This paper is a review of the series of investigations carried out at the S. A. Khristianovich Institute of Theoretical and Applied Mechanics (ITAM, Siberian Branch of the Russian Academy of Sciences (RAS)) aimed at solving the sonic boom problem. It has been shown, with the example of flow over a body of revolution at Mach number M = 2, that a decrease in the flow temperature near the body leads to a change in the flow structure in the region of the formation of a hanging shock wave and a decrease (by 12%) in the sonic boom intensity on the ground. The results are presented of investigations of the influence of the relative position and geometrical shape of configuration elements of a supersonic passenger airplane on the sonic boom parameters at long distances from the disturbance source. The prospective aspect of the supersonic passenger airplane providing the minimum level of sonic boom in cruising flight has been determined. The scheme (IZS method) for measuring in the experiment disturbed pressure profiles at a given distance from the investigated model has been described.

As a result of optical and pneumometric measurements is defined the flow shock wave structure that is formed by the optical breakdown, due to focused repetitively pulsed CO2 laser radiation when entering perpendicular to a supersonic (M = 1.36, 1.9) air flow direction. The dynamics of the how shock formation in front of the energy input area is shown, depending on the frequency of energy impulse sequence. A flow structure is defined in the thermal wake behind pulsing laser plasma as well as wake's length with low thermal heterogeneity. A three-dimensional configuration of the energy area is defined in accordance with pneumometric and optical measuring results. It is shown that Pitot pressure decreases in thermal wake at a substantially constant static pressure, averaged flow parameters weakly depend on the energy impulse's frequency in range of 45-150 kHz.

We report a study of the wave structure formed by an optical discharge plasma upon the absorption of repetitively pulsed CO2 laser radiation in a supersonic (M = 1.36) air flow. Experimental data are presented on the configuration of the head shock wave and the geometry and characteristic dimensions of breakdown regions behind a laser plasma pulsating in the flow at a frequency of up to 150 kHz. The data are compared to calculation in a point explosion model with allowance for counterpressure, which makes it possible to identify the relationship between laser radiation and supersonic flow parameters that ensures quasisteady-state energy delivery and is necessary for extending the possibilities of controlling the structure of supersonic flows.

The paper presents the results of numerical investigation of the effect of relative area of the leading wing and nose part shape on the forming middle zone of the sonic boom (minimization region) with the tandem-location of the wings of the fuselage. It is demonstrated that the modified power-law body used as the nose part provides the middle-zone length above the cruising flight altitude, as well as the distance between the head and intermediate shock waves, which permits significantly reducing the sonic boom affect.

A method of measuring the parameters of supersonic flow with shock waves of arbitrary strength present in the flow is considered. An analytic relationship by means of which all the parameters of the disturbed flow may be determined with the use of a total-pressure tube (Pitot head) from a measured pressure behind the shock wave is obtained. Techniques for eliminating the resulting ambiguity in the determination of the shock wave strength are proposed.

Based on the analysis of various aspects of creating a supersonic transport aircraft of the second generation, the necessity of developing unconventional active methods of sonic boom level reduction is demonstrated. Surface cooling is shown to exert a significant effect on formation of the disturbed flow structure up to large distances from the body by an example of a supersonic flow around a body of revolution. A method of reducing the intensity of the intermediate shock wave and excess pressure momentum near the body is proposed. This method allows the length of the reduced (by 50%) sonic boom level to be increased and the bow shock wave intensity in the far zone to be reduced by 12%. A possibility of controlling the process of formation of wave structures, such as hanging pressure shocks arising near the aircraft surface, is demonstrated. The action of the cryogenic mechanism is explained.

The European EXPErimental Re-entry Test bed (EXPERT) vehicle is intended for studying various basic phenomena, such as the boundary-layer transition on blunted bodies, real gas effects during shock wave/boundary layer interaction, and effect of surface catalycity. Another task is to develop methods for recalculating the results of windtunnel experiments to flight conditions. The EXPERT program implies large-scale preflight research, in particular, various calculations with the use of advanced numerical methods, experimental studies of the models in various wind tunnels, and comparative analysis of data obtained for possible extrapolation of data to in-flight conditions. The experimental studies are performed in various aerodynamic centers of Europe and Russia under contracts with ESA-ESTEC. In particular, extensive experiments are performed at the Von Karman Institute for Fluid Dynamics (VKI, Belgium) and also at the DLR aerospace center in Germany. At ITAM SB RAS, the experimental studies of the EXPERT model characteristic were performed under ISTC Projects 2109, 3151, and 3550, in the T-313 supersonic wind tunnel and AT-303 hypersonic wind tunnel.

The influence of the basic factors of cryogenic forcing on formation of the middle zone on the sonic boom and aerodynamic characteristics of the flying vehicle is studied by experimental and numerical methods. Experimental data obtained with alcohol or liquid nitrogen as an injected liquid are used for comparisons; as a result, the total effect of temperature and coolant evaporation can be determined. The influence of temperature is studied by means of numerical simulations of the cryogenic action of distributed injection of air. A comparison of numerical and experimental data reveals the effect of the coolant evaporation process on perturbed flow formation. It is demonstrated that evaporation of the coolant outgoing onto the vehicle surface should be intensified to increase the efficiency of cryogenic forcing (to decrease the coolant flow rate).

Results of numerical and experimental investigations of the sonic boom parameters for two configurations of civil supersonic transport are presented. Numerical modelling is performed by a combined method based on calculating the spatial flow in the near zone of the aircraft configuration and subsequent determination of disturbed flow parameters at large distances from the examined model. Numerical results are compared with experimental sonic boom parameters measured in the near zone and with results of their recalculation to large distances within the framework of the quasi-linear theory. This validation allows the degree of adequacy of the inviscid Euler model for solving the posed problem to be determined. Reasons for certain disagreement between the calculated and experimental data are discussed. The analysis confirms the possibility of attenuating the sonic boom generated by supersonic transport with an unconventional configuration based on a tandem arrangement of two wings on the fuselage.

The paper presents the results of the study of the CO2 laser radiation absorption in the optical-breakdown plasma in a supersonic air stream. The experimental facility and procedures of the absorption coefficient measurement in plasma are described. Experimental dependencies of the radiation absorption have been obtained within the wide range of the gasdynamic parameters of the supersonic air stream (velocity, static pressure, density, Mach number). The results are helpful to choose the working modes of the wind tunnel to choose the influence of the energy supply into the supersonic stream on the sonic boom formation and its level.

The possibility of improving the efficiency of cryogenic forcing on the parameters of the hanging shock determining the length of the region of minimization of the sonic boom (middle zone) generated by a modified power-law body is studied. The effect of distributed injection of the coolant from the body surface on the formation of a perturbed flow near the body and at large distances from the body is considered. The scheme of distributed injection and the regime of coolant exhaustion are demonstrated to exert a significant effect on the length of the middle zone of the sonic boom. A scheme of cryogenic forcing is determined, which ensures reduction of bow shock wave intensity by more than 40% at distances corresponding to 7000 body diameters. The mechanism of cryogenic forcing on the flow structure near the body is discussed.

Results of tests of the technology for preventing deposit formation through periodic pneumoimpulsive actions, which was developed at the Institute of Engineering and Applied Mechanics, Siberian Division, Russian Academy of Sciences (Novosibirsk), are presented. Based on an analysis of the causes of the appearance of solid formations on the inner surface of pipelines ( d = 80 mm) of the system for the pneumatic transport of alumina on the electrolytic tanks of OAO RUSAL Sayanogorsk, the test object, modes of the pneumoimpulsive treatment, and methods that it uses to monitor effectiveness are established. On the basis of results of laboratory and full-scale investigations, the flowchart of the cleaning system, including 12 points of action from which the pneumatic treatment are performed with the use of the PG-1/100 portable compact pneumogenerator, is determined, and the level of the initial pressure of the compressed air (4–5 MPa) in them, which provides effective action without breakdowns in the process of the mainline production, is selected. Tests lasting over 2.5 months showed that the pneumatic treatment on the experimental part of the pneumatic pipeline allowed us to enhance the alumina feed capacity by 30% over the similar untreated part.

The possibility of controlling the sonic boom level by means of cooling the surface of a flying vehicle is discussed. The effect of surface cooling on the formation of the perturbed flow structure at large distances from the vehicle is demonstrated by an example of a modified power-law body of revolution. The intensity of the intermediate shock wave and the perturbed pressure pulse near the body are seen to decrease, which expands the altitude range of the region where the sonic boom is reduced (down to 50%). At larger distances from the body, cryogenic forcing ensures a 12% decrease in the bow shock wave intensity. The possibility of controlling the process of formation of wave structures near the surface, such as barrel shock waves, is demonstrated. An explanation of the cryogenic forcing mechanism is offered.

Results of numerical investigations of the influence of lift redistribution along the length of the airframe of an airplane arrangement on the parameters of the acoustic shock produced by this arrangement and its aerodynamic characteristics are presented. The airplane arrangements investigated were constructed by disposition of wings in tandem at definite values of the aerodynamic lift and the lifting-surface area. The gasdynamic parameters of the flow near an arrangement were calculated by the numerical scheme based on the integral Euler equations, and the disturbed-pressure distribution at a large distance from the arrangement was determined using the quasi-linear theory. It is shown that the acoustic-shock level is substantially decreased in the case where there arises a middle-zone effect and an excess-pressure profile with an N-like shape. The arrangement of a supersonic airplane of weight 40 t making a cruise at a height H = 18 km and a Mach number M ∞ = 2.0, which makes it possible to decrease the acoustic shock produced by this airplane with no decrease in its lift-drag ratio, was determined.

The structure and principle of operation of a new wind tunnel AT-303 with adiabatic compression are described. Results of systematic investigations are presented in terms of velocity distributions both at the nozzle exit and in the region where the models are located. The velocity fields are obtained with the use of total pressure probes in the ranges of Mach numbers from 7.6 to 19.7 and Reynolds numbers per meter Re 1 = (0.25−3.64)·10 7 .

Results on a hyperboloid-flare model tested in a new hypersonic wind tunnel with adiabatic compression AT-303 based at ITAM SB RAS at M ∞ = 10 and 15 and in a wide range of Reynolds numbers are presented. Pressure and heat-flux distributions along the model are compared with data obtained previously in various European hypersonic wind tunnels (Longshot — Belgium, HEG — Germany) and with results of numerical computations. Pressure and heat-flux coefficients measured in the attached flow region are demonstrated to be in good qualitative agreement. Reasons for the differences in results measured in regions of flow separation and reattachment are discussed. Significant viscous effects on characteristics of the flow around the model are demonstrated; a particularly strong effect is exerted on the heat-flux distribution. This fact confirms that it is important to model real Reynolds numbers in wind-tunnel testing of aerospace plane models.

The efflux of an axially symmetrical ideal-gas jet generated by a pulsed-gas generator has been mathematically simulated. The structure and parameters of nonstationary gas jets have been determined. The influence of the geometric parameters of a pulsed-gas generator and the initial pressure in its accumulation reservoir on the characteristics of the jet, determining the efficiency of its action on an obstacle, has been investigated. The calculation data were compared with the corresponding experimental data.

: During 30 years in the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences different pneumatic devices were developed and used for aerospace industry. These devices can produce an air flow with desired level of parameters within a small time lag (less than 0.1 seconds). The short creation time greatly reduces the complexity and cost of the device and allows one to reach extreme parameters of the flow, which are impossible to obtain in similar devices of the stationary action. For example, in pulsed mode it is very easy to get an air flow rate equal to tens and even hundreds of kilograms per second, what is possible only by means of ultra big power compressor installations.