introduction to flight location iSde l culate 3 ft. At a given the flow Mach num
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introduction to flight location iSde l culate 3 ft. At a given the flow Mach number at this location. Hint: Use Eq. (4.88) y Johnson at hnson at to use a boundary nted on the the Lockheed Skunk Works, was one of the first jet airplanes to use a bound t layer bleed device. This was a duct with a rectangular entrance mounted o side of the fuselage at the entrance of each side inlet. The boundary laver duct was designed to entrain the low energy boundary layer on the fuselage it could enter the inlet. This way, the flow entering the inlet and passing i engine was of a higher aerodynamic quality with a minimal loss of total 63 The Lockheed F-80, designed by the famous airplane designer Kelly Johnso et. The boundary layer bleed before nto the jet ine was of a higher aerodynamic quality with a minimal loss of total pressureExplanation / Answer
Properties of air at a definite altitude is found from tables
To convert from slug/ft3 to kg/m3 the conversion factor is 515.3788184
Density of air at 20000ft = 12.67 × 10-4 slug/ft3
Therefore, after conversion density = 0.6529849629128 kg/m3
Dynamic Viscosity of air at 20000ft = 3.324 ×10-7 lb.s./ft2
= 0.000015915398 N/m2
1mach = 340 m/s
Therefore 0.6 Mach = 204 m/s
X is the distance downstream from the start of the boundary layer =2.98m
U0 is the freestream velocity
Rex is the Reynolds Number = Density × X × U0 / Dynamic viscosity
Rex = 0.65298 × 2.98 × 204 /0.000015915398
= 24941858.2935
H is the overall thickness (or height) of the boundary layer
H = 0.382 X / (Rex(1/5)) -------- For turbulent and incompressible flow
= 0.03774799297 m
= 37.74 mm
Therefore, the necessary height of the rectangular entrance of the boundary layer bleed device
is 37.74 mm
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