N O T I C E

THIS DOCUMENT HAS BEEN REPRODUCED FROM MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT

CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED IN THE INTEREST OF MAKING AVAILABLE AS MUCH

INFORMATION AS POSSIBLE

https://ntrs.nasa.gov/search.jsp?R=19800006585 2018-06-27T10:17:49+00:00Z

NASA Technical Memorandum 81,377

ACOUSTIC CONSIDERATIONS OF FLIGHT

EFFECTS ON JET NOISE SUPPRESSOR NOZZLES

(NASA-TM-81377) ACOUSTIC CONS IDERATIGNS OFFLIGHT EFFECTS ON JET NOISE SUPPRESSORNOZZLES (NASA) 26 p HC A03ZMF A01 CSCL 20A

U. von GlahnLewis Research CenterCleveland, Ohio

N80-14843

UnclasG3/71 46442

1

/^^ zGl^;j^ ^'4)

Prepared for the ^^^^6Z^^

lZ^^4Eighteenth Aerospace Sciences Meetingsponsored by the American Institute of Aeronautics and AstronauticsPasadena, California, January 14-16, 1980

piY

AIAA Paper No, 80-0164ACOUSTIC CONi,?DERATIONS OF FLIGHT EFFECTS

ON JET NOISE SUPPRESSOR NOZZLES

U, von Glohn

National Aeronautics and Space AdministrationLewis Research CenterCleveland, Ohio 44135

NCoN

w

Abstract

Insight into the inflight acoustic charncteris-tics of high-velocity jet noise suppressor nozzlesfor supersonic cri,ise aircraft (SCA) is provided,Although the suppression of jet noise over the en-tire range of directivity angles is of interest,the suppression of the peak noise level in the rearquadrant is frequently of the most interest. Con-sequently, the paper is directed primarily to theinflight effects at the peak noise level. Both sin-gle and inverted-velocity-profile multistream sup-pressor nozzles are considered. The importance ofstatic spectral shape on the noise reduction due toinflight effects is stressed.

Introduction

In order for supersonic cruise aircraft tomeet at least the FAR -36 (1969) noise rule, the useof variable cycle engines (VCE) utilizing coannularinverted-velocity-profile nozzles or low bypass(two stream) engines with suppressor nozzles havebeen advocated in recent years, With the introduc-tion of the FAR -36 (1977) noise goals, and evenmore stringent noise goals proposed for the future,all practical current engine cycles being consideredwill require jet noise suppressor nozzles.

In order to assess the impact of supersoniccruise aircraft jet noise on the community, the ef-fect of flight on the jet exhaust noise must bo as-sessed and be predictable. While it is well knownthat jet noise associated with conical nozzles isreduced by flight speed, conflicting acoustic re-sults have been obtained with suppressor nozzles.Indeed, for the most part, Little reduction in sup-pressor nozzle jet noise with flight speed has beenobtained.

Measured inflight jet noise data have beenpublished in the open literature for only a limitednumber of nozzle configurations. These latter in-clude conical, 8-lobed, and 104-tube nozzlen.1,2

A much larger data base of simulated flighteffects on both unsuppress6d and suppressed nozzleconfigurations has been compiled at model scale.Most of these data have been generated as part ofthe comprehensive FAA/DOT program with the GeneralElectric Company. This program concentrated on highvelocity jet noise source location and reduction(DOT-OS- 30034) using a free jet as a flight simula-tion facility. The author is grateful for the co-operation of the cognizant contract officers at FAA(Mr. R. S. Zuckerman) and GE (Mr. V. L. Reed) inreleasing some of the data for inclusion herein.Finally, simulated flight acoustic data obtainedwith engines as well as scale-model nozzles in theNASA Ames 40- by 0-foot wind tunnel are containedin the data bank. )4

The purpose of this paper is to provide anasseusment of and an insight into the inflightacoustic performance of a variety of jet noise sup-pressor nozzles. The suppression of jet noise overthe entire range of directivity angles is of gener-al interest (Fig. 1), However, for supersonic air-craft, the jet exhaust noise in the rear quadrantis of particular interest because the rotationangle of the aircraft during takeoff and approachis very high coopared with present subsonic air-craft. Consequently, this paper will consider pri-marily the flight effects at the peak perceivednoise level (PNL) angle associated with suppressornozzle configurations (nominally 0 — 1300).

Photographs of some of the suppressor nozzlesconsidered herein are shown in Figs. 2 and 3.

The model scale acoustic data u-ad in thispaper were scaled up, in the references, to an"engine" nozzle exh oust total area of 2181 cm2(J-79 engine size) and to a sideline distance of732 m. For this study, most of the model scaledata used are for a nominal jet velocity (mixed orsingle stream) of about 701 m/sec, except wherenoted.

Backgroundound

Inflight

Perceived noise level. A comparison of staticand inflight PNL as a function of directivityangle is shown schematically in Fig. 1. The figurerepresents typical inflight effects on jet exhaustnoise for a conical nozzle operating with superson-ic flow. It is apparent that the noise in flightis significantly reduced from the scatic conditionin the rear quadrant, particularly near the peakPNL angle.

Jet noise reduction in flight is a function ofthree factors:

(1) A source alterationf.) A kinematic, effect(3) A dynamic effect

Detailed equations for these terms are given inRef. 5. The static noise level is reduced in:Flight by the summation of these three terms, AtB = 900 , only the source is altered by forwardvelccity. In the forward quadrant, the source termand the combined kinematic and dynamic terms act inopposition to each other. The combined kinematicand dynamic terms can be expressed for a close ap-proximation to the exact values by 40 log(1 - Me cos 0). This simplified expression, de-fined as the moving medium effect, is used hereinfor convenience in later comparison calculations ofinflight effects on suppressor nozzle jet noise.Similarly, the source alteration is simplified, forthe purposes herein, to 50 log (1 - Vo/Vj).

Y

Spectra. The effect of flight on jet noisespectra near the peals PNL angle is shown in Fig. 4,The spectra shown were obtained from infllght stud-ies with a General Dynamics F-106 using a 385.13enginc l o 2 and a Gates - Learjet using a civilianderivative of the ,85 engine. 2 The spectra shown inFig. 4 include conic (baseline) nozzles and two sup-preasor nozzles, an 8-lobe nozzle and a 10/4 tubenozzle. The spectrum for each nozzle shows a do-croaae in SPL level at all frequencies with ilight.The amount of SPL reduction due to flightdepends,in the absence of other noise sources, such as corenoise, on the type of nozzle, magnitude of the jetvelocity, anti flight velocity,

Flight Simulation

The effect of flight on jet noise has been mea-sured in both wind tunnels and free jet facilities.The measured at.oustic data from each of these facil-ities require a correction or transformation whencompared with flight data.

Wind tunnel data. Data obtained in acousticwind tunnels (microphones mounted within the freestream) show PNL or spectral source reductiou;, ofabout equal magnitudeat all angles. These data,however, require both a moving medium correction tothe measured PNL or spectral data and a frequencyshift.4

Free Jet data, Model-scale spectra for a coni-cal nozzle obtained in a free jet flight simulationfacility are shown in Fig. 5 for a static andflight simulation case. The spectra shown are forthe peak PNL angle (0 = 1300).

11c measured flight-simulated jet noise re-quires both the moving medium correction and, be-cause the microphones are located outside the freejet boundaries, a shear layer correction. Po,. thedata reported in Refs. 7 to 10 transformation proce-dures have been developed to achieve these correc-tions. These trans forms tions result in a reductionof the flight simulated spectrum level from the mea-sured SPL values as indicated in Fig. 5, taken fromRef. 6. The transformed flight simulation spectrumthen exhibit similar trends and SPI, magnitudes withforward velocity, relative to the static spectrum,to those observed previously for the inflight spec-tra shown in Fig. 4.

The transformation procedures from Refs. 7 and8 are somewhat similar in concept and yield similarresults. However, the procedure developed for thedata in Refs. 9 and 10 includes a turbulence absorp-tion parameter that is not included in the proce-dures of the other two references. Initially, thisparameter attained a peak value of 6 dB at the high-er model-scale frequencies and was angle dependentthrough an additive procedure. 9 Subsequently, thepeak value was reduced to 3 dB. 10 Presently (unpub-lished NASA contractual work) the peak value of 3 dBhas been retained; however, the variation withdirectivity angle is now a multiplicat.:on factorrather than an additive factor, In Figs. 6 and 7are shown the static measured data ,nd the trans-formed flight simulation spectep with and withoutthe turbulence absorption parameter for a conicalnozzle and a 104 tube suppressor nozzle. 9 The re-moval of the turbulence absorption effect is approxi-mate due to the nature of the procedures; this cor-rection was made prior to the dynamic transforma-

tion. The spectra shown are the for engine size.Considering the flight effects shown in Fig. 4, Citetransformed flight simulation data without the tur-bulence absorption parameter oppear to represent thetrends and magnitude variations with forward veloc-ity such better than with this parameter, particu-larly at the higher frequencies. Consequently, thetransformed spectral data from Refs. 9 and 10 havebeet. adjusted herein by the approximate deletion ofthe turbulence absorption parameter, The betteragreement resulting from deletion of this turbulenceabsorption parameter suggests that the transforma-tion procedures used in Refs, 9 and 10 should be re-examined in order to validate the absolute spectralSPL levels for the flight-simulated data in theabsence of this factor.

Stspressi n: mcchaniama

Static

An excellent discussion in given in Ref. 11 onsuppression mechanisms applicable to suppressor noz-zles under static operation. As stated in Ref. 11,the noise reduction characteriatica of a suppressornozzle are intimately asaocint#:d with a rapid mean-velocity decay of the exhaust plume. This rapidvelocity decay is caused by the breakup of the ex-haust plume into many discrete flow elements by themultfclements of the suppressor nozzle. A schematicsketch of the pertinent aero-acoustic relationshipsof flow region, suppressor nozzle, spectrum, and ex-haust plume velocity decay is shown in Fig. 8. Theexhaust plume consists of two major flow regimes,the premerged and the merged flow regions. The pre-merged flow region is that portion of the plumedirectly downstream of the nozzle exhaust planewhere the flow issuing from a multiclement suppres-sor nozzle consists of distinctly individual streams.The merged flow region, farther downstream of thenozzle exhaust plane, is that portion of the plumewhere the flow from the individual nozzle elementshas merged into a single large stream similar tothat for a conical nozzle. The usual suppressornozzle (spoke, chute, tube, etc.) spectrum in theliterature has a Bactrian (two frump) spectral shapecompared with the Dromedarian (one-hump) spectralshape of a conical nozzle spectrum. The low fre-quency portion of the spectrum, as shown in Fig, 8,is associated with the downstream merged flow re-gion. The high frequency portion of the spectrum isassociated with the individual jel. streams createdby the suppressor elemental nozzles in the pre-merged flow region. The relative peak level betweenthese two flow regions is a function of the suppres-sor nozzle design.

The plume velocity decay shown in Fig. 8 isalso related to the flew regions. in the premergedflow region, the local jet velocity is maintainedat or near the jet exhaust velocity. In the mergedflow region, the plume velocity has decayed to amuch lower average velocity, generally of the orderof 50 to 75 percent of the initial jet exhaustvelocity, depending on the suppressor nozzle design.

The rapid plume velocity decay for suppressornozzles suggests that the noise producing eddies inthe plume are convected downstream at much lowervelocities than in a conical nozzle case. 11 Thisshould result in the best noise reduction beingachieved by suppressor nozzles that produce the mostrapid plume decay and, hence, lowest convection

velocities. Tito nozzle design factors that promotestatic noise reduction include both larger numbersof suppressor elements and discrete element arearatio in order to promote more rapid plum y velocitydecay. Finally, It is concluded in Rof. 11 thatmuLtiolement suppressors do not reduce the turbu-lent mixing noise but instead redistribute it tohigher frequencies. At these higher frequenciesatmospheric attenuat'nn can reduce thin effectthereby lowering tb ,- o, Ise transmitted from thesource to the obanrver. The convective amplifica-tion is reduced with multielement suppressor nozzlesbecause of the reduction in the plume velocities;however, this is offset to some extent by a loss influid shielding, Although not pertinent to thisstudy, which concentrates on the peak PNL angle,suppressor nozzles also reduce forward quadrantshack noise compared with that for conical nozzles.Here, the small discrete nozzles of a suppressornozzle cause the shock cell spacing and cross sec-tions to be smaller and possibly fewer in nmubor,resulting in lower noise production at higher fre-quencies.11

Flight

When flight effects (forward velocity) on multi-element suppressor nozzle noise are considered, thestatic spectrum and plume velocity decay curves arealtered as shown schematically in Figs. 9(a) and (b),respectively. The largest inflight noise reductionoccurs in the merged flow region (low frequencies,downstream portion of plume), Tito SPL levels de-crease vith increasing forward velocity. At thesame came, the velocity at a given axial distancefrom the nozzl exhaust plane, X/Dn, increases withforward speed, 2 These differences in SPL reduc-tion for the two flow regions will be discussed laterherein. For a rigorous analysis of the flight ef-fects on the jet noise spectrum, information on theplume velocity decay must be related to the frequen-cy content of the spectrum, Through multiple side-line measurements 13 or other techniques (such asacoustic mirrors 2 ) the necessary spectral Informa-tion can be obtained, An example of this type ofinformation is shown in Fig. 9(c) in which theStrouhal number, given by fDo/Vj - Vo is plottedas a function of noise source location, X/Dc, Thecurve represents typical information for a super-sonic jet exhaust velocity. 14 Finally, the relationof the spectral frequency to the local plume veloc-ity is shown in Fig. 9(d). From this latter informa-tion and appropriate source alteration calculationprocedures, analogous to those discussed in Ref. 5,the flight effects on the local spectral SPL's canbe obtained.

Measured Spectral Flight Effects

The flight effects on the jet noise at 9 = 900and 1300 (approx.peak PNL angle) for several model-scale suppressor nozzles are examined. The nozzlesare divided into two categories, single struam anddual stream.

900 nirectivity Angle

Single stream nozzles. The spectra for twosingle etream nozzles are shown in Fig. 10. In gen-eral, reductions in SPL are obtained in flight inthe merged flow region of the spectra. This flow

region for the nozzle size herein contain frequen-cies generally leas titan 630 Hz, The amount ofauppreaaion due to flight effects in the mergedflow region vt.rlen with the particular nuppreunordesign; the b.gheat suppression being ossociatedwith the largest plume velocity decay. 11 Tile highfrequency is little affected by forward velocity,From this it in apparent that the source alterationdue to flight effects is obtained only, or at leastmainly in the merged flow region of the jet; thatis, at low frequencies for the engine size used inthis paper. in the premerged flow region, the pump-ing action of the individual nozzle streams inducesan outside airflow around each of the multielementflows. Thin induced airflow constitutes a pseudoforward velocity effect on the individual elementstreams which is included in the static SPL mea-aurementa, Consequently, in the flight cone nofurther noise reduction is afforded by forwardvelocity at normal takeoff or landing npeedn.

Dual stream nozzles, The spectra for severaldual scream suppressor nozzles are shown in Figs. 11and 12. The suppressor nozzles for which the dataare shown in Fig, 11 consisted of coannular invertedvelocity-profile nozzles (higher ,jet velocity inouter stream than that in inner stream) with outerstream suppressors. The spectra, taken fromRef. 10, as in the case of the single stream sup-pressor nozzles show little noise reduction itt thepremerged flow region. In the merged flow region,significant SPL reductions are obtained. Fromthese data it is evident that the source alterationdue to flight is again confined primarily to themerged flow region.

The flight effects on the spectrum of a 54-element coplanar mixer nozzle are shown in Fig. 12.In this nozzle design, the core and fan streamsefflux from alternating adjacent nozzle elements.it is evident from the spectra that a source altera-tion is achieved over the entire frequency range;that is, over both premerged and merged flow re-gions. The SPL reductions due to flight effects issubstantially similar in trend to that for a coni-cal nozzle.

1300 Directivity Angle

Single stream nozzles. The effect of flighton suppressor nozzles is shown in rig. 13 for thepeak PNL angle (0 = 1300), in all cases, themerged flow region (f < 630 11z) shows much largerSPL suppressions than those at 0 = 90 0 , This re-sults from a combined source alteration and themoving medium effects, In addition, the premergedflow region also indicates suppressed SPL values.These SPL suppressions in the permerged flow region(Fig, 8) are due to the moving medium term (approxi-mated herein by 40 log (1 - Mo cos 0)), and amountto from 2.5 to 3.5 dB for Vo values of 84 and110 m/s, respectively. Actually the moving mediumeffects, which depend on source convection velocityshould differ somewhat for the merged and premergedregions. The variation in SPL suppression in themerged flow region and its signt.riconcL on PNLwill be discussed in more detail later herein,

Dual stream nozzles. The flight effects onthe spectra at 0 = 1300 for two dual stream multi-element suppressor nozzles are shown in Fig. 14.In general, the flight effects are similar to thosenoted for the single-stream nozzles.

The flight effects on a multiclement coplanarmixer nozzle are shown in Fig. 15. As in the caseof 0 M 900 , the flight effects suppress the entirespectrum, with substantially, equal SPL reductionsat all frequencies. Th.s indicates that a sourcealteration occurs over the entire spectrum togetherwith reductions due to the moving medium tffeet.It should be noted that the SPL reductOns due toforward velocity with this nozzle ex%:ccd those fora conical nozzle with the some maximum exhaustvelocity (790 m/s), The larger SPL suppression isattributed to the mixing between the adjacent high/low flow nozzle elements enhanced by interactionwith the flight velocity.

Morged-Flow Noise Source Alteration Due to Flight

The noise source alteration due to flight inthe merged flow region can be obtained from Ref. 5and can be approximated closely for the present pur-poses by 50 log (1 - Vo/Vc) where Vc is the localconterline or mean ,jet velocity in the plume in themerged flow region (Fig. 9(b)) instead of Vj, 1romthis equation the average or local velocities in themerged flow region can be estimated from Ose spec-tral data. For the nozzles herein, the followingaverage merged flow velocities booed on the spectralstatic-to-flight differences at 0 = 900 were cal-culated according to the preceding equation;

gtommary of Flight Effects on Suppressor

Nozzle Noise at Peak PNL Angle

The flight effects on the ,let spectrum at thepeak PNL angle can b2 summar£zod as follows;

1. The local SPL values with muitielem2nt sup-preasor nozzles are reduced inflight over the entirefrequency spectrum, but more so in the downstreammerged flow region than in the premerged flow re-gion, In the case of a multiclement mixer nozzle,the local SPL vp l.ues in flight are lowered nearlyequally at all frequencies.

2. With multiclement suppressor nozzles, theSPL in the premorged flow region is reduced inflight only by the moving medium effects with nosource alteration (reduction). The SPL in themerged flow region, however, is reduced inflight byboth a source alteration and the moving medium ef-fect.

3. An increase in ,jet velocity, either Vi fora single-stream suppressor nozzle or VJo for adual-stream suppressor nozzle (coannular IVP typenozzle with outer stream suppressor), increases themerged flow SPL relative to that for the premergedflow region. (Not zhown hereinl0.)

Refer- Nozzle Type Calculated merged Vc/V ,j Vc/Vjo Vc/Vmonce flow region aver-

age velocity,

Vc^,M76s

9 104-tube Single flow 479 0.66 ---- ----

9 32-chute Single flow 362 .52 ---- ----

10 40-shollow chute Dual flow 523 ---- 0.67 0,75

10 36-chute Dual flow 345 ---- .44 .4910 54-element mixer Dual flow 476 ---- .60 .68

The preceding calculated ,jet velocities andvelocity ratios are of the same order as might beexpected from plume velocity decay data given inRefs. 11, 12, and 15 for similar nozzle configura-tions and flow conditions. It follows from thisexercise, that the reverse procedure can be used tocalculate the 6SPLs when the plume velocity decayinformation for the merged flow region is available.

The moving medium effect becomes zero or0 = 900 for both the merged and premerged flow re-gions and, as discussed previously, only the sourceterm, SPLs, in the merged flow region is altered byforward velocity. For the suppressor nozzles here-in, except for the 54 element coplanar mixer nozzle,`he sum of the ISPLp at 0 = 900 (Figs. 10 and 11)and the tISPLM at ach frequency in the mergedflow region when hobtracted from the SPLSTAT at0 = 1300 should yield the SPLFLT at 0 = 1300.The validity of this procedure is shown in Figs. 16and 17, Except for the 36-chute nozzle (Fig, 17(b))agreement between the "calculated" and measured SPLSPL values at 0 = 130 0 in the merged flow regionis good.

4. Wi:.n a coannular IVP suppressor nozzle de-creasing the inner flow velocity, Vji , with constantouter flow velocity, Vyo, causes an increase insource alteration in flight. (Not shown herein, un-published NASA data.)

5. Increasing the inflow velocity between theindividual jet streams in the premerged flow regionof a suppressor, as with the 54-element coplanarmixer nozzle, causes large static source altera-tions and consequent significant noise reductions;that are maintained or even amplified in flight.

Effect of Spectral Shape on PNL

The measured data in the preceding section ofthis paper have shown that for suppressor nozzlesinflight source alteration occurs only for themerged flow region. Note that this conclusion doesnot apply to the 54 element coplanar mixer nozzle.Consequently, the effect of changing the magnitudeof the merged flow SPL source alteration on thePNL is now further examined.

In order to assess the effect of suppressingthe SPL's in the merged flow region on the totalpeal, PNL, three static spectra representative oftypical suppressor nozzles were examined. These

Y

spectra, shown in Fig. 18, are lsbele:l A, B, and C.Spectrum A represents nozzles having significantly

higher static SPL values In the merged flow re-gion than in the premerged flow region. For theselected spectrum, the peak SPL level in themerged flow region was 8 dB higher than that in thepremerged region. Spectrum B represents suppressornozzles having equal peak SPL values in themarged and premerged flow regions, Finally, open-trum C represents suppressor nozzles having a 5 dBlower peak SPL value in the merged flow regionthan that in the premerged flow region. The aboo-lute SPL levels for the three spectra are of thesome order of magnitude as those shown in Refs. 9and 10 and are based on a total nozzle exhaust areaof 2181 cm2 , a jet exhaust velocity of 701 m/B andfor a sideline distance of 732 m.

Peak PNL Angle, 0 a 1300.

;he flight spectra for the three represontativestatic spectra are shown in Fig. 19. As discussedpreviously, the flight effects on the SPL at thepeak PNL angle reduce the static values by botha source alteration and a moving medium effect, InFig, 19, the static data are reduced by a movingmedium effect of -3.5 dB (due to a forward velocityof 122 m/s) and arbitrary merged flow region sourcealterations of -5 and -10 dB. Thus, summing t4PLsand 6SP1%, total suppressions of -8.5 and -13,5 dBare obtained in the merged flow region, In the pre-merged flow region, the flight effect consists onlyof the moving medium effect which, in flight, re-duces the static SPL by -3.5 dB. in all casesthis latter flight effee,ts suppression was calcu-lated by 40 log (1 - Me cos 0).

The inflight PNL reductions are summarized inthe following table:

Spectralshape

APNL due to flight effects, PNdB

Merged flow -5 -10region laSPLB,

dB

A-5.4 -6.8

B -4.9 -5.9C

11 -4.4 1 -5.0

of the total .6PNL listed in the preceding table,-3.5 dB was contributed by the moving medium effectwhich applied at all frequencies. The contributionof the merged flow region source alteration is as-sessed by 6PNL - WNLM in the following table:

Spectralshape

APNL - WNIM, PNdB

Merged flow -5 -10region OSPL.,

dB

A -1.9 -3.3B -1.4 -2.4C -.9 -1.5

The spectral shape for most suppressor nozzles atthe peak PNL are represented by the A-shape of

Fig. 19, with the 4SPL peaks for the two flow re-gions, varying from 3 to 10 dB. Thus, at the peakPNL angle, the merged flow region source altera-tion due to flight influences the PNL suppressionby about 1/2 to an equal amount (in dB) of the sup-

ro

proosion due to thAUng me-dium Y effects for theassumed conditions of V' - 701 m/a andVo n 122 m/s.

If the turbulence absorption Plactor had beenretained, the SPL levels in Figs. 10 to 15 would beincreased, by at least 3 dB in the higher frequencyrange. Thin would emphasize the fact that the pro-merged flow region is the dominant noise source,When the PNL is calculated for a particular noz-zlo, the noise weighting factors maximize in thefrequency range associated with the premerged flowregion, A change in engine-neele nozzle size wou'dnot significantly alter hoe fact that the premergedflow region generally .onBtitutes the dominantnoise source for sideline PNL considerations.

in the following two sections, the flight ef-fects on the PNL at 0 - 90 0 and in the fu wardquadrant, 0 o 500 , are briefly considered,

900 Directivity Angle

As previously shown in FigB. 10 and 11 at0 = 900 only the morged flow region has a sourcealteration due to forward velocity, Also, at thisangle the moving medium effect, MIM, is zero. InFig. 20, are nhown the name three static spectralshapes that were used to examine the effect of for-ward velocity on the spectra and PNL at 0 - 1300.Also shown are the spectral shape variations formerged flow source alterations of -5 and -10 dB,The inflight PNL reductions caused by thesesource alterations are the Boma an those listed inthe preceding table in which the 6PNL - MNLM isgiven. From these calculations it is obvious thatlarge source alterations (LISPLB ) in the merged flowregion do impact the PNL for a nozzle significant-ly. For the suppressor nozzles shown in Figs, 2and 3, the impact of 45PLB on the PNL for thesenozzles amounts tQ less than 2 PNdB and, in mostcases, more like 1 PNdB, For 0 - 900 , spectralshape A is representative of the acoustic resultsobtained from a suppressor nozzle such no the 104-tube suppressor nozzle (Fig. 2(a)) while spectralshapes B and C represent those shown in Figs. 2(b)and 3(a) and (b) .

Forward Quadrant, 0 = 500

In the forward quadrant, the moving medii,m ef-fect increase; the local SPL, hence the cNL, com-pared to the static value. At the same time, thesource alteration decreases the local SPL and,hence, the PNL. In Fig. 21 are shown the somethree static spectral shapes used previously for0 = 900 and 1300. At e = 500 with forward veloc-ity, the moving medium effect, ZISPIM increases thestatic SPL by +3.5 dB (Vo = 122 m/s) over the en-tire spectra. Source alterations due to forwardvelocity of -5 and -10 dB are then applied to theSPLSTAT + &SPLM in the merged flow region, result-ing in the inflight spectral shapes shown in Fig 21.The PNL variations caused by these inflight ef-fects on the spectra are summarized in the follow-ing table:

Y

Spectralshape

<'`XNL due to flight effects, PNdA

Merged flow -5 -10region ^SPLs,

dD

A •^ +1.6 +0.1B +2.0 +1.1C I

1 +2.7 1 +2.2

It is apparent from thin table that the movingmodium effect dominates the flight effects, evenwith a source alteration of -10 dB in the mergedflow region.

At 0 - 500 , opectrol shapeA is representa-tive of a suppressor nozzle such an the 104 tub.nozzle (Fig. 2(a)) while spectral shapes D and Care representative of suppressor nozzles ouch asshown in Figs. 2(b) and 3(a) and (b),

Considerations for Future Suppressor

Nozzle Designs

On the basis of the data and acouatie trendsshown by the suppreasor nozzles included herein, anumber of possibilities appear feasible for improv-ing the noise reduction effectiveness of suppressornozzles for supersonic cruise aircraft.

The 54-clement coplanar mixer nozzle acousticresults suggest that if the naturally induced flowbetween suppressor nozzle elementu produced by thepumping action of the individual nozzle streams isaugmented or replaced by forced flow, the premergedflow region at the peak PNL angle (as well asother directivity angles) will respond to flight ef-fects. This noise source then will be reduced in amanner similar to that for the merged flow regionnoisy source. In addition, because the mixed localjet velocity is less than the peax jet velocity, theflight effects will be increased over that with aconical nozzle. The flow between these jets perhapscould be implemented for a turbojet engine by pro-viding long external airflow channels upstream ofthe nozzle exhaust plan- or providing better pumpingaction by introducing compressor bleed iir into theregion between the jets, thereby promotingmorerapid mixing of the multielement jets with the sur-rounding air. For a low-bypass engine, the fan flowcould be exhausted between the core engine multi-element nozzles and jets. For the VCG-IVP nozzles,a portion of the inner stream (fan flow) could bechanneled to provide the required mixing with theouter stream in a modified mixer-type suppressornozzle.

The 54-clement coplanar mixer nozzle meets mostof the preceding needs for good suppressor nozzledesign; however, it does have some shortcomings inperformance. In particular, the peak static PNLis too high relative to that of a conical nozzle.In addition, the peak static suppression occurs ata lower jet velocity than that desired for super-sonic cruise aircraft application. However, thisshortfall perhaps can be surmounted by changes inthe aspect ratio and/or number of the nozzle ele-ments.

A comparison of the spectra for the 54-elementcoplanar mixer nozzle with that for a coannularinverted-velocity-profile suppressor nozzle (36 chute

toazle configuration) is shown in Fig. 22 ford a 900 and 1300 , The data shown are for nearlythe same Via although the Vji are somewhat dif-ferent. Roth inflight sets of data are for a flightvelocity of 110 m/a, At 0 - 90 0 , the static spec-trum for the mixer and chuted suppressor nozzleaare somewhat similar with the mixer nozzle havinghigher SPL values in the 315 to 1250 llz frequencyrange and lower SPL values at frequencies greaterthan 2000 liz range than those for the chuted nozzle.The inflight spectra, however, indicate that theSPL'o for the mixer nozzle are significantly lessfor frequencies over 1000 liz than those for thechuted nozzle. This results in an inflight PNLreduction of 2,8 PNdB for the mixer nozzle com-.3red v"th the 36 -chute nozzle.

A" u P 1300 , the static SPL values for themixer nozzle are cubstnntially higher than thosefir the 36 chute suppressor nozzle over the greaterportion of the spectra, In tormo of PNL, the mixernozzle PNL is 4.4 dB higher than that for thechute suppressor nozzle, However, the inflightspectra for the two nozzles show trends similar tothose noted for 0 o 900. The mixer nozzle PNLis 1.6 dA leas than that for the chute suppressornozzle.

In summary then, future suppressor nozzles foroupersonie cruise aircraft should include the fol-lowing design criteria in order to provide maximumjet noise suppression:

(1) The high frequency regime associated withthe premerged flow region should be provided withan augmented flow between the high velocity nozzizelements. This provision yields a source altera-tion in flight with a consequent noise suppression.

(2) The PNL of the premerged flow region isthe dominant noise source for most practical sup-pressor nozzles; consequently, the level for thisnoise source should be minimized, again within ac-cpetable thrust performance, by suitable design ofthe individual nozzle elements with respect to ele-ment aspect ratio and number.

(3) The axial velocity decay of the jet streamshould be rapid and to as low a velocity an feasi-ble while maintaining a high thrust levee.. Thisprovides a low noise level for the merged flow re-gion (low frequency regime).

Concluding Remarks

The data herein and that in the references,suggest a possible method for estimating the flighteffect on engine-size jet suppressor nozzle noiseon the basis of spectral changes, in the mergedflow region (low frequencies), the static-to-flightsource noise suppression can be estimated by use ofplume velocity decay data and the source alterationmethods of Ref. 5 applied to the spectrum. For thepremerged flow region, no source alteration occursfor conventional suppressor nozzles (spoke, chute,tube, etc.). A moving medium effect applies toboth flow regions. Use of an ejector with acousti-cally treated walls is probably the most effectivemeans to reduce the premerged flow region noiselevels. Such an ejector must be sized and designedfor the supersonic cruise condition, but must alsoperform wall in any subsonic portion of the air-craft mission. In the latter operational mode,

which includes takeoff, an ejector usually is sub-ject to aerodynamic performance penalties. An ojec-tor, with its associated controls, also tends topenalize the aircraft range due to its added weight.Tile offsetting effects of an elector system requirea careful trade-off study in order to ascertain itsoptimum environmental/performance benefits.

For novel suppressor nozzles, such as themultielement coplanar mixer type, the source altera-tion die to flight extends over all the frequencybands. Thus, the source alteration due to flight,

as obtained from Ref. 5 is coupled with the plumevelocity decay over both the merged and premergedflow regions. As in the case of conventional sup-pressor nozzles the moving medi.um effect is appliedto the entire spectrum,

THE

t"

4 directivity angle referred to inlet axis

Subscripts:

c centerlino

D dynamic effect

FL1 flight

j jet

ji inner stream ,let

jo outer stream jet

K kinematic effect

I local

M moving medium effect

M mean

In summary, the effect of flight on the spec- a source

tra of suppressor nozzles of the type using spokes, STAT static

chutes, tubes, etc, an herein can be estimated to afirst order approximation from the following equa-tions: References

(a) Merged flow region

SPLFLT 0

SPISTAT - lSPLM + ASPLs

(b) premerged flow region

SPLFLT ° SPLSTAT - !\SPLM

where

QSPLM n 40 log (1 - Me cos 9)

and

6SPLs A 50 log (1 - Vo/Vc)

More exact SPL variations s-jo to flight ef-fects can be obtained by the use of the more complexrelatiouships involving the_ kinematic, dynamic, andsource alteration given in Ref. 5.

For a multielement coplanar mixer type suppres-sor nozzle it appears that the preceding SPL rela-tionship for the premerged flow region applies overthe entire spectrum. However, further work isneeded to verify this conclusion.

Appendix

Symbols

AR suppressor area ratio; total suppressed noz-zle area, excluding plug, divided by sup-pressed nozzle flow area

Deequivalent diameter

f 1/3-octave band center frequency

Meflight Mach number

PNL perceived noise level, PNdB

SPL 1/3-octave band sound pressure level,dB re 20 u,N/m2

V jet exhaunt velocity

Vo forward or free stream velocity

X axial distance downstream of nozzle exhaustplane

p difference

1. Burley, R, R„ "Flight Velocity Effccta on theJet Noise of Several Variations of a 104-TubeSuppressor Nozzle." NASA TM X-3049, 1974.

2. Clapper, W. S. and Stringas, E. J., "High Veloc-ity Jet Noise Source Location and Reduction,Task IV-Devolopment/Evaluation of Techniquesfor "Inflight" Investigation," General Elce-tric Co., Cincinnati, Ohio, R77AEG189, Feb.1977, (FAA-RD-76-79-4; AD-A041849).

3. Stone, J. R., Miles, J. H., and Sargent, N. B.,"Effects of Forward Velocity on Noise for aJ85 Turbojet Engine with Multi-Tubc Suppressorfrom Wind Tunnel and Flight Tests," NAPA TMX-73542, 1976.

4 Jaeck, C. L., "Static and Wind Tunnel Near-Field/Far-Field Jet Noise Measurements fromModel Scale Single-Flow Baseline and Suppres-sor Nozzl4a, Volume 2 - Forward Speed Effects,"Boeing Commercial Airplane Co., Seattle, Wash.,D6-44121-2-VOL-2, Nov. 1976. NASA OR-137914,

5. Stone, J, R., "An Improved Method for Predictingthe Effects of Flight on Jet Mixing Noise,"NASA TH-79155, 1979.

6. Paekman, A. B,, Ng, K. W., and Patterson, R. W „"Effect of Simulated Forward Flight on SubsonicJet Exhaust Noise," AIAA Paper 75 869, June1975.

7, Ahuja, K, K., Tester, B, J., and Tanna, 11, K.,"The Free Jet as a Simulator of Forward Veloc-ity Effects on Jet Noise," NASA CR-3056, 1978,

8. Amiet, R. K,, "Correction of Open Jet Wind TunnelMeasurements for Shear Layer Refraction," AIAAPaper 75-532, Mar. 1975,

9. Clapper, W. S., Baumgardt, N., Brausch, J. F.,Mani, R,, Stringas, E, J., Vogt, P., andWhitaker, R., "High Velocity Jet Noise SourceLocation and.Reduction," Task III - Experiment-al Investigation of Suppression Principles,Vol. 2 - Parametric Testing and Source Measure-ments," Federal Aviation Administration, Wash-ington, D.C., FAA-RD-76-79, III-II, May 1978.

7

A

Y

10. Clapper, W. S., Daumgardt, N., Drausch, J. F.,Mani, R., Stringao, 1, J., Vogt, P., sndWhitaker, R., "Nigh Velocity Jot Noise SourceLocation and Reduction," Task V - Investiga-tion of 'In-Flight' Acroacoustic Effects onSuppressed C'shausts," Federal Aviation Admin-iatraticu, Washington, D.C., FAA-RD-76 .79, V,July 1978.

11. Giiebe, P. R., "t)iagnootic Evaluation of JetNoise Supprossion Mechanisms," AIAA Paper79-0674, Nor. 1979,

12, von Glahn, 0., Groesbeck, 0. E., andGoodykoontz, J. R., "Velocity Decay and Acous-tic Characteristics of Varioua Nozzle Geome-tries with Forward Velocity," NASA TM R- 68259,1973.

13. Stone, J. R., Goodykoontz, J. 11., andGutierrez, 0. A., "Effects of Geometric andFlow-Field Variables on Inverted-Volocity-Profile Coaxial Jet Noise and Source Diotri-butions," NASA 111-79095, 1979.

14. Moore, M. T., "Flight Effects on the Jet NoiseSignature of a 32-chute Suppressor Nozzle at)Measured in the NASA Amen 40 x88 Foot WindTunnel," General Electric Co., Cincinnati, 011,Jan. 19'). NASA CR-152175,

m

a1a

w

cWVLLJl.tJM

DOMINANT NOISE SOURCES

JET

\ STATIC

^SHOCK^/'"

FLIGHT

PEAK PNL

ANGLE, 8 R 1300

0 90 180

DIRECTIVITY ANGLE, 8, deg

Figure 1, - Comparison of typical stailc PNL with flight PNL asa function of directivity angle, Supersonic jet velocity.

k: /.

r (a) 104-TUBE SUPPRESSOR NOZZLE ON r-106 AIRCRAIt. REF.4.

Figure 2.- Phato ,iraF~s of typical sin,le-stream suppressor.

(b) 32 CHUTE SUPPRESSOR NOZZLE. REF, 10.

Figure 2. - Concluded.

(a) 40-SHAULM GHUTE NUME.

lb) 30-CHUTE NOME.

Figure 1,- PhotNraphs of typical dual-stream suppressor nwles. RFF.10.

I0 54-ELEMENT COPLANAR MIXER NOZZLE.

Figure 3... Concluded.

0

a

C7w

s' .000'

i^

9P 'ldS '13A31 3dnSS3dd aNf io

0

0P4

NH 5Ed

v

p,

u.

0r-r

HCi

U.1wSo®

a

NQN

I

GdU

^y¢

^ NN

<

W. g

re

c.^Nr„^^52

I I

Hn.^ m

m^t7^^

mh

A

a

c w at11w °°'1 Lt^

1

c^

L^ W

1n u (

11

^ a

w i^''rn u

H

a NW o

a^

G

i_ Lw C,!tou w

Oa,

. fC C SO

R3J G

n^

^ VI-.4 VId

U a. NI ^ ^LN - N

L ^ ^

NWQl

V) N N

p II (..^ W II L

N O

1 w

o ,H ^^

CZ H

OP '1dS '13A31 38nsS38d aNnos

Y

u EC Nd h

"^ O 4100

,^ N

O ^NN G `

ppO N O

G

>. C N

w II

0.07

`

UWU-

d>^N+

S

.cu

N a;d VN^^ vut NI h

I:NC'y >

rn in

Oul

u.

8P 'ldS '13A31 3dnss38d GNnos

0

W U

gm in

U w>,v

ce Cd m aO»'

u^ ^00rWw QV)

II

07

s

"IAr Iy x (III' '1.`HE

1.9 POOR

I

C

I. ^• mE

3 ,

^

^-

O ^ ^-/ N O VW QU i

^/ C Cin F,

z

o em l `•g

5 om \ r

_ O N Cc^

O O = ^=U ^N^O %^/

r-I a)p

z ^Co ' gZ>$

tA

¢ ¢ ¢ ¢in

J u^w, E

mit ^ Qo n -

rC14 ^ ;=

1 ' 1

\w 00

N^, EM cu N

O

8P 'ldS '13/131 3dnsS38d ONnos

AXIAL DISTANCE, x/De

0

Cv0W

1.0

f

t

w

CO

CLN

W

W

NNWCL

Za0N

MERGED PREMERGED

FLOW FLQW

FREQUENCY, f, Hz

(a) S P L vs f

PREMERGED FLOW MERGED FLOW

(b) V^/V j vs x/De

Figure 8. - Schematic sketch defining static SPL and jet velocitydecay characteristics for a representative suppressor nozzle.Peak PNL angle,

tm

^ ^ OWr _

U H W Oz>

'^ W ?

w ^+O.4

OA-fAi°t,-7A'OIIVd u10013A 13r

U ^ N

N Z •= ! JLLW o

u-uri^, S2

I>

U -^ wU--

LM ► a^ cLAJ

LUI W o'

OP `1dS

`13A31 38nSS38d GNnOS

°A-IA/'OJ'838WnN I'dROMS

O

^ t

WW

E ON

aio.

.-7

rAi7A`Ohba 00013A IN

dt 4a. a ^. I a .^

Q

J IS POOR

P

qO 0 0 d

a>

13D co W ^ Nm 0.' 6 ^mss

^, q u!O OA ►- Oq ° ^O O im ^;"' 4 00 ^^ 00 6°'p>$ Nr Lw-- 0 N W r- C N C

¢ oho O q w^ _ 00 6 _! f°

4L 8O

r~-r O p N 00 a O A, ^^ 'O0 = 00 °- '-' E cW in L-

0 ._

000 0 O O 8 aLINO q

N O O = ¢if CY ' E

N

O p O O ;= ,^

p Jo w W o Nw u. m O w u.. o »° a^i 6

O p O O z z 1 v00 O 0 ^`' ' a

000 O g ^.% N

^-y^ O O O l_7.J O 0

m 0 m m

O 11.

SP `ids '33A33 Mnmdd nNnos

ta^ C

tom'.,' N •^e > d

o N o^i c

m a^z

rnV1 C aLi

b E

c

NoyL Q1t u^^

G E p Jc

X N CD C^.

U ^ N %^ y> I L Q

0 0

Ln

J .V.. =1XLi` > .

i

CD

0 q § Nu1 E0 0 C-4

m CY)

0 0

0 q LLJ V)

0 0 cr.

W tV N0 q LL.C::a no

14 .2

V-40

0

0 0 q EM

E cu

0 q

0 q z L)

Ln CD C=fN -40 q cr

C3W

0 q LU 1=CD U-

0 0 LLJ LL-0 0

0 q V) w u22j-q0 q 2 00 0)0 11

00=3

I ol

° 7'1 M 0

SP 'IdS '131131 38nsS38d ONnos

9.?D CQviCC] :* 00

CD u` CD -1GO 00 C4 00

mco 00

00 o j 00 wco w 00 000q 00 wi C) LoZEwo -1 - -;jW

0 0 U- = w U- CD LU > I

00 at i>l> o o 0 0cm > ^ ^ clm 0 0 0 0 cli r-I

CD C^ >:V) w

< C7, r-4 0 0 0 0 .- rCy 0 0 O zC) U-1 w

00 0 > Ln U

NLLI C: N

000 0 q

0 0 0z © LL. 0 m0 Lu 0 0 Lu

LLJ )C.D =

LL.J U- S00 0 0 V) d)LLJ LL_ a

0 0 0 0 a EEloo

0 0 0 0 u4 V)

0 0 0 0 V)

< L E

0 q 0 0 C': cjr7 al 0 111 01r-

LL.

9 P 'IdS '13A31 3dnsS38d GNnos

ik

i

FORWARD VELOCITY,

NU^

0 0(STATIC)q 84

00000 0 110

^

O

°°

0 q ° qq OM q q

q 0

q ° °°°000r^q d- MERGED PREMERGEDO

FLOW FLOW q

m

JLl,N

Uj

WNNW

0z0N

(a) 104-TUBE NOZZLE; V j, 732 MIS; REF. 9.

° 00O000008800

0000000(:]

q °°° °0000

q MERGED PREMERGEDI FLOW FLOW q

10 O1

(b)36-CHUTE NOZZLE; AR, 2.5; V j, 732 MIS; REF. 9.

0000O 0000000000000000 00000

O 000p400

O

MERGED PREMERGED O

FLOW FLOW10

850 100 200 500 1000 2000 5000

FREQUENCY, Hz

(c) 32-CHUTE NOZZLE; AR, 21; V j, 701 MIS; REF. 10,

Figure 13. - Static and flight simulation spectra at 0 =1300 for several single-stream nozzles. Nozzle area,2181 cm 2; 732 m sideline distance.

FORWARD VELOCITY,VolMIS

O 0 (STATIC)

q 91

O 110

000000

000000

qq °Oq o

10 MERGED . -x,. PREMERGED° 0FLOW FLOW

a O

NJw q

(a)40-SHALLOW CHUTE NOZZLE; V jo , 780 MIS; V ji , 380Uj

380 MIS.NNWn- 10 0000

1 00 000000

0 00000000000

0 00 080

O

O MERGED PREMERGED 0

FLOW FLOW 0

OO

O

50 100 200 500 1000 2000 5000FREQUENCY, Hz

(b)36-CHUTE NOZZLE; AR, 2.0; V jo , 780 MIS; V Ji , 512MIS.

Figure 14. - Static and flight simulation spectra and 0 t 1300for two coannuiar inverted-velocity-profile nozzles with outerstream suppressors. Nozzle area, 2181 cm 2; 732 m side-line distance; ref. 10.

Y

L,

04

3ECL

C^

Ln

LLJ

VI

0

U:

O

LLJ

LLIOn

FO

0

T

C^-f

SP IdS '13A31 mnsMd ONnos

0 ti C40

0 LL: V)

N

LLIa

p—

Lr%LU

21 i7;-0 —

DLLJ ti Q) a)L)=3C),w Is

E Ea —Ix

=

C,

mc0

*-<^C,C,n0

o

0 q

0 q L;

0 q

m CQJ

0 q0

in0 LAJ

0 q Lu C:)0 q L,

0 q CL M

0 q >:

0 0Ul% LLJM, (D C)

-4 0 0 QXI%i L)E E

0 0 M

0U-

00 0q LU

C) Ln ..a0 q Ui CLJ0 0 V)0 q

Lrl COE

0 qI- rnCM CD r--

0 qJ.

SP 'IdS '13A31 3dnSS3dd GNnOS

r

W

O Q

N

N P <

LLJ

CL WCL Ul

N

^` PO fl- s U'% NTT

SP '1dS '13A31 38nsS38d dNnos

I

m "

g^ p cd^

C C

UUO

O' tL> _pV)

C Os .a

^ H

C dr-^1

^"' C̀71 M

tll ^W^!! p_ E

a0^% 0000

^ ^N

8N Q V O

^^' L Ci v in

=3c iA

aN .

C^

M N

c4%. pf

U QdN u

CD

R cr

^ Ja^

c o c

^ d Nd ^E f°0 0 °c "^

c o a

E n E

U ^

Op~ M Cy r^-1 .L ^I Qrnm Ei^

NNZujuj

L

Q

G..OU

w

CLN

^^ OQ QI r-1 O

CDi 0- 8f\l

NJ O

u

CLV)

O

O

Q

0 U ^5S2I

0^^

gz

:5 N iY ^ U U2 O Z

J fn dppO =

O

U = N O8 CrM LLJ

w

OI

'-+w 00z g

O ^ c

c8 O '`^ ov^

V ^n

O ^

gO

M "'IQS

Q t^IH Oo :°

OP '1dS '13/131 38nsS38d aNnos

Y

ASPL SUPPRESSION DUE TO Vo, dB

0 (STATIC) "'I NCLUDES -3.5 dB

\FROM MOVINGMEDIUM EFFECT

-8.5"'

-13.5' '*+ \ —.

1MERGED PREMERGED

FLOW FLOW

(a) SPECTRA A.

0 (STATIC)

N 10 ^3.5

8.5" ~\

MERGED 0 PREMERGED

f FLOW FLOWz

^oN

(b) SPECTRA B.

10 0 (STATIC)

-8.5^<

-13.5''

^ ^ eMERGED FLOW a ^.. PREMERGED 1

i i I ► i FLOW i

50 100 200 500 1000 2000 5000

FREQUENCY, Hz

(c) SPECTRA C.

Figure 19. - Static and flight spectra for analysis offlight effects on suppressor nozzle noise at peak PNLangle (0 - 1300). Vi , 701 MJS; Vo = 122 MIS; 132 msideline.

v

ASPL VARIATION DUE TO Vo, dB

0 (STATIC)

;0 ^5

^tMERGED ^--► PREMERGEDFLOW ^ FLOW

(a) SPECTRA A.

0 (STATIC)

105

1

^ MERGED PREMERGEDFLOW FLOW

(b) SPECTRA B.

10 00 (STATIC)

7/ MERGED PREMERGEDFLOW FLOW

50 100 200 500 1000 2000 5000

FREQUENCY, Hz

(c) SPECTRA C.

Figure 20. — Static and flight spectra for analysis offlight effects on suppressor nozzle noise at 0 - 900,Vj , 701 MIS; Vo, 122 MIS; 732 m sideline,

Fe

aHci

LU

NWa0.DZOGn

r

10 0 (STATIC)

.-10 to ^^ ...

I^

I'

7W

INCLUDES +3.5 dB FROMMO VI NG MEDIUM EFFECT

ASPL VARIATION DUE TO Vol dB

0 ((STATIC)

+3.5 N\

ocnJaNG's

W

NW

a0z00

MERGED PREMERGEDFLOW FLOW

(a) SPECTRA

X3.5 ~`^

1

rMERGED PREMERGED r

f FLOW FLOW

(a) SPECTRA B,

/ +3.5

0 (STATIC)

MERGED PREMERGED

FLOW FLOW

I/ I I I I 11 L GI50 100 200 500 1000 2000 5000

FREQUENCY, Hz

(c) SPECTRA C.

Figure 21. - Static and flight spectra for analysis of flighteffects on suppressor nozzle noise in forward quadrant(0 4 500). Vj, 701 MIS; Vol 122 MIS; 732 m sideline.

r

II

V"

4 3n ^ pw ^

Il^ I^w

9

CAM

JCI..

ci

e

r+Y

11

CD

u

Ncli 00

LryCl9

C^.

U

w ^a^

tycugQ

q^`i C

N

Ld

SCU N

d

~ X ^

t^

H C].

y: zC p,

V)

Ln

o uO n uCD

.ai^ M

cN Iy

iN

8 N CN Iv►- X

E_,^E

1 wax

aC.)

I

I

m

V,V

miv

rI

OP ''IdS '13/01 38nSS3dd aNnos

SP '1dS '13A31 3anSS38d aNnos

L

1 fda, at N,7 : to rtftloTnt At (yy:^tn tJ3 d fit t ,t°t t rry ,) t„ -NASA-141 !11377

4 t t t ai 1 tt P t t o - - h fit, 11 Pjw

At OUSTIC' CONSID RA`1'ION.8 01' YIX,ll`t I 1 h'I-1'C I'S ON JETNf)I^ I1 1 r 11I^ItT^.tiSQIt N04VI 'S

!t A t, 3e ft li tt , f ,. t'^ r ,r ,.n ^, c A ktra t ^^

1`. voll Malln 11 28

10 A-?), ti t y

i,) f'arh3rrmn;) ( 1 r^.}n,IIattan P;,rmO a 17 d Addrt'S5

National Aeronautics and Space Administration =I+e1ti'is Itet cart'i1 Center

Cleveland,

0 inira t r 6ratat rr

Cleveland, Ohlo 4413-1) -— _ 13 Ty1it rat firt^ .^rt and fait),) tsi.r r t1 q.1? S1xinlor,np A^ ni y Name an,t Attotm + , <q t „:lutical Memoran d um

National Aeronauticta and Space Adminlstratioll — -lA Gpiinsor,ng A^cncy

Watihinl,ton, I), C. 20590

is Stipp 'entary

10 Absty t

Insight Into the Inflil,lit acoustic characteristies of high-velocity jet noise suppressor nozzlesfor Bupersnnle erulne aircraft (SCA) I; provided, Althuugh the suppression of jet nuke overthe entire Lange of directivity tinkles is of Interest, the suppression of the peals noise level inthe rear quadrant is frequently of the most interest, Consequently, the paper Is directed pri-marily to the Inflight effects at the peak noise level, Ruth single and Inve2ted-velocity-profilemultistream suppressor nozzles are considered, The Importance of static spectral shape oft

the noise reduction due to inflikllt effects Is stressed,

17. Key Words (Suggested bV Author(s) )

10. Distribution Statement

Jet 110180 Unclassified - unlimited

STAR Category 71

10. Security Classif. (of this report) 20. Security Classif. (of this page)121. No. of Pages 22, Price'

Unclassified Unclassified$sl,

For 9,110 by the National Technical Information SefvicV, Sllringtield V"011i,1 22161