1、NaCxamlw%E NATIONALADVISORYCOMMITTEE2 FOR AERONAUTICSTECHNICAL NOTE 3963A CORRELATION OF LOW-SPEED, AIRFOIL-SECTIONSTALLING CHARACTERISTICS WITH REYNOLDSNUMBER AND AIRFOIL GEOMETRYBy Donald E. Gard.tAmes Aeronautical LaboratoryMoffett Field, Calif.WashingtonMarch 1957, .Provided by IHSNot for Resale
2、No reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NMIv.TECHNICALNOTE 3963.a71 “A CORRELATION OF LOW-SPEED, AIRFOIL-SECTIONSI!AIJLINGCHARACTERISTICSWITH REYNOLDSNUMBER AND AIRFOIL GECMEITHBy Donald E. GaultThe low-speed stalltig characteristics of a large number
3、of airfoilsections have been correlated with Reynolds number and a single airoilordinate near the leading edge as the correlating parameters. The corre-lation is appropriate only to airfoils without high-ldft devices in flowsof very low turbulence and tith aercdymamically smooth surfaces.INTRODUCTIO
4、NIt is often of interest, from consideration of wing design andanalysis of related aerodynamic data, to bow the effects of variablessuch as Reynolds number and airfoil geometry on the low-speed stallingcharacteristics of airfoil sections. Toward this end, there is presented,hereina correlationwhich
5、has been detised between the stalling charac-teristics of airfoil sections and (as the independent variables) Reynoldsnumber and a simple geometric measurement from an airfoil. The correlaticmis restricted to airfoils without high-lift devices and to airfoih withaerodynamically smooth surfaces. Expe
6、rimental force and moment data forapproximately 10 airfoils are employed to form the correlation and, horder to eliminate the influence of stream turbulence insofar as possible,the data are limited to measurements obtained in the two-dimensional.,low-turbulence wtnd-tunnel facilities of the NACA (se
7、e ref.1).GENERAL CCKZDERATICINSClassification of StallReference 2 describes three types of stalll for airfoil sections atlow speed. The three types are:Reference 2 defines S Reynoldsnumber, 6XJ.OS; combined type of stall). This inconsistentbehavior isalso true for the N/KM 23012 and 23015 airfoil se
8、ctions (note the leading-edge and combined type stalls shown in the figure for values of theordinate of 2.67 and 3.34, respectively). These three NACA 230-series Aprofiles are the only airfoil sections of those investigatedwhosestalling characteristicsare considered to be definitely inconsistentwith
9、 the general results of the correlation.“It is possible, however, +that the stalls of these airfoils were preceded by an extremely rapidforward proession of the position of turbulent boundary-layer separa-tion (i.e., a trailing-edge type of stall) and as such would agree withthe correlation. This be
10、ing a possibility illustratesthat the decisionsas to the types of stall are arbitrary for some cases and umcertain fora few cases. The inconsistentresults for the NACA 230-series of airfoils,therefore, serve to emphasize the limitations and qualitative nature ofthe analysis presented herein.The boun
11、daries between what are consideredthe three fundamentaltypes of stall are reasonably distinct, particularly between the leading-edge and thin-airfoil types of stall.which are inherent to the thinnerairfoils of current interest and applications. The boundaries for thecombined type of stall are also f
12、airly well defined and, as might beexpected, the region encompassed by its boundaries lies on both sides ofthe boundary which separates the leading-edge and trailing-edge types ofstall. There are, therefore, five regions defined in figure 1: (1) aregion for only the thin-airfoil stall; (2) a region
13、for only theleading-edge stall; (3) a region in which both the leading-edge stallProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NAc!A!l?N3963 5.and the combined type of stall occur; (4) a region in which both the*4 trailing-edge stall and the combin
14、ed type of stall occur; and (5) a regionfor only the trailing-edge stall. The combined type of stall is,effectively, a transitiona any reduction in Reynolds numberto very low values would tend to delay the occurrence of transitionfrom laminar to turbulent flow in the boundary layer. This, in turn,sh
15、ould lead to more etiensive regions of separated laminar flow whichwould faver the prominence of the thin-airfoil stall at the expense ofthe l-ding-edge stall. This line of reason suggests that anincrease in the Reynolds number should hasten the occurrence of transi-tion and should either preclude o
16、r greatly reduce any extents of seatedlaminar flow. This, in turn, would tend to eliminate or at least lessenthe occurrences of leading-edge and thin-airfoil.stall with the resultantpredomhance of the trailing-edge type of stall. The results in thefigure are consistent with such reasoning for Reynol
17、ds numbers between106 and 107; the available data for higher values of Reynolds number aremeager, however, and the trends are by no means conclusive.CONCLUDING REMARKSSince the phenomena of stalling sre inseparably related to thebehavior of the boundary-layer flow, there is some physical basis fora
18、correlation between stalling characteristicsand Reynolds number.However, the relationship between stalling characteristicsand an upper-surface ordinate near the leading edges of airfoils has no apparentphysical significance. The degree of correlation obtained, therefore, issurprising and would seem
19、to be a fortuitous result from strictly anempirical approach to the problem of stalling. Jn this connection it isto be emphasized that the decisions as to the types of stall.were admit-tedly arbitrary for so?qecases and in a few cases uncertain. The prti-cipal justificationfor the correlation is its
20、 simplicity snd thereasonable distinctness of the boundaries dividing the three pure typesof stall.*t Ames Aeronautical LaboratoryNational Advisory Committee for AeronauticsMoffett Field, Cali.f.,Jan. 7, 1957Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IH
21、S-,-,-6 NAC!ATN 3963REFERENCES.*1. Abbott, ha E., von Doenhoff,Albert E., and Stiwrs, Louis S., Jr.ssUIMllUyof Atifoil ;-zu&66:OXX66-2m66-4xx63Aon64AOXX65AOXXo0.12.25.3600.11.210.I.l.210.11.210.11.2100061.111.251.42.65*77.891.02a71 75.881.01.72.84a71 97.69.81a71 93.75.74.728.-1.011.14-a71 95-.92-1.0
22、0.98a71 95Thickness mtio,mrcent chord.9 101.42 1.X1.62 1.781.81 -2.02 -.97 -1.15 1.271.29 1.411.44 -1.13 1.251.26 1.401.41 -1*O6 1.171.19 1.301.32 1.471.03 1.141.16 1.281.30 - 1.25- 1.23- 1.1812m2.152.442.671.291.521.691.851.491.651.831.391.541.701.361.511.671.491.461.41152.713.073.341.611.882.082.3
23、01.842.032.251.701.882.071.671.852.031.841.811.7518a3.283.764.091.942.222.462.762.182.492.702.012.212.431.952.152.36-213.313.874.454.872.262.532.783.102.522.773.ti2.302.542.782.242.462.68-243*954.445.205.65- - -%4Provided by IHSNot for ResaleNo reproduction or networking permitted without license fr
24、om IHS-,-,-NACA TN 3963 93 I IaD I a 000 0 0 Thin-airfoil stall. u Leading-edge stall.2 ! I Combined leading0 edge and trailing-1.5” 0 Trailing-edge stal.,7oI 1 II I Ito I o I It I.:. . Combined leading-edgeand trailing-edge stall10:8765I I 1 1 I I40 .4 .8 1.2 .6 Z.O 2.4 z-e 3.2 Upper-surface ordina
25、te at 0.0125 chord, percent chordIW3= l.- The low-speed stalling characteristics of airfoil sectionscorrelated with Reynolds number and the upper-surface ordinates ofthe airfoil secticms at the O.0125-chord station.NACA - Lmey iel Va.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
