Pleiades Publishing Ltd

The process of acceleration of air in a Faraday-type MHD channel is analyzed for a thermodynamically nonequilibrium model of gas seeded with an alkaline element such as potassium. It is demonstrated that the use of existing electric-arc gas heaters with P 0= 200 atm and T 0= 4700 K, in the presence of magnetic fields B= 12 T, makes possible an almost exact simulation of the gasdynamic parameters at the inlet to the combustor of a hypersonic scramjet engine (HSJE) in the range of values of the Mach number of the flight from 12 to 20 (direct connect mode). In so doing, the concentration of atomic oxygen O does not exceed 2%, and that of nitrogen monoxide NO, ∼5%. When the gas is expanded in the secondary nozzle to static temperature values corresponding to the conditions of free flight, an exact simulation of the latter is possible at an altitude H= 65 to 70 km (u= 7.5 km/s, M = 20 to 25).

In this paper, we consider the dynamics of plasma in a high-power plasma-microwave amplifier with a submicrosecond pulse duration. It is shown that, in the case of a linear mode (a short system length or a small input signal level), a discontinuity in the plasma density can form near the output boundary due to the escape of particles towards the amplifier input, which can lead to radiation breakdown. When the amplifier operates in the saturation mode, the plasma displacement has a multidirectional character, and a density discontinuity is not formed. At an increase in the initial plasma density, the effect of its pushing out weakens.

The article presents the results of numerical simulation of the thermal problem based on the distribution of electrical contact resistivity along the length of a cylindrical graphite sample, determined experimentally. First, the temperature distribution along the length of the sample was found in the absence of a contact surface at temperatures of 400 and 700 K. The problem is solved in a one-dimensional approximation along the length of the cylinder, with maximum simulation of the experimental conditions. Free convection and radiative heat transfer on the outer surface of the cylinder are taken into account. Next, the temperature distribution along the axis of the sample is estimated in the presence of one contact surface. The calculation results showed that the temperature increase in the region adjacent to the contact surface is about 1 at 400 K and 10 at 700 K.

A carried out numerical simulation showed that a considerable difference can be achieved between the temperatures of a gas in the boundary layer and a suctioned gas under the gas suction from a turbulent boundary layer in a supersonic flow on a permeable surface. The effect of the Prandtl and Mach numbers of the incident flux on the temperature stratification, which depends on the gas suction intensity, is studied. The stratification is the most pronounced for low-Prandtl-number gases. It was established that, due to laminarization of the boundary layer under an intense gas suction, in the region of the impermeable plate following the permeable wall, the wall temperature drops abruptly.

The vortex-induced intensification of the laminar (at Re = 308) flow of transformer oil and heat transfer in a microtube with an in-line package of dimples with a depth of 0.26 of the tube diameter is calculated based on the Navier–Stokes equations and the energy equation. The heat-transfer increased by nearly 20 times for eight inclined oval-trench dimples spaced around the circumference and by 13 times for spherical dimples equal in area in comparison with that for a smooth tube; moreover, the relative hydraulic losses grow by approximately 30 and 60%, respectively.

The influence of the coflow wind on the flow in a hot, nonisobaric, supersonic airdrome jet from a biconical nozzle and its interaction with a jet blast deflector (JBD) are studied by the RANS/ILES method. The conditions at the external boundary of the computational domain are formulated for the problem of jet interaction with the JBD. All calculations were performed at the Joint Supercomputer Center of the Russian Academy of Sciences with a MVS-10P supercomputer. The features of method parallelization for the supercomputer with modern architecture are described. The total temperature of the jet at the nozzle output is T0 = 1050 K and πс = 4. The wind velocity ranges from 0 to 20 m/s. Two JBD positions are examined: at distances of 5 and 15De of the nozzle cross section. The computation grids consist of (6.33–8.53) × 106 cells. Fields of the flow parameters and of their turbulent pulsations near the jet are obtained. The dimensions of the “safety zone” for people and machinery is determined by the temperature, pressure pulsations, and velocity near the airdrome surface. The influence of wind velocity on the size and shape of the safety zone are revealed. The distributions of pressure and temperature and their pulsations over JBD altitude are presented as a function of JBD position and wind velocity.

The results of experimental studies of a microwave antenna based on plasma jet created by a pulsed discharge in a capillary with an ablative wall are presented. It is shown that the electromagnetic parameters of the plasma jet are close to metal, which enables its efficient operation in the mode of an asymmetric quarterwave dipole for transmitting and receiving electromagnetic waves in the centimeter–decimeter range. The influence of the discharge parameters, the flow regimes of the plasma jet (subsonic and supersonic), and various impact factors (high-speed gas flow, a source of low-temperature plasma with n e ~ 1012 cm–3, etc.) on the receiving and transmitting operating modes have been studied. The possibility of using a plasma jet for radio communication of hypersonic flying vehicles and related problems is discussed.