Aerodynamic characteristics of the NACA 747A315 and 747A415 airfoils from tests in the NACA two-dimensional low-turbulen...

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Title:
Aerodynamic characteristics of the NACA 747A315 and 747A415 airfoils from tests in the NACA two-dimensional low-turbulence pressure tunnel
Alternate Title:
NACA wartime reports
Physical Description:
10, 4 p. : ill. ; 28 cm.
Language:
English
Creator:
Von Doenhoff, Albert E
Stivers, Louis S
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Aerofoils   ( lcsh )
Drag (Aerodynamics)   ( lcsh )
Lift (Aerodynamics)   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: Two low-drag airfoils, the NACA 747A315 and the NACA 747A415, designed to have reduced pitching moments about the quarter-chord point and moderately high values of the design lift coefficient have been tested in the NACA two-dimensional low-turbulence pressure tunnel. Section lift, drag, and pitching-moment coefficients are presented for Reynolds numbers of 3 x 10⁶, 6 x 10⁶, and 9 x 10⁶, together with section lift and section drag data for a Reynolds number of 6 x 10⁶ for the same airfoils with roughened leading edges.
Bibliography:
Includes bibliographic references (p. 7).
Statement of Responsibility:
by Albert E. von Doenhoff and Louis S. Stivers, Jr.
General Note:
"Report no. L-156."
General Note:
"Originally issued September 1944 as Confidential Bulletin L4I25."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

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University of Florida
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
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oclc - 71833574
System ID:
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CB No. IAI25


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WA11RTIMIE REPORT
ORIGINALLY ISSUED
September 1944 as
Confidential Bulletin 4II25

AERODYNAMIC CHARACTERISTICS OF THE NACA 747A315 AND
747A415 AIRFOILS FROM TESTS IN THE
BACA TWO-D3MENSIONAL LOW-TURBUIENCE PRESSURE TUNNEL
By Albert E. van Doenhoff and Louis S. Stivers, Jr.

Langley Memorial Aeronautical Laboratory
Langley Field, Va.











WASHINGTON

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
advance research results to an authorized group requiring them for the war effort. They were pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.


L 156


DOCUMENTS DEPARTMENT


L- Kt






































Digilized by Ihe Inieinei Archive
in 2111 with funding Irom
University ol Florida, George A. Smaillers Libraries wilh support Iroin LYRASIS and tie Sloan FoLndaloilon


hlIp: www.archive.oig details aeiodynamiciesisO"lang




- I :" -


NACA CB No. L4125

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS


COIFTDE.NTIAL BULLETIN


AERODYNAMIC CHARACTERISTICS OF THE NACA 747A315 AID

747A415 AIRFOILS FROM TESTS IIN THE

NACA TWO-DIMEN-TSIONAL LOW-TURBULENCE PRESSURE TUNNEL

';; Albert E. von Doenhoff and Louis S. StiverT, Jr.


SUMMARY


Two low-drag airfoils, the 1'ACA 747AZ15 and the
TACA 747A415, designed to have reduced pitching moments
about the quarter-chord point and moderately high values
of the design lift coefficient have been tested in the
D.ACA two-dimensional low-turbulence pressure tunnel.
Section lift, drag, and pitching-moment qcefficients are
presented for Reynolds numbers of 3 x 103, 6 x 106, and
9 x 106, together with section lift and section drag data
for a Reynolds number of 6 x 106 for the same airfoilr
with roughened leading edges.

A comparison of the characteristics, at a Reynoliis
number of 9 x IC6, of the MACA 747A315 aand NACA 747A415
airfcils with characteristics of the MACA G62-415 airfoil
is riven in the following table:


N;ACA Minimum Range of Section pitching- Maximum Critical Mach
airfoil section section moment coeffi- section number at
section drag lift coef- cient about lift design section
coef- ficient quarter chord at coef- lift coeffi-
ficient for low design section ficient client
drag lift coefficient

-747A15E 0.0038 0.22 to 0.62 -0.017 1.43 0.626
747A415 .0041 .32 to .72 -036 1.5[ .C12
:5i-415 .0042 .08 to .58 -.071 1.62 .C41
1.- .---41-i








NACA CD Nj. 1.4125


INTRODUCTION


The type of mean line usually used to camber the
C-se-'es airfoils presented in reference 1 led to rela-
tively high. pitching-moment coefficients about the
quarter-chord point for a given design lift coefficient.
For example, the measured pitching-moment coefficients
for airfoils having a mean line of type a = 1.0
caO.,Ered for a design lift coefficient of 0.1 were
approxziately -0.070. This -nmo.nent coefficient is sore-
what hither than is desirable for many applications.

The I'ACA 7-serier airfoils were derived in an attempt
tf obtain moderately high values of the design lift coef-
ficient and to retain the lIw-drag characteristics of the
6-srcies airfils, but with reduced pitching moments.
Tle iACA 7-s,-'ries airfoils differ from the S-series air-
foils in that the 7-series airfoils have a slightly modi-
fi-edr thicl-Mess distribution and are combined with mean
line" in such & -a.irner that more eLtensive reCions of
la..iinar flow are p-':siblL over the Icwer surface than
over the upper surface. The chordwise load distribution
is so chosen that tle main portion of the lift is carried
by the forward part of The airfoil and the p't.ching
moments about the quarter-chora point are tnus reduced.

The pre-r-r.t report give data for two airfoils of
th:i.s t-,p,, d rn -n i. d -th1 e AC.-. 7 747711 and the
.tAA 747.415 rirf. 1, from tests in the rA3A two-
'di.-.'-nsional low.-tu'l-:n' pressure tu'..nel (TDT). Lift,
drT, and pit:1-:c' r.-.:-ts ofi tlhc': se *:r:ns .,ere meas-
urd fo:, a r.;Ar :< c~crolds nluwb rs from 3 to 9 x 10.
The effect f roa.j-c.-s at the leading edge on the lift
and cr.:-. charactterlsticn. of tng sections was determined
at a Reynolds nunter of 6 x 10


SYB'. .OLS


x distance from airfoil leading edge measured
al-.ng chord line

Co section angle of attack

c airfoil chord length


COT 0IDE iTIAL


CCNFIDENTIAL









iTAZA CE H1o. L4125


P7 section lift coefficient

e1. design lift coefficient for mean line

cd section drag coefficient

Cmc/4 section pitching-moment coefficient about
quarter-chord point

v local velocity over airfoil surface

V free-stream velocity

a mean-line designation described in reference 1

R Reynolds number

Mc critical Mach number


DERIVATION OF AIRFOIIS


In the derivation of the INACA 747A.115 airfoil, an
attempt was made to have uniform load from the leading
.edge to 0.4c back of the leading edge, to have this load
decrease linearly to zero at 0.7c, and to have zero load
from 0.7c to the trailing edge. This object was attained
by combining a mean line of type a = 0.4 for a design
lift coefficient of 0.763 with a mean line of type
a = 0.7 for a design lift coefficient of -0.463. Ordi-
nates and load distributions for these mean lines may be
derived from data presented in reference 1.

In order to maintain a favorable pressure gradient
to 0.7c along the lower surface of the :jACA 747A315 air-
foil, the resulting mean line was combined with a modi-
fication of the IACA 64,2-015 airfoil section. The
64,2-015 airfoil section was modified to reduce the slope
of the pressure gradient from 0.4c to 0.7c. Figure 1
shows the pressure distribution over the modified sym-
metrical MNCA 64,2-015 airfoil section, together with
the pressure distribution of the hIACA 747A315 airfoil at
the design lift coefficient. Table I gives the ordinates
of the modified 64,2-015 airfoil section. Table II gives
the oj-dinates of the 747A315 airfoil section.


COiFFIDENTIAL


CONFIDENTIAL







NACA CB Uo. L4T25


The P'ACA 747A415 airfoil was obtained by combining
the modified 64,2-015 airfoil section with the following
mean-line combination: a = 0.4, cli = 0.763; a = 0.7,
ej = -0.463; and a = 1.0, cl. = 0.100. Figure 2
shows the theoretical pressure distribution of the
NACA 747A415 airfoil at the design lift coefficient,
together with that of the basic sy-ietrical section (the
modified NACA 64,2-015 airfoil). Ordinates for the
:UACA 747A415 airfoil section are given in table III.


ATRFCIL DESIOGATICN


The significance of the numbering system for these
airfoils is explained by the following example: In the
designation 7IACA 747A415, the first number "7" indicates
the new series number; the second number "4" indicates
the extent over the upper surface, in tenths of the
chord from the leading edge, of the region of favorable
pressure gradient at the de- gn l,2t coefficient; the
third nun-iber "7" indicates the ext-nt over the lower
surface, in tenths of the chord fr.: the leading edge,
of the region of favorable pressure gradient at the
design lift coefficient. The significance of the last
group of three numbers is the same as for the previous
6-series airfoils (reference 1); that is, the first
number following the letter gives the design lift coef-
ficient in tenths, and the last two numbers give the
airfoil thickness in percent of the chord. The letter
"A", which follows the first three numbers, is a serial
letter to distinguish different airfoils having parame-
ters that would correspond to the same numerical desig-
nation. For example, a second airfoil having the same
extent of favorable pressure gradient over the upper and
lower surfaces, the same design lift coefficient, and
the same maximum thickness as the original airfoil but
having a different mean-line combination and thickness
distribution would I-iave the serial letter "u."


TEST PROCEDURE


The models of the !!ACA 747A315 and 747A415 airfoil
sections had a chord of 24 inches and a span of 35.5 inches.
The methods of constructing and testing these models were
CC NF ID,'T TIAL


CONFIDENTIAL








"'7ACA CB No. 14T2E


the sar'e qs those described in reference 1. The norr.al
corrections for wind-tunnel wall intcrferencs were r-,ic
to the data obtained in the TDT accordin-. to the fol-
lowing formulas, in which the primed quantities refer
. LD-. values measured in the wind tunnel:


ao = 1.015 ao'

cd = 0.990 cd'

cy = 0.975 cL'

Cm = 0.990 cm3/4


7n addition to tests at Reynolds nux-ibers of 3, C, and
9 x 'C0 itn the smooth condition, tests were made at a
Feynolds number of G x 1h6 with the leading edges of
the airfoils roughened. The roughness contr:ited of
carborundum grains with a maxirmii.ur. diameter of about
C.01G to 0.015 inch. The-e grains were thinly sprinkled
over the leading-ed:-e pp-,tion of the win,T Fection
covering a region of 1- inches from' the leading edge
on the upper and lower surfaces across the spar. of the
model. A thin coat of shellac was used to hold the
Rains on the surface.

Since the presentation of the data in reference 1,
certain charges have been made in the method of com-
puting lift coefficients from munnel data. M'"Are accurate
factors have been derived, which .ivc the proportion of
lift actually transfErred co the floor and the ceiling
of the tunnel in the finite length covered by the floor
and ceiling orifices. The revi.-ed factor.- result in a
decrease in the slope of the lift curve and a decrease
in the values of the raximu mr lift coefficient of approxi-
rately 4 Ie recent. In addition to the change in these
factors, a correction for increased blocking effect at
-,na7iles of attack in the neiphbborhood of m-qaximum lift has
been applied to the data presented herein. For the
Present data, this additional blocking correction derived
from yre-sure measurements along the floor and ceiling of
the tunnel resulted in a further reduction cf the maxi:-umn
lift coefficient by between 1 and 2 percent.


CO I vFIDEITT IAL


CC7FIDE;TITAL








IIACA CB No. 14T25


RESULTS AND DISCUSSION


>-ction lift, drag, and pitching-moment data obtained
.?!. thc IDT testy are presented for the NACA 747A115 ar.d
S7A-115 airfoils in figures 3 and 4, respectively. F-r
e.:ch alrf il, the extent of the low-drr-g range is nearly
:- ar:'e as woul- be expected fro-i, the tests of a 15-
srce'-.t thick 6-series alrfoil. r!be cErter of the. low-
".'.z- ra!.ge for both airfoils, however, Is abcut O.1c,
fhi her c-han Lhe design lift coefficient given from the
ct'tbin.tion of mean lines used for each airfoil. Thi.
lffer*.r-:ec i probably due to the auproximaticis ii':vilved
in the :,-ean-line theory in '.hicii the increments in
-:]ocity over the upper and lcwer surfaces are assumed to
:e S-...ll cor- .sr l with the free- tr.es:i %elocity.

A co.- nrison of the characteristics Ff the MTACA 747A315
-and tje I.ACA 7477.415 airfoils witl. thi.e of the ';ACA 652-415
irfAil at a iRhynclds number' of 9 x 106 is given in the
uabie that fo]lol-s. The data for the "A.CA 652-.15 airfoil
eiven ir. the table were o-uained from tcsta in the TDT and
have been reduced in t:.e sa:.e manner as ffr the 7-series
atirf ll The values of critical ach n-ibt-r i;c were
ot t ac. front: tnce theoretical low--speec pressure cistri-
b'uti.nF: by rsinr the chart presented on page 20 of the
".r- ie.ernc to r;fer-ence 1.


.A",A Rarge of at c at
;Lr~roil c ^ c f~r .m ,./ at i rra
Sdm:n Ifor -- max design
sect'-ion lw 1 drag design e cz

L7A7 15 0.-'038 '0.22 to 3.62 -0.017 1.43 0.626
77.Al415 .,r-y 1 .72 to .72 -.D36 1.50 .612
6 ^- .002 .3) to .*3 -.071 1.62 .6 1


Langley Memorial Aeronautical Laboratory
'Tational Advisory Comnittee for Aeronautics
Langley Field, Va.


CO'T-.T DE-T 'IAL
.^ ,.,m: T !r I-. L


CONFIDLiITIAL








!JACA CB No. L4125


REFERZTiCE


1. Jacobs, Eastman IN., Abbott, Ira H., and Davidcon,
Milton: Preliminary Lovw-Lrag-Airfoll and Flap
Data from Teots at Large Reynolds INumbers and Low
Turbulence, and 3upple.nent. UIACk ACE, "arch 1942.


CO3FID.'ETIAL


CO!ITFIDETTIAL








PACA CB No. L4I2:'


TABLE I.- MODIFIED NACA 64,2-015 AIRFOIL ORDINAT3S
L{-t-o4r.s and ordirate iven in percent of airfoil c-h rj


Station Crdinate


S.5

1.5
2.5

7.5
10
15
20
30
35

4 0
45
50
5
60

701
75
8O
-5
90
95
100


0
1.199
1.4?5
1.801
2.4 C 2
3.419
4 .143
4.74Z
5.684
6.364
6.898
7,253
7. 54
7.494
7.316
'7 Z'C36
7. C, C
6.5 4
6.04
5.449
4.73.8
3.921


1.193
.443


L.E. radius: 1.544


NATIONAL ADVISORti CC-,CNMITT:LE FCR ALROCAUTICS


CCfIDE-ITITAL


SC;F-IDE7"TIAL








:'^CA CB IPo. L4125


TABLE II.- NTACA 747A315 AIRFOIL ORDTNATES
C stations and ordinates given in percent of airfoil ch,-rdl


Upper surface Lc.wer surface

Station Ordlnate Station Crdinate

0 D 0 0
.229 1.305 .771 -1.0 1
.449 1.599 1.051 -1.207
.911 2.065 1.5C9 -1.47,5
2.109 :;.935 2.351 -1.927
4.564 4.2534 5.136 -2.51S
7.053 3.226 7.347 -2.952
9. a8 6.140 1C. ...2 -5 .-C4
14 9 7.497 15.401 -3.843
19.6e8 3.503 20. 7.C2 -4.247
24.758 9.242 25. '42 -1.546
29.067 0.731 Z0.1 -1.773
35.C001 9.982 34.99'9 -4.026
40.200 9.962 39.800 -.C.20
45.375 9.572 44.'53'5 -5.040
50.347 8.964 49.5 3 -5.,14
55.463 8.206 54.527 -4.030
60.435 7.Z224 9.365 -4.772
.5. 66 6.355 64.3,4 -4.509
70.241 5.351 69.759 -4. 110
75.3 0 4.536 74.370 -3.5C2
,?C.073 3.295 79.927 -2.743
85.028 2.257 84.9,32 -1.915
90.016 1.239 9.984 -1.097
95.004 .431 94.996 -.405
100 0 I1CO 0


L.E. radius: 1.544
Slone of racAlu through L.E.: 0.232






"ATICiIAL ADVTSCRY CO MITTL rCR RCN AUTICS
T.....ITAT_ "'OR -7 RCNAUJTICS


CC ON TIDFT' AL


CONFIDENTIAL









NiACA CE No. L412~


TABLE III.- !,ACA 747A415 AIRFOIL ORDTIAT7.
F9tationr and ordinates given in percent of airfoil chords


npper surface Lower surface

Station Crdinate Station '-'rdirite


0
1. 18
1.622
2.1,.6
3.016
4.411
5.483
C.390
r- r, r-
',
9.687
',.2161
1 '.497
10.49 9
10.121
9.516
5.755




S.632
,.592
1.546
.639


L.E. radius: 1.544
Sl]pe of radius through L.Z.: 0.274


.183
.398
.352
2.041
4.4c7
6.972
9.4 56
14.521
13 .59 S
24.698
29.,13
34.964
40.176
45.264
50.447
55.474
60.454


75.164
j.107
85.063'
90.037
95.015
1i0


IN'TIOIAL ADVISORY COM .i!TTEE FOR AERONAUTICS


C FI I E'T I AL


.817
1.10 2
1.643
3*.959
.' 03
8.o08
10.5c4
15.47.'
20.402
2C. ,9 C.
30.1,22

39. -24
4 1.t 6
49.3 3
54. 526
59 546
64 607
69 9 Z C.13
7 4 36
79.389
54.934
$9.9C3
94.985
1C.O0


-0
-.994
-1. 16C
-1.40C6
-1 .ci22
-2.349
-2.730
-".028
-3.0.01
.45
-4.0C5

--4. 1. 1

i '-1.49
-4.4c2
-4. 81
-4.235
-.9V 2
-5.. .C22
-3.C53

-1.547
D. C. ',,

-.247
0


CO:F IDL!TIAL







.NACA CB No. L4125


MNACA 7h7A315
S.-- --- Upper Surface
S,--- -- Lower Surface
S Modified NACA 64,2-015





















NiW1OAL ADVISORY
COMMITTEE FOR AER NAU ICS


CONFIDENTIAL


0 .1 .2 .3 .5 .6 .7 .8 .9 1.0
x/c
Figure l.- Theoretical pressure distribution for NACA 747A315 and modified
NACA 61,2-015 airfolls.


1.2



1.0



.8



.6


CONFIDENTIAL


Fig. 1







NACA CB No. L4125


0 .1 .2 .5 .4 .5 .6 .7 .8


.9 1.0


Figure 2.- Tneoretical pressure
NACA 64,2-015 airfoils.


x/e CONFIDENTIAL
distribution for NACA 747Ah15 and modified


NACA 7h7A415
S/- Upper Surface
S/ ,- Lower Surface
-Modified NACA 64,2-015




T ~7~~~ -- -__- ---- -















NA10NAL AD ISOIY
-----------------COMIT EE OR RAUI
LZZZZZZZZZZZZLZZ


CONFIDENTIAL


Fig. 2









NACA CB No. L4125 Fig. 3






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NACA CB No. L4I25 Fig. 4







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UNIVERSITY OF FLORIDA .'

3 1262 08105 008 9


UNIVERS!rT OF FLORIDA
DOCUMENTS DEPARTMENT
12' MARSTON SCiENCE UBRARY
P.O. BOX 117011
GAINESVILLE, FL 32611-7011 USA

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