470
J. SPACECRAFT, VOL. 39, NO. 3: ENGINEERING NOTES
2Dolling,D. S., andMurphy,M.T.,“UnsteadinessoftheSeparationShock
Wave Structure in a Supersonic Compression Ramp Field,” AIAA Journal,
–
Vol. 21, No. 12, 1983, pp. 1628 1634.
3Maull, D. J., “HypersonicFlow over Axially Symmetric SpikedBodies,”
–
Journal of Fluid Mechanics, Vol. 8, Pt. 4, 1969, pp. 584 592.
4Dolling, D. S., and Bogdonoff, S. M., “An Experimental Investigation
of the Unsteady Behaviour of Blunt Fin-Induced Shock Wave Turbulent
Boundary layer Interaction,” AIAA Paper 81-1287, June 1981.
5Horstman, C. C., and Owen, F. K., “New Diagnostic Technique for the
Study of Turbulent Boundary Layer Separation,” AIAA Journal, Vol. 12,
–
No. 10, 1974, pp. 1436 1438.
6Verma, S.B., and Koppenwallner,G., “ExperimentalStudyofShockUn-
steadiness on an Hyperboloid Model Using Laser Schlieren,” 9th AG-STAB
¨
Workshop, edited by H. J. Heinemann, DLR-Standort, Gottingen, Germany,
1999, pp. 156, 157.
)
)
b X/L = 0.86
a X/L = 0.80
7Koppenwallner, G., Friehmelt, H., and Muller-Eigner, R., “Calibration
and First Results of Redesigned Ludwieg Expansion Tube,” AIAA Paper
93-5001, Nov. 1993.
Fig. 7 Simultaneoustime traces of voltagesignalsnear the mainshock
region above the bubble ; P0 = 50 bar.
(
)
8Funk, B. H., and Johnston, K. D., “Laser Schlieren Cross-Beam Mea-
surements in a Supersonic Jet Shear Layer,” AIAA Journal, Vol. 8, No. 11,
1970, pp. 2074, 2075.
9Garg, S., and Settles, G. S., “Unsteady Pressure Loads Generated by
Swept-Shock-Wave/Boundary-Layer Interactions,” AIAA Journal, Vol. 34,
–
No. 6, 1996, pp. 1174 1181.
10Willmarth, W. W., Kuethe, A. M., and Crocker, G. H., “StagnationPoint
Fluctuationson a Bodyof Revolution,”Physics ofFluids, Vol. 2, No.6, 1959,
–
pp. 714 716.
M. Torres
Associate Editor
)
)
b X/L = 0.66
a X/L = 0.40
(
Fig. 8 Space-timecorrelation functionsforphotodiodelocations close
to the surface near the oscillating separation shock; P0 = 50 bar.
)
Modeling of Performance of anArtillery
Shell Using Neural Networks
R
y
Figure 8 shows the space-time correlation pp.0; ; ¿/ for chan-
(
Y
nels separatedin the direction,as a function of time delay ¿ mil-
liseconds betweenthe voltagesignalsfromA and B and locationsB
)
and C. The pointof interestis the value of the correlationat approxi-
A. K. Ghosh,¤ S. C. Raisinghani,† and S. K. Dehury‡
Indian Institute of Technology Kanpur,
Kanpur 208016, UP, India
(
)
mately zero time delay.Far upstreamof separation Fig. 8a the plot
–
–
shows a positive value for locations A B and B C. For axial loca-
X L D
Y D
tions
B andCare
=
0:40, 0.66, A is
0:6 mm from the surface,whereas
Y D
1:6and2.6mm, respectively,awayfromthesurface.
Y D
For downstream locations A is
B and C are
surface. These distances were chosen wherever mirror imaging of
signalsfrom neighboringchannelswere observedand indicatesthat
all locationsexperiencesimilar density ow with the absenceof any
1:6 mm from surface, whereas
Introduction
Y D
2:6 and 3.6 mm, respectively, away from model
RTILLERY comprises an important wing of an army in pro-
viding repower,duringboth war and cross-borderskirmishes
A
with the enemy. Artillery shells are a class of projectiles around
which much of aeroballistictheory was originallydeveloped,and it
continuesto form a signicantpartof aeroballistician’s interest.The
performanceof the artillery shell is governedby many factors,such
as muzzle velocity irregularity, jump and throw off; ambient mete-
orological conditions such as temperature, density, head/tailwind,
and crosswind; and manufacturing procedures resulting in differ-
ences in shape, size, mass, and yawing behavior. The conventional
approach hitherto used for predicting behavior and performance of
a projectilesuch as an artilleryshell was via mathematical models.1
Beginning with the simplest, but relatively inaccurate, in-vacuo
trajectory mathematical model, more and more sophisticated mod-
els of increasing accuracy, such as the point mass model, the modi-
ed point mass model, and the six-degree-of-freedom model, have
been developed. However, even the best of these models have their
(
)
uctuatingdensity gradients.At separation Fig. 8b the space-time
correlationvalue between these locationsshow oppositetrends. Lo-
(
)
cationsA andB whichare incloseproximityto one another showa
largenegativevalue,whereasBandCshowa relativelylargepositive
value indicatingthat, when photodiodeA experiencesa rise in den-
(
)
sity as acrossa shock , the photodiodeB experiencesa fall and vice
versa.LocationsB andC experiencea similarrise and fall of density.
Conclusions
The unsteadinessassociatedwith the shock-waveboundary-layer
(
)
interaction SWBLI ow eld on a HALIS axisymmetric con gu-
rationmodelisdemonstratedin a Mach 9.68 ow with airas test gas.
The SWBLI ow eld investigatedgenerateshigh-pressureloads in
the vicinity of separation and reattachment points. Near reattach-
ment the pressure on the are approachesthe stagnationpoint pres-
sure level. Off-surface ow study using the laser schlieren system
revealedincreasedenergylevelsneartheseparationpointsuggesting
random uctuations in the instantaneousposition of the separation
shock. Space-time correlation of voltage signals from neighboring
channels,exhibitingmirror-imagingeffects, shows a negative value
at zero time delay. The observation is consistent with the view that
the separation shock translates back and forth, in response to the
expansion and contraction motion of the separation bubble, in the
vicinityof separationpoint on the HAC model, and henceis respon-
sible for high-pressureloads at these locations.
)
limitations because of 1 an inability to model all of the problem
(
variables e.g., the initial conditions at the time of shell leaving the
barrel, the jump and throw off, the variable atmosphericconditions,
Received 1 May 2001; revision received 10 February 2002; accepted for
°c
publication 18 February 2002. Copyright
2002 by the American Insti-
tute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of
this paper may be made for personal or internal use, on condition that the
copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc.,
222 Rosewood Drive, Danvers, MA 01923; include the code 0022-4650/02
$10.00 in correspondence with the CCC.
¤Assistant Professor, Department of Aerospace Engineering. Member
AIAA.
References
1Kistler, A. L., “Fluctuating Wall Pressure Under a Separated Supersonic
†Professor, Department of Aerospace Engineering. Senior Member
AIAA.
Flow,” Journal of the Acoustical Society of America, Vol. 36, No. 3, 1964,
pp. 543 550.
‡Graduate Student, Department of Aerospace Engineering.
–