1、I NASACONTRACTOR - REPORT LANDING GEAR AND CAVITY NOISE PREDICTION BOLT BERANEK AND NEWMAN INC. Cambridge, Mass. 02 138 for Langley Research Center NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTPN, D. C. JULY 1976 Provided by IHSNot for ResaleNo reproduction or networking permitted without l
2、icense from IHS-,-,-TECH LIBRARY KAFB, NU 1. Report No. 1 -2. Government Accession No. 4. Title and Subtiile I“ NASA . . CR-2714 . . “ - - i - Landing Gear and Cavity Noise Prediction 7. Author(s) - - . - “ . Donald B. Bliss and Richard E. Hayden - . .“ 1-9. Perii =_ . . “ Sponsoring Agency Name and
3、 Address National Aeronautics E Space Administration - Washington, DC 20546 I 3. Recipients Catalog No. 5. Repon Date July 1976 6. Performing Organization Code 8. Performing Organlzation Report No. 10. Work Unit No. 505-06-23-01 11. Contract or Grant No. L18051A 13. Type of Repon and Period Covered
4、Contractor Report 14. Sponsoring Agency Code I Supplementary Notes . . Langley technical monitor: Jay C. Hardin 6; Abstract .“ .“ . . . . . “ - This paper is concerned wit? prediction of airframe noise radiation from the landing gear and wheel wells of commercial aircraft. Measurements of these comp
5、onents on typical air- craft are presented and potential noise sources identified. Semiempirical expressions for the sound generation by these sources are developed from available experimental data and theoretical analyses. These expressions are employed to estimate the noise radiation from the land
6、ing gear and wheel wells fora typical aircraft and to rank order the component -I(FIWord.ggested by Authoris) Airframe Noise, Component Sources 10. Distribution Statement Unclassified - Unlimited Subject Category 71 - 19. Security Classif. (of this report) 22. Rice 21. NO. of pages 20. Security Clas
7、sif. (of this page) Unclassified $4.25 56 Unclassified * For sale by the National Technical Information Service, Springfield, Virginia 22161 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking pe
8、rmitted without license from IHS-,-,-TABLE OF CONTENTS LIST OF FIGURES AND TABLES . INTRODUCTION . 1 TYPICAL CONFIGURATIONS . 3 NOISE SOURCE IDENTIFICATION 13 Cavity Discrete Pressure Oscillations . 13 Cavity Leading Edge Noise . 13 Cavity Trailing Edge Noise 13 Landing Gear Direct Radiated Noise 14
9、 Cavity and Gear Wake Interactions with the Wing Trailing Edge and Flaps . 14 Landing Gear Wake/Landing Gear Interactions . 14 CAVITY DISCRETE PRESSURE OSCILLATIONS 14 Main Gear Fuselage Cavity . 30 Main Gear Wing Cavity . 30 Nose Gear Cavity 30 CAVITY LEADING EDGE NOISE 32 CAVITY TRAILING EDGE NOIS
10、E . 36 LANDING GEAR DIRECT RADIATED NOISE . 41 CAVITY AND GEAR WAKE INTERACTIONS WITH THE WING TRAILING EDGE AND FLAPS 45 COMPOSITE NOISE PREDICTION . 47 REFERENCES . 51 “ iii . “ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF FIGURES AND TA
11、BLES Figure 1. 2. 3. 3. 4. 5. 6. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. Typical sequence of gear and flap deployment . 2 Example aircraft for landing gear/cavity noise calculations . 4 Boeing 727 main landing gear (continued) . . . 5 Boeing 727 main landing gear (concluded) . 6 Boeing 727 n
12、ose landing gear . 7 McDonnell-Douglas DC-9 landing gear 8 McDonnell-Douglas DC-9 main landing gear (continued) 9 McDonnell-Douglas DC-9 main landing gear (concluded) 10 McDonnell-Douglas DC-9 nose landing gear . 11 Simple rectangular cavity 15 Typical pressure spectrum measured in a rectangular cav
13、ity . 15 Typical oscillation cycle 18 Typical experimental mode shapes and the pseudopiston analogy (data for M = 0.8) 19 Strouhal frequencies of cavity modes as a function of Mach number 21 Comparison of Mach number dependencies of resonant mode levels: leading-edge area . 22 Comparison of Mach num
14、ber dependencies of resonant mode levels: trailing-edge area 23 Typical cavity external radiation pattern in high speed subsonic flow (Mm0.5) . 25 Nondimensional spectrum for the calculation of cavity leading edge noise . 35 Cavity edge noise mechanisms and their approximate directivity 37 Radiated
15、noise from an edge in a free shear layer 38 iV Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF FIGURES AND TABLES (Cont.) Figure 19. 20. 21. 22. 23 24. Table 1. 2. 3. Estimated landing gear cavity edge noise sources for a Boeing 727 . 40 Land
16、ing gear direct radiation sources 43 Spectrum relative to overall level for noise from bluff bodies 44 Landing gear direct radiated noise . 46 Illustration of possible cavity and gear wake impingement on the wing trailing edge and flaps 48 Composite of all sources for the Boeing 727, 73 m/sec (240 f
17、t/sec), 112.8 m (370 ft) altitude . 49 Summary of experimental data (turbulent boundary layer) 28 Cavity geometry for the Boeing 727 aircraft. 29 Vented enclosure frequencies for Boeing 727 landing gear cavities 33 V Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
18、e from IHS-,-,-LANDING GEAR AND CAVITY NOISE PREDICTION By Donald B. Bliss and Richard E. Hayden Bolt Beranek and Newman Inc. INTRODUCTION Airframe (nonpropulsive) noise is presently of concern since it represents a potential barrier to successful implementation of proposed noise regulations on comm
19、ercial aircraft. In particular, the most commonly accepted future noise regulations are thought to be 10 PNdB below Federal Air Regulation 36 (FAR-36). Meeting this so-called FAR 36-10 criterion cannot be achieved by treating propulsion sources alone if airframe noise sources are at or above the FAR
20、 36-10 dB level. Thus, it is important to identify the aircraft components and noise mechanisms responsible for air- frame noise radiation and to attempt to predict the component noise levels. Troublesome airframe noise occurs during the approach phase of flight, when power settings are relatively l
21、ow and the air- craft is in a high lift, high drag configuration by virtue of deployment of flaps, slots, and landing gear and the presence of open cavities. The present work is confined to the effect of landing gear and cavities only. A broader treatment of the pro- blem can be found in Hayden et a
22、Z. (1974 and 1975) and Hardin et aZ. (1975). Since typical glide slopes for CTOL aircraft are 3“ from horizontal, the aircraft fly at low altitude for a long distance, thus potentially exposing a large area to noise. Before con- sidering the landing gear/cavity noise mechanisms and predictions in de
23、tail, it is instructive to review the typical sequence of events undertaken by an aircraft preparatory to landing, since the airframe component configuration, airspeed, and altitude all play a role in the observed airframe noise, and all vary sig- nificantly during an approach. Figure 1 shows a typi
24、cal sequence of flap and gear deployment as a function of distance from the airport along with the respective altitudes and airspeeds for CTOL jets in the current commercial fleet. Reduced speed and increased flap angle characterize the early stages of final approach, which may begin 16 km (10 miles
25、) from the touchdown point. At altitudes .of 460 to 550 m (approxi- mately 1500 to 1800 ft), the 3“ glide slope is intercepted and the landing gear is deployed, involving the opening of various doors in the fuselage and wing. On many aircraft, some of the doors will reclose shortly after the gear de
26、ployment. When the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-H = kLTITUDE FAA F.IIllSE CERTIFICATION oOli.iT FOR GEAR DOORS RECLCSED (FLAPS FULLY DEPLOYED) GEAR DEPLOYED/ j FLAPS 1 u= 82mIsec u98m/sec(320fs) R U r.1 a, .;Y I xZ1.9 km (1 NAUTICA
27、L MILE) x Z 9.3 km (5 x Z 9.3-13 km x 18.5 -37 km TKESOLD NAUTICAL (5-7 NAUTICAL (10-20 NAUTICAL X=DISTb.NCE FRC3 MILES MILES 1 MILES RUNWAY THRESHOLD USUAL GLIDE SLOPE INTERCEPT FIG. 1. TYPICAL SEQUENCE OF GEAR AND FLAP DEPLOYMENT. Provided by IHSNot for ResaleNo reproduction or networking permitte
28、d without license from IHS-,-,-aircraft crosses the FAA noise certification point, 1.85 km (1 nautical mile) from the threshold, it is traveling 66 to 73 m/sec (215 to 240 ft/sec) at an altitude of 113 m (370 ft). The noise is measured on a direct flyover. The allowable levels for air- craft noise a
29、re a function of aircraft gross weight. The typical components of concern are pointed out in Fig. 2 for a typical modern aircraft . The details of flap geometry, setting angle, landing gear arrangement, and exact airspeed vary between aircraft types, and even between different aircraft of the same t
30、ype, due to load factors, weather, traffic, and pilot techniques. The following list is believed to include all the major con- tributors to airframe noise: Wings and stabilizers, Flaps, Landing gear “self-noise,“ Landing gear cavity (wheel well) oscillations, Separated flow interaction of edges of c
31、avities, Doors associated with gear deployment, Interaction of gear and cavity wakes with trailing edges and flaps. In practice, one finds various configurations of flaps, e.g., one-, two-, or three-flap systems, leading-edge devices, and landing gear (single carriage, multiple carriage, in-line str
32、uts, etc.). The component noise prediction method enables one to account for the differences between configurations; this method may be important in determining and reducing the overall noise signature of the aircraft. TYPICAL CONFIGURATIONS In order to determine the gross geometry and characteristi
33、cs of typical landing gear configurations, measurements and photo- graphs were made of a Boeing 727 and a McDonnell-Douglas DC-9 (see Figs. 2 through 7). The landing gear arrangement in both aircraft is seen to be quite similar. Since the measurements were made on actual service aircraft, and not ta
34、ken from detailed engineering drawings, the information given must be viewed as approximate. It is, however, quite adequate for present purposes. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-r- -.i;,.*“?. u -._ q,-, “. ,.; ,.?*,: BOEING 727- 200
35、 SPAN: 32.9 m ( 108) LENGTH: 48.0 m (1577“) LEFT MAIN GEAR NOSE GEAR (LOOKING AFT) FIG. 2. EXAMPLE AIRCRAFT FOR LANDING GEAR/CAVITY NOISE CALCULATIONS. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SCALE IN METERS - 0 1 SCALE IN FEET I“n I WING CAV
36、 I TY FUSELAGE WING LOWER SURFACE WING CAVITY FUSELAGE -CAVITY DOOR (SHOWN OPEN) m I W uu -WHEELS e. roo VIEW FUSELAGE I CAVITY I I 0123 / / FRONT OF AIRCRAFT + I FIG. 3. BOEING 727 MAIN LANDING GEAR - Continued. 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license
37、from IHS-,-,-c s/D V/W SCALE IN METERS c I 6 I 1 r- 1 SCALE IN FEET - 0123 - 2 f“ 7 ,TO WING CAVITY I I SIDE OPENING SIDE PROJ ECTlON e f I /SIDE PROJECTION “ .L“L OF MAIN DOOR CROSS-SECTIONAL OF WING DOOR 7- SHAPE 1 “0 . W/NG CAV/TY DTA/L INNERMOST CROSS-SECT I ON d FLOW I OUTERMOST CROSS-SECTION F
38、LOW - FIG. 3. BOEING 727 MAIN LANDING GEAR - Concluded. 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SCALE IN METERS A. FRONT YEW b I 1 SCALE IN FEET 0 T7-l ,“-“.- /FORWARD VOLUME DEFLECTORS .AGE 8. Sill VIEW “ 4- OF FRONT 1 “ - 1 AI RCR AF FUSE
39、LAGE CAVITY I I FRONT DOORS REAR DOORS DEFLECTORS FIG. 4. BOEING 727 NOSE LANDING GEAR. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Main Gear Approach Condition as Seen from the Front FIG. 5. MCDONNELL-DOUGLAS DC-9 LANDING GEAR. Main Gear with Fu
40、selage Doors Open as Seen from Behind Nose Gear Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SCALE IN METERS 0 I 1 SCALE IN FEET A. FRONT YEW m 01 23 WING LOWER SURFACE - WHEELS 8. TOP V/W r-= FUSELAGE CAVITY I LL I k L“ e 1 WING CAVITY “,J FRONT
41、OF AIRCRAFT 4 FIG. 6. MCDONNELL-DOUGLAS DC-9 MAIN LANDING GEAR (Continued). 9 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SCALE IN METERS I 0 1 SCALE IN FEET m c, S/D V/W 0123 ,“_ I FUSELAGE CAVITY f-“ I FRONT OF +“ AIRCRAFT D FUSLAG CAVITY DE TA
42、 1L c SIDE OPENING TO WING CAVITY -“ SI DE PROJECTION OF MAIN DOOR FLOW- E WING CAVITY D TA lL 1 I FLOW- I OUTERMOST ROSS-SECTION L L FLOW- FIG. 6. MCDONNELL-DOUGLAS DC-9 MAIN LANDING GEAR (Concluded). 10 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,
43、-,-I A. FRONT VIEW SCALE IN METERS - 0 1 SCALE IN FEET 0123 m I“ 1 k“ -I I FUSELAGECAVITY I fl I-FUSELAGE FRONT DOORS/m REAR DOORS (SHOWN CLOSED) “A MAN WHEELS FRONT OF I p-. +AIRCRAFT a - “ 1 FRONT DOORS GE . I r DOORS FIG. 7. MCDONNELL-DOUGLAS DC-9 NOSE LANDING GEAR. Provided by IHSNot for ResaleN
44、o reproduction or networking permitted without license from IHS-,-,-Both aircraft have a two-wheel nose gear supported by a single strut. When the gear is lowered two sets of doors open. The larger forward doors reclose once the gear is in place. During the lowering process, the large rectangular ca
45、vity which houses the nose gear is open and exposed to the flow. However, the flow over this cavity is seriously disturbed during part of this time by the landing gear itself. Once the gear is in place, the rear doors remain open, producing a relatively small opening into a large internal enclosure.
46、 The flow over this opening is seriously disturbed by the presence of the strut which is typi- cally very cluttered with braces, lights, etc. The small doors on the Boeing 727 are also fitted with large curved flow de- flectors, whose purpose appears to be to force air into the cavity. On each side,
47、 the main landing gear of both aircraft has a single main strut to support two wheels. There is a diagonal brace running from the main strut, just above the wheels, to the fuselage interior. In their retracted position, the wheels are contained in the fuselage, and the main strut and its pivot point
48、 are located in the wing. Thus, there is a small wing cavity and a relatively large fuselage cavity. The door for the wing cavity is open and exposed to the flow whenever the gear is in place. On the Boeing 727, this door also covers a small por- tion of the fuselage cavity. The fuselage cavity door ope
