Record Details

A Model for Jet-Surface Interaction Noise Using Physically Realizable Upstream Turbulence Conditions
NTRS Full-Text: Click to View  [PDF Size: 781 KB]
Author and Affiliation:
Afsar, Mohammed Z.(Imperial Coll. of London, London, United Kingdom);
Leib, Stewart J.(Ohio Aerospace Inst., Cleveland, OH, United States);
Bozak, Richard F.(NASA Glenn Research Center, Cleveland, OH, United States)
Abstract: This paper is a continuation of previous work in which a generalized Rapid Distortion Theory (RDT) formulation was used to model low-frequency trailing-edge noise. The research was motivated by proposed next-generation aircraft configurations where the exhaust system is tightly integrated with the airframe. Data from recent experiments at NASA on the interaction between high-Reynolds-number subsonic jet flows and an external flat plate showed that the power spectral density (PSD) of the far-field pressure underwent considerable amplification at low frequencies. For example, at the 90deg observation angle, the low-frequency noise could be as much as 10 dB greater than the jet noise itself. In this paper, we present predictions of the noise generated by the interaction of a rectangular jet with the trailing edge of a semi-infinite flat plate. The calculations are based on a formula for the acoustic spectrum of this noise source derived from an exact formal solution of the linearized Euler equations involving (in this case) one arbitrary convected scalar quantity and a Rayleigh equation Green's function. A low-frequency asymptotic approximation for the Green's function based on a two-dimensional mean flow is used in the calculations along with a physically realizable upstream turbulence spectrum, which includes a finite decorrelation region. Numerical predictions of the sound field, based on three-dimensional RANS solutions to determine the mean flow, turbulent kinetic energy and turbulence length and time scales, for a range of subsonic acoustic Mach number jets and nozzle aspect ratios are compared with experimental data. Comparisons of the RANS results with flow data are also presented for selected cases. We find that a finite decorrelation region in the turbulence spectrum increases the low-frequency algebraic decay (the low frequency "roll-off") of the acoustic spectrum with angular frequency thereby producing much closer agreement with noise data for Strouhal numbers less than 0.1. Secondly, the large-aspect-ratio theory is able to predict the low-frequency amplification due to the jet-edge interaction reasonably well, even for moderate aspect ratio nozzles. We show also that the noise predictions for smaller aspect ratio jets can be fine-tuned using the appropriate RANS-based mean flow and turbulence properties.
Publication Date: Jan 01, 2016
Document ID:
20160001108
(Acquired Jan 29, 2016)
Subject Category: ACOUSTICS; AERODYNAMICS
Report/Patent Number: NASA/TM-2016-218898, AIAA-2015-2529, E-19152, GRC-E-DAA-TN26439
Document Type: Technical Report
Contract/Grant/Task Num: NNC13BA10B; WBS 110076.02.03.04.01
Financial Sponsor: NASA Glenn Research Center; Cleveland, OH United States
Organization Source: NASA Glenn Research Center; Cleveland, OH United States
Description: 28p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: JET AIRCRAFT NOISE; UPSTREAM; TURBULENCE; TRAILING EDGES; FLAT PLATES; FLOW CHARACTERISTICS; LOW FREQUENCIES; AEROACOUSTICS; AERODYNAMIC NOISE; GREEN'S FUNCTIONS; ACOUSTIC VELOCITY; PREDICTION ANALYSIS TECHNIQUES
Other Descriptors: JET; AIRCRAFT; NOISE
› Back to Top
Facebook icon, External Link to NASA STI page on Facebook Twitter icon, External Link to NASA STI on Twitter YouTube icon, External Link to NASA STI Channel on YouTube RSS icon, External Link to New NASA STI RSS Feed
Find Similar Records
 
NASA Logo, External Link

NASA Official: Gerald Steeman

Sponsored By: NASA Scientific and Technical Information Program

Site Curator: STI Support Services

Last Modified: January 29, 2016

Privacy Policy & Important Notices Disclaimers, Copyright, Terms of Use Freedom of Information Act USA.gov NASA.gov NASA OCIO Free Adobe PDF Reader Free MS Word Viewer