CUED Publications database

Large eddy simulation of serration effects on an ultra-high-bypass-ratio engine exhaust jet

Wang, ZN and Tyacke, J and Tucker, P (2018) Large eddy simulation of serration effects on an ultra-high-bypass-ratio engine exhaust jet. Comptes Rendus - Mecanique, 346. pp. 964-977. ISSN 1631-0721

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Abstract

Serrated jet nozzles are considered to be an efficient and practical passive control approach for jet noise. However, some fundamental mechanisms of serration effects on jet noise are not fully understood, especially in terms of the sound source. In this paper, a high-fidelity simulation framework using large-eddy simulation (LES) is demonstrated to predict near-field turbulence and far-field acoustics from an ultra-high-bypass-ratio engine with round and serrated nozzles. Far-field sound is predicted using Ffowcs Willams–Hawkings (FWH) integration. The results show that the serrated nozzle increases mixing near the nozzle and hence the turbulence decay rate, reducing the turbulence level downstream. The serrations shift the energy from the low frequencies to the high frequencies and decrease overall sound pressure levels by about 3 dB over the low-frequency range. Sound sources are analysed based on fourth-order space–time correlations. There are six major source components (R1111, R2222, R3333, R1313, R1212, and R2323) inside the jet shear layers. The serrations are able to reduce the amplitude of these source terms, causing them to decay rapidly to a level below the round nozzle jet within 2D downstream of the nozzle.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div A > Fluid Mechanics
Div A > Turbomachinery
Depositing User: Cron Job
Date Deposited: 31 Aug 2018 20:14
Last Modified: 09 Sep 2021 01:23
DOI: 10.1016/j.crme.2018.07.003