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High Speed Tests of a Ducted Body with Various Air Outlet Openings

SUMMARY

Test of a ducted body with internal flow were made
in the 8-foot high—speed wind tunnel for the purpose of
studying the effects on external drag and on critical
speed of the addition of efficient inlet and outlet open-
ings to a basic streamline shape. Drag tests of a 13.6-
inch—diameter streamline body of fineness ratio 6.14 were
made at Mach numbers ranging from 0.20 to 0.76. The model
was centrally mounted on'a 9-percent—thick airfoil and was
designed to have an efficient airfoil—body Juncture'and a
high critical speed. An air inlet at the nose and various
outlets at the tail were added: drag and internal—flow
data were obtained over the given speed range.

The critical speed of the ducted bodies was found to
be as high as that of the streamline body. The external
drag with air flow through the body did not exceed the drag
of the basic streamline shape. No appreciable variation
in the efficiency of the diffuser section of the internal
duct occurred throughout the Mach number range of the tests.

INTRODUCTION

The tests of ducted bodies reported in reference 1
showed that the external drag of bodies with well-designed
air inlet and outlet openings did not exceed the drag of
the basic streamline body to which the openings were added.
Pressure—distribution and boundary-layer data were pre—
sented_that satisfactorily accounted for the drag charac~
teristics. Further tests of a ducted fuselage (reference 2)
yielded the same results as the tests of reference 1.

The ducted bodies of the tests of references 1 and
2 were supported by lzgpercent-thick airfoile. and some
local separation of the flow at the airfoilwbody Junctures
was found to exist and was reported. The'airfoils were
located near the center of each body. well out of the
measurable‘field of influence of the openings. Never—
theless, it has been suggested that the drag measured
with internal air flow might have been affected by the
alleviation of the local separated condition at the
Junoture.

One purpose of the present tests was to compare
the drag of a ducted body with the drag of a streamline
body under conditions that would be free from any pos—
sible interference effects at the airfoil-body Juncture.
The tests were planned to include several types of outlet
opening. to cover a wide range of internal mess—flow co—
efficients, and to extend to Mach numbers of about 0.75.
Pressures were measured at the outlet openings and behind
the diffuser section of the duct throughout the range of
test Mach numbers in order to determine the internal drag
and the diffuser efficiency.

The model employed in these tests has been used in
a subsequent investigation employing a heated radiator.

SYMBOLé

V0 free—stream velocity. feet per second
v local velocity. feet per second
p static pressure, pounds per square foot, absolute
p density, slugs per cubic foot
q dynamic pressure. pounds per square foot (% pVB)
Ah total—pressure loss, pounds per square foot
1 maximum cross—sectional area of fuselage. 1.059
square feet
A area. square feet
quantity of flow. cubic feet per second
PQ