Nonstationary supersonic flow around a body

It is found that a nonstationary regime of supersonic flow around bodies that differs radically from the standard stationary flow can occur for high Mach numbers and low specific heat ratios of a gas. This regime is characterized by large-scale vortices in a shock-compressed region in front of the body, a curved shock-wave profile, and oscillation of all flow parameters. Zh. Tekh. Fiz. 69, 95–97 (December 1999)     

Effect of air on the concentration of molecular hydrogen in the conversion of ethanol by a nonequilibrium gas-discharge plasma

The effect of air on the concentration of molecular hydrogen in the conversion of ethanol by a nonequilibrium gas-discharge plasma is theoretically studied. Two models are developed to calculate plasma kinetics in two operation regimes of an experimental setup used for ethanol conversion into free hydrogen in order to increase the efficiency of the combustion of heavy hydrocarbon fuels. A comparison with the experimental results demonstrates that both of the models adequately describe the kinetics of the discharge reactions.     

Supersonic flow about a body exposed to electric and magnetic fields

The feasibility of using nonmechanical (electrogasdynamic, EGD, and magnetohydrodynamic, MHD) methods to control shock-wave configurations emerging in supersonic flows is investigated. In the EGD method, the flow is heated by a gas discharge; in the MHD one, the flow is influenced by a Lorentz force arising in a gas discharge upon applying a magnetic field. The influence of the gas discharge and MHD interaction on the position of a detached shock wave appearing in a supersonic xenon flow about a semicylindrical body is studied. A discharge is initiated in the immediate vicinity of the leading edge of the body, and the variation of the shock wave position with the intensity of the discharge (discharge current density) is traced when the influence of the EGD action increases and/or an external magnetic field is applied (the influence of the MHD action increases). Preliminary data for a supersonic air flow about a body are presented.     

Formation of compression shocks in a nonequilibrium plasma flow in a magnetic field

Plasma flow in a linearly widening, ideally sectioned, short-circuited magnetohydrodynamic (MHD) channel is studied. MHD flows are classified into two types: continuous flows and flows with a compressional MHD shock in plasmas that are stable and unstable against the onset of ionization instability. Specific features in the evolution of a stationary compression MHD shock are investigated, and its position as a function of the Stewart number is determined. It is found that, in a plasma flow in which ionization instability develops, a compression MHD shock arises at lower values of the MHD interaction parameter than in a stable plasma flow. An unidentified type of instability of MHD discontinuities is revealed.     

Cylindrical body in a collisionless plasma flow

The perturbed region in the vicinity of a charged cylinder in a collisionless plasma flow is investigated using mathematical simulation. The results qualitatively reflect the features of the atmosphere of a satellite or its individual cylindrical parts streamlined by a collisionless plasma and can be used for probe diagnostics of rarefied plasma flows.     

Simulation of turbulent flow around a tear-shaped body with a tapered flare

The axisymmetric flow around a tear-shaped body with a flare is analyzed by solving the continuity equation, Reynolds equations (closed with the Menter model of shear stress transport), and energy equation. In the solution, a factorized multiblock finite-volume technique embedded in a VP2/3 program package is used. Numerical estimates are compared with aeroballistic tests of a model. Direct-shadow flow patterns are recorded and the trajectory parameters are calculated with the aim of determining the aerodynamic drag at a close-to-zero angle of attack. Interferograms of the axisymmetric flow around the body (M = 4.35) are also taken. The calculated and experimental data for the flow density transverse (radial) distribution are in good agreement. Agreement between the calculation and experiment in the drag coefficient at a close-to-zero angle of attack is also observed.     

Generation of a gas-discharge air plasma in a supersonic magnetohydrodynamic channel

A method for ionizing a supersonic air flow is developed to obtain a flow conductivity sufficient for a magnetohydrodynamic (MHD) interaction and generation of a magnetically induced current in a supersonic nozzle. The efficiencies of several (high-frequency, multiple-pulse high-voltage, and combined) methods for initiating a gas discharge used for ionizing air are compared. The supersonic air flow is ionized by a pulse-periodic high-voltage discharge producing an air plasma with a conductivity of up to 20 S/m. The experimentally obtained magnetically induced current of 0.1 A is smaller than the rated value owing to the Hall effect and the electrode voltage drop. The theoretical possibility of obtaining a magnetically induced current in a supersonic air flow is demonstrated; such currents can subsequently be used for controlling the flow in air inlets of aircraft.     

Production of nanodiamond composites in a low-pressure microwave gas-discharge plasma

Kinetically favorable regions are determined for the production of film carbon materials of different allotropic modifications in the microwave plasma of the low-pressure ethanol vapor. Self-organization effects and polymorphic transformations caused by kinetic factors are detected. These phenomena are used to design a low-temperature technology of diamond-graphite and diamond-hydrocarbon nanocomposite materials with controlled surface concentrations and sizes of vertically bonded nanodiamond clusters from 4–5 to 100 nm in size located in a heterogeneous matrix. The influence of the technological parameters of the production of diamond-graphite nanocomposite film materials on their field-emission properties is determined. The emission properties are improved due to a change in the electrophysical properties of the material that is induced by an increase in the role of surface states on the strongly developed surface and by a decrease in the diamond micro-crystallite size in the heterogeneous hydrocarbon matrix.     

Dust-acoustic instability in an inductive gas-discharge plasma

Spontaneous excitation of a dust-particle density wave is observed in a dust cloud levitating in the region of the diffused edge of an rf inductive low-pressure gas-discharge plasma. The main physical parameters of this wave and of the background plasma are measured. The analytic model proposed for the observed phenomenon is based on the theory of dust sound and successfully correlates with experimental data in a wide range of experimental conditions. The effect of variable charge of dust particles on the evolution of the observed dust-plasma instability is studied analytically. It is shown that the necessary condition for the development of the dust-acoustic instability is the presence of a dc electric field in the dust cloud region.     

Liquid plasma crystal: Coulomb crystallization of cylindrical macroscopic grains in a gas-discharge plasma

Ordered structures formed of 300-μm-long cylindrical nylon grains with diameters of 15 and 7.5 μm are obtained. In contrast to conventional spherical monodisperse grains, which, under certain conditions, form the plasma-dust Coulomb crystal, the cylindrical grains in the plasma acquire a charge of ～7×10⁵ electrons and form a structure similar to a liquid crystal. The parameter characterizing the nonideality of the dusty component of the plasma attains 10⁶. Grains are suspended in the striation in the horizontal plane and line up in parallel with each other.     

Anomalous heating of a system of dust particles in a gas-discharge plasma

The coexistence of regions of negatively charged macroparticles with substantially different kinetic temperatures in a highly nonideal dusty plasma in a dc glow discharge has been observed experimentally. An explanation of the observed anomalous heating of the system of dust particles in a gas-discharge plasma is proposed on the basis of a molecular-dynamics model. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 6, 392–397 (25 September 1997)     

Nonclassical transport in a nonequilibrium laser plasma

The onset of a nonequilibrium distribution function in a plasma produced by laser radiation at fluxes I - 10¹⁴ W/cm² is considered. The model employed takes consistent account of the nonlocality of the electron distribution at large density and temperature gradients, the demaxwellizing effect of the external hf field of the laser, and the nondiffusion of the transport in the high-energy part of the electron-distribution spectrum. Numerical solution of the corresponding kinetic equations shows that establishment of a nonequilibrium electron distribution in the corona suppresses the heat transport substantially. Good agreement is obtained between the kinetic value of the heat flux and the phenomenological value needed to reconcile the hydrodynamicsimulation results with the experimental data.Quantum Radiophysics Division, Lebedev Physics Institute. Translated from Preprint No. 179 of the Ledebev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.