 26, 1999)     

The investigation of transient wave propagation in a dipping layered medium overlaying a half space

Abstract

The responses of transient wave propagation in a single dipping layered medium overlaying a half space was investigated in this study. To obtain the responses, a point source located in the dipping layered medium was assumed, and in order to make the results more consistent with real situations, the time functions for source mechanism, such as parabolic ramp function and triangular time function, were considered in this research. Finally, the famous mathematical tool with physical significance, the generalized ray theory [4], was employed to solve the foregoing problem, and the ray paths and responses for the distinct locations on the surface were then obtained and shown in sketches. It was found from the obtained results that the responses decay with the distance from the focus just as expected.     

Preliminary investigation into the application of scratch testing to marine coatings

Controlled scratch testing has been applied to experimental coatings of the kind used on marine structures, based on epoxy-amine resins. Measurements of the scratch hardness and the critical load to failure have been made. Inspection of the scratch tracks by reflected light microscopy and scanning electron microscopy enabled identification of the failure mechanism. Failure could be by though-thickness cracking or adhesion failure. The failure mechanism is sensitive to the coating thickness and detachment from the substrate was obtained only from coatings less than 300 m thick in the as-prepared state for tests conducted with a limiting load of 80 N. The deterioration of properties of samples immersed in hot seawater was very sensitive to composition.     

Numerical investigation of stationary and fluctuating vibrational convection modes in a rectangular cavity with variable boundary temperature in weightlessness

The configuration, amplitude, and evolution of average vibrational-oscillatory flows in a rectangular cavity are determined under weightlessness conditions. The convection mode transition is discussed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 1, pp. 33–37, July, 1989.     

Numerical investigation of the effect of a recess on the characteristics of a pulsating gas flow

A supersonic flow past a recess with pressure fluctuations in the separation zone is simulated numerically. The effect of the gasdynamic and geometric parameters determining the flow in the recess on the character of the pressure fuctuations is studied. Different shapes of the recess are considered. To simulate flow in the recess kinetically consistent difference schemes that have proved themselves good in describing complex flows are used. Obtained results of numerical calculations are compared with experimental data. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 477–483, May–June, 1998.     

Numerical investigation of the characteristics of radiant heat transfer in a turbine grid

The Monte Carlo method is used to investigate the distribution of radiant heat fluxes in the interblade channel of a turbine grid and directionality diagram of the emitted radiation.