This work studies the influence of a growing boundary layer on the process of supersonic flow around an aerodynamic body. The task is to select and implement in an experiment the parameters of a supersonic flow and to study the flow pattern near the surface of an aerodynamic body at different viscosity values for the incoming flow. Visualization of the shock wave configuration in front of the body and studying the change in the pressure field in the flow region under these conditions is the main goal of this work. The experiment was carried out on an experimental stand created on the basis of a shock tube. The aerodynamic body under study (a semi-cylinder pointed along a circle or an ellipse) was placed in a supersonic nozzle. The model was clamped by lateral transparent walls, which were simultaneously a source of boundary layer growth and the viewing windows for visualizing the flow. For selected modes with Reynolds numbers from 8200 to 45,000, schlieren flow patterns and pressure distribution fields near the surface of the streamlined models and the plate of the growing boundary layer were obtained. The data show a complex, unsteady flow pattern realized near the model which was caused by the viscous-inviscid interaction of the boundary layer with the bow shock wave near the wall.

The applicability of the calibration method for heat flux sensors based on anisotropic bismuth thermoelements and a heterogeneous copper-nickel structure using a reflected shock wave to determine the volt-watt coefficient is demonstrated. The coefficient obtained for a sensor based on anisotropic thermoelements is close to the stationary calibration data, and for a sensor based on a heterogeneous structure, to the results of numerical simulation. Keywords: heat flux, calibration, shock tube, shock wave, ghfs, hghfs.

The work studies the influence of a growing boundary layer on the process of the supersonic flow around an aerodynamic body. The task is to select and implement in an experiment the parameters of a supersonic flow and to study the flow pattern near the surface of an aerodynamic body at different viscosity values of the incoming flow. Visualization of the shock wave configuration in front of the body and to study the change in the pressure field in the flow region under these conditions is the main goal of the work. The experiment is carried out on an experimental stand created on the basis of a shock tube. The aerodynamic body under study (a semi-cylinder pointed along a circle or an ellipse) is placed in the supersonic nozzle. The model is clamped by lateral transparent walls, which are simultaneously a source of boundary layer growth and the viewed windows for visualizing the flow. For selected modes with Reynolds numbers from 8200 to 45000, schlieren flow patterns and pressure distribution fields near surface of the streamlined models and the plate of the growing boundary layer were obtained. Data show a complex unsteady flow pattern is realized near the model that is caused by the viscous-inviscid interaction of the boundary layer with the bow shock wave near the wall.

We present the results of measuring the heat flux using sensors based on anisotropic thermoelements and a thin-film resistance sensor for cases of shock-wave reflection from the end of a shock tube and an external supersonic gas flow around the model. The obtained data demonstrate that such sensors can be applied in gas-dynamics experiments in a wide range of characteristic times.

The results of experiments and numerical simulations of the interaction of a plane shock wave with an area of ionization strata formed by a glow gas discharge are presented. For the experimentally obtained phenomena transformations of kinetic and internal energy have been studied numerically using Euler and Navier-Stokes approaches under the assumption that ionization unstable plasma has stratified gas temperature. Energy transfer between a region of layered energy deposition and heated gas zone behind the shock wave was considered. It has been established that a layered energy deposition can provide the distortion and destruction of a shock wave front and in addition, to create a lot of zones with higher internal and kinetic energy beyond it. These phenomena were shown to be connected with generation in many points of the Richtmyer-Meshkov instability resulting from the interaction of thermal strata with a front of the shock wave.

This paper demonstrates the possibility of active magnetohydrodynamic (MHD) control of supersonic flows containing shock waves. The shock wave configurations that occur at the inlet to a supersonic diffuser and in front of a streamlined semicylindrical model are used for the purpose of investigation. The impact is carried out by organizing local gas discharge regions when applying a magnetic field transverse to gas discharge currents. It has been shown that by changing the local region of application, the intensity and the direction of the gas discharge currents, it is possible to change the intensity and direction of the ponderomotive force acting on the gas flow during MHD interaction. The ponderomotive force control allows for acting locally on the shape and position of shock waves, the speed and direction of the flow, and the increase or reduction of pressure near the surface of the streamlined body. The experiments were carried out on a gas dynamic setup based on a shock tube in a gas dynamic path, capable of creating supersonic flows in a wide range of Mach numbers at M = 4–7. There was a possibility of organizing the electric and pulsed magnetic fields with an intensity of up to 1.5 T. The given experimental Schlieren flow patterns and the analysis of the obtained data demonstrate the MHD effect on: the change in the angle of inclination of the attached shocks, both into increase and decrease; the bow shock wave approaching the body or the removal from it; and the change in the aerodynamic drag and lift force of the streamlined bodies.

The applicability of the calibration method for heat flux sensors based on anisotropic bismuth thermoelements and a heterogeneous copper-nickel structure using a reflected shock wave to determine the volt-watt coefficient is demonstrated. The coefficient obtained for a sensor based on anisotropic thermoelements is close to the stationary calibration data, and for a sensor based on a heterogeneous structure, to the results of numerical simulation.

The problem of the bow shock wave control using a near-surface gas discharge in a supersonic flow past a semi-cylindrical body at Mach number M = 4 in the air is investigated experimentally and numerically. The possibility of controlling the position of a steady bow shock wave and the characteristics of a streamlined body by creating a volumetric plasma region using a surface gas discharge organized on the entire front surface of the body is shown. An increase in the stand-off distance of a steady bow shock is experimentally and numerically obtained, which is the greater, the higher the discharge power and the greater the adiabatic index in the plasma region created by the discharge. A comparison of the numerical and experimental data showed good agreement. It is established that the relative value of the steady bow shock stand-off distance increases linearly in the power range from 1.5 × 105 to 2.4 × 105 W at the discharge current from 430 to 670 A, and the adiabatic index in the plasma region can be estimated as 1.3. It is also found that at higher values of the discharge power, the adiabatic index in the plasma region decreases. The average plasma parameters were expressed as functions of the discharge specific power and the adiabatic index. The mechanism of the gas discharge effect on the bow shock wave is established, and it is shown that the plasma parameters in the region created by the discharge, including the degree of ionization and the degree of nonequilibrium, affect the position of the steady bow shock wave.

An analysis of main features of unsteady heat flux measuring in shock tubes experiments with a characteristic process time of ~1 μs - 1 ms using sensors based on anisotropic bismuth thermoelements is made. The heat flux behind the reflected shock wave and at the blunt body stagnation point has been measured. Testing of the heat flux calculation method was carried out. The difference between the experimental data and the theoretical value of the heat flux does not exceed 50%. The possible reasons influencing the magnitude of measurement uncertainty are analyzed. The experiments performed have shown the applicability of a sensor based on anisotropic thermoelements and the method for calculating the heat flux from its electrical signal for typical conditions of experiments on shock tubes.

The study is devoted to assessing the applicability of the manufactured thermoelectric sensor for functioning in shock tubes to measure instantaneous heat fluxes occurring in shock-wave processes. The gas-dynamic parameters of supersonic and hypersonic flows in test sections of such facilities can be quite harsh due to high values of enthalpies. At the same time, the typical operating period in such experiments is several milliseconds, which imposes specific requirements on the instruments used for registering heat fluxes. Thermoelectric heat flux sensors have been constructed in-house. The sensitive element of the sensor is a thin film of artificially anisotropic chromium obtained by oblique deposition on a high-resistance silicon substrate. This technology is used in laser systems to measure the power of laser radiation. The results of experiments on the generation of low-intensity reflected shock waves in nitrogen are presented. The new thermoelectric detector was used to register the heat flux from a hot gas heated by a shock wave reflected from the end of the shock tube. At the same time, the heat flux was measured using a sensor based on anisotropic thermoelements with a known sensitivity. Experiments have shown that the sensor has a high speed (similar to 1 mu s), a high signal-to-noise ratio, and a high electrical signal. The results obtained demonstrate the applicability of the sensor for measuring convective heat flux in shock tube experiments.

A partially automatic method of digital processing images (photographs, shadow and Schlieren pictures) for the analysis of experimental data is proposed. The method is utilized to investigate the effect of the region of ionization instability created by a glow gas discharge on the front of an initially flat shock wave. The proposed method is based on a composition of simple image processing operations and makes it possible to perform simulations taking into account the real geometry of the ionization strata and the shape of the front of a shock wave based on the obtained experimental images. First, as a result of digital processing the geometry of experimental objects is extracted from the images. This information is then embedded in the Navier-Stokes code for conducting simulations. New results for the real geometry of ionization strata of different scales are presented which confirmed the previous ones obtained for the density homogeneously stratified source model.

The emission spectra of the CaO molecule behind the front of a reflected shock wave in a shock tube with a diameter of 50 mm has been studied. The spectra are recorded using a specially designed compact spectrometer with a CCD array, as well as using a spectrometer based on an upgraded MDR-12 monochromator and a Sony SLT-A77 camera as a radiation detector. The emission spectra of CaO are recorded at different gas temperatures. The obtained results can be used to test theoretical models of the emission spectra of the CaO molecule at different temperatures.

The article refers to the field of supersonic flow control via external energy deposition. Passing a strong shock wave (M=5-6) through the region of pre-formed ionization instability in gas discharge plasma has been studied experimentally and numerically. In the experiments the ionization spherical strata have been obtained arising in the gas discharge region due to the development of the ionization instability in air. As a result of the interaction of an initially plane shock wave with the plasma region of ionization instability the formation of new complicated shock-wave configurations was obtained the shape of which changed from smooth to gear. These configurations were shown to acquire an unstable character. Numerical simulations were carried out on the basis of the Euler system of equations with the parameters corresponding to the experimental conditions with the use of the complex conservative difference schemes. The stratified energy source was modelled by a set of thermal layers with varying characteristics. Changes in the physic-chemical properties of the medium were described by varying the adiabatic index. Stratified shock-wave structures consisting of modified wavy shock-wave and contact discontinuities have been obtained as a result of the interaction of the shock wave with the region of ionization instability. Generation of the Richtmyer-Meshkov instabilities has been obtained on the thermal strata in the vicinity of the shock wave front curvatures which confirmed the unstable character of the shock wave front. Comparison of the obtained experimental and numerical shock front evolution showed a good agreement. Results of the study can be used to control of high speed flows and shock-wave configurations, as well as mixing processes

Experimental investigations of the emission spectrum of a CaO molecule behind the front of a reflected shock wave on a 50 mm diameter shock tube at the Ioffe Institute are carried out. The spectra were obtained using a compact spectrometer, as well as using a spectrometer based on an upgraded MDR-12 monochromator and a Sony SLT-A77 camera as a radiation detector. The emission spectra of CaO at different gas temperatures were obtained. The results can be used to test theoretical models of the emission spectrum of the CaO molecule at different temperatures.

The study is devoted to assessing the applicability of the manufactured thermoelectric sensor to measure pulsed heat fluxes in shock-wave processes. It is shown that the created thermoelectric sensor has fast response time and sufficient level of electric signal and can be successfully used in short duration high speed gas dynamic experiments.