1、NASA TECHNICALMEMORANDUMCOCOIXNASA TM X-3437SIDE FORCES ON A TANGENT OGIVE FOREBODYWITH A FINENESS RATIO OF 3.5 AT HIGHANGLES OF ATTACK AND MACH NUMBERSFROM 0.1 TO 0.7Earl R. Keener, Gary T. Chapman,Lee Cohen, and Jamshid TaleghaniAmes Research CenterMoffett Field, Calif. 94035NATIONAL AERONAUTICS A
2、ND SPACE ADMINISTRATION WASHINGTON, D. C. FEBRUARY 1977Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I. Report No. 2. Government Accession No.NASA TM X-34374. Title and SubtitleSIDE FORCES ON A TANGENT OGIVE FOREBODY WITHA FINENESS RATIO OF 3.5 AT
3、HIGH ANGLES OFATTACK AND MACH NUMBERS FROM 0.1 TO 0.77. Author(s)Earl R. Keener, Gary T. Chapman, Lee Cohen,and Jamshid Taleghani9. Performing Organization Name and AddressAmes Research CenterMoffett Field, California 9403512. Sponsoring Agency Name and AddressNational Aeronautics and Space Administ
4、rationWashington, D.C. 205463. Recipients Catalog No.5. Report DateFebruary 19776. Performing Organization Code8. Performing Organization Report No.A-660910. Work Unit No.505-06-9511. Contract or Grant No.13. Type of Report and Period CoveredTechnical Memorandum14. Sponsoring Agency Code15. Suppleme
5、ntary Notes16. AbstractAn experimental investigation was conducted in the Ames 12-Foot Wind Tunnel to determine the subsonicaerodynamic characteristics, at high angles of attack, of a tangent ogive forebody with a fineness ratio of 3.5. Theinvestigation included the effects of nose bluntness, nose s
6、trakes, nose booms, a simulated canopy, andboundary-layer trips. The forebody was also tested with a short afterbody attached. Static longitudinal andlateral-directional stability data were obtained at Reynolds numbers ranging from 0.3X 106 to 3.8X 10s (based onbase diameter) at a Mach number of 0.2
7、5, and at a Reynolds number of 0.8X106 at Mach numbers ranging from0.1 to 0.7. Angle of attack was varied from 0 to 88 at zero sideslip, and the sideslip angle was varied from -10to 30 at angles of attack of 40, 55, and 70.The investigation was particularly concerned with the possibility of large si
8、de forces and yawing moments athigh angles of attack at zero sideslip. It was found that a side force occurs, starting at angles of attack ofabout33 and continuing to angles of attack as high as 80. The side force is as large as 1.5 times the maximum normalforce; the side force is repeatable with in
9、creasing and decreasing angle of attack and from test to test. Themaximum side force varies considerably with Reynolds number and decreases to near zero as the Mach numberincreases to 0.7. The side force is very sensitive to the nature of the boundary layer as indicated by large changeswith boundary
10、 layer trips. The direction and magnitude of the side force is sensitive to the body geometry nearthe nose. Rotating the nose tip changes the direction of the side force; nose booms and boundary-layer trips nearthe nose tip significantly reduce the side force, and nose strakes and small bluntness te
11、nd to eliminate the sideforces. The angle of attack at which onset of side force occurs is not strongly influenced by either Reynoldsnumber or Mach number. The short afterbody reduces the angle of onset by about 5. Maximum normal force-occurs at angles of attack near 60, rather than at 90.17. Key Wo
12、rds (Suggested by Author(s)Aerodynamic characteristicsSubsonicBodiesHigh angle of attackSide forcesIB. Security Qasslf. (of this report)Unclassified18. Distribution StatementUnlimitedSTAR Category - 0220. Security Oassif. (of this page) 21. No. oUnclassified 1f Pages 22. Price14 $5.25For sale by the
13、 National Technical Information Service, Springfield. Virginia 22161Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NOMENCLATUREThe data are presented in the body axis coordinate system with the moment center located atthe base of the fprebody models
14、. Since the data were computer plotted, the corresponding plotsymbol, where used, is given together with the conventional symbol.Conven-tionalSymbolCAFCm,RCNCnCPRCRCYCYdS.MPPbPlotSymbolCACAFCLMCRMCNCYNCPRCPBCRCYACYDLMACHDefinition. . P ff. . . balance axial force17Oaxial-force coefficient adjusted f
15、or base pressure equal to free-stream staticpressure, (CA + Cpb). , -, . pitching momentTiiTfninc* motnpnt POPttifMpnTqSaresultant-moment coefficient, ( sin + Cm cos ) I fitnormal force coefficient normal forcellL/lillu lUlt WUVl llJt/11 L , qSfc. . yawing momentviwint* moTTipnT ffPttiPipnrqSaresult
16、ant-force center of pressure location, fraction of length, fi, from noset. tCm,R dCR CPjj pase pressure coe icien , resultant-force coefficient in body axis system, /Cpf + Cy2side-forceside force coefficient, absolute value of Cybase diameter, 15.24 cmlength of forebody, 53.3 cmfree-stream Mach numb
17、erfree-stream static pressurebase pressurePreceding Page Blank inProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Conven-tionalSymbolSxa0PlotSymbolRSALPHABETADefinitionfree-stream dynamic pressureReynolds number, based on model base diameterarea of fo
18、rebody basedistance behind forebody apex along body axisangle of attack, degangle of sideslip, degTHETA meridian angle measured from bottom center line; right side is positivelooking upstreamPHI-BPHI-NPSIroll angle of model forebody about body axis of symmetry; clockwise ispositive looking upstreamr
19、oll angle of removable nose alone about axis of symmetry; clockwise ispositive looking upstreamangle between the resultant and normal forces, resultant force inclined toCYthe right is positive angle looking upstream, tan 1 Model Configuration CodeAA afterbody attached to forebodyAD afterbody detache
20、d from forebody (separated by 0.16 cm gap), butattached to stingBl nose boom, length = 2.54 cmB2 nose boom, length = 5.08 cmC canopynFT1 tangent-ogive forebody, J- = 3.5NB1 blunt nose, radius t= 0.317 cmNB2 blunt nose, radius = 0.635 cmNB3 blunt nose, radius = 1.27 cmNS sharp nose, radius = 0IV “cyc
21、; “6 and CAFMost of the data are plotted versus angle of attack at zero sideslip angle; however, in a few figuresthe data are plotted versus angle of sideslip. Since the results for ICyl/Qv and CPR are spurious atlow angles of attack, and undefined at a = 0, these results have been deleted for a 33)
22、. This increasein C/v curve slope implies that the normal force and, hence, the resultant force, are increased by theflow asymmetry that causes the side force.The center of pressure, CP/j, of the resultant normal force is located at about x/C = 0.5 forangles of attack less than 30. This is in genera
23、l agreement with the slender-body theory value of0.46 5. for this forebody. At higher angles of attack, CP/j moves slightly rearward until at a = 88 itis close to the centroid of planform area x/9. 0.624.A small rolling moment was recorded that occurred at high angles of attack when the sideforce wa
24、s large. Since the asymmetric pressures that produce the side force do not produce a rollingmoment for a circular body, the small recorded rolling moment was probably due to an asymmetryin the boundary-layer skin-friction forces. Evidently, a rolling moment due to asymmetric skin-friction forces sho
25、uld be anticipated on flight vehicles when large side forces exist. The data are notpresented because the measured rolling moment was small (maximum |C/| R = 270.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-More startling results (fig. 9) were obt
26、ained when the removable nose tip (length of 0.192) wasrolled to several fixed positions, resulting in an effect that was similar to that of rolling thecomplete body. Apparently, the asymmetry in the vortex flow is very sensitive to the body geom-etry near the nose. Note that the angle of onset does
27、 not change more than about 5 with rollposition.These roll tests indicate that body models should be tested in several positions of roll, ifpossible, when determining the asymmetric characteristics at high angles of attack. In addition, theorientation of model parts and of surface discontinuities, s
28、uch as junctions and set screws, should benoted. Some insight into the possible effect of the junction of the removable nose section may beobtained from the results of tests that were made with a ring of roughness elements located at thejunction (fig. 14). Because the side force was greatly reduced,
29、 it was believed that the effect of alarge discontinuity at the junction would act as a boundary layer trip and would likewise reduce theside force. Since the side force is large without the ring of trips it is believed that the junction effectis negligible.Sideslip Figure 10 shows the effect of sid
30、eslip angle for a = 40, 55, and 70 atRd = 0.8X106. At sideslip angles between 5 and 15 the side force changes sign (direction). Theangle of sideslip range where the change occurs is generally repeatable. The data show nearlyidentical results for both increasing and decreasing angles of sideslip. The
31、 data also show that thedirection of sideslip is not sensitive to small variations in stream angles such as those produced bythe model support system fairing on the floor of the wind tunnel.Note that the effect of sideslip on a body is identical to testing at zero sideslip at a slightlyhigher angle
32、of attack and at a roll angle of both the body and the balance. The change in directionof side force from left to right between however, it must not beassumed that oil will not induce large changes. In oil flow tests, the forces should be measured todetermine if changes occur.These results with boun
33、dary-layer trips show that the side force is sensitive to the nature of theboundary layer (i.e., whether it is laminar, transitional, or turbulent), especially near the forebodyapex.Nose bluntness Based on the results presented in references 5 and 10, it was expected, butnot certain, that the side f
34、orce would be maximum for pointed noses and would decrease withincreasing nose bluntness. To investigate this effect, three nose radii were tested (figs. 16-18). Eventhe smallest nose radius of 4 percent of the base radius (NB1) (fig. 16) greatly reduces the sideforce. The next larger radius of 8 pe
35、rcent (NB2) has the lowest side force at R 0.8X106,although at the higher Reynolds numbers (fig. 17) the side force is larger. Increasing the nose radiusfurther to 16.7 percent increases the maximum side force. The variation of the side force with sideslip(fig. 18) is almost linear; no abrupt change
36、s occur as for the pointed-nose results (fig. 10). The flowmechanism associated with nose bluntness is not understood at his time, but it must be related tothe effect of the shape of the nose section on the local flow, perhaps in spreading the initial vorticesfarther apart. Evidently, some caution s
37、hould be exercised in the use of nose bluntness to reduceside forces, because it is possible that there is an optimum nose radius for a particular configuration.Strokes Previous studies have shown that strakes placed on each side of the body near thenose can reduce the asymmetric force (ref. 10). To
38、 investigate the effect of strakes, a slot was madein a duplicate, pointed nose section. Three removable, flat, sharp-edged plates were made to insertin the slot; the plates had exposed widths on each side of 0.32, 0.64, and 1.27 cm. Even thenarrowest strake (NST1 in figs. 19 and 20) essentially eli
39、minated the side force at all except thelowest Reynolds number of 0.3X 106, where the side force is greatly reduced. As expected, a sideforce occurs with sideslip angle (fig. 21), which is identical to rolling the forebody. Note that theside force and yawing moment variations with sideslip angle are
40、 directionally stable at a = 40.Figure 22 shows that when the roll angle of the removable nose with the narrowest strake isvaried, the effect produces mixed variations in the side force. Note that at angles of attack of up toabout 50 the side force and yawing moment increases with roll angles up to
41、30. In this angle ofattack range a rotatable nose with strakes might, perhaps, be used to provide high angle-of-attackyawing moment control.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Nose booms Many aircraft use nose booms that extend ahead of t
42、he fuselage to mountpitot-static pressure systems and systems that measure the flow angle. Consequently, tests wereconducted with short rods (0.319-cm in diameter) of two different lengths (2.54 and 5.08cm)inserted in the blunt noses and one of one length (2.54 cm) inserted in the sharp nose of theS
43、./d = 3.5 tangent ogive forebody. No significant effect was obtained with nose booms mounted inthe blunt noses. On the other hand, a nose boom mounted in the pointed nose greatly reduced thelarge side force (fig. 23). The side force varies somewhat with Reynolds number and it is noted thatthe data a
44、re not repeated very well at R = 0.8X106 . Although the angle of onset appears to varywith Reynolds number the lowest angle of onset is about 35, similar to the results without thenose boom.Canopy The simulated canopy had no effect on the asymmetric forces at M = 0.25 at zerosideslip (data not shown
45、).Much number It was expected from the results of reference 5 that the side force woulddecrease with increasing Mach number. To investigate this effect, tests were made at several Machnumbers from 0.1 to 0.7 at R = 0.8 X106 . The results in figure 24 show that the magnitude of theside force decrease
46、s with increasing Mach number. AtM = 0.7, the maximum absolute value of Cyis less than 0.5. Note that the angle of onset does not vary much with Mach number.Forebody With AfterbodyEffect of Reynolds number Figure 25 shows the results at several Reynolds numbers for theforebody attached to the $./d =
47、 3.5 afterbody. The magnitude of the side force is generally as largeor larger than for the forebody alone and it changes direction with increasing angle of attack,indicating that additional vortices might be forming and shedding due to the increased length of theafterbody. At R 0.8X 106, the side f
48、orce is noticeably smaller than at any of the other Reynoldsnumbers, whether higher and lower. The reason for this is not known, although it is possible thatsome intermediate transitional flow condition exists at Reynolds numbers near this value. The angleof onset of side force is between 25 and 30,
49、 about 5 to 10 lower than for the forebody alone.Similar to the forebody results, the normal-force-curve slope increases noticeably when theside force increases, as does the resultant force (compare the curves for C/y, |Cy|/C/v and CR - C/y).The maximum normal force occurs near an angle of attack of 55 and is noticeably greater than themagnitudes at a = 88. The resu
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