1、NASA TECHNICAL NOTE I n NASA d. / - TN - D-5805 BUFFET AND STATIC AERODYNAMIC CHARACTERISTICS OF A SYSTEMATIC SERIES OF WINGS DETERMINED FROM A SUBSONIC WIND-TUNNEL STUDY by Edward J. Ray und Robert T, Taylor Langley Reseurch Center Hdmpton, Va. 23365 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WA
2、SHINGTON, D. C. JUNE 1970 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM I I 0132569 1. Report No. 2. Government Accession No. 3. Recipients Catalog No. 1. NASA TN D-5805 4. Title and Subtitle BUFFET AND STATIC AERODYNAMIC CHAR
3、ACTERISTICS OF1 June 1970 5. Report Date A SYSTEMATIC SERIES OF WINGS DETERMINED FROM A SUBSONIC WIND-TUTUTNEL STUDY 6. Performing Oganization Code Edward J. Ray and Robert T. Taylor 9. Performing Organization Name and Address NASA Langley Research Center Hampton, Va. 23365 12. Sponsoring Agency Nam
4、e and Address National Aeronautics and Space Administration Washington, D.C. 20546 15. Supplementary Notes I “I I 8. Performing Organization Report No. L-7011 10. Work Unit No. 126-14-12-02-23 . 11. Contract or Grant No. 13. Type of Report and Period Covered Technical Note 1 14. Sponsoring Agency Co
5、de -. .- I “ 16. Abstract - A wind-tunnel investigation has been conducted in the Langley high-speed 7- by 10-foot tunnel to determine the buffet and static aerodynamic characteristics of a systematic wing series at Mach numbers ranging from 0.23 to 0.94. The results have indicated that for a given
6、Mach number the wings which display superior aerodynamic efficiency characteristics generally display the highest buffet-free lift coefficient. The characteristics exhibited by the wings which were considered have indicated that correlations can be made between the onset of buffeting and selected di
7、vergences in the static aerodynamic characteristics. Axial force has been found to be the most sensitive static component to the onset of buffeting. I 17. Key Words (Suggested by Author(s) ) Buff et Thickness-to-chord Static aerodynamic ratio Camber Aspect ratio Sweep characteristics Position of max
8、imum thickness 18. Distribution Statement Unclassified - Unlimited 19. Security Classif. (of this report) 20. Securlty Classif. (of this page) Unclassified I Unclassified For Sale by the Clearinghouse for Federal Scientific and Technical Informatmn Springfield, Virginia 22151 Provided by IHSNot for
9、ResaleNo reproduction or networking permitted without license from IHS-,-,-BUFFET AND STATIC AERODYNAMIC CHARACTERISTICS OF A SYSTEMATIC SERIES OF WINGS DETERMINED FROM A SUBSONIC WIND-TUNNEL STUDY By Edward J. Ray and Robert T. Taylor Langley Research Center SUMMARY A wind-tunnel investigation has
10、been conducted in the Langley high-speed 7- by 10-foot tunnel to determine the buffet and static aerodynamic characteristics of a sys- tematic wing series at Mach numbers ranging from 0.23 to 0.94. The results have indi- cated that for a given Mach number the wings which display superior aerodynamic
11、 effi- ciency characteristics generally display the highest buffet-free lift coefficient. The characteristics exhibited by the wings which were considered have indicated that corre- lations can be made between the onset of buffeting and selected divergences in the static aerodynamic characteristics.
12、 Axial force has been found to be the most sensitive static component to the onset of buffeting. INTRODUCTION The maneuverability and performance of aircraft engaged in air-to-air combat at high subsonic speeds are limited by the flow separation on the wing which manifests itself in a buffeting of t
13、he airframe and pronounced increases in drag. There are several approaches which the designer of new aircraft may employ in order to alleviate buffeting and its effects. An obvious method is the use of low wing loadings; however, this approach is limited by such considerations as cruise performance,
14、 structural weight, gust response, and so forth. A more desirable approach would be to determine methods of increasing the Lift coefficient at which buffeting occurs by proper selection of planform, airfoil section, and variable-geometry devices. As a contribution to the information needed for a pro
15、per selection of wing design parameters such as planform and airfoil section, a research program has been conducted to study the effects of systematic variations in wing design parameters on buffeting ten- dencies. The primary method for determining buffeting onset in this study has been by the wing
16、-root bending-gage technique. However, another objective of this study was to evaluate other methods of determining buffet onset, such as particular variations in the static aerodynamic .characteristics. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-
17、,-The study made use of 11 buffet models covering systematic variations of sweep, thickness-to-chord ratio, position of maximum thickness, camber, and aspect ratio. The study has been conducted over a range of Mach number from a minimum of about 0.23 to a maximum of 0.94. The purpose of this paper i
18、s to present the results of this buffet research program and to interpret the various wind-tunnel measurements with respect to buffeting. SYMBOLS The coefficients of forces and moments for the plotted longitudinal aerodynamic results are referred to the stability axis system with the exception of th
19、e axial-force and normal-force coefficients, which are referred to the body axis system. In addition to the plotted presentation, tabulations of the static longitudinal and lateral characteris- tics utilizing both body and stability axis systems are presented herein. The static aero- dynamic forces
20、and moments have been nondimensionalized by using the individual geo- metric characteristics of each wing (shown in table I). Pitching moments are referred to the quarter-chord point of the individual wing mean geometric chords. The units used for the physical quantities in this report are given bot
21、h in the U.S. Customary Units and in the International System of Units (SI). Factors relating the two systems are given in reference 1. A b C C - Cr Ct cA (CA)at.O 2 aspect ratio wing span, in. (cm) local chord of wing, in. (cm) mean geometric chord, in. (cm) wing root chord, in. (cm) wing tip chord
22、, in. (cm) axial-force coefficient, Axial force axial-force coefficient at angle of attack of 0 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CD drag coefficient, - Drag qs D ,i theoretical induced-drag coefficient CL lift coefficient, - Lift qs C
23、Lo! lift-curve slope (near angle of attack of Oo) C lift coefficient at maximum lift-drag ratio L(L/D)max pitching-moment coefficient, Pitching moment qSE static margin (taken at low-lift coefficients), - aCm aCL normal-force coefficient, Normal force ss lift-drag ratio root-mean-square moment of wi
24、ng bending gage, in. lb (m-N) free-stream dynamic pressure, lb/ft2 (N/m2) radius, in. (cm) Reynolds number per foot (per meter) wing reference area, ft2 (m2) ratio of actual to theoretical leading-edge suction force (ref. 2) angle of attack, deg wing quarter-chord sweepback, deg 3 Provided by IHSNot
25、 for ResaleNo reproduction or networking permitted without license from IHS-,-,-. _ . .“ Subscript: max maximum ABBREYIATIONS FS fuselage station (measured from nose of model), in. (cm) L.E. leading edge rms root mean square MODELS A two-view sketch of the general model arrangement is shown in figur
26、e 1. The reference center of gravity was assumed to be in the plane of symmetry of the fuselage at the quarter-chord point of the wing mean geometric chords. The geometric character- istics of the various wings which were studied in this investigation are presented in table I. Eleven buffet wings we
27、re used in the study which covered systematic variations of sweep, thickness-to-chord ratio, position of maximum thickness, camber, and aspect ratio. Each wing was constructed of a solid SAE 4130 steel panel, and particular care was taken to insure that the steel wings were rigidly attached to the s
28、teel portion of the fuselage to minimize structural damping. The buffet gages, which constituted a complete moment bridge of four active strain gages, were embedded beneath the upper and lower surface of one wing panel near the fuselage juncture on the 50-percent-chord line. (See fig. 1.) The recess
29、es over the gages were filled in and faired to the contour of the wing surface. All wiring was routed internally through the model into the balance chamber. Most of the wings were tested in combination with the fuselage having the rounded forebody. Several tests, however, were performed with a fusel
30、age having a pointed fore- body (see fig. 1) to determine whether the buffet-onset or buffet-intensity characteristics were affected by forebody bluntness. MEASUREMENTS AND CORRECTIONS Measurement of Buffet Characteristics The primary source of buffet information for this investigation was obtained
31、by the wing-root bending-gage technique (ref. 3). The buffet gages consisted of four active 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-strain gages forming a complete bending-moment bridge. As shown in figure 1, the gages were located near the
32、 wing-fuselage juncture and oriented along the 50-percent- chord line of the wing. The gages located in this manner, that is, on or near the effec- tive flexural and cantilever axes, respond readily to any fluctuating aerodynamic load disturbance on the wing panel due to flow separation. Prior to th
33、e wind-on investigation of the buffet models, each wing was oscillated with a vibrator through a range of frequencies varying from about 0 to 600 Hz to deter- mine the bending characteristics of the wings and to insure that the gages were sensitive to oscillations at the fundamental bending frequenc
34、y. The equipment used in this static survey included an oscillator with associated electronic equipment, a hand-held vibration pickup, and an oscilloscope. The models were driven through the known frequency range, and the phase relationship and amplitude of the oscillator and vibrator pickup were mo
35、nitored on the oscilloscope. Because the vibration probe could be held at various locations on the models, the fundamental bending frequencies could be identified, and the nodal patterns of the various buffet wings could be determined. At the outset of this investigation, the onset of buffeting was
36、determined by visually monitoring the wind-on root-mean-square outputs of the wing-bending gages on a simple root-mean-square voltmeter (test 768). This method for determining buffet onset appeared to be adequate in most cases; however, at the higher values of gage output it became difficult to asce
37、rtain a quantitative level of buffet intensity because of large fluc- tuations of the root-mean-square meter. This was particularly true in the high-subsonic Mach number range where the rise in buffet intensity appeared to become a more gradual process in contrast to the well-defined, abrupt onset o
38、f buffeting indicated at the lower Mach numbers. In order to establish a higher degree of repeatability of the buffet responses, a root- mean-square meter which linearly converts alternating-current input into direct-current outputs (test 778) and a direct-current integrator were incorporated into t
39、he system. The final arrangement of the buffet instrumentation is shown in figure 2. A brief study was conducted to determine a realistic integration time with respect to available test time and repeatability of the buffet results. The bending-gage outputs were monitored on strip charts for interval
40、s ranging from 2 minutes to 30 seconds at several angles of attack and Mach numbers. It was determined that for a typical test wing at several different tunnel conditions, an acceptable degree of repeatability could be obtained by integrating the output of the bending gages for a period of about 45
41、seconds. Therefore, the buffet results presented herein (with the exception of the results for wing 4) represent the average root-mean-square values of the alternating currents emitted from the wing moment bridge during a 45-second sampling interval. (The buffet 5 Provided by IHSNot for ResaleNo rep
42、roduction or networking permitted without license from IHS-,-,-results shown for wing 4 (test 768, see fig. 7(g) were determined by the earlier method which relied on visual observation of the simple-root-mean-square meter.) Measurements of Static Aerodynamic Forces and Moments The static aerodynami
43、c forces and moments were measured by means of a six- component electrical strain-gage balance which was installed within the model. The static aerodynamic data were recorded simultaneously with the integrated root-mean- square output of the wing bending gages. 9 Transition strips of No. 150 carboru
44、ndum grit were placed 0.50 inch (1.27 cm) behind the leading edges of the wings and 1.00 inch (2.54 cm) aft of the fuselage nose in the manner described in reference 4 to insure turbulent flow in the model boundary layer at Mach numbers above approximately 0.50. It should be emphasized here that sev
45、eral studies were made with transition at Mach numbers below 0.50, and therefore, the drag results at the low subsonic Mach numbers should be used with caution. Wings 8 and 9 were investigated with the transition strips completely removed to determine the effects of the artificial roughness on the b
46、uffet and static aerodynamic characteristics. Corrections to Static Aerodynamic Results The angles of attack shown herein have been corrected for the combined bending of the sting and balance system due to aerodynamic loading. Balance cavity pressures were monitored throughout the investigation by m
47、eans of differential pressure gages and the axial-force and drag-coefficient data have been adjusted to correspond to a condition of free-stream static pressure at the base of the model. Jet boundary and blockage correc- tions were applied to the results as prescribed in references 5 and 6. TEST CON
48、DITIONS The investigation was conducted in the Langley high-speed 7- by 10-foot tunnel which is a continuous-flow facility having, for this study, a closed test section. The Mach numbers for the various tests performed are listed in the run schedule contained in table II. The variations of the avera
49、ge Reynolds number and dynamic pressure with Mach number are shown in figure 3. In general, the Mach number range of this investi- gation extended from a minimum of about 0.23 to a maximum of about 0.94. The models were tested at Oo of sideslip through an angle-of-attack range which was varied from about 0 to a maximum of about 22. At the higher Mach numbers, the angle-of-attack
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