1、COPY i; _ RM A51Clk NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS . WASHINGTON UNCLASSFiED l May 17, 1951 RESEARCH MEMORANDUM A SEMIEMPIRICAL METHOD FOR CALCULATING THE PITCHING MOMENT OF BODIES OF REVOLUTION AT LOW MACH NUMBERS By Edward J. Hopkins Ames Aeronautical Eaborator y Moffett Field, Calif.
2、. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1 1 EACA RM A5lCl4 , IKf c ItiYl?IONAL ADvIsfRY coffTpE FOR AERoNAuTIcS l ASEMIEMElRICALMETBUDFQRCALCT moments calculated by the method of this report gave the best agreement with the expermntal data
3、for nearly all the bodfes. The agreementwiththe experimentallift and dragcharac- teristics as givenby the method of this report was generally as good as that given by EACA EM AgI26. Cue of the ffrst attempts to utilize potentfal theory for the esti- mation of the aerodynamLc forces and moments for b
4、odLes of revolution Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NACA HM A51C14 was made by Munk in connection with his work on airship8 (reference 1). . Several other investigators have developed similar methods which gFve essentially the same
5、results (references 2 and 3). It has been shown - (references 4 and 5) that for the expanding porticn of the body at an angle of attack these methods give an accurate prediction of the trans- verse forces. However, for the contracting portion of the body where the effects of viscosity become Importa
6、nt, the predicted transverse forces do not agree with experiment. In reference 6 an approxtite theory to account for the effects of viscosity was developed for inclined bodies of revolution. This approxixmte theory.results insatisfactory agreePlent between the predicted and,eerimentay Horace: Hydrod
7、.yaamics. Dover Publications, N.Y., 1945, . . Goldstein, S., ea.: Modern Developments in Fluid Dynamics. Oxford, The Clarendon Press. Vol. 2, sec. 195, 1938, pp. 439-440. Jones, J. Lloyd md Demele, Fred A.: Aerodynamic StudyofaWing- Fuselage Conibination Employing a Wing Swept Back 63O - Characteris
8、tics Throughout the Subsonic Speed Range with the WFng Canibered and Twisted for a Uqiform Load at a Lift Coefficient- of 0.25 IWX RMAgD25, 1949. Hoggard,.H. Page, Jr.: Windunnel Investigation of Fuselage Stability in Yaw with Various Arrangeents of Fins. ITACA TN 785, 1940. Lange, G.: Force and Rre
9、smristribution Measurements on Eight Fuselages. NACA TM 1194, 1948. Jacobs, Eastman N., mmax dianwtw at .4OOL, fuss ma= d nw# dtameter at .4.?5L, rsL f8 Fhwsa rOtb n-IOJ; mox dimwar ol .I.?a! * d?L, ret I7 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-
10、,-,-NACA I34 A51C14 15 I.0 .S .8 . .5 Q Ano/yfical point - -Line of regression, PO.378 f 0.527 xs/, .5 .6 .I .8 -9 I.0 “I/c. Figure S.- Gofrelafion between assumed exfenf of app/icab/fy of pofsntiai fheory and the posifion of the maximum negative rate of change of body cross- sectional area with bod
11、y length. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-16 IWX RM A51C14 tiil I I I I ii1 0 expartmmt - - - method herein 3.6 -method 0fref.6 - -potmt/al theory potenthi term -0 4 8 12 /6 20 Angle of uffuck , a, deg -mthud or rat 6 -paiwttlal theor
12、y potmtmf mm t i i i i T /Vi i I 1; i I I I I I v- 0 4 8 12 16 20 Angle of of fuck , a, deg (a, Model I. (b) Model 2. Figure 6- Conporison between the ekperhen fo/ and fhe esfi- nwfed Liff, drag and pifchhg-monmf chmcferisf/cs of wurious bodies of f e vohfion . . Provided by IHSNot for ResaleNo repr
13、oduction or networking permitted without license from IHS-,-,-3 EKA RM A53214 17 I -. - -.-r- -method of r deg Angie of offock, 0; deg /cl Mode/ 3. to/ Mode/ 4. potaaliol t*rm - c Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-18 (I -I - IY. deg (e)
14、 Mode/ 5. figure 6.- Continued 0 4 8 /2 /6 20 Angle of attack, Q, deg (i) Mode/ 9. - - method hers - - method af ref - -method herah -mrthod of r# 4 8 12 16 20 Angie of oftock, U- deg (/j Mode/ IO. Figure 6.- Continued . Provided by IHSNot for ResaleNo reproduction or networking permitted without li
15、cense from IHS-,-,-c RACA RM A51C14 PL- 4 I I I I I I I I I I - - - method- borafn - method of rat6 - -pof*ntial theory natsntiol term 4 8 12 16 20 Ang/e of oftack, aa deg (4) Mode/ I/. Figure 6.- Q l aperimsnt - - metbod bare0 - -mrthod of ref: 6 4 8 /2 16 20 Angie of oifuck, 4 deg (f/ Mode/ 12. Co
16、niinued . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-22 NACA RMA51C14 otenflal term - for mothod hersa 0 4 8 12 16 20 0 4 8 12 16 20 - method - - method d roll 6 -potential theory Angle of attack, 8, deg Ang/e of attock, 0; deg (m) Mode/ 13. (n)
17、 Model 14. figure 6.-Continued. - I . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IUGA RMA51C14 * 23 - - - mefhod of ref. 6 -w- - pofen f iul theory m-m pofenf/u/ ferm for method herein 0 0 4 8 Angle of uffuck , cc, deg 5 c (0) Model 15. Figure 6
18、 .- Concluded . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-0 expsrhen t - -8qUtTtiOn fi) c- pofsntiol term in equath f/ moment - couple part of -s- equation f/I fineness rotio , n = 4.0 0 4 8 12 16 20 0 4 8 I2 I6 20 Anflle of ottock, a, uefl fif
19、lure z - The compon8nts of the pitchinfl-mom8nt coefficient coufat8d by the method of this report for fW0 different bodies. I , c Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4 . NACA RM A51C14 25 4 .7 .6 .5 .4 .3 .2 ./ 0 .8 Model 3 moment center.
20、 0.572L .6 I I I I I I I I “iI 4 8 1.2 16 20 0 4 8 12 16 20 0 4 8 12 /6 20 0 experimenf - - mefhod herein -mefbod of ref: 6 Angle of offock, a, deg (u.lhfode/s / fo 5. Figure 8.- Comparison befween fhe experimenful ond the esfimafed pifching-moment churacferisfics of various bodies of revohfion. Pro
21、vided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26 NACA RM A51C14 ldel 6 moment center, 0.500L .I .6 2 2. 5 .* c .4 .3 .2 ./ 0 i 7 .6- .wouef a 4 8 12 16 20 Mode/ 7 moment center, 0.5OOL I I I I I t I I I 0 4 8 12 16 20 Angle of uffuck, a, deg (bMode/s
22、6 to /O. 0 experimenf - -me fhod berein -method of ref 6 0 4 8 12 /6 20 .- Y- 4 Figure 8.- Continued Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EACA RM A51C14 J a .9 .8 .7 .6 .5 .4 .3 .4 OV 0 4 8 12 16 20 0 experimen f - mefhod herein -mefhod of ref: 6 0 4 8 12 /6 20 0 4 8 12 16 20 Angie of uf fuck , a, deg (cl Models / to 15. r . Figure 8. - Conchded *-Lpnp,*, - 6-17-61 -376 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
