Study of the Position of Sound Sources in a Turbulent Jet Using Nozzles of Different Configurations

Abstract

The aim of this work is to study the position of dominant sound sources in a small-scale turbulent jet using the beamforming method. Two nozzles of equivalent diameter and different geometric configurations (conical and chevron) were used to create different initial conditions for the outflow. Based on the analysis of the results obtained, it can be concluded that they are in good agreement with the well-known concepts of the physics of noise generation processes by turbulent jets: higher-frequency sources are generated by smaller-scale turbulent structures located closer to the nozzle edge, which is confirmed by the localization of high-frequency noise sources also closer to the nozzle edge. The chevron nozzles loosen the initial section of the jet, making it less short and thereby facilitating a faster displacement of noise sources to the nozzle edge, as seen when comparing localization maps for conical and chevron nozzles at the same frequencies. The results of localization were compared with the data obtained by other researchers. The results obtained were found to provide confidence in the use of acoustic beamforming to measure the location of the jet noise source with accuracy similar to other methods that have been used in the past.

Localization of Noise Sources in Jets Flowing from Lobed Nozzles

“…The most common direction of work for further reduction of jet noise is to change the design of engine exhaust devices, leading to a change in the conditions of jet outflows and their mixing with the environment. Such methods include slot-shaped (rectangular), chevron, bevelled and lobed nozzles [1][2][3][4][5][6]. The most common are chevron nozzles, which have triangular teeth along the nozzle edge.…”

“…This leads to the fact that the sound sources are distributed inside the jet. A change in the nozzle shape leads to a transformation of the jet flow structure itself and can lead to a change in the distribution of sound sources of a given object [4,8]. This information is especially important for the development of shielding computational models.…”