Study of the Peak Frequency in Turbulent Vortex Ring Noise

Abstract

The aeroacoustic characteristics of vortex rings of different sizes have been studied using multimicrophone methods. The experiment recorded the acoustic emission upon initiation of a vortex ring and its movement along a trajectory. In order to apply the self-similarity theory of vortex motion on the entire trajectory, the formation of a vortex ring was numerically simulated in the starting area during ring initiation from nozzles of different sizes, taking into account the experimentally determined law of piston motion for each initiation. Computations are performed to obtain the geometrical dimensions of the vortices used in the self-similarity theory. Thus, the required vortex ring parameters were found throughout the entire trajectory, which made it possible to compare the characteristic frequency of noise emission from freely flying turbulent vortex rings of different sizes with the theoretical value.