N. P. Mende

Magnetohydrodynamic control of a supersonic flow about a body

The structure and principle of operation of an electromagnetic facility capable of controlling a supersonic flow about a body of revolution are described, by means of which gas-discharge plasma formed between electrodes flush-mounted on the body is driven over its surface by a magnetic field. It is shown that the frequency of rotation of the gas-discharge plasma strongly depends on the direction of electric current flowing through the facility, as well as on the pressure of ambient gas. Experimental results demonstrating the effective magnetohydrodynamic control over the structure of supersonic nitrogen flow about the body of revolution at a Mach number of 4 are presented.

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.

Magnetic field control of a supersonic nitrogen flow

Magnetohydrodynamic impact on a cold supersonic nitrogen flow with external magnetic field was realized in an experimental complex based on the Big Shock Tube at the Ioffe Physicotechnical Institute. A pulsed supersonic flow with a Mach number of M=4 and steady phase duration of about 1.5 ms was created by expansion of the shock-heated nitrogen flow from a supersonic nozzle. The gas was ionized by pulsed discharge between two electrodes mounted on the nozzle wall so that an electric current of up to ∼500 A passed in the direction perpendicular to the gas flow at the dielectric wall. External magnetic field ∼0.3 T was perpendicular to the gas flow and the current direction. It is established that the magnetic field significantly modifies the shock wave structure in the flow.

Thermal measurements at the body surface in a supersonic nitrogen flow

Measurements of the heat flux toward the surface of a body of revolution in a supersonic nitrogen flow with Mach number 4 were carried out. Inside the body, an electromagnetic facility is mounted which generates a gas-discharge plasma between electrodes flush-mounted at the body surface. The plasma rotates around the body surface and significantly influences the supersonic flow. During operation of the electromagnetic facility, the heat flux toward the body surface increases and depends on the direction of the electric current flowing through the plasma. The heat flux was measured by fast-response gradient heat flux sensors based on anisotropic bismuth crystals.

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.

Algorithm for solving the inverse problem of ballistics in the case of an asymmetric object

An algorithm to identify the aerodynamic characteristics of an asymmetric object from its trajectory data obtained in a ballistic experiment is developed based on the technique for estimating the nonlinear system’s parameters. Using the method of successive approximations, the coefficients of the aerodynamic function polynomial representation are found that best describe measuring data. The essence of the algorithm is the solution of the direct problem of the symmetric object’s dynamics using the complete set of Euler dynamic equations. The variation of the desired parameters is statistically estimated during calculations. The algorithm allows for jointly processing data of a series of experiments with similar models. Thereby, the volume of processed data is augmented and the final result becomes more accurate.

Experimental investigation of the gas discharge dynamics in a solenoidal magnetic field

An electric gas discharge is initiated at the end face of a nonconducting cylinder between a central electrode coaxial with the cylinder and a ring electrode on the lateral surface of the cylinder. The axis of the cylinder and that of a magnetic coil wound on its lateral surface coincide. The dynamics of the gas discharge in a solenoidal magnetic field is studied by observing its position and shape and monitoring the variation of the thermionic center distribution on the surface of the ring electrode with discharge current and magnetic induction. The discharge develops in air at a pressure of 2 kPa.

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.

Experimental and numerical investigation into the supersonic flow of a weakly ionized plasma around a dihedral angle: Magnetohydrodynamic control of the flow pattern and heat fluxes toward the wall

The results of experimental and numerical investigations into magnetohydrodynamic actions on the supersonic flow of a weakly ionized xenon plasma around a wedge are presented. The conditions of numerical simulation correspond to the conditions of experiments carried out on the Bol’shaya shock tube at the Ioffe Physicotechnical Institute.