1、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA TM X-1658 AERODYNAMIC CHARACTERISTICS OF BODIES OF REVOLUTION AT MACH NUMBERS FROM 1.50 TO 2.86 AND ANGLES OF ATTACK TO 180 By Lloyd S. Jernell Langley Research Center Langley Station, Hampton, Va.
2、 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Clearinghouse for Federal Scientific and Technicol Information Springfield, Virginia 22151 - CFSTI price $3.00 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AERODYNAMIC CHARACTERISTICS
3、OF BODIES OF REVOLUTION AT MACH NUMBERS FROM 1.50 TO 2.86 AND ANGLES OF ATTACK TO 180 By Lloyd S. Jernell Langley Research Center SUMMARY An investigation has been conducted in the Langley Unitary Plan wind tunnel to determine the aerodynamic characteristics of a series of cylinder, cone-cylinder, a
4、nd ogive-cylinder bodies with various nose and afterbody fineness ratios for angles of attack from 0 to 180 and Mach numbers from 1.50 to 2.86. The data indicated that with the center of gravity located at 50 percent of the body length, none of the test configurations were statically stable at angle
5、s of attack near 0 or 180. The magnitude of the normal force was primarily dependent upon the magnitude of the planform area. Generally, the more rearward the planform-area centroid, the more rearward the center of pressure. INTRODUCTION In studies of the upper atmosphere and outer space, a parachut
6、e is frequently used as a means for payload recovery. The recovery of the intact payload by this means generally requires that substantial reductions in vehicle velocity be achieved prior to parachute deployment. To insure the relatively high drag levels needed for decelera- tion, it is desirable th
7、at the payload be unstable so as to avoid trim conditions at low- drag orientations, such as angles of attack near 0 and 180. Thus, it is necessary to determine the longitudinal stability characteristics of a given payload throughout the angle-of-attack spectrum so that the center of gravity of the
8、payload may be appropriately positioned. vary considerably, a systematic study of the aerodynamic characteristics of bodies with various nose shapes and fineness ratios was deemed desirable in order to gain an insight into the variables that might affect trim conditions. Since the length and shape o
9、f payloads Accordingly, an investigation was initiated to determine the longitudinal aero- dynamic characteristics of a series of cylinder, cone-cylinder, and ogive-cylinder bodies with various nose and afterbody fineness ratios. The investigation was performed Provided by IHSNot for ResaleNo reprod
10、uction or networking permitted without license from IHS-,-,-in the Langley Unitary Plan wind tunnel at Mach numbers from 1.50 to 2.86 throughout an angle-of-attack range from about -5 to 185. The test Reynolds number was 1.0 x lo6 per foot (3.28 X IO6 per meter). the aerodynamic characteristics of s
11、imilar configurations for angles of attack to about 90 and Mach numbers from 2.37 to 3.90 are presented in reference 1. The results of an investigation of the effects of fineness ratio and nose shape on SYMBOLS The data are referred to the body-axis system with the moment center of each configuratio
12、n located along the model center line at 50 percent of the body length. b A *plan CA Cm CN CN d I? LA IN M 4 xCP model cross-sectional area model planform area axial-force coefficient, pitching-moment coefficient, Axial force SA Pitching moment qAd normal -force coefficient, Normal force qA Normal f
13、orce qAplan normal-force coefficient based on planform area, body diame te r total model length length of afterbody section length of nose section free-stream Mach number free-stream dynamic pressure distance of center of pressure from model nose apex 2 Provided by IHSNot for ResaleNo reproduction o
14、r networking permitted without license from IHS-,-,-distance of planform-area centroid from model nose apex angle of attack of model center line, deg APPARATUS AND METHODS Models Drawings of the models are shown in figure 1. A straight sting was used for the nominal angle-of-attack ranges from Oo to
15、 45O and 135 to 180. For the latter range, enough of the nose was removed to allow for sting clearance. from 45O to 90 and 90 to 135O, the sting entered the model through a side cavity (shown the sting with the balance. n) For the angle ranges 4 by dashed lines in fig. 1) and had a 45O bend (enclose
16、d by model) that alined the end of Tunnel The investigation was conducted in the low Mach number test section of the Langley The nozzle leading to the test Unitary Plan wind tunnel, which is a variable-pressure, continuous-flow facility. The test section is 4 feet square by approximately 7 feet long
17、. section is of the asymmetric, sliding-block type, which permits a continuous variation in Mach number from 1.47 to 2.86. Measurements, Corrections, and Test Conditions Aerodynamic forces and moments were measured by means of a sting-supported, six-component, strain-gage balance housed within the m
18、odel fuselage. The axial-force coefficients presented herein represent the total axial force; that is, no adjustment was made for the model base-pressure conditions. The angles of attack were corrected for tunnel flow angularity and for the deflection of the model support system due to aero- dynamic
19、 load. The tests were conducted at Mach numbers from 1.50 to 2.86 and a Reynolds number of 1.0 x lo6 per foot (3.28 X lo6 per meter). The angle-of-attack range was approximately -5O to 185O. The dewpoint was maintained below -30 F to prevent significant tunnel condensation effects. Boundary-layer tr
20、ansition was effected by bands of small triangular pieces of (pressure-sensitive plastic film) tape, 0.0075 inch (0.0191 cm) thick, affixed 1 inch (2.54 cm) aft of the nose apex for angles of attack from 0 to 90 and 1 inch (2.54 cm) from the base for the angle-of-attack range from 90 to 180. 3 Provi
21、ded by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-DISCUSSION Presented in figure 2 is a sequence of schlieren photographs obtained at M = 1.50 showing typical shock patterns generated by the model and its support system in the , regions of overlapping angle
22、 of attack; that is, at angles of attack of approximately 45O, 75O, 105O, and 135. Longitudinal data for the two cylindrical models with fineness ratios of 6 and 8 are presented in figure 3. An increase in fineness ratio results in an increase in normal- force coefficient at angles of attack from Oo
23、 to 90. This increase in normal force, in turn, is reflected in a positive increment in pitching-moment coefficient at the /lower Mach numbers. The difference in CN due to an increase in fineness ratio pears to become slightly greater with increase in Mach number, whereas the effect of fineness rati
24、o on Cm vanishes as the Mach number is increased to 2.86. For the cylinders investigated, fineness ratio has little effect on axial-force coefficient. characteristics of the cone-cylinder models with a nose fineness ratio of 3 is shown in figure 4. An increase in afterbody fineness ratio leads to an
25、 increase in normal-force coefficient throughout the test Mach number and angle-of-attack ranges. At angles of attack to 45O, an increase in afterbody fineness ratio results in a positive increment in Cm, whereas, at angles of attack from 45O to 180, an increase in afterbody fineness ratio leads to
26、a negative increment in Cm. The effects of afterbody fineness ratio on the longitudinal stability characteristics of the ogive-cylinder models with a nose fineness ratio of 5 (fig. 5) are similar to those discussed for the cone-cylinder models of figure 4. k. 7) P1 The effect of afterbody fineness r
27、atio 1 A/d on the longitudinal stability The discontinuities exhibited by the data are believed to be due primarily to inter- ference effects of the model support system. of figure 2(a), for a! = 45O, shows the trailing shock from the model base being influenced by the flow field surrounding the sti
28、ng flare. This condition would be expected to affect the axial force. With the 45 bent sting installed, figures 2(b) to 2(e) show that as the angle of attack approaches 90 the aft portion of the model comes under an increasing influence of the high-pressure field induced by the support-system flare;
29、 thus, normal force and pitch characteristics as well as axial-force characteristics are affected. As would be expected, the data indicate that the degree of influence is greater for those configurations having larger portions of the body in close proximity to the sting flare. These data indicate th
30、e need for further study of model support-system techniques for extremely high angle-of-attack testing in order to minimize these interference effects. For example, the schlieren photograph 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The effect
31、s of nose fineness ratio on the longitudinal stability characteristics of the ogive-cylinder models having an afterbody fineness ratio of 6 are shown in figure 6. An increase in nose fineness ratio results in an increase in normal-force coefficient at all test angles of attack (Oo a! 180) and at all
32、 test Mach numbers. The pitching- moment coefficient becomes more negative with increasing nose fineness ratio. This negative trend reflects, as expected, a more rearward location of the center of pressure on the models with higher nose fineness ratio. The data of figures 3 to 6 indicate that none o
33、f the configurations having the center of gravity at 50 percent of the body length are statically stable at angles of attack near Oo or 180. The effects of nose shape on the longitudinal stability characteristics of the models e having a nose fineness ratio of 3 and an afterbody fineness ratio of 6
34、are shown in figure 7. The ogive-nose configuration exhibits slightly greater values of normal-force coefficient, and less negative values of pitching-moment coefficient than does the cone- cylinder model. The effect of nose shape (cone or ogive) on axial-force coefficient is negligible. The variati
35、on of the normal-force coefficient based on planform area CN with overall fineness ratio Z/d is shown in figure 8 for Mach numbers of 1.50 and 2.86 and arbitrarily chosen angles of attack of 30, 70, llOo, and 150. At M = 1.50, although a small decrease in the normal-force parameter is generally note
36、d as fineness ratio is increased, no effect due to nose shape is discernible. At M = 2.86, neither fineness ratio nor nose shape has an effect on the normal-force parameter. Thus, these data indicate that the magnitude of the normal force is primarily dependent upon the magnitude of the planform are
37、a. The variation of the center of pressure in percent of body length, xcp/l, with angle of attack is presented in figures 9 to 12. All models exhibit a rapid rearward travel of the center of pressure with increasing angle of attack to approximately 20 and above approximately 160. For the interim ang
38、les (20 , a! 2 160), the rate of change of the center of pressure with angle of attack is relatively low and approaches a linear variation. The variation of center of pressure with the planform-area centroid at several angles of attack is shown in figure 13. Generally, the more rearward the planform
39、- area centroid, the more rearward the center of pressure. CONCLUSIONS An investigation has been conducted in the Langley Unitary Plan wind tunnel to determine the aerodynamic characteristics of a series of cylinder, cone-cylinder, and 5 Provided by IHSNot for ResaleNo reproduction or networking per
40、mitted without license from IHS-,-,-ogive-cylinder bodies with various nose and afterbody fineness ratios for angles of attack from Oo to 180 and Mach numbers from 1.50 to 2.86. The results of the investi- gation indicated the following conclusions: 1. With the center of gravity located at 50 percen
41、t of the body length, none of the test configurations were statically stable at angles of attack near 0 or 180. 2. The magnitude of the normal force was primarily dependent upon the magnitude of the planform area. 3. Generally, the more rearward the planform-area centroid, the more rearward the cent
42、er of pressure. * Langley Research Center, National Aeronautics and Space Administration, Langley Station, Hampton, Va., June 14, 1968, 124-07-05-01-23. REFERENCE a 1. Smith, Fred M.: A Wind-Tunnel Investigation of the Aerodynamic Characteristics of Bodies of Revolution at Mach Numbers of 2.37, 2.98
43、, and 3.90 at Angles of Attack to 90. NASA TM X-311, 1960. 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-0 6 d 3 4 3 6 3 a 3 6 4 Figure 1.- Model drawings. Dashed lines indicate the various 45O bent sting arrangements. 7 Provided by IHSNot for Re
44、saleNo reproduction or networking permitted without license from IHS-,-,-(a) Model mounting for a = 8 to 45O, shown at a“ 45O. (b) Model mounting for a = 45 to 98, shown at a“ 45O. (c) Model mounting for a = 45O to 904 shown at a =: 750. (d) Model mounting for a=98 to 135O, shown at a“ 105O. (e) Mod
45、el mounting for a = 90 to 135O, shown at a“ 135O. (f) Model mounting for a = 135O to 1800. shown at a“ 135. L-68-5640 Figure 2.- Schlieren photographs of ogive-cylinder model showing typical shock patterns and model mountings for the various nominal angle-of-attack ranges. M = 1.50; 2 = 5; a A = 4.
46、8 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Cm d CN 10 0 -10 (a) M =1.50. Figure 3.- Effect of fineness ratio on longitudinal stability characteristics of cylindrical models. 20 10 0 -10 -20 0 20 40 60 80 100 120 140 160 180 200 a, deg 9 Provid
47、ed by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-(b) M=1.90. Figure 3.- Continued. h 10 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Cm CN 10 0 -10 20 10 0 -10 -20 0 20 40 60 80 100 120 140 160 180 200 a,
48、 deg (c) M =2.36. Figure 3.- Continued. 11 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Crn CN 10 0 -10 20 10 0 -10 -20 0 20 40 60 80 100 120 140 160 180 200 a, deg (d) M =2.86. Figure 3.- Concluded. 1 CA 0 12 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CN 10 0 -10 -20 20 10 0 -10 20 40 60 80 100 120 140 160 180 200 -20 0 a, deg (a) M =1.5
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