Vadim A. Lebiga , Vitaly N. Zinovyev , Aleksey Yu. Pak , Aleksandr I. Ivanov , Anton R. Gorbushin
DOI Number XXX-YYY-ZZZ
Conference Number HiSST 2018-1158
The results of measurements of background fluctuations in various high-speed wind tunnels are presented. It is shown that the hot-wire method allows not only obtaining information on the total level of fluctuations of mass flow and the total temperature, but also determining the types of flow fluctuations (turbulence, acoustics, temperature inhomogeneity) and their contribution to the total intensity. While turbulent fluctuations and temperature inhomogeneities are carried by the flow velocity, acoustic disturbances can propagate at any direction, which can be determined with the help of the hot-wire anemometry method. It makes possible to identify sources of fluctuations, and therefore, if necessary, to control them purposefully. The characteristics of fluctuations in high-speed wind tunnels of various research centers were measured – TsAGI, ITAM SB RAS, ETW (Cologne, Germany), TWT (ASTRC NCKU, Taiwan). The fluctuation diagrams were obtained, representing the dependence of normalized output signal of the hot-wire anemometer on the probe overheating, and the signal spectra, which made it possible to determine the mode and spectral composition of the fluctuations. It is shown that in blow-down wind tunnels the most significant are the acoustic disturbances generated in the test section itself, while in wind tunnels with closed circuit the temperature inhomogeneities can be dominating, especially in cryogenic wind tunnels, and also in the absence of heat exchangers or its ineffectiveness.