An experimental investigation was performed at a Mach number of 3.0 to determine the friction and pressure drags of a pylon and a 20 deg- and a 40 deg-included-angle wedge diverter over a range of Reynolds number. The results indicated that the measured friction drag coefficients agreed reasonably with that predicted by flat-plate theory. The pressure drag coefficients of the 20 and 40 deg wedges agreed with those presented in the literature. The total drag coefficient of the pylon and the 20 deg wedge diverter was about 0.36, based on diverter frontal area, while the drag coefficient of the 40 deg wedge was about 0.47

Anderson, Bernhard H.

Stitt, Leonard E.

English

NASA Technical Reports Server

NASA TM x-147
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TECHNICAL MEMORANDUM
X-1_7
FRICTION AND PRESSURE DRAG OF BOUNDARY-LAYER DIVERTER
SYSTEMS AT MACH NUMBER OF 3.0
By Leonard E. Stitt and Bernhard H. Anderson
Lewis Research Center
Cleveland, Ohio
Declassified April 23, 1962
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON January 1960
https://ntrs.nasa.gov/search.jsp?R=19980227873 2020-06-15T22:59:18+00:00Z

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
TECHNICAL MEMORANDUM X-147
FRICTION AND PRESSURE DRAG OF BOUNDARY-LAYER DIVERTER
SYSTEMS AT MACH NUMBER OF 3.0
By Leonard E. Stitt and Bernhard H. Anderson
SUMMARY
An experimental investigation w_s performed at a Mach number of 3.0
to determine the friction and pressure drags of a pylon and a 20 °- and a
40°-included-angle wedge diverter over a range of Reynolds number. The
results indicated that the measured friction drag coefficients agreed
reasonably with that predicted by flat-plate theory. The pressure drag
coefficients of the 20 ° and 40° wedges agreed with those presented in
the literature. The total drag coefficient of the pylon and the 20 °
wedge diverter was about 0.36, based on diverter frontal area, while the
drag coefficient of the 40 ° wedge was about 0.47.
INTRODUCTION
The majority of the published force data on wedge type boundary-
layer diverter systems treats primarily the pressure drag (refs. 1 to
5). A few measurements of skin-friction drag are reported in references
1 and 2_ but they appear to be in disagreement as to magnitude. To pro-
vide additional information obviously needed in this area a study has
been conducted at the Lewis Research Center to obtain the friction and
pressure drag at a Mach number of 5.0 of three representative boundary-.
layer diverter systems_ a pylon and a 20°- and a 40°-included-angle
wedge. In this investigation two different scale models of each diverter
system were used to obtain data over a large range of Reynolds number and
to provide overlapping data at a given Reynolds number.
This study was conducted in the Lewis I0- by lO-foot supersonic wind
tunnel at a Mach number of 3.0 and a range of Reynolds number from 0.50
to 2.50><106 per foot.
CD
CD,f
CD,p
Cf,i
%
h
L
P
q
Re x
Re s
x
8
SYMBOLS
drag coefficient
friction drag coefficient
pressure drag coefficient
incompressible skin-friction coefficient
pressure coefficient, (Pw - Po)/q3
diverter height
wedge length
axial distance measured from splJtter-pl_te leading edge to
diverter leading edge
static pressure
dynamic pressure
Reynolds number based on length cf run
Reynolds number based on splitter-plate length
axial distance
boundary-layer thickness
Subscripts:
w wedge
0 free-stream conditions
APPARATUS AND PRO( EDURE
Models and Configauations
Two complete configurations were tested simultaneously; a large-
scale model was mounted on the floor of tle wind tunnel and a geometri-
cally similar one-fifth scale model was mounted on the ceiling, as shown
in figure l(a). The boundary-layer diverter models were mounted on a
base plate (figs. l(a) and (b)) which was supported by force balances.
Extensions were provided on the sides of the base plate to keep the end
3effects to a minimum(fig. l(a)) but were not connected to the balance.
Boundary-layer buildup wasprovided by generator plates installed im-
mediately ahead of the base plate (figs. i and 2) that were independent
of the balance. Strips of number20 Carbortuudumgrit were placed span-
wise across the generator plates to ensure a turbulent boundary layer
ahead of the diverter systems. Total-pressure surveys were made of the
boundary layer by two rakes located near the leading edge and two rakes
near the trailing edge of each of the two base plates with the diverter
systems removed.
As shownin figure 2, the diverter configurations consisted of 20°-
and 40°-included-angle wedgesand a pylon type diverter, each mounted on
the base plate. Twodiverter heights were provided to vary h/8. A
splitter plate was mountedon top of each diverter to simulate the floor
of an inlet. Strips of number20 Carborundumgrit were also used on the
splitter plates to provide boundary-layer transition. For each model_
two splitter-plate lengths were used to vary _/8.
Data Reduction
The total drag of the diverter system was obtained by subtracting
from the measuredaxial force (balance reading) the sumof the following:
(I) Base drag of the splitter plate_ base plate, and diverter
configuration, obtained from static-pressure measurements
(2) Pressure drag of the 5° wedgeon the splitter plate, obtained
from theoretical two-dimensional flow considerations
(3) Friction drag on the surface of the base plate not in the
"shadow" of the splitter plate
(4) Friction drag on the upper surface and sides of the splitter
plate
The friction drag on the surface of the base plate (item (3)) was ob-
tained by running a "clean" base plate and converting the measureddrag
to coefficient form by referencing it to the wetted area of the base
plate. The measuredskin-friction drag coefficients (fig. 3(a)) are
comparedwith the turbulent skin-friction coefficient at Mach3.0_ which
is shownin reference 4 to be about 61 percent of the incompressible
value. A friction drag coefficient to be used in obtaining the splitter-
plate tare (item (4)) was obtained by adding an estimated drag of the
generator plate to the measureddrag of the "clean" base plate and ref-
erencing the drag coefficient to the combined surface area of the base
and generator plates. These results are comparedwith the Mach3.0 tur-
bulent skin-friction coefficient in figure 5(b).
The pressure drag of the diverters _as obtained by integrating
static pressures on the face of the wedgeand multiplying by the diverter
frontal area. Both the total drag and pressure drag for all the diverter
configurations are presented herein in coefficient form, based on an area
equal to the splitter plate width multiplied by the diverter height. The
diverter friction drag was obtained by subtracting the pressure drag from
the total drag. The diverter friction drag coefficient is presented as a
function of Reynolds numberand is based on the total wetted area under
the splitter plate.
RESULTSANDDISCUSSION
The boundary-layer thicknesses on the base plates of the two models_
with diverters removed, are presented for a range of Reynolds number in
figure 4 and comparedwith the theoretical thicknesses for smooth flat
plates. Included are data from both front and rear total-pressure rakes.
Even with roughness near the leading edge of' the generator plate, it ap-
pears that the boundary layer on the small model at Reynolds numbersbe-
low about I million was in a region of transition. The boundary-layer
thickness determined on the model in reference i is included in figure 4.
For that model the boundary layer at the lowest Reynolds numberalso ap-
pears to be in the transition region. A cuxve was faired through the ex-
perimental data (dashed line) and values of h/8 and Z/8 were computed
for all the configurations tested and are presented in table I over the
range of test conditions.
Typical diverter pressure distributions for the three diverter con-
figurations are presented in figure 5 for the large and small models at
the sameReynolds numberbased on splitter-_late length. At any given
station along the wedgethere was very little vertical variation in
static pressure. For both the 20°- and the 40°-included-angle wedgethe
initial pressure coefficient washigher than the theoretical two-
dimensional value. The bow shock that existed aheadof the wedgewas
probably contained by the splitter plate_ since no such shock wasvisible
from schlieren observations. For the 20° wedgethe flow expandedto near
stream pressure in about 40 percent of its length, and for the 40° wedge
in about 80 percent of its length. The differences in pressure coeffi-
cient between the large- and s_ll-scale models could have resulted from
the differences in h/8 and Z/8 that are indicated at the top of the
figure_ since the data were obtained at the sameReynolds number.
The pressure and total drag coefficients for all the configurations
are presented in figure 6 over a range of Reynolds numberbased on
splitter-plate length. The drag coefficient is referenced to an area
equal to the splitter-plate width times the diverter height. Values of
h/8 and Z/8 are presented in table I, since these parameters vary with
Reynolds number. The decrease in total drag coefficient at Reynolds
numbersbelow about 3 million resulted from the laminar flow on the small
model_ as discussed in connection with figure 4. The pressure drag was
only a small part of the total drag of the pylon model and was the larger
part of the total drag for the 40O-included-angle wedge. The total drag
coefficient of the 20° wedgewas about the sameas for the pylon, that
is, about 0.36 based on frontal area, while the drag coefficient of the
40° wedgewas about 0.47.
The wedgepressure drag coefficients obtained in the present inves-
tigation appear to be in general agreement with those obtained in ref-
erences i to S, as shownin figure 7. Data obtained from the other
sources are presented as shaded symbols. The theoretical Mach 3.0 two-
dimensional pressure coefficient is also included for comparison purposes.
The main object of this investigation was to obtain the friction
drag coefficient as a function of Reynolds number. The skin-friction
drag coefficient was obtained by subtracting the pressure drag coeffi-
cient from the total drag coefficient in figure 6 and changing the ref-
erence area to wetted area. In this investigation the wetted area in-
cludes all surfaces between the splitter plate and the base plate that
would be in the "shadow" of the splitter plate. The skin-friction drag
coefficient is presented in figure $ for each of the three diverter con-
figurations without regard to variations in h/_ and _/8. These drag
coefficients are comparedwith the Mach3.0 flat-plate turbulent skin-
friction coefficient_ which, as mentioned before, is about 61 percent Of
the incompressible value. The data are presented over a range of Reyn-
olds number_based on splitter-plate length, and indicate that the theo-
retical curve (CD,f = 0.61 Cf_i) maybe adequate in the design of
boundary-layer diverter systems of this type.
The skin-friction drag coefficients obtained at low Reynolds nmm-
bers in the present program agree with the single value of 0.003, pre-
sented in reference 2, which wasalso obtained at a low value of Reynolds
number. The skin-friction drag coefficients computedfrom wake total-
pressure surveys in reference i were higher than those obtained in the
present tests. For example_ skin-friction drag coefficients from refer-
ence i ranged from 0.008 at a Reynolds numberof 1.3XlO6 to 0.023 at a
Reynolds numberof 0.65XI06. These higher values might possibly be a
direct result of the wake survey method of obtaining skin friction. How-
ever, it should be noted that in the low Reynolds numberrange of these
small tunnel models (less than l.OXl0 G) a slight decrease in Reynolds
numberhas a very large effect on skin-friction coefficient_ as can be
seen in figure 8.
SUMMARYOFRESULTS
The following results were obtained at Mach5 for three boundary-
layer diverter systems_ a pylon_ a 20°-, and a 40°-included-angle wedge:
I. The measuredskin-friction drag coefficient over a range of Reyn-
olds numberagreed fairly well with that predicted by compressible flat-
plate theory.
2. The measuredpressure drag coefficients for the 20°- and 40°-
Included-angle wedgediverters agreed with those presented in the
literature.
5. The measureddrag coefficient of the pylon and the 20° wedgedi-
verter was about 0.36 based on frontal area, while the drag coefficient
of the 40° wedgewas about 0.47.
Lewis ResearchCenter
National Aeronautics and SpaceAdministration
Cleveland, Ohio, September50, 1959
REFERENCES
1. Piercy_ ThomasG., and Johnson, Harry W.: Experimental Investigation
at Mach Numbers 1.88, 5.16_ and 5.83 of Pressure Drag of Wedge
Diverters Simul_ting Botmdary-Layer-Rez_oval Systems for Side Inlets.
NACARME55L14b, 1954.
2. McLafferty, G. H., et al.: Investi_tio_1 _of Turbojet Inlet Design
Parameters. R-0790-15, United Aircraft Corp., Dec. 1955. (Contract
NOas 55-153-c.)
3. Campbell, Robert C., and Kremzier, Emil I.: Performance of Wedge-
Type Boundary-Layer Diverters for Side Inlets at Supersonic Speeds.
NACA RME54C23, 1954.
4. Wilson_ Robert E.: Turbulent Boundary-L_yer Characteristics at Super-
sonic Speeds - Theory and Experiment. Jour. Aero. Sci., vol. 17_
no. 9, Sept. 1950, pp. 585-594.
TABLEI. - BOUNDARY-LAYERCHARACTERISTICS
Re/ft Rex Res
xl0 -6 xl0 -6 xlO-6
118 hi8
in.
h = 1.00 in. h = 1.25 in
Large model - short splitter plate
0.50
.75
i. O0
i. 50
2.00
2.50
2.92
4.4
5.85
8.8
11.7
14.6
5.0
7.5
9.9
14.9
19.9
24.8
1.27
i .20
1.14
i .07
i .03
i .00
4.9 0.79
5.2 .85
5.5 .88
5.8 .94
6.1 .97
6.5 i .00
0.99
i .04
I. i0
1.17
1.21
1.25
Large model - long splitter plate
O. 50
.75
I. O0
i .50
2. O0
2.50
2.66
5.98
5.3!
7.98
10.60
15.30
5.2 1.18 10.6 0.85
7.8 i.i0 11.4 .91
10.5 1.06 11.8 .94
15.7 .99 12.6 1.O1
20.9 .95 15.2 1.05
26.2 .92 13.6 1.09
Re/ft Re x Re s
xlO -6 XlO -6 XlO -6
i .06
1.1%
i .18
1.26
1.32
i .36
h = 0.20 in. h = 0.25 in.
Small model - short splitter plate
0.50
.75
1.00
! .50
2.00
2.50
0.46
.69
.92
1.38
i .84
2.30
0.99 0.144 8.70 1.39
1.49 .140 8.93 1.43
1.98 .145 8.60 1.38
2.98 .176 7.10 1.14
3.97 .191 6.55 1.05
4.96 .198 6.3 1.01
1.74
1.78
1.72
1.42
1.31
i .26
Small model - long splitter plate
O. 50
.75
i .00
i. 50
2.00
2.50
0.41
.61
.82
1.22
1.63
2.04
1.05
1.57
2.09
3.13
4 .i_
5.23
0.130 19.2 1.54
.124 20.2 1.61
.125 20.0 1.60
.146 17.1 1.37
.165 15.1 1.21
.174 14.4 1.15
I. 92
2.02
2.00
1.71
i .51
1.44
S(a) General view,
Figure i. - Boundary-layer diverter models mounted iu i0- by lO-foot
supersomic wind tuunel.
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(a) Base plate.
I I I I I
Model
0 Large
D Small
----0.61Cf, i (ref. 4)
I L I
n
0
0
"?" --4-- _
-0_
.0012
0 8 12 16 20 24 28
Reynolds number: Re x
(b) Splitter plate.
Figure 3. - Boundary-layer diverter models tare forces.
32Xi06
15
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15
.8
.6
.4
I I I I
Short splitter plate
I J
bk
O
O
I I I I I I
Model h,
in.
Plain symbols Large 1.00
Tailed symbols Small .20
1 i I I i J
u
I
t/h
6.25
6.25
O Total
A
£9
@
®
o
O
t_
h
>
.2
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.8
.6
.4
1 1 1 1
Long splitter plate
l I
)
_'_
I
Pressure
lu i
I
blodel h_ Z/h
in.
Plain symbols Large
Tailed s_nbols Small
0 0 0 0
(
1. O0 12. S
.20 12.5
1
Total-
)
.2
0
/
lip [] 0 []
8 12 16 20
Reynolds number, Re s
(a) Pylon models.
Figure 6. - Boundary-layer diverter drag.
!
Pressure
£4 28x106
16
.4
.2
O
O
•4 0
o
.4
.6
O
O
bD
h
.4
>
.2
0
Short splitter plate
O
O
D []
1 I 1 I
Long splitter plate
i I I
, b_b
)
-_ o
"o (
4
0
I
Model h, I/h.
in.
Plain s;:_nbols Large 1.25 5.0
Tailed ._;ymbols Small .25 5.0
t
(_ ? 0 Total
Pressure
C O C
0
! ! I I I I I
Model h_ _/h
in.
Plain symbols
- Tailed symbols
o 1
[ [] [] []
8 12 L6 20
Reynolds numbe_, Re s
(a) Concluded. PyLon models.
Large
Small
1ol
i .25 i0.0
.25 I0 .O-
ld
Total
I
I
Pressure
Figure (_. Continued. Boundary-layer diverter drag.
17
.6
A
_D
.S
5
o
0
O
_D
_0 6
h
40
> .4
A
.S
"o
[]
_0_ u JU
_o
O Short
'_o o
[]
I I I I
Short splitter plate
I
o "o k
1 I I I I
Model
Plain symbols Large
Tailed symbols Small
III I ,
splitter plate
I
h_ Z/h
in.
1.00 6. SS
.SO 6 .SS
I
0 Total
[] O
U _ LJ LII
[] n
Pressure
c 0
I I I I I I I
Model h, Z/h
in.
Plain symbols Large I.SS S.O
--Tailed symbols Small .SS S.O--
v Total
f_
8 IS 16 SO
Reynolds number_ Re s
ib) SO°-Included-angle wedge.
Pressure
n
24 28x106
Figure 6. Continued. Boundary-layer diverter drag.
18
A
o
U
q_
q_
O
<]
q_
@
40
@
>
o4
.6
.4
.2
0
.6
.4:
.2
Short splitter plate
"o -
_ n
"o []
N.
J '_ []'U
I | I I
Long splitter plate
I l
0 0
I
Model h, _/h
in.
Plain symbols Large 1.00 6.25
Tailed s_abols Small .20 6.25
0
Total
O
)
Pressure
] 13 3 13
0 4 8
O!
0
Total
(
--Plain symbols Large 1.00 12.5--
Tailed symbols Small .gO 12.5
I I I l I I l I
12 16 20 24 28xi06
Reynolds number_ Re s
(c) 40°-Included-angle wedge.
Figure 6. Concluded. Boundary-layer diverter drag.
Pressure
ioli I?
__ Model h_ Z/h --
in.
19
1.0
.8
g_
o
q_
q-a
o
o
bD
,-c::l
4
::zl
@
.q
¢1
ba
3:
J
I--- 1
Mach h/_ _/8
nura0er
0 5. O0
3.oo
• 3.16
i 3.16
• 1.52
• 2. O0
i .00 6.25
i .03 6.40
I
I
i Mach 3.0 two-
i dimensional pres-
sure coefficient-_
Y
/
/
/
//
I i I I i ]
Present report - large model
Present report - small model--
z_5_
1.00 4.90 _ Ref. I
1.00 9.80 ]
.97 5.00 Ref. 2
1.00 2.00 Ref. 3
!
b/i 'i
_/ , I!
-- 1
1
I
!
i
I i
o 20 40 60 80
Wedge included angle, deg
I
i
i
/
i
I
J
i00 120
Figure 7. - Comparison of diverter wedge pressure drag with data from
literature.
20
S
o
u
o_
.0030
.0026
.0022
0
.0018
0
.0014
.0010'
.0034
• 0030 / O,
\
• 002 C
• 002_
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• 001 z
.004_
,003_
.0054
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O o
_o
o\
bo
O
0
O-- tO. 61
0
0
0
8
0
_ 0
e_ c
cf, 1 (re£. 4)
"i°---<__ o
(a) Pylon models•
0 q
° I I I I_I
"--" "-- "-- --L/-U°'6] cf,111 (ref.i 4)1
I
(b) 20O-Included-angle w !dge.
•,:hOS (
• Do26
.002;
•0 01 ,_
.0014
\
o\
\
_0.61 C£, I
(ref, 4) O
O_ .._ O
.0©I£
0 4 9 12 16 20 24 28 32xlO 6
Reynolds number, Re s
(c ) 4OC-]nel _ded-ang: e wedge.
Fl_ure 8. - Fz'Ictton i:.&_ of boundaly-layer dlverter models.
NASA - Langley Field, Va. E-597


Friction and Pressure Drag of Boundary-Layer Diverter Systems at Mach Number of 3.0

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