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The results of experimental studies on the impact of periodic flow modulation on the development of natural disturbances and artificial localized wave packets in the boundary layer of a swept wing with a leading edge swept angle of 40 degrees at a Mach number M = 2.5 are presented. The boundary layer was modulated using periodic roughness on the model surface. Artificial wave packets were generated by a pulsed glow discharge. Hot-wire anemometer measurements showed that, according to the experimental conditions, periodic modulation of the boundary layer leads to the stabilization of the development of controlled localized disturbances and to an increase in the growth of natural disturbances.

The paper is devoted to an experimental and theoretical study of effect of moderate angle-of-attack variation on disturbances evolution and laminar-turbulent transition in a supersonic boundary layer on swept wing at Mach 2. Monotonous growth of the transition Reynolds numbers with angle of attack increasing from −2° to 2.7° is confirmed. For the same conditions, calculations based on linear stability theory are performed. The experimental and computational results show a favourable comparison.

The evolution of a controlled broadband wave packet in flat-plate and swept-wing supersonic boundary layers was experimentally investigated at Mach number M = 2. The wave packet was introduced into the boundary layer by a localized pulse electrical discharge. The structure and evolution downstream of the wave packet were studied by hot-wire measurements. It was found that the wave packet has a symmetric shape in a flat-plate boundary layer, whereas there is asymmetry in case of a swept-wing one. The spectral analysis of the development of different modes of the wave packet was provided.

The work is devoted to the study of the regularities of laminar-turbulent transition in supersonic boundary layers. New experimental data are presented on the evolution downstream of natural disturbances in the boundary layer of a flat plate. The experiments were carried out in a low-noise supersonic wind tunnel T-325 of ITAM SB RAS at Mach number M=2.5. The measurements were made by a constant-temperature hot-wire anemometer in the scanning mode. The procedure of decomposition of the fluctuations of the boundary layer into temperature and mass flux disturbances is carried out.

The influence of the parameters of the impulse action on the laminar supersonic flat-plate boundary layer on the excited localized perturbations is investigated at Mach 2. The influence of the duration of a pulsed discharge on the generated disturbances is studied experimentally. Also, a direct numerical simulation of the influence of the parameters of pulse injection on generated perturbations is carried out. It is obtained that as the duration of the action on the supersonic boundary layer increases, the amplitude of the generated disturbance increases. The velocity of the propagation downstream of localized disturbances in Mach 2 supersonic flat-plate boundary layer is estimated.

The evolution of the artificial wave packet in laminar flat-plate boundary layer was experimentally studied by hot-wire measurements at M=2. The localized disturbances were generated by pulse glow discharge. The wave analysis of evolution of wave packet was provided. It was found, that the most unstable waves are oblique, that consistent with results of linear theory.

The nonlinear evolution of modulated wave train with large amplitude have been investigated. Strong amplification of two-dimensional disturbances in supersonic boundary layer has been found which cannot be explained within the framework of existing theoretical models and have no analogues in other experiments.

The paper is devoted to an experimental study of natural disturbances evolution and laminar-turbulent transition in a three-dimensional supersonic boundary layer on swept wing at different Mach numbers. Characteristic zones of disturbances evolution are determined. It is found that for Mach numbers 2 and 2.5 measurements were performed in the region of linear stage of disturbances evolution, and the experimental data can be compared with the results of the calculations on linear stability theory. Oscillograms, amplitude-frequency spectra, pulsation profiles and statistical diagrams of natural fluctuations are obtained. Secondary instability of supersonic boundary layer on swept wing is under consideration