Shock Wave Configuration Research Articles

Influence of gas-dynamic characteristics of a wide-range engine on energy-information exchange during flights at high supersonic speed

Using a conical nozzle as an example, the gas-dynamic and thrust characteristics of high-altitude nozzles are studied in a wide range of atmospheric pressures. A geometric model of the nozzle block and the computational domain is developed in a two-dimensional axisymmetric formulation. A calculation was carried out with setting the parameters of the standard atmosphere in the altitude range from 0 to 80 km. In one of the parts of this work, the most common shock-wave structures (triple configurations of shock waves) that arise during flights at supersonic and high supersonic speeds are considered, during jet outflows from propulsion systems. We also studied the influence of the extreme values of the discontinuities of the flow field parameters on the transmitted electromagnetic signals.

Some pioneering research in laboratory simulation of scaled astrophysical phenomena by Russian physicists

The review about the problems of astrophysical phenomena pioneering researching by Russian recognized physicists – S.Anisimov, I.V.Minin, O.V.Minin, V.F.Minin and A.Velikovich - is carried out. For the first time, a mode of hypercumulative collapse of a conical cavity was proposed for the formation of an ultra-high-speed plasma jet. The description of “cumulative plasma jets” is presented. The main parameters of the cumulative plasma jet and the results of laboratory studies on the creation of a hyper cumulative plasma jet are described. It was shown that the proposed mechanism allows one to obtain record characteristics of such a jet, which have not been surpassed so far. Test data description of the numerical simulation of the inter action between plungers and a conic cavity on the explosive initiation of the D-D reaction with the aid of aluminum plungers is discussed. The mechanisms of the plunger surface acceleration are described. The generation of the Mach configuration of shock waves in the target was also used for the explosive production of wurtzite with a record yield of the mass of the synthesized material and to focusing of the shock waves in water using plane diffractive optics.

Features of the interaction of shock waves with regions of a gas-discharge plasma of different structure

The work considers the possibility of influencing supersonic flows and shock-wave configurations by ionizing the propagation medium or flow around by creating a low-current gas discharge of different configurations. The experimental setup is a shock tube with a connected square working chamber with built-in electrodes to create a glow gas discharge of different intensity and uniformity. The process of the passage of a shock wave created in a shock tube through a region of a pre-arranged gas-discharge plasma having a uniform structure or stratified with ionization inhomogeneities of different scale is investigated. The formation of a new shock-wave configuration during the interaction of a shock wave with an ionized medium, as well as a strong distortion of the waveform up to its complete destruction during interaction with ionization-unstable plasma, has been found.

Impact of homogeneous and ionization unstable glow discharge plasma on a shock wave in air

The work is aimed at exploring the possibility of control of strong shock waves up to their completely destruction. The impact on shock waves by creating a region of gas-discharge plasma in propagation media is proposed. A diffuse or ionization unstable discharge with the ionization strata of different scale on the path of a shock wave propagation is organized. As a result, the shock wave propagates over the region of homogeneous highly non-equilibrium plasma or over the medium of layered structure with higher degree of ionization and electron temperature in the layers. Numerical simulation of the propagation of a shock wave over the region of energy impact was carried out on the basis of the systems of Euler and Navier-Stokes equations with the flow parameters obtained in the experiment. The homogeneous plasma region was simulated by a rarefied gas region with increased temperature and constant pressure. The area formed by the ionization unstable discharge was simulated by a thermally stratified gas area. The strong influence of the ionization of the propagation medium on the transformation of the shock wave with the formation of a new shock wave configuration is shown. Stratification of the medium leads to a distortion of this configuration up to complete destruction of it.

Extreme Triple Configurations with Negative Slope Angle of the Reflected Shock

The triple configurations of stationary shock waves with negative slope angle of the reflected shock to the velocity vector of the supersonic stream in front of the triple point (“inverse” triple configurations) are considered. “Inverse” configurations with the maximum relations of flow parameters at the tangential discontinuity after the triple point are determined. Extreme relations of the flow parameters downstream the “inverse” configurations are compared with the analogous extreme parameters attained on the whole set of the triple-shock configurations that appear in supersonic streams of the inviscid perfect gas.

Interaction of a plane shock wave with an area of ionization instability of discharge plasma in air

The conducted study is devoted to the research area of control of high speed flows and shock-wave configurations. Experimental and numerical results on the interaction of a plane shock wave (M = 5–6) with the area formed by ionization instability in gas discharge plasma at a pressure of 3–7 Torr and gas-discharge current of 100–400 mA are presented. The region of ionization instability in plasma of high degree of ionization and non-equilibrium (gas temperature T ∼ 300–600 K, electron temperature Te∼5⋅103 K) has been obtained experimentally in air. This instability is characterized by spherical strata of changing shape. Two types of a shape of the ionization instability have been obtained: large-scale type and small-scale type. Also, the transitional type from large-scaled strata to low-scaled ones has been obtained. The influence of the ionization instability was established to cause the distortion of an initially plane shock wave up the complete disappearance of its front. Numerical modeling the interaction of the initially plane shock wave with ionization-unstable plasma using the Euler system of equations has been conducted. The area formed by ionization unstable plasma was modeled via a set of thermal layers with varying densities (and temperatures). Changing the physical–chemical properties of the gas medium was taken into account varying the ratio of specific heats. Layered structures with wavy shock-wave and contact discontinuity fronts have been observed. The multiple generations of shear layer instabilities and the Richtmyer–Meshkov instabilities have been obtained as the result of the interaction of a shock wave with thermal strata. It has confirmed that the shapes of the both discontinuities change acquiring an unstable character. Examples of the flow modes with the disappearance of the shock wave front causing by the origination of a structure with cellular order of shear layer instabilities have been presented. A good agreement at the qualitative level with the experimental Schlieren images has been demonstrated.

Regular refraction of an oblique shock wave at the tangential discontinuity

This article is devoted to the regular refraction of an oblique shock wave at the tangential discontinuity. The calculations were performed for an ideal gas model using the numerical and analytical methods for solving the equations called the dynamic compatibility conditions at the tangential discontinuity. Basic equations are given. This article examines the domains of shock wave configurations with various types of reflected discontinuities within them, including characteristic refraction (induced by the change in char), and refraction patterns with a reflected shock and a reflected rarefaction wave. Each refraction domain was mapped by type with regard to the Mach number, adiabatic exponents of two flows, and the intensity of a refracted oblique shock wave. The boundary between the regular and irregular refractions was found. Research results can be applied to simulate the shock waves processes that occur in rotating detonation engines, as well as in stationary detonation engines.

Detonation in a Three-Dimensional Elbowed Channel

The results of simulation of detonation in a curved three-dimensional channel with a circular cross section of constant width blown through by a supersonic flow of a stoichiometric propane−air mixture are presented. In the bending zone, the channel wall was toroidal. The study was carried out within the framework of the one-stage combustion kinetics by the numerical method based on Godunov’s scheme in the original software package developed for multiparameter calculations and visualization of flows. The initiation of detonation occurs as a result of the formation of the shockwave configurations associated with the flow turn in the channel. Unsteady flow patterns are obtained, and their dependence on the parameters of the problem is investigated. The flow regime without detonation, the mode with the detonation wave emerging from the channel through the input cross section, and the mode with steady detonation are obtained.

Influence of shock waves from plasma actuators on transonic and supersonic airflow

This paper presents experimental and numerical investigations of high-current sliding surface discharges of nanosecond duration and their effect on high-speed flow as plasma actuators in a shock tube. This study deals with the effectiveness of a sliding surface discharge at low and medium air pressure. Results cover the electrical characteristics of the discharge and optical visualization of the discharge and high-speed post-discharge flow. A sliding surface discharge is first studied in quiescent air conditions and then in high-speed flow, being initiated in the boundary layer at a transverse flow velocity of 50–950 m s−1 behind a flat shock wave in air of density 0.04–0.45 kg m−3. The discharge is powered by a pulse voltage of 25–30 kV and the electric current is ~0.5 kA. Shadow imaging and particle image velocimetry (PIV) are used to measure the flow field parameters after the pulse surface discharge. Shadow imaging reveals shock waves originating from the channels of the discharge configurations. PIV is used to measure the velocity field resulting from the discharge in quiescent air and to determine the homogeneity of energy release along the sliding discharge channel. Semicylindrical shock waves from the channels of the sliding discharge have an initial velocity of more than 600 m s−1. The shock-wave configuration floats in the flow along the streamlined surface. Numerical simulation based on the equations of hydrodynamics matched with the experiment showed that 25%–50% of the discharge energy is instantly transformed into heat energy in a high-speed airflow, leading to the formation of shock waves. This energy is comparable to the flow enthalpy and can result in significant modification of the boundary layer and the entire flow.

Optimal triple configurations of stationary shocks

The triple configurations of stationary shock waves with negative slope angle of the reflected shock to the velocity vector of the supersonic stream before the triple point (“inverse” triple configurations) are considered. “Inverse” configurations with maximum relations of flow parameters at the slipstream after triple point are determined. Extreme relations of the flow parameters downstream the “inverse” configurations are compared with the parameters achieved on the whole set of the triple-shock configurations that appear in supersonic streams of the inviscid perfect gas.

Triple configurations of pursuit shock waves in conditions of ambiguity of the solution

The article studies triple configurations of shock waves in supersonic flows of a perfect gas in view of the fact that it is not always possible to determine unambiguously the parameters of the remaining shocks in the configuration by specifying the properties of the oncoming flow and the branching shock wave. The values of the parameters of triple configurations with maximum relations of the parameters of the flow on the sides of the outgoing tangential discontinuity (extremal configurations) in conditions of the ambiguity of the physically realizable solution are found analytically and numerically.

Computational analysis of vortices near casing in a transonic axial compressor rotor

Complicated flowfields near casing in a transonic axial flow compressor rotor have been numerically investigated in this paper. Two vortex identification methods, namely the Eigenvector Method and Lambda 2 Method, are introduced as important tools for the graphical representation of the concentrated vortices arising from tip leakage flow and blade boundary layer separation. The analysis of the numerical results reveals that multiple tip vortices whose development are dependent on the variation of shock wave configuration are observed at conditions around the peak efficiency point. However, with the decrease of the massflow rate, only the well-known tip leakage vortex and the second tip vortex are left in the tip region due to the disappearance of the second shock wave. Then when the massflow rate further decreases to the stall limit, an deceleration flow region emerges downstream of the shock wave due to an increasing interaction between the first shock wave and the well-known tip leakage vortex. The tip leakage vortex further experiences a bubble-type and then spiral-type breakdown at near stall flow conditions. In addition, the validity of the two vortex identification methods is also discussed in this paper. It is found that both methods are able to identify and accentuate the concentrated streamwise vortices near casing when a vortex is not disrupted. However, if the vortex breakdown occurs, only Eigenvector Method can describe the breakdown region in a deep view.

Three-dimensional shock wave configurations induced by two asymmetrical intersecting wedges in supersonic flow

This study explores the three-dimensional (3D) wave configurations induced by 3D asymmetrical intersecting compression wedges in supersonic and hypersonic inviscid flows. By using the “spatial dimension reduction” approach, the problem of 3D steady shock/shock interaction is converted to that of the interaction of two moving shock waves in the characteristic two-dimensional (2D) plane. Shock polar theory is used to analyze the shock configurations in asymmetrical situations. The results show that various shock configurations exist in 3D asymmetrical shock wave interactions, including regular interaction, transitioned regular interaction, single Mach interaction, inverse single Mach interaction, transitional double Mach interaction, weak shock interaction, and weak single Mach interaction. All of the above 3D steady shock/shock interactions have their corresponding 2D moving shock/shock interaction configurations. Numerical simulations are performed by solving the 3D inviscid Euler equations with the non-oscillatory, non-free parameters, dissipative (NND) numerical scheme, and good agreement with the theoretical analysis is obtained. Furthermore, the comparison of results show that the concept of the “virtual wall” in shock dynamics theory is helpful for understanding the mechanism of two-dimensional shock/shock interactions.

Inviscid vortex structures in the shock layers of conical flows around V wings

The applicability of the criteria of existence of inviscid vortex structures (vortex Ferri singularities) is studied in the case in which a contact discontinuity of the corresponding intensity proceeds from the branching point of the λ shock wave configuration accompanying turbulent boundary layer separation under the action of an inner shock incident on the leeward wing panel. The calculated and experimental data are analyzed, in particular, those obtained using the special shadow technique developed for visualizing supersonic conical streams in nonsymmetric, Mach number 3 flow around a wing with zero sweep of the leading edges and the vee angle of 2π /3. The applicability of the criteria of existence of inviscid vortex structures is established for contact discontinuities generated by the λ shock wave configuration accompanying turbulent boundary layer separation realized under the action of a shock wave incident on the leeward wing panel. Thus, it is established that the formation of the vortex Ferri singularities in a shock layer is independent of the reason for the existence of the contact discontinuity and depends only on its intensity.

Effect of heat release on movement characteristics of shock train in an isolator

In this paper, the effect of heat release on movement characteristics of shock train is numerically investigated in an isolator. It is found that the combustion heat release has a distinct effect on the shock train movement characteristics in the isolator. With increasing heat release, a shock train gradually forms and then propagates toward isolator entrance. In process of shock train formation, separation bubbles before injection ports entrain the high temperature burning gas into the boundary layer, which causes the shock train to shrink and stretch, and changes in configuration and number of shock waves. At the same time, the system force fluctuates. In addition, the shock train movement is divided into three stages, which have different wall pressure distribution. It is believed that these findings have a help the better understanding of the effect of heat release on the movement characteristics of shock train in an isolator.

Experimental investigation on the characteristics of supersonic fuel spray and configurations of induced shock waves

The macro characteristics and configurations of induced shock waves of the supersonic sprays are investigated by experimental methods. Visualization study of spray shape is carried out with the high-speed camera. The macro characteristics including spray tip penetration, velocity of spray tip and spray angle are analyzed. The configurations of shock waves are investigated by Schlieren technique. For supersonic sprays, the concept of spray front angle is presented. Effects of Mach number of spray on the spray front angle are investigated. The results show that the shape of spray tip is similar to blunt body when fuel spray is at transonic region. If spray entered the supersonic region, the oblique shock waves are induced instead of normal shock wave. With the velocity of spray increasing, the spray front angle and shock wave angle are increased. The tip region of the supersonic fuel spray is commonly formed a cone. Mean droplet diameter of fuel spray is measured using Malvern’s Spraytec. Then the mean droplet diameter results are compared with three popular empirical models (Hiroyasu’s, Varde’s and Merrigton’s model). It is found that the Merrigton’s model shows a relative good correlation between models and experimental results. Finally, exponent of injection velocity in the Merrigton’s model is fitted with experimental results.

Numerical study of shock wave interaction in steady flows of a viscous heat-conducting gas with a low ratio of specific heats

Specific features of shock wave interaction in a viscous heat-conducting gas with a low ratio of specific heats are numerically studied. The case of the Mach reflection of shock waves with a negative angle of the reflected wave with respect to the free-stream velocity vector is considered, and the influence of viscosity on the flow structure is analyzed. Various issues of nonuniqueness of the shock wave configuration for different Reynolds numbers are discussed. Depending on the initial conditions and Reynolds numbers, two different shock wave configurations may exist: regular configuration interacting with an expansion fan and Mach configuration. In the dual solution domain, a possibility of the transition from regular to the Mach reflection of shock waves is considered.

Trends in the development of detonation engines for high-speed aerospace aircrafts and the problem of triple configurations of shock waves. Part II - Research of counterpropagating shock waves and triple shock wave configurations

Trends in the development of detonation engines for high-speed aerospace aircrafts and the problem of triple configurations of shock waves. Part II - Research of counterpropagating shock waves and triple shock wave configurations

The influence of incident shock Mach number on radial incident shock wave focusing

Experiments and numerical simulations were carried out to investigate radial incident shock focusing on a test section where the planar incident shock wave was divided into two identical ones. A conventional shock tube was used to generate the planar shock. Incident shock Mach number of 1.51, 1.84 and 2.18 were tested. CCD camera was used to obtain the schlieren photos of the flow field. Third-order, three step strong-stability-preserving (SSP) Runge-Kutta method, third-order weighed essential non-oscillation (WENO) scheme and adaptive mesh refinement (AMR) algorithm were adopted to simulate the complicated flow fields characterized by shock wave interaction. Good agreement between experimental and numerical results was observed. Complex shock wave configurations and interactions (such as shock reflection, shock-vortex interaction and shock focusing) were observed in both the experiments and numerical results. Some new features were observed and discussed. The differences of structure of flow field and the variation trends of pressure were compared and analyzed under the condition of different Mach numbers while shock wave focusing.

Trends in the development of detonation engines for high-speed aerospace aircrafts and the problem of triple configurations of shock waves. Part I. Research of detonation engines

Trends in the development of detonation engines for high-speed aerospace aircrafts and the problem of triple configurations of shock waves. Part I. Research of detonation engines