The instantaneous and average structure of a supersonic underexpanded jet is studied numerically and experimentally. The photos obtained in experiments with different exposure times and the Pitot pressure measurements are compared with the results of the numerical simulation performed using an implicit large-eddy method. We note that the jet flow instability, disturbance growth, and transition to turbulence lead to the situation, in which the instantaneous flow structure can be considerably different from the average structure. The flow pattern observable in the calculations is in good agreement with that presented in the experimental photos obtained with short exposure times. Both calculated and experimental data indicate that an important role in the jet flow dynamics is played by large-scale vortex structures that exist against the background of small-scale turbulence. The calculated and experimental Pitot pressure distributions are similar with each other, up to a certain distance from the nozzle exit section. Further downstream, the experimental and calculated Pitot pressures start to increase rapidly but the calculations predict the onset of this growth at a greater distance from the nozzle than it is observable in the experiments.

This paper presents a method for reconstructing the gas-dynamic parameters of gas flow based on non-contact PIV measurements of the velocity field. The wake flow past a model single rocket nozzle of an emergency escape system in the normal transonic (Mach number is 0.85) flight regime of the manned spacecraft rocket is considered. The flow around the nozzle is numerically simulated using the RANS and LES methods. The results obtained by the proposed reconstruction method are compared with numerical and experimental data.

The article considers the development of a near-wall separation vortex arising at a supersonic flow around the external dihedral corner due to the pressure drop between its faces, in the range of angles of attack α = 0.5°–6°. The processes of the origin and development of separation and secondary vortices at the angle increase are investigated in detail. Particular attention is paid to the flow structure change in the vortex location zone. A clear violation of the flow self-similarity in the front part of the model in the zone of vortex system formation is shown.

A high-velocity flow in an axisymmetric nozzle containing a central body and pylons is studied. The influence of the geometry of the main and additional pylons on the gas-dynamic and thrust characteristics at the nozzle exit in the flow regime with n_pr= 2.25 ( n_pr is the ratio of the pressure in the settling chamber to the ambient pressure) is determined. Azimuthal nonuniformity of the flow at the nozzle exit is detected. The maximum azimuthal nonuniformity is observed in the wake behind the pylons. It is shown that a three-dimensional transonic flow is formed in the nozzle duct with the pylons mounted in the minimum free cross section; local supersonic regions closed by weak shock waves are formed in this flow. It is found that the formation of such a shock wave structure is responsible for nozzle thrust reduction by 12

Using the example of studying the supersonic underexpanded jet initial section, the issue of interpreting the experimental visualization data and Pitot pressure measurement data using the results of numerical calculations (2d RANS k-ω SST) is discussed. It is shown that the gradient S-shaped feature of the gas-dynamic structure near the nozzle exit, observed in the form of a barrel shock, is a characteristic that separates the expansion and compression regions, and downstream is transformed into a barrel shock. It has been established that the reason for the observed S-shaped curvature of this feature is the axisymmetric nature of the jet flow.

The influence of the Pitot probe on total pressure measurements in the near-wall flow in the zone of reattachment of a supersonic separated flow past a compression corner is considered. If the total pressure is measured near the model wall, a local maximum is observed in the region downstream of the reattachment line. This maximum can be either a physical structural element of the separated flow (high-pressure layer in which the total pressure reaches 0.8–0.95 of the free-stream total pressure) or a possible measurement error. The present study reveals the existence of a measured total pressure peak in the boundary layer on a horizontal flat plate and flat wedges. This peak is not associated with the high-pressure flow, but is rather a result of probe interaction with the model wall. The amplitude of this peak is found to depend on the ratio of the probe size and the boundary layer thickness. It is shown that the degree of the probe influence leading to distortion of the measurement results is smaller approximately by an order of magnitude than the maximum value of the measured total pressure in the high-pressure layer in the reattachment zone.

Detailed data on the measurement of the gas-dynamic parameters of the flow in the jet field at a large value of the relative total pressure (Npr = 70) are presented. A significant increase in the measured total pressure in the first cell of a supersonic weakly underexpanded jet has been experimentally revealed. An explanation is given of this effect associated with the mixing process in the region behind the Mach disk of the peripheral high-pressure flow and the axial flow behind the Mach disk. This explanation based on the data of the numerical calculation of the flow. Experimental data can be used to verify the results of numerical calculations.

The concept of the turbulent-boundary layer control on a low-speed airfoil by combined air blowing / suction method through high-technology finely perforated sections, that are parts of the airfoil panel, is verified numerically and experimentally. Extensive studies of the mean flow parameters and turbulence characteristics in the boundary layer, pressure distribution on the airfoil surface, as well as drag and lift are performed. The flow rates coefficients varied in the range 0 − 9.33·10−4 and 0 − 8.48·10−4, respectively. Evaluation of the aerodynamic efficiency of this control method in the ground conditions shows that in the studied range of flow rate coefficients, the lift of the wing can be increased by at least 10%. The mechanism responsible for changing the physical properties of the flow and the aerodynamic characteristics of the airfoil with distributed air suction and blowing of various intensity is discussed. Particular attention is paid to the problems of applying the momentum method for the measurements of profile drag and the need for improvement of this technique in the conditions of suction / blowing on a low-speed airfoil.