Aerodynamic Design of Unmanned and Scaled Supersonic ...

K. Yoshida and Y. Makino
2) Flow-plug tests for the nacelle flow effect on drag characteristics
In order to collect the complete drag data of the NEXST-2 airplane in the system design
phase, we had to investigate the mass flow effect of
the nacelle on the airframe drag characteristics.
Therefore, we produced a large test model with two
flow control plugs behind each nacelle shown in
Figure 14. This model was a 17.0% scaled model. A
flow plug test was conducted in the 2m x 2m
transonic wind tunnel of JAXA [27].
Figure 20 shows drag characteristics with respect
to mass flow ratio (A0/Ai) of nacelle flow at Mach
1.4. Here A0 and Ai mean the cross-sectional area of
actual flow stream tube at forward infinity and the
capture area at the front of the intake. The figure
indicates an increase of the nacelle drag as the mass
flow ratio decreases. The total drag strongly depends
on the nacelle drag. Figure 21 shows pressure
distributions measured by the pressure sensitive paint
(PSP) technique [28] at the typical two cases of small and
large values of A0/Ai. As shown in the figure, the strong
shock wave was observed in front of the intake at small
mass-flow ratio condition. This flow pattern corresponds
to the unstart condition. On the other hand, at the
condition of large mass flow ratio, there was no
remarkable shock wave in front of the nacelle.
4. CONCLUDING REMARKS
Nacelle flow effect : M=1.4, α=0°, β=0°
CDFc
0.03
C D 0.025
0.02
Wing-Body
0.015
0.01
Nacelle(Left)
0.005
0
-0.005
0 0.2 0.4 0.6 0.8 1
Ao/Ai(Left)
A 0 /A i (L
Figure 20. Interference test of NEXST-2 :
JAXA developed some original advanced design concepts and procedures in the
unmanned and scaled supersonic experimental airplane program. The supersonic NLF wing
design concept and the CFD-based inverse design procedure were developed for the first
airplane. The non-axisymmetrical area-ruled body concept and the CFD-based optimum
design procedure were developed for the second airplane. The NLF wing concept was
validated in the wind tunnel test qualitatively, but not quantitatively, because of the existence
of freestream turbulence in any supersonic wind tunnels. The flight test is expected to validate
it both qualitatively and quantitatively.
In reducing strong interference drag between the airframe and two large nacelles of the
second airplane, the effect of the non-axisymmetrical area-ruled body concept was confirmed
numerically. However, the concept has not been validated experimentally, because it is not
easy to simulate the complete flowfield around a complicated configuration with engine
operation condition in wind tunnel tests. The flight test is valuable in validating the design
concept. We expect to continue to develop the advanced aerodynamic design technology after
the successful flight test of the NEXST-1 airplane.
0.045
0.04
0.035
Total
Plug test (“0-2nd Configuration”)
Nacelle flow effect : M=1.4, α=0°, β=0°
Ao/Ai=0.33 Ao/Ai=0.86
Figure 21. Interference test of NEXST-2:
PSP test (“0-2nd Configuration”)
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