Features of background acoustic disturbances in high-speed wind tunnels

Based on the hot-wire method for studying the fluctuations of compressible flows, the issues of determining the acoustic characteristics of the flow in the test sections of wind tunnels at transonic and supersonic speeds are considered. It is shown that at supersonic flows, in addition to the Mach waves described by Kovasznay, generated by stationary sources of disturbances on the walls of the test sections, and Mach waves generating the most intense fluctuations, distributed and moving in a supersonic turbulent boundary, described by Laufer, there may be Mach waves, the sources of which is a turbulent boundary layer. Using the hot-wire approach, it is possible to determine the characteristics of each type of these waves and their sources. It is also established that simple sound waves can be both produced by the turbulent boundary layer and those penetrating into the test section from sources located in the prechamber of the wind tunnel through the critical section of the Laval nozzle. In wind tunnels of high subsonic speeds, acoustic disturbances are produced from sound waves identified by intensity, direction and spectral composition using developed methods of thermal anemometry. The characteristics of acoustic disturbances (intensity, direction, location of sources) determined using the hot-wire allow them to be purposefully preserved or reduced, or their influence on phenomena under investigation can be taken into account. The article was prepared based on the materials of the report at the 10th Russian conference “Computational experiment in aeroacoustics and aerodynamics”, September 16–21, 2024, Svetlogorsk, Kaliningrad region, http://ceaa.imamod.ru/.