1、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No. NASA TM X-3438 Ames Research Center, NASA Moffett Field, California 94035 2. Government Accession No. 3. Recipients Catalog No. 11. Contract or Grant No. 4. Title and Subtitle SIDE FORCES
2、ON FOREBODIES AT HIGH ANGLES OF ATTACK AND MACH NUMBERS FROM 0.1 TO 0.7: TWO TANGENT OGIVES, PARABOLOID AND CONE 7. Author(s) Earl R. Keener, Gary T. Chapman, Lee Cohen, and Jamshid Taleghani 9. Performing Organization Name and Address 5. Report Date 6. Performing Organization Code February 1977 8.
3、Performing Organization Report No. A-6670 10. Work Unit No. 505-06-95 17. Key Words (Suggested by Author(s) 18. Distribution Statement 12. Sponsoring Agency Name and Address National Aeronautics and Space Administration Washington, D. C. 20546 Aerodynamic characteristics Subsonic Bodies High angle o
4、f attack Side forces 13. Type of Report and Period Covered Technical Memorandum 14. Sponsoring Agency Code Unlimited STAR Category - 02 19. Security Classif. (of this report) 20. Security Classif. (of this page) Unclassified Unclassified 21. NO. of Pages 22. Price 141 $5.75 d Provided by IHSNot for
5、ResaleNo reproduction or networking permitted without license from IHS-,-,-NOMENCLATURE The data are presented in the body axis coordinate system with the moment center located at the base of the forebody models. Since the data were computer-plotted, the corresponding plot symbol, where used, is giv
6、en together with the conventional symbol. Conventional symbol b CA CAF Plot symbol span of elliptic forebody at base (major or minor axis of base depend- ing on orientation of model; major or minor axis horizontal) CA CAF CLM CRM CN CYN CBL CPB balance axial force axial-force coefficient, 4s axial-f
7、orce coefficient adjusted for base pressure equal to free-stream static pressure, CA + C P, b pitching-moment coefficient, pitching moment 4Sd resultant-moment coefficient in the body axis system, Cn sin * + Cm cos k normal-force coefficient, normal force 4s yawing moment qSd yawing-moment coefficie
8、nt, rolling-moment coefficient, rolling moment SSd Pb - P base pressure coefficient, - 4 CPR resultant-force center of pressure location, fraction of length Q from nose tip, 1 -(T)(-) cm,R d CR CR CY CY Icy1 ACY d D resultant-force coefficient in body axis system, JC? side-force side-force coefficie
9、nt, qs absolute value of Cy base diameter (for an elliptic body it is taken to be the span b at the base) iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Conventional Plot symbol symbol R L M MACH P pb 4 Rd R S S X cx P 0 B N ALPHA BETA THETA PHI
10、-B PHI-N PSI AA AD FC length of forebody free-stream Mach number free-stream static pressure base pressure free-stream dynamic pressure Reynolds number based on base diameter, d base reference area (circular bodies: area of base; elliptic body: area of an equivalent circular base with a diameter equ
11、al to span b of base) distance behind forebody apex along body axis of symmetry angle of attack, deg angle of sideslip, deg meridian angle measured from bottom center line, right side is positive looking upstream, deg roll angle of model forebody about axis of symmetry, clockwise is positive looking
12、 upstream, deg roll angle of removable nose alone about axis of symmetry, clockwise is positive looking upstream, deg angle between the resultant and normal forces, resultant force inclined to the right is positive angle looking upstream, tan- (s) , deg Model Configuration Code afterbody attached to
13、 forebody afterbody detached from forebody (separated by 0.16 cm gap), but attached to sting conical forebody iv Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Plot symbol FEH FEV FP FT2 NS NB 1 NB2 NB3 NP T1 T2 T2R T3 T4 T5 T6 elliptic tangent-ogiv
14、e forebody , major axis horizontal elliptic tangent-ogive forebody , major axis vertical parabolic forebody tangent-ogive forebody, - = 5.0 sharp nose, radius = 0 R d blunt nose, radius = 0.3 17 cm . blunt nose, radius = 0.635 cm blunt nose, radius = 1.27 cm parabolic nose boundary-layer transition
15、strip along forebody meridians at 0 = rt 15“ , full length boundary-layer transition strip along forebody meridians, 0 = +30, full length boundary-layer transition strip along forebody meridian on right side, 0 = 30, full length boundary-layer transition strip encircling model, = 0.03 boundary-layer
16、 transition strip encircling model, - = 0.10 Q Q X boundary-layer transition strip encircling model at junction of nose X and forebody, - = 0.20 R boundary-layer transition strip encircling model, - X = 0.33 R V d Provided by IHSNot for ResaleNo reproduction or networking permitted without license f
17、rom IHS-,-,-SIDEFORCES ON FOREBODIES AT HIGH ANGLES OF ATTACK AND MACH NUMBERS FROM 0.1 TO 0.7: TWO TANGENT OGIVES, PARABOLOID AND CONE Earl R. Keener, Gary T. Chapman, Lee Cohen, and Jamshid Taleghani Ames Research Center SUMMARY An experimental investigation was conducted in the Ames 12-Foot Wind
18、Tunnel to determine the subsonic aerodynamic characteristics of four forebodies at high angles of attack. The forebodies tested were a tangent ogive with fineness ratio of 5, a paraboloid with fineness ratio of 3.5, a 20“ cone, and a tangent ogive with an elliptic cross section. The investigation in
19、cluded the effects of nose bluntness and boundary-layer trips. The tangent-ogive forebody was also tested in the presence of a short afterbody and with the afterbody attached. Static longitudinal and lateral/directional stability data were obtained at Reynolds numbers ranging from O.3X1O6 to 4.6X106
20、 (based on base diameter) at a Mach number of 0.25, and at Mach numbers ranging from 0.1 to 0.7 at a Reynolds number of O.8X1O6 (nominal). Angle of attack was varied from 0“ to 88“ at zero sideslip, and the sideslip angle was varied from - 10“ to 30“ at angles of attack of 40, 55“, and 70“. The inve
21、stigation was conducted to investigate the existence of large side forces and yawing moments at high angles of attack and zero sideslip, It was found that all of the forebodies exper- ience steady side forces that start at angles of attack of from 20“ to 35“ and exist to as high as 80, depending on
22、forebody shape. The side force is as large as 1.6 times the normal force and is generally repeatable with increasing and decreasing angle of attack and, also, from test to test. The side force is very sensitive to the nature of the boundary layer, as indicated by large changes with boundary trips. T
23、he maximum side force varies considerably with Reynolds number and tends to decrease with increasing Mach number. The direction of the side force is sensitive to the body geometry near the nose. The angle of attack of onset of side force is not strongly influenced by Reynolds number or Mach number b
24、ut varies with forebody shape. Maximum normal force often occurs at angles of attack near 60“. The effect of the elliptic cross section is to reduce the angle of onset by about 10“ compared to that of an equivalent circular forebody with the same fineness ratio. The short afterbody reduces the angle
25、 of onset by about 5“. INTRODUCTION When bodies of revolution are pitched at high angles of attack, a side force can occur at zero sideslip angle. This side force results when the separation-induced vortex flow field on the lee side of the body becomes asymmetric. This is a well-known phenomenon (re
26、fs. 1 and 2) and one on which research has focused in recent years, particularly with the advent of highly maneuverable aircraft, because the side force and yawing moment might contribute to the onset of aircraft spin (ref. 3). To date, much of the research on asymmetric forces has been directed tow
27、ard determining fixes for specific configurations and on studies of vortex flow fields on long slender bodies (e.g., refs. 4-9). However, a recent test of three forebody models at low Mach number and Reynolds Provided by IHSNot for ResaleNo reproduction or networking permitted without license from I
28、HS-,-,-number (ref. 10) showed that large side forces can be generated on the forebody alone at zero sideslip. Since the configuration of the forebody might play an important role in the spin characteris- tics of the aircraft, a comprehensive wind tunnel test program has been undertaken at Ames Rese
29、arch Center to obtain static aerodynamic data for forebody-alone models, covering a wide range of forebody shapes and a wide range of Reynolds numbers and Mach numbers. The objective was to determine the effect of forebody shape on the forces and moments so that criteria could be established for air
30、craft and missiles with good, high angle-of-attack, aerodynamic characteristics. Reports thus far generated from this test program are listed in references 11 to 14. As part of the forebody test program, aerodynamic force and moment characteristics were measured at subsonic speeds over a large Reyno
31、lds number range for five forebody models. Test data for one of the forebody models, a tangent ogive having a fineness ratio of 3.5, were reported in reference 12, and selected results were reported in reference 1 1. The present report presents experi- mental data for the four forebody models: a tan
32、gent ogive having a fineness ratio of 5, a paraboloid having a fineness ratio of 3.5, a 20“ cone, and a tangent ogive having an elliptic cross section whose major and minor axes at the base results in fineness ratios of 5 and 3.5, respectively. Tests prior to the present investigation (ref. 10) at l
33、ow speed and low Reynolds numbers showed that side forces and yawing moments occurred at zero sideslip (asymmetric forces and moments) for a tangent ogive and a cone, each having fineness ratios of 3.5. On the other hand, test results for a paraboloid did not exhibit side forces and yawing moments.
34、Test results for the tangent ogive with fineness ratio of 3.5 from the present investigation (refs. 11 and 12) showed asymmetric forces similar to those of reference 10 at high angles of attack. The side force was as large as 1.5 times the maximum normal force, varied considerably with Reynolds numb
35、er, and decreased with Mach number. The side forces were reduced or eliminated by bluntness, nose strakes, or nose booms. The objectives of the present investigation were to determine the effects on the asymmetric forces due to forebody geometry, hysteresis, repeatability, Reynolds number, roll angl
36、e, sideslip, boundary-layer trips, nose bluntness, and Mach number. To determine the effects of flow around the base of the forebody-alone configuration, the fineness-ratio 5 tangent ogive was tested in the presence of an R/d = 3.5 cylindrical afterbody. The forebody was also tested with the afterbo
37、dy attached to determine the effect of a short afterbody on the side force. This investigation was conducted in the Ames 12-Foot Pressure Wind Tunnel at Mach numbers ranging from 0.1 to 0.7 and at Reynolds numbers ranging from O.3X1O6 to 4.6X106. Six- component static forces and moments were measure
38、d at angles of attack from 0“ to 88“. This report presents the basic data that show the effects on the aerodynamic characteristics due to model configuration, Reynolds number, and subsonic Mach numbers up to0.7. Selected results from this investigation were reported in reference 11. 2 Provided by IH
39、SNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TEST FACILITY The aerodynamic data presented here were obtained from wind tunnel tests conducted in the Ames 12-Foot Pressure Wind Tunnel. This wind tunnel is a variable-pressure, low-turbulence facility with a Mach
40、number range from 0.1 to about 0.9 and a unit Reynolds number capability up to about 26X106/m at a Mach number of 0.25. Eight fine-mesh screens in the settling chamber, together with a contraction ratio of 25 to 1 , provide the airstream of exceptionally low turbulence. MODEL DESCRIPTION Test result
41、s are presented for four forebody models. Sketches of the models are presented in figure 1, model dimensions are given in table 1, and photographs of the models and wind-tunnel installation are presented in figure 2. The models were designed to represent forebodies of aircraft fuselage or missiles.
42、Three of the forebodies were bodies of revolution: an J?/d = 5 tangent ogive, an Q/d = 3.5 paraboloid, and a 20“ cone. All of these bodies were designed with removable nose sections of various nose radii up to 1.27 cm. The paraboloid was provided with a pointed nose (resulting in a short conical tip
43、) with an apex angle of 32.9“; identical to that of the Q/d = 3.5 tangent ogive (ref. 12). A fourth forebody was designed with an elliptic cross section that could be tested with either the major or the minor axis perpendicular to the crossflow velocity. The major and minor axes of the base were sel
44、ected so that the respective Q/b (lengthlbase span) ratios were 3.5 and 5.0 to coincide with the circular tangent-ogive model fineness ratios. In addition, an Q/d = 3.5 afterbody was designed to be clamped to the sting behind the Q/d = 5 tangent ogive but free of the forebody (approximately 0.16 cm
45、gap) so that forebody forces could be measured in the presence of the afterbody. The afterbody could also be attached to the forebody so that the forebody plus afterbody force could be measured. The junctions between the removable nose and the forebody and afterbody were carefully machined so that t
46、he surface discontinuity was less than 0.025 mm and had rearward facing steps. The removable nose sections were held by a set screw located on the leeward side and covered with smoothed dental plaster. A balance pin access hole was located on the leeward side, covered with dental plaster, and smooth
47、ed. The afterbody was built in two halves; the parting surface was oriented perpendicular to the windward side so that the retaining bolts were located on the windward side. The bolt holes and the small gap on each side between the cylindrical halves were filled with dental plaster and smoothed. TES
48、TING AND PROCEDURE The investigation was conducted over a Reynolds number range from 0.3X lo6 to 4.6X lo6 (nominal, based on model base diameter) at a Mach number of 0.25, and over a Mach number range from 0.1 to 0.7 at a Reynolds number of O.8X1O6 (nominal). The models were mounted from a floor sup
49、port system that provides a high angle-of-attack range. Since it was not possible to pitch the model continuously from 0“ to 88“, two different sting supports were used. The sting support systems shown in figures 2(c) and 2(d) were used for angle-of-attack ranges of 0“ to 45“ and 36“ to 88“, respectively. Angle of sideslip was varied from - 10“ to 30“ at a = 40“, 55“, and 70“. 3 Pr
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