P. A. Popov

Peculiarities of interaction of a shock wave with gas discharge plasma

Using a double electrical probe, distribution of charged particles behind the front of a shock wave in gas discharge plasma in the presence of the electric field and in decaying plasma without the electric field was studied. A significant difference between the distributions of the charged particles in these two cases was revealed.

Using anisotropic heat flux sensors in aerodynamic experiments

We present the results of comparative measurements of the heat flux to a flat plate in a supersonic flow at a Mach number of M = 6, which were performed using the two following anisotropic heat sensors with different thicknesses of sensor elements: (i) Atomic Layer Thermo Pile (ALTP, Fortech GmbH, Germany) with a thickness of ∼0.5 × 10−6 m and (ii) gradient heat flux sensor (GHFS, St. Petersburg State Polytechnic University, Russia) with a thickness of ∼2 × 10−4 m. The ALTP sensor can be used for directly measuring heat fluxes in processes with a characteristic time above 10−6 s. A method for mathematically processing the GHFS response signal is proposed that allows heat flux oscillations to be revealed in gasdynamic process with a characteristic time on the order of 10−4 s.

Experimental investigation of magnetohydrodynamic action on a heat flux toward the surface of a model

Experimental data for magnetohydrodynamic (MHD) action on a supersonic nitrogen flow about an axisymmetric model are presented. The experiments were carried out in the Big Shock Tube (Ioffe Physical-Technical Institute), at the end of which a test section equipped with a supersonic nozzle was mounted. A test conic model coupled with a cylinder is attached to the output cross section of the nozzle. A magnetic field is produced by a solenoid placed on the cylindrical part of the model through which a pulsed current due to an external voltage source discharging passes. Electrodes on the conic part of the model initiate a gas discharge, which rotates about the axis of the model in the solenoidal magnetic field. The influence of the magnetic field on the gasdynamic pattern of the flow near the model and on the heat flux toward its surface is investigated. Schlieren patterns of the flow about the model, photographic scans of the discharge glow, and heat flux measurements are taken. It is found that the magnetic field has an effect on the gasdynamic pattern of the flow near the model and on the heat flux toward its surface. The dependence of MHD effects on the external voltage polarity is also revealed.

Algorithm for determining the aerodynamic characteristics of a freely flying object from discrete data of ballistic experiment. Part I

An algorithm for solving the inverse problem of dynamics is described. It is intended for processing trajectory data for a freely flying object that are acquired in ground-based (laboratory) simulation on a ballistic range with the aim of determining the aerodynamic characteristics of the object.

The influence of thermophysical substrate properties of an anisotropic thermoelement on thermopower in the nonstationary thermal regime

We have calculated the fields of temperature and electric potential in the model of a thermal sensor based on anisotropic thermoelements in the nonstationary thermal regime. It is shown that the effect of thermal-conduction anisotropy of a material of a thermoelement is insignificant at the initial stage of heating, and the distribution of temperature is close to one-dimensional. With further heating, the thermo-physical properties of the substrate have a significant effect on the field of temperature and potential. The use of a substrate with high thermal diffusivity makes it possible to simplify significantly the processing of measurement results and increase the electrical signal of the sensor.

Interaction of shock wave with free glow discharge

The distribution of charge particles in glow-discharge plasma during shock wave propagation through it is measured by a double electric probe. It is established that a decrease in the ion concentration in front of the shock wave is related to the occurrence of ion-acoustic oscillations in the plasma.

An experimental study of the effect of humidity on the distribution of charged particles in a glow-discharge plasma

The charged-particle distribution in a glow-discharge plasma in air with differing moisture concentration was studied using a double electric probe. An important difference is found in the distribution of charged particles in the discharge, depending on the humidity of the air. The amount of water vapor with a relative concentration of 2% does not affect the distribution of charged particles in the plasma, and, with an increase in moisture content up to 15%, a twofold increase in the ion concentration along the discharge axis is observed.

The influence of thermophysical properties of an anisotropic heat-element substrate on the value of thermal emf in the stationary thermal mode

Thermal and thermoelectric processes in anisotropic heat elements located on substrates made of different materials have been numerically simulated. It is shown that, when an invariable heat flux passes through a heat element, the thermophysical properties of the substrate and heat transfer coefficient at its rear surface affect significantly the temperature distribution and the value of generated thermal emf.

Measuring pulsed heat flux by anisotropic thermoelement

The relationship between the electric response signal of a thermal sensor and the temperature change caused by pulsed thermal load on the working surface is established within the framework of a one-dimensional model of the anisotropic thermoelement. A signal from the gradient heat-flux sensor based on an anisotropic bismuth single crystal that occurs on a steel plate exposed in a pulsed supersonic flow is analyzed in terms of the model. The results of the heat flux calculation using the temperature sensor response are compared to the data of direct measurements.

Identification of aerodynamic characteristics with discontinuities of the first kind from trajectory data for a free-flying object

A method is proposed for identifying the aerodynamic characteristics of a model the flow about which varies considerably in the course of motion. In this method, the trajectory of the model is split into sections with different types of the flow and then similar data from these sections are collected into groups and processed. The aerodynamic characteristics are identified by the method of successive approximation using a differential correction algorithm. The accuracy of the results is analyzed.