Aerodynamic Design of Unmanned and Scaled Supersonic ...

K. Yoshida and Y. Makino
minimum pressure drag characteristics were
estimated over the whole Mach number range as
shown in Figure 17. We made best use of the nonaxisymmetrical
area-ruled body concept and
obtained remarkable improvement in aerodynamic
performance. Consequently, the “2.5th
Configuration” was selected as the final
aerodynamic configuration for the NEXST-2
airplane.
2.0th Configuration
2.5th Configuration
3.3 Wind Tunnel Tests
Figure 17. Minimum pressure drag of NEXST-2
To understand the strong airframe/nacelle
interference completely, and to develop the reliable and effective database for supersonic
intake, several wind tunnel tests were conducted [22-24, 26-27]. In this section, principal
results on fundamental research activity except intake tests are summarized below.
1) CFD validation tests of the airframe/nacelle
interference configuration model
The test model of the “0-8th Configuration” with
flow-through-nacelle was used to conduct the CFD
validation for a complicated configuration with
nacelles. Figure 18 shows the force test model with a
modified intake shape and a CFD grid. The scale of
the test model was 8.3% of the NEXST-2 airplane.
Both supersonic and subsonic tests were conducted at
JAXA [26]. In the test at flow-through-nacelle
condition, the drag measured by a force balance
should be corrected using the relation of momentum
balance of internal flow of the nacelle.
Figure 19 shows measured and corrected drag
polar curves, comparing them with CFD(NS)
computation results. An open circle and triangle
symbols indicate test results of drag characteristics
without and with the internal flow correction
respectively. Our CFD computation results on both
conditions without and with the internal flow
correction are fairly smaller than those of the test
results. It strongly depends on the turbulence model in
our CFD code. If we assumed the drag characteristics
with an off-set value 0.0049 of the minimum drag, we
found very high correlation between those assumed
5.06 million points:
supersonic flow case
Figure 18. W/T model & CFD grid of
“0-8th configuration”
0.01 0.02 0.03 0.04 0.05 C D
drag polar curves and test results. Therefore, the pressure drag characteristics estimated by the
CFD code were well validated.
CL
0.4
0.3
0.2
0.1
0
-0.1
NEXST-2-08 : Wing+Body+Nacelle
M=1.7
No Int. Correc.
With Int. Correc.
BWT(20099) NS Off-set(0.0049)
Figure 19. Comparison of test and CFD
results
17