Study on the generation and propagation mechanism of supersonic jet noise in pipeline

Abstract

When the flow velocity in the pipeline reached high speed, especially the supersonic speed, the strong pipeline aerodynamic noise would be formed, which not only adversely affected the fatigue life of the pipeline structure, but also affected the hearing and comfort of people. In this paper, the pressure recovery system was constructed to simulate the flow of air in the pipeline system, and the influence of different pipeline structures on the noise characteristics was studied by combining numerical simulation and experimental research. The results showed that when the inner diameter of the pipe was equal, the supersonic flow phenomenon was obvious in the nozzle and downstream area of the nozzle, while the flow velocity in the pipe was lower than the sound velocity, which would cause strong aerodynamic noise in the nozzle and downstream area of the nozzle. When the non-equal diameter pipe was set at the inlet of the pipe, the aerodynamic noise intensity decreases with the decrease of the pipe inner diameter. Through mechanism analysis, it was found that the velocity and pressure pulsation values of the nozzle and the nozzle core region were much larger than those of other regions, forming a large gradient. At the same time, according to the results of pressure recovery test, the whole pressure recovery process was an unsteady process, regardless of equal diameter pipeline or non-equal diameter pipeline, the pulsating pressure at the monitoring point displayed a step jump transient characteristic with the change of pressure recovery time. In the pressure recovery system, there were many different loud whistlers, but the non-equal diameter pipeline compared with the equal diameter pipeline, this phenomenon was not so obvious, which was very beneficial to the noise reduction of the pipeline system. The conclusions could provide reference for reducing pipeline noise.