Jet-installation noise and near-field characteristics of jet-surface interaction
Open Access
- 25 July 2020
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Fluid Mechanics
Abstract
The link between jet-installation noise and the near-field flow features of the corresponding isolated jet is studied by means of lattice-Boltzmann numerical simulations. The computational set-up consists of a flat plate placed in proximity to a jet, replicating the interaction benchmark study carried out at NASA Glenn. Installation effects cause low-frequency noise increase with respect to the isolated case, mainly occurring in the direction normal to the plate and upstream of the jet's exit plane. It is shown that the Helmholtz number, based on the wavelength of eddies in the mixing layer and their distance to the plate trailing edge, predicts the frequency range where installation noise occurs. Based on the isolated jet near field, scaling laws are also found for the far-field noise produced by different plate geometries. The linear hydrodynamic field of the isolated jet shows an exponential decay of pressure fluctuations in the radial direction; it is shown that the far-field spectrum follows the same trend when moving the plate in this direction. In the axial direction, spectral proper orthogonal decomposition is applied to filter out jet acoustic waves. The resultant hydrodynamic pressure fluctuations display a wavepacket behaviour, which can be fitted with a Gaussian envelope. It is found that installation noise for different plate lengths is proportional to the amplitude of the Gaussian curve at the position of the plate trailing edge. These analyses show that trends of jet-installation noise can be predicted by analysing the near field of the isolated case, reducing the need for extensive parametric investigations.This publication has 44 references indexed in Scilit:
- The near pressure field of co-axial subsonic jetsJournal of Fluid Mechanics, 2008
- Instability waves in a subsonic round jet detected using a near-field phased microphone arrayJournal of Fluid Mechanics, 2006
- An advanced time approach for acoustic analogy predictionsJournal of Sound and Vibration, 2003
- The proper orthogonal decomposition of pressure fluctuations surrounding a turbulent jetJournal of Fluid Mechanics, 1997
- Sound generation in a mixing layerJournal of Fluid Mechanics, 1997
- Shear-layer pressure fluctuations and superdirective acoustic sourcesJournal of Fluid Mechanics, 1990
- Noise generation by a low-Mach-number jetJournal of Fluid Mechanics, 1983
- A review of propeller discrete frequency noise prediction technology with emphasis on two current methods for time domain calculationsJournal of Sound and Vibration, 1980
- Scattering of aerodynamic noise by a semi-infinite compliant plateJournal of Fluid Mechanics, 1970
- Aerodynamic sound generation by turbulent flow in the vicinity of a scattering half planeJournal of Fluid Mechanics, 1970