Investigation of Sonoluminescence Amplification under the Interaction of Ultrasonic Fields Widely Differing in Frequency

The laws of sonoluminescence generation under the interaction of ultrasonic fields widely differing in frequency have been investigated. It is shown that nonadditive amplification of the sonoluminescence is observed not only under the simultaneous action of the fields on a liquid, but also in a highfrequency field after preliminary insonification of the liquid by a lowfrequency field. The phenomenon of a longduration aftereffect of the lowfrequency field on the cavitation generated by the highfrequency field has been revealed. On the basis of the obtained results the conclusion has been drawn that the main mechanism of increasing the cavitation activity in the interacting fields is the generation of new cavitation nuclei as a result of the collapse of bubbles excited by the lowfrequency field.     

Modern Problems of Intensification of Heat Exchange in Channels

The current achievements in the field of intensification of heat exchange in tube heatexchange apparatus are considered. Requirements for highefficiency heattransfer surfaces have been formulated. Problems of intensification of heat exchange in bundles of finned tubes and in heatexchange apparatus under conditions of condensation and boiling of heattransfer agents and under scaling conditions have been investigated. Highefficiency designs of heatexchange apparatus are presented.     

Influence of Multiple‐Scattering Processes on the Laser Probing of Biological Tissues

Theoretical aspects of multiplescattering processes in laser probing of biological tissues have been considered. The method of digital dynamic specklephotography has been described. The results of experimental studies of the nearsurface blood flow and stressedstrained states in a pinstructure–toothroot model are presented.     

One Method of Determination of the Effective Absorption Coefficient in Pulsed Laser Irradiation of Metals

An experimentaltheoretical method of determination of the absorption coefficients in laser treatment of metals has been proposed based on the solution of the boundaryvalue axisymmetric problem of heat conduction for a halfspace and metallographic measurements of the dimensions of the thermalhardening zone.     

Pulse High‐Speed Action of a Hot Gas Flow on a Wall of Chromium‐Nickel Steel

Consideration has been given to the pulse action of a hot gas flow on a wall of chromiumnickel steel; an analysis has been made of the processes and phenomena of mechanical and thermoerosive wear and fatigue failure of the wall. A structural model of thermal fatigue of chromiumnickel steel has been developed. The wear of the wall of a tube with an inside diameter of 0.03 m under the pulse action of the gas flow and thermal stresses of the second kind has been evaluated numerically. The results of shortduration mechanical tests of 12Kh18N10T steel after thermocycling have been given.     

Solution of Mixed Contact Problems in the Theory of Nonstationary Heat Conduction by the Method of Summation‐Integral Equations

The laws governing the development of spatial nonstationary temperature fields in a bounded cylinder and a halfspace where one of the end surfaces of the cylinder touches the surface of the halfspace in a circular region are determined. A solution of a mixed axisymmetric nonstationary problem of heat conduction is obtained in the region of Laplace transforms. In solution of this problem, there appear summationintegral equations with the parameter of the integral Laplace transform (Lparameter) and the parameter of the finite integral Hankel transform (Hparameter).     

Numerical Modeling of Turbulent Flow inside a Wind‐Driven Plant with Allowance for the Forces on the Impeller

The operating efficiency of a winddriven plant based on a confuserdiffuser accelerator is evaluated within the framework of the multiblock approach to solution of steadystate Reynolds equations closed with the use of a twoparameter dissipative turbulence model.     

Possibility of Acoustic Control of Excited Turbulent Jets

The results of experimental investigation of the influence of highfrequency (lowfrequency) acoustic action on a turbulent jet preexcited by sound of low (high) frequency are presented. It is shown that the qualitative character of the action remains the same as that for an unexcited jet. However, the quantitative results here are somewhat different; in particular, the possibilities of suppressing turbulence in the jet in its highfrequency excitation are reduced in this case.     

Numerical Analysis of the Effect of Viscosity on the Vortex Dynamics in Laminar Separated Flow Past a Dimple on a Plane with Allowance for Its Asymmetry

Based on numerical solution of the Navier–Stokes threedimensional stationary equations by a factorized finitevolume method, the influence of physical viscosity on selforganizing jetvortex structures in a dimple on a plane immersed in a laminar flow is analyzed with allowance for the asymmetry of the dimple shape.     

Numerical Analysis of the Jet‐Vortex Pattern of Flow in a Rectangular Trench

Numerical simulation of the vortex structure of threedimensional laminar flow in a rectangular trench of square cross section has been carried out on the basis of the finitevolume solution of steadystate Navier–Stokes equations.     

Bypass Laminar‐Turbulent Transition in a Thermal Boundary Layer

We present results of four series of experimental investigations of the bypass laminarturbulent transition (BLTT) initiated by actions of different nature (higher than usual degree of turbulence of the external flow, closed laminar separation at the leading edge, and their combination) on a flat surface in gradientfree flow. Our findings have supported the idea that strongly disturbed flows have a tendency toward the formation of an upper thermal bypass laminarturbulent transition whose heattransfer coefficient changes monotonically because of the formation of a pseudolaminar boundary layer before it. The influence of the scale of turbulence on the position of a bypass laminarturbulent transition and the intensification of the transfer processes in the boundary layers formed before and after the bypass laminarturbulent transition has been evaluated. We have developed a complex method for diagnostics of a bypass laminarturbulent transition, which allows one to establish the fact of formation of the bypass laminarturbulent transition and determine its starting and end points.     

Study of Interaction of Disturbances in an Internal Flow

Data on narrowband acoustic disturbances that arise in manifold pipes with one or two blind branches and in wind tunnels with an open working section are analyzed. The ranges of acoustic instability that correspond to excitation of selfoscillations in a flow in the cases mentioned are determined. The dependence of the intensity of acoustic radiation in two blind branches and in the manifold between them on the multiplicity of the length of the resonance section to the length of halfwaves of resonance frequency is considered. The possibility of attenuation of selfoscillations by organizing hydrodynamic structures that interact with formations generating acoustic oscillations is determined.     

Computational‐Experimental Approach to Prediction of Mass‐Transfer Processes in Metallic Coatings of Gas‐Turbine Blades and Their Service Life

A computationalexperimental approach to analysis of longtime processes of mass transfer of aluminum in metallic MCrAlY coatings of gasturbine blades and to prediction of their service life is proposed. The approach is based on the mathematical model describing the oxidation and diffusion processes in the coating and in the alloy of a blade, the parameters of which are identified by the data of shorttime experiments. The results of theoretical and experimental determination of the aluminumconcentration distributions in the coating and in the basic alloy of a gasturbine blade and the results of prediction of the service life of the coating are presented. It is shown that this approach allows one to perform analysis of longtime processes of masstransfer in metallic coatings of gasturbine blades and predict their service life with a high degree of accuracy.     

Study of the Temperature Fields in Oil and Gas Strata with Water Injection Based on the Perturbation Method

The problem of the thermal action on oil and gas strata by injection of a heating medium using expansion in a small parameter is reduced to an infinite sequence of boundaryvalue problems that are solved by the method of integral transforms. It is shown that, with an appropriate selection of the small parameter, the zerothorder approximation corresponds to a spaceaveraged (across the stratum thickness) solution of the main problem and leads to a concentratedcapacity scheme that is constructed assuming that the stratum temperature is independent of the vertical coordinate. The first approximation permitted marked refinement of calculations according to the concentratedcapacity scheme and an evaluation of its error. Spacetime temperature distributions are presented that have been calculated using the analytical solutions obtained.     

Widening the Scope of Working of Solid‐State Nd‐Glass Lasers

With the example of the serial model of a pulsed Ndglass laser, it is shown that the use of an unstable resonator with a semireflecting homogeneous exit mirror makes it possible to significantly decrease the laserbeam divergence and increase the uniformity of the radiationintensity distribution in the near zone. We were the first to obtain a laserbeam quality of (40–50) mm·mrad for technological glass lasers and to attain a depth of fusing of of 6.3 mm for steel (aspect ratio 10) for an energy of 23 J. The obtained uniformity of the radiationintensity distribution was estimated at the level of ±10%. The beamquality level attained for the Ndglass laser beam allows us to recommend it for both realization of deepfusion regimes and laser hardening without the use of external integrating optical elements.     

Calculations of the Passage of Gamma‐Quanta through a Polymer Radiation‐Protective Composite

We have investigated the radiationprotective characteristics of a thermoplastic polystyrene composite material filled with a highdispersion modified lead oxide as well as the dependences of the energy (flux) buildup and transmission factors and albedos on the energy and protectiveshield thickness. Calculations of the integral characteristics of the radiationprotective properties of materials have been done.     

Motion of Trains of Vortex Rings

A numerical experiment on investigation of the dynamics of the interaction of three coaxial vortex rings formed from thermics is performed. As a mathematical model of the phenomenon, the system of Navier–Stokes equations for a compressible heatconducting gas in a cylindrical coordinate system is chosen. The calculations are performed using a finitedifference method based on an explicit threestep scheme of splitting by physical processes. The influence of the position of the thermics on the common axis of symmetry on the character of their motion and interaction is investigated.     

Description of the Shape Memory Effect of Radiation‐Modified Polymers under Thermomechanical Action

The shape memory effect of crystallizing polymer materials is simulated. The polymer is considered to be an inhomogeneous medium with a moving boundary (temperaturedependent phase composition). Using a model based on the frozen strain hypothesis, the temperature dependences of stresses under isometric heating and cooling have been obtained. On the basis of the known data on the influence of irradiation on the thermomechanical characteristics the dependences of thermorelaxation and thermoshrinkage stresses on the absorbed dose for highdensity polyethylene have been found.     

Influence of the Viscosity of Filled Epoxy Resins on Their Spreading on a Horizontal Surface

The rheological properties of ÉD20epoxyresinbased compositions filled (10–50 vol.%) with quartz sand, quartz flour, or their mixture have been investigated on Reotest2 and RV8 rotational viscosimeters. The relative viscosity of the filled compositions increased with their free volume according to the exponential equation with an exponent of 2.6. The compositions began to show an anomaly of viscosity in flowing for a content of the filler of more than 40 vol.%; the yield stress appeared for 50 vol.%. The rate of spreading of the compositions on a horizontal surface decreased with increase in the composition viscosity according to the exponential equation with an exponent of 1/8, which is similar to that calculated theoretically. The experiments conducted allowed calculation of the formula of epoxybased, selfleveling pouring floors.