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Jet Surface Interaction Noise in a High Aspect Ratio Rectangular Exhaust
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Author and Affiliation:
Khavaran, Abbas(Science Applications International Corp., Dayton, OH, United States)
Abstract: A physics-based prediction model is employed to simulate jet surface interaction (JSI) noise in a transversely sheared jet exhaust. The methodology finds application in jets with a high aspect ratio (AR) rectangular exhaust in the proximity of a flat surface. Two component spectra are simulated: (i) mixing/scrubbing noise; (ii) trailing edge noise--and are superimposed to obtain the far field exhaust noise on either side of a nearby surface. This document describes the necessary input parameters (including mean flow and turbulence information for the nozzle exhaust of interest) that should be prepared in order to initiate the simulation for each noise component. Sample input/output files in connection with an 8:1 aspect ratio rectangular exhaust at Mach 0.98 near a rigid surface are described. Jet noise spectra are examined below at operating conditions listed in Table IV. Individual noise components, designated as Scrubbing Noise and Trailing Edge Noise, are presented and their sum Total Noise (Analysis) is compared with Measurement (Refs. 8 and 9) at selective number of observer polar angles at azimuth f = 90deg. Results are presented on an arc R = 17.80-ft (i.e., R = 100Deq) on both sides of a nearby surface. Although the predicted TE noise component is symmetric with respect to the edge due to symmetry in the propagator, measurements for the majority of cases are not quite symmetric and exhibit a slightly larger peak on the reflected side of the surface. Turbulent mixing/scrubbing noise component has a greater presence on the reflected side, as expected. Figure 13 to Figure 18 show that the peak in the predicted TE component could differ from measurements by as much as 4 dB due to lack of symmetry in measured data, however, the general trend is in agreement with data across the three Mach numbers. The overall sound pressure level (OASPL) associated with the TE noise component follows a U5 velocity scaling in the current modeling (Ref. 4). Directivity predictions for the TE noise component as well as the total noise are shown in Figure 19 (bottom)-and are compared with measurements (top figure) at conditions of Table IV. As anticipated, the TE noise component (dashed-line) overwhelms the directivity factor due to its dominant spectral peak level. Only at small angles to the jet axis the mixing noise component contributes significant enough to weight noticeably on the total noise.
Publication Date: Jul 01, 2017
Document ID:
20170007294
(Acquired Aug 08, 2017)
Subject Category: AERODYNAMICS; AIRCRAFT DESIGN, TESTING AND PERFORMANCE
Report/Patent Number: E-19385, GRC-E-DAA-TN36367, NASA/CR-2017-219528
Document Type: Technical Report
Contract/Grant/Task Num: NNC12BA01B; WBS 473452.02.03.07.06.01.02
Financial Sponsor: NASA Glenn Research Center; Cleveland, OH United States
Organization Source: NASA Glenn Research Center; Cleveland, OH United States
Description: 38p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution under U.S. Government purpose rights
NASA Terms: AEROACOUSTICS; AERODYNAMIC NOISE; HIGH ASPECT RATIO; JET AIRCRAFT NOISE; JET EXHAUST; MATHEMATICAL MODELS; NOISE SPECTRA; SIMULATION; SURFACE REACTIONS; TRAILING EDGES; TURBULENT MIXING; COMPUTER PROGRAMS; FAR FIELDS; FLAT SURFACES; FORTRAN; JET MIXING FLOW; MACH NUMBER; SOUND PRESSURE
Other Descriptors: NOISE; JET SURFACE INTERACTION NOISE; PROPULSION NOISE
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