Performance of Twin-Duct Variable-Geometry Side Inlets at Mach Numbers of 1.5 to 2.0 Page: 6 of 34
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NACA RM E56Kl5
The two boundary-layer bleed ducts used to capture some of the fuse-
lage boundary layer were each instrumented at model station 66.87 with a
three-tube total-pressure rake and two wall static-pressure orifices.
Mass-flow calculations were made from these measurements.
The axial force on the model was measured with an internal strain-
gage balance system with the 0-cant inlets only.
RESULTS AND DISCUSSION
Local flow angularity and Mach number were computed at the two posi-
tions on each of the wedges. These four values for Mach number and an-
gularity were averaged and are presented as a function of free-stream
Mach number for several angles of attack in figure 3(a). For the yaw
data shown in figure 3(b), the four values of Mach number were averaged
and the two values of angularity for each wedge were averaged. These
data indicate that the average local Mach number ahead of the inlet did
not vary appreciably for angles of attack up to 50 nor for angles of yaw
and was always higher than the free-stream value. In addition, the local
flow angularity with respect to the plane of the wedges was always more
positive than the model angle of attack. At angle of yaw the upper wedge
indicated a higher flow angularity than the lower wedge. (The wedges were
on the windward side of the fuselage for positive angles of yaw.)
The survey-rake data (fig. 4) indicate that for all positive angles
of attack the fuselage boundary layer thickened ahead of the upper portion
of the inlet; at angles of yaw it thickened ahead of the bottom portion
of the lee inlet. In both cases the position of the first-rap leading
edge shows that the thickening effect was sufficient to cause some
boundary-layer air to enter the inlet. This can also be seen in figure
5 from the profiles of the 0o-cant inlets, where low recovery air is
present near the ramp surface for these conditions. Some typical
compressor-face profiles are also shown in this figure.
Compression-Surface Boundary-Layer Removal and Effects
of Second-Ramp Position
The effect of compression-surface boundary-layer removal on the dif-
fuser airflow characteristics with s = 0 is shown in figure 6. As
shown, the slot configuration considerably increased the subcritical sta-
bility range over that obtained without boundary-layer bleed, while the
perforations had no effect on stability. Both configurations slightly
increased the total-pressure recovery over the no-bleed case, with a
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Yeager, Richard A.; Beheim, Milton A. & Klann, John L. Performance of Twin-Duct Variable-Geometry Side Inlets at Mach Numbers of 1.5 to 2.0, report, January 21, 1957; (https://digital.library.unt.edu/ark:/67531/metadc63208/m1/6/: accessed March 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.