Experimental investigation at supersonic speeds of twin-scoop duct inlets of equal area 3: inlet enclosing 37.2 percent of the maximum circumference of the forebody Page: 4 of 27
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2 IgbI@ N=== NACA RM No. A8E04
showed that the recovery of total pressure after diffusion and
the stability of the flow in regard to separation were improved if
the inlet consisted of twin scoops instead of an annular opening.
(See reference 1.) The reason for the improvement was that less
boundary-layer air could enter the ducts through the scoops because,
although the entrance area was equal to that of the annular entrance,
the scoops enclosed only a portion of the forebody circumference.
Further tests of the twin-scoop inlet showed that slots in the walls
of the ducts immediately behind the inlet and contiguous to the
forebody produced an additional increase in the pressure recovery.
(See reference 2.) The slots permitted the pressure difference
between the inside and the outside of the diffusor to force some of
the boundary layer that had entered the inlet to flow with a lateral
component and out of the ducts. The maximum total-pressure recovery
attained during tests of a slotted inlet that enclosed 61.5 percent
of the forebody circumference was about 10 percent less than that
through a normal shock wave occurring at the test Mach number.
Since an improvement in pressure recovery was attained by
reducing the portion of the forebody circumference that the inlet
enclosed from 100 to 61.5 percent while maintaining the same entrance
area, it was reasoned that a further reduction might produce an
additional improvement. It is the purpose of the present report
to describe the results of tests of a model having a twin-scoop
inlet that enclosed 37.2 percent of thb forebody circumference.
H total pressure
M Mach number
m rate of mass flow
ct angle of attack
V angle of yaw
c forebody circumference
Subscripts (The subscripts indicate the station of the measured.gquantity.)
o free stream
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Davis, Wallace F. & Edwards, Sherman S. Experimental investigation at supersonic speeds of twin-scoop duct inlets of equal area 3: inlet enclosing 37.2 percent of the maximum circumference of the forebody, report, July 22, 1948; (digital.library.unt.edu/ark:/67531/metadc57767/m1/4/: accessed January 21, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.