1、fNASA“,4,:f“C,4ZZTECHNICAL NOTE NASA TN D-2042EFFECT OF AFTERBODY GEOMETRY ANDSTING DIAMETER ON THE AERODYNAMICCHARACTERISTICS OF SLENDER BODIESAT MACH NUMBERS FROM 1.57 TO 2.86by Dennis E. Fuller and Victor E.LangleyLangleyResearch CenterStation, Hampton, VaLanghansNATIONALAERONAUTICSAND SPACEADMIN
2、ISTRATION WASHINGTON,D_ C. NOVEMBER1963Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-wx_Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECHNICAL NOTE D-2042EFFECT OF AFTERBODY GEOMETRY AND STING DI
3、AMETER ON THEAERODYNAMIC CHARACTERISTICS OF SLENDER BODIES ATMACH NUMBERS FROM 1.57 TO 2.86By Dennis E. Fuller and Victor E. LanghansLangley Research CenterLangley Station, Hampton, Va.NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONProvided by IHSNot for ResaleNo reproduction or networking permitted w
4、ithout license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EFFECT OF AFI_ERBODY GEOMETRY AND STING DIAMETER ON THEAERODYNAMIC CHARACTERISTICS OF SLENDER BODIES ATMACH NUMBERS FROM i.57 TO 2.86By Dennis E. Fuller and Victor E. Langhan
5、sSUMMARYAn investigation has been made in the low Mach number test section of theLangley Unitary Plan wind tunnel to determine the effects of afterbody boattail,camber, and length, and of variations in sting diameter on the aerodynamic char-acteristics of slender bodies. A common forebody was utiliz
6、ed for all configura-tions tested. Tests were performed at Mach numbers from 1.57 to 2.86 and at aReynolds number per foot of 3.0 X 106 .The results indicate that wind-tunnel models of airplanes with afterbodieswhich are appreciably altered to accommodate a rear-mounted sting-support systemwill prod
7、uce different drag characteristics than those which would be obtainedfrom true representations of the aircraft with closed afterbodies. It is furtherindicated that negative afterbody camber may be beneficial in minimizing the trimperformance penalty of airplanes. There is little effect of sting diam
8、eter onthe aerodynamic characteristics in pitch of the wind-tunnel models that have tur-bulent flow over their length. There is, in general, little variation in the_4 4.base-pressure coefficients with angles of attack from toINTRODUCTIONWind-tunnel tests of airplane models generally require distorti
9、on of themodel afterbody in order to permit installation of the sting-support strut andinstrumentation. With the current and anticipated development of high-performancesupersonic aircraft it becomes increasingly important that the effects of modelafterbody distortion be known so that a more accurate
10、 definition of full-scaleperformance characteristics may be obtained from results of wind-tunnel modeltests.The investigation of reference I provided drag information on the effectsof variation in sting size, and limited effects of afterbody boattailing at zeroangle of attack. These tests were limit
11、ed to a few configurations at a Mach num-ber of 1.5. In an attempt to define more clearly the effects of afterbody con-figuration over a range of supersonic Mach numbers, the present investigation wasundertaken with a series of afterbodies which varied in boattail angle, camber,Provided by IHSNot fo
12、r ResaleNo reproduction or networking permitted without license from IHS-,-,-and length. The effect of varying sting diameter was also investigated. Thetests were performed in the Langley Unitary Plan wind tunnel at Machnumbersfrom 1.57 to 2.86 through an angle-of-attack range from about -4 to 4 . T
13、heReynolds numberof the tests was about 3.0 X 106 per foot.SYMBOLSThe coefficients of forces and momentsare referred to the stability axissystem. For all models_ the aerodynamic momentswere taken about a point located15.01 inches aft of the nose.A body reference area, 0.049038 sq ftCD drag coefficie
14、nt, DragqACD,mi n minimum drag coefficientCD,c chamber drag coefficient, ChamberdragqACL lift coefficient, LiftqAslope of lift curve at _ = 0 _CL, _-_-,per degACL, o incremental CL at _ = 0 between a given body and body I-4CmPitching momentpitching-moment coefficient; qAd_C mslope of pitching-moment
15、 curve at _ = 0, _-, per deg_Cm_ o incremental Cm at _ = 0 between a given body and body 1-4Cp pressure coefficientd exit diameter of afterbodydmax maximum body diameter, 3.00 in.M free-stream Mach numberProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-
16、,-PtqTtC_stagnation pressure, ib/sq in.free-stream dynamic pressure, ib/sq ftstagnation temperature, Fangle of attack of fuselage center line, degAPPARATUS AND TESTSWind TunnelTests were conducted in the low Mach number test section of the LangleyUnitary Plan wind tunnel which is a variable-pressure
17、 continuous-flow tunnel.The test section is approximately 4 feet square and 7 feet long. The nozzleleading to the test section is of the asymmetric sliding-block type which per-mits a continuous variation in test-section Mach number from about 1.5 to 2.9.ModelsA dimensional drawing of the models is
18、presented in figure I, and a photo-graph of one of the models and its support system is presented as figure 2. Theforebody used for all the models consisted of a conical ogive nose 15 inches inlength which was faired into a 3-inch-diameter cylindrical section 5 inches inlength. Two families of after
19、bodies were tested, consisting of seven afterbodies14.50 inches in length, and three afterbodies 19.00 inches in length. Herein-after the afterbody designations shown in figure i will be used for purposes ofidentification of the various configurations.Configurations I-i through I-4 are models with a
20、fterbody boattailing_varying from a cylinder to a symmetrical ogive. Configurations I-4 through I-6are cambered afterbody models varying from a symmetrical ogive (1-4) to a cam-bered ogive with a 1 -inch offset at the rear (1-6). Configuration 1-7 is amodel with a conical afterbody. The three config
21、urations with 19.00-inch after-bodies are: II-i, a cylinder; 11-2, partially closed ogive comparable to con-figuration I-2; and 11-4, a symmetrical ogive comparable to configuration I-4.All configurations were strut supported from the bottom (see fig. 2), andthus allowed various cylindrical stings t
22、o be inserted from the rear without con-tacting the model. Stings with diameters of 0.75, 1.50, and 2.25 inches wereused where applicable.3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Test ConditionsTests were performed at the following conditions
23、:M1.572.162.5O2.86Tt_oF125125150150Ptib/sq in. abs11.1713.9817.6721.35The Reynolds number was constant at 3.0 106 per foot.The dewpoint_ measured at stagnation pressure_ was maintained below -30 Fto assure negligible condensation effects. The angle of attack was varied fromapproximately -4 to 4 and
24、the sideslip angle was maintained near 0. In orderto assure turbulent flow over the length of the body_ a _6-inch-wide strip of15No. 60 carborundum grit was fixed around the nose of the model _ inch aft of thetip.The aerodynamic forces and moments were measured by means of an internallymounted strai
25、n-gage balance which was, in turn, rigidly fastened to a bottom-mounted strut support_ and thence to the tunnel support system.Balance chamber pressure was measured by means of orifices located in therear of each open-end afterbody.Corrections and AccuracyAngles of attack have been corrected for def
26、lection of sting and balance dueto aerodynamic loads.The drag coefficients presented have been adjusted to correspond to free-stream static pressure acting over the base. Variation of chamber drag coeffi-cients with angle of attack is presented in figure 3. No attempt was made toapply corrections fo
27、r flow angularity to the data presented herein because ofthe undefined effects of the support strut on the flow over the afterbodies.Based upon calibrations and repeatability of data, it is estimated that thevarious measured quantities are accurate within the following limits:M 0.015_3 deg . 0.i0CD,
28、 c 0.009Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CD +0. 001CL +0. 008Cm +0.01RESULTS AND DISCUSSIONSting EffectsThe effects of sting diameter on the aerodynamic characteristics in pitchof a cylindrical afterbody (I-l) configuration and two aft
29、erbody configurationswith different degrees of boattailing (I-2 and I-3) indicate that within theaccuracy of these tests, there are no appreciable effects of sting diameter onthe aerodynamic characteristics in pitch of any of the test configurations throughthe test Mach number range. (See fig. 4.) T
30、he drag coefficient results are inagreement with the data of reference 1 (M = 1.), only) which concluded that thebase or chamber drag coefficient of a symmetrical body with turbulent flow overits length is the only parameter affected by change in sting diameter.Afterbody Boattail EffectsThe effects
31、of afterbodyboattailing on the aerodynamic characteristics inpitch of a body without the sting are also shown in figure 4, and a summary ofcorresponding sting-off characteristics is presented in figure _. As would beexpected from geometrical consideration of the bodies, the cylindrical afterbodyconf
32、iguration (I-l) has the greatest lift-curve slope and is the most stable ofthe test configurations throughout the Mach number range of the test.There is little difference in CL_ and Cm_ between the closed afterbodyconfiguration (I-4) and the d = 0.33 configuration (I-3). The d = 0.67dmax dmaxconfigu
33、ration (I-2) has intermediate values of CL_ and Cn_ to those for theclosed and cylindrical afterbody configurations except at Mach numbers of 2.50and 2.87 where Cm_ for all of the boattail configurations is essentially thesame The effect of afterbodyboattail on drag coefficient (adjusted for chamber
34、drag coefficient) is appreciable throughout the Mach number range of the testswith CD,mi n progressively increasing from the cylindrical afterbody configura-tion (I-l) to the fully closed configuration (I-4). It is therefore apparentthat a wind-tunnel model that has its afterbody appreciably altered
35、 to accommo-date a rear-mounted sting support will produce different drag characteristicsthan those which would be obtained from a true representation of an airplanewith a closed afterbody.5Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The effect o
36、f afterbody boattail on base-pressure coefficient is presentedin figure 6 which shows a decrease in the base-pressure coefficient with decreasein d/dma x for both the 14.50-inch- and the 19.00-inch-long afterbody configura-tions. These results are in general agreement with the results of reference 2
37、.The decrease in Cp with decrease in d/dma x appears, within the scope of thepresent paper_ to be independent of afterbody length.With respect to base pressures, it should be noted (fig. 3) that there is,in general, little variation in base-pressure coefficient within the angle-of-attack range prese
38、nted. The largest variations are realized with the cylindricalafterbodies (I-i and II-i) at the lower Mach numbers of these tests.Afterbody Camber EffectsThe effects of afterbody camber on aerodynamic characteristics in pitch arepresented in figure 7 and summarized in figure 8. Positive camber leads
39、 toincreases in stability level_ in lift-curve slope, and in minimum drag coeffi-cient (see fig. 8). Further, a positive increment in CL_ o is produced by thepositive camber, and perhaps of more significance, is the substantial decreasein Cm, o which indicates that negative afterbody camber should p
40、rovide positiveincrements of Cm, o that would relieve the trimming requirements.The aerodynamic characteristics of a symmetrical conical afterbody configu-ration (1-7) are also shown in figure 7 and are compared in summary form with thesymmetrical ogive afterbody configuration (1-4) in figure 9. The
41、re are no largedifferences in CI_ or CD,mi n between these configurations; however, the con-ical afterbody configuration produces a slightly lower Cm_ than does the ogiveafterbody configuration.Effect of Afterbody LengthResults of tests on the basic forebody configuration with lengthened after-bodie
42、s are presented in figure i0. The same general effects of sting and after-body boattailing noted on the aerodynamic characteristics of the shorter after-body configurations are observed on the longer configurations.A comparison of the results presented in figures 4 and i0 indicates that theaerodynam
43、ic characteristics in pitch for the 14.50-inch and the 19.00-inch after-body configurations differ only superficially except for the minimum drag-coefficient values of the cylindrical afterbody configurations. For these con-figurations, the longer model has the greater CD,min, which is obviously due
44、 toan increase in wetted area over that for the shorter model. For the boattailconfiguration (11-4 with respect to I-4) it would appear that the drag coeffi-cient due to added wetted area is compensated for by a decrease in boattail angle.6Provided by IHSNot for ResaleNo reproduction or networking p
45、ermitted without license from IHS-,-,-CONCLUSIONSTests of afterbody configurations with changes in the diameter of the rear-mounted sting, afterbody boattailing, camber, and length at Mach numbers fromI.DO to 2.86 lead to the following conclusions:I. Wind-tunnel models with afterbodies appreciably a
46、ltered to accommodate arear-mounted sting-support system will produce different drag characteristicsthan those which would be obtained from true representations of the aircraftwith closed afterbodies.2. Negative afterbody camber may be of significant benefit in minimizingthe trim performance penalty
47、 of airplanes.3. There is little effect of sting diameter on the aerodynamic character-istics in pitch of wind-tunnel models that have turbulent flow over their length.4. There is, in general, little variation in base-pressure coefficient withangle of attack from -4 to 4.Langley Research Center,Nati
48、onal Aeronautics and Space Administration,Langley Station, Hampton, Va., August 30, 1963.REFERENCESi. Perkins, Edward W.: Experimental Investigation of the Effects of SupportInterference on the Drag of Bodies of Revolution at a Mach Number of 1.5.NACA TN 2292, 1951. (Supersedes NACA RMA8B05.)2. Love, Eugene S.: Base Pressure at Supersonic Speeds on Two-Dimensional Air-foils and on Bodies of Revolution With and Without Fins Having TurbulentBoundary Layers. NACA TN 3819, 1957. (Supersedes NACA RML53C02.)7Provided by IHSNot for ResaleNo reproduction or networking permitted
