Numerical simulation of flows in a high-frequency induction plasmatron and of heat transfer in underexpanded air jets

Some results of numerical simulation of flows in the discharge channel of the IPG-4 induction plasmatron installed at the Institute for Problems in Mechanics of the Russian Academy of Sciences (IPM RAS) and in underexpanded jets of dissociated and partially ionized air from sonic nozzles are discussed. These results are in good agreement with experimental data on heat fluxes and on the pressure at the stagnation point of a blunt cylindrical body. These experimental data were obtained at the IPM RAS Laboratory for Interaction of Plasma and Radiation with Materials.     

Flow and Heat Transfer in Underexpanded Air Jets Issuing from the Sonic Nozzle of a Plasma Generator

We present the results of an experimental investigation and numerical simulation of the gasdynamic structure of underexpanded dissociated-air jets and the heat transfer in these strongly nonequilibrium flows under the test conditions realized in the 100-kW electrodeless VGU-4 plasma generator of the Institute for Problems in Mechanics of the Russian Academy of Sciences (IPM RAS). The flow and heat transfer analysis is carried out on the basis of measurements of the static pressure in the plenum chamber, at the sonic nozzle exit, and on the low-pressure chamber wall, the stagnation pressure on the jet axis using a Pitot tube, and the heat transfer at the stagnation points of water-cooled models placed along the jet axis. The numerical simulation, based on complete Navier-Stokes equations, includes the calculation of (1) equilibrium air plasma flows in the discharge channel of the VGU-4 plasma generator; (2) underexpanded nonequilibrium dissociated-air jet outflow into the ambient space; and (3) axisymmetric jet flow past cylindrical models.     

Separation of chemical elements in the discharge channel of an inductive plasma gun

Zones of separation of chemical elements in the air plasma flow in the discharge channel of the VGU-4 100-kW inductive plasma gun with a sonic nozzle of the Institute for Problems in Mechanics of the Russian Academy of Sciences are determined from an analysis of numerical solutions obtained within the framework of the Navier-Stokes equations. The occurrence of these zones and their possible influence on heat transfer to bodies in underexpanded jet flows in physical experiments are explained.     

Development of a liquid-fuel jet at high-speed pulse injection into a gaseous medium. II. Calculation and experiment

A three-stage calculation scheme developed previously on the basis of a complex experimental study is used to calculate the parameters of a gas-liquid jet formed at pulse high-speed injection of a liquid fuel into a gaseous medium. The results obtained using this model are in good qualitative and quantitative agreement with experimental data, and a physically grounded explanation is offered for the discrepancies observed in some ranges of parameters. 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. 166–173, January–February, 1999.     

Investigation of the Influence of Different Heterogeneous Recombination Mechanisms on the Heat Fluxes to a Catalytic Surface in Dissociated Carbon Dioxide

A kinetic model of heterogeneous recombination in dissociated carbon dioxide on high-temperature heat-shield coatings is developed; the model takes into account the nonequilibrium adsorption-desorption reactions of oxygen atoms and their recombination in the Eley-Rideal and Langmuir-Hinshelwood reactions. On the basis of a comparison of the calculated heat fluxes in dissociated carbon dioxide with those measured in the VGU-3 plasma generator of the Institute for Problems in Mechanics of the Russian Academy of Sciences (IPM RAS) and the available literature data, the parameters of the catalysis model are chosen for the glassy coating of the Buran orbiter tile heat shield based on the SiO₂–B₂O₃–SiB₄ system. The effects of heterogeneous recombination proceeding in accordance with the Langmuir-Hinshelwood mechanism, as well as the processes involving carbon atoms and those involving physically adsorbed oxygen atoms, on the heat fluxes to the glassy coating are analyzed on the surface temperature range from 300 to 2000 K.     

Three-dimensional computer model of nonequilibrium aerophysics of the spacecraft entering in the Martian atmosphere

A three-dimensional computer model of nonequilibrium aerophysics of the spacecraft entering in the Martian atmosphere and landing on the planet surface is presented. The model is based on the system of Navier-Stokes equations, the energy conservation equation in the form of the Fourier-Kirchhoff equation for the translational temperature, the system of equations of vibrational kinetics for six vibrational modes of N₂, O₂, CO₂ and CO molecules, and the equation of selective thermal radiation transfer in the multigroup spectral approximation. The results of two-dimensional and threedimensional calculations of the nonequilibrium flowfield and the convective and radiative heating of the EXOMARS spacecraft surface are presented. The calculations are performed on regular multiblock curvilinear grids using the NERAT-2D and NERAT-3D computer codes developed in the Institute for Problems in Mechanics of the Russian Academy of Sciences.     

Three-dimensional problems of mechanics of deformable bodies of noncanonical shape

The paper is based on the author's report at the General Jubilee Meeting of the Mechanics Division on the occasion of the 80th anniversary of the National Academy of Sciences of Ukraine. Results obtained in the subject area “mechanics of deformable bodies of noncanonical shape” are discussed. This subject area was formed at the S. P. Timoshenko Institute of Mechanics of the National Academy of Sciences of Ukraine on the basis of variants of the analytical method of boundary-shape perturbation proposed and developed at the Institute. The objects of investigation and the classification of three-dimensional boundary-value problems for noncanonical areas are analyzed. Tests of the accuracy of approximate solutions obtained using the developed analytical methods are indicated. Presented at General Meeting of Mechanics Division of National Academy of Sciences of Ukraine (Kiev, November 30, 1998). S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 35, No. 10, pp. 3–20, October, 1999.     

Simplified variant of calculation of the stability of cylindrical shells under axial compression

Design formulas for calculating the critical stresses of unreinforced and reinforced cylindrical shells in axial compression are derived by analyzing experimental data. The curves obtained with the formulas bound the experimental data from below. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 35, No. 11, pp. 75–78, November, 1999.     

水泥土细观破裂过程的实时观测试验

利用中科院武汉岩土力学研究所的岩石破裂过程细观力学实验系统,对不同水泥掺量的水泥土试件进行了单轴压缩细观实验,该试验系统可通过显微镜和数码视频装置实时观测水泥土试件的细观结构及其破坏的全过程,试验得到了水泥土破裂过程中的细观图像及其相应应力应变关系曲线.分析了不同水泥掺量的水泥土试件的细观破坏特征及其与宏观力学行为的关系,研究为水泥土细观损伤本构模型的建立提供了实验依据.     

Numerical modeling of an underwater explosion in an air cavity

An efficient numerical algorithm based on Godunov method is proposed that permits qualitative and quantitative calculations of the hydrodynamic flows resulting from the detonation of explosive charges in an air cavity. Calculations are performed by a difference scheme using moving difference grids in which the moving boundaries are the contact surfaces between the detonation products and air and between air and water, and the shock-wave front. The reliability of the calculations is confirmed by experimental data. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev 252057. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 4, pp. 33–37, July–August, 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.     

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.     

Some features of the flow of gas that occurs as a result of the interaction between a shock-wave and a cloud of particles

Institute of Theoretical and Applied Mechanics, Siberian Division of the Russian Academy of Sciences, 630090 Novosibirsk. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 2, pp. 8–18, March–April, 1995     

Discontinuous velocity fields in a hardening rigid-plastic material

The proposed model and the properties obtained on the surface of velocity discontinuity are used to study two processes of plastic deformation: lateral extrusion and torsion of a hollow disk. In both cases, analytical solutions are obtained. The limits of applicability of the solution to lateral extrusion are determined. Institute of Problems of Mechanics, Russian Academy of Sciences, Moscow 117526.¹Bauman Moscow State Technical University, Moscow 105007. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 198–203, January–February, 2000.     

Experimental investigation of the dynamics of shells of revolution (review)

The results of experimental investigations carried out at the S. P. Timoshenko Institute of Mechanics of the National Academy of Sciences of Ukraine are analyzed in this review. The analysis suggests that experimental investigations of shell dynamics must be contained and developed if the method used to calculate the stressed-strained state and stability of dynamically loaded shells is to be developed further and made more precise. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, 35, No. 7, pp. 3–11, March, 1999.     

Longitudinal nonlinear oscillations of a gas in a closed pipe

Results of an experimental study of longitudinal nonlinear oscillations of a gas in a closed pipe are reported. Pressure waves in a broad range of excitation amplitudes and frequencies are studied. Strong nonlinear oscillations at a frequency thrice as low as the first natural frequency of the gas column are discovered. Institute of Mechanics and Mechanical Engineering, Kazan' Scientific Center, Russian Academy of Sciences, Kazan' 420503. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 60–62, November–December, 1999.     

Some primal problems of the axisymmetric theory of elasticity for space with a flat slit bounded by a circle

We consider the first and second primal problems of the axisymmetric theory of elasticity for space with a round slit and a mixed problem in which forces are specified on one side of the slit and displacements are specified on the other side. The problems reduce to conjugation problems for generalized analytic functions on rectilinear segments, whose solution is obtained in closed form. Institute of Applied Mechanics, Russian Academy of Sciences, Moscow 117334. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1 pp. 144–151, January–February, 2000.     

Technique for experimental determination of the total thrust-aerodynamic characteristics of aircraft models

A method of experimental determination of the force characteristics of nozzles (thrust, lift, and pitching moment) simultaneously with the aerodynamic characteristics of an aircraft model in a supersonic flow in proposed. The tests were conducted for a special methodical model, with equilibrium of the thrust and drag jorces being reached. It is shown that the internal force characteristics of the nozzle and the drag of the model, as well as the effective lift and pitching moment (with account of propulsion), can be determined from the measured thrust of the propulsion simulator. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 73–82, 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.     

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.