suppressor 1
TRANSCRIPT
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CFD APPROACH TO FIREARMS SOUND SUPPRESSOR DESIGN
M. Keith Hudson* and Chris Luchini[
Department of Applied Science
University of Arkansas at Little Rock, Little Rock, Arkansas
J. Keith Clutter] and Wei Shyyw
Department of Aerospace Engineering, Mechanics & Engineering Science,
University of Florida, Gainesville, Florida
Abstract
Suppression of muzzle blast is important in both large
and small caliber gun designs. Key goals in the case of
small caliber systems are the reduction in the incidence
of hearing loss due to the acoustic signal and signature
reduction for military applications. Various devices
have been used to reduce the muzzle blast and the design
of these devices have relied heavily on experimental in-
vestigation. The current study evaluates the utility of
computational models in the design of suppressors for
small caliber guns. Experimental measurements are
made for a representative suppressor design and simula-
tions are performed to determine the level of model so-
phistication needed to correctly predict the effects of the
device. The current simulations correctly capture both
the levels and characteristics of the acoustic signal gen-
erated by the bare muzzle and suppressor configura-
tions. These findings support the use of computational
models in the suppressor design process.
Introduction
Devices for the suppression of overpressures from fire-
arms have been known and utilized for some time dating
back to the work of Maxim around the turn of the centu-
ry [1]. Currently, suppressors are used on both large and
small caliber guns for somewhat different purposes. In
the case of large caliber guns, the primary goal of over-
pressure suppression is to reduce the effects of blast on
structures and supporting vehicles. The design process
of the suppression devices has relied heavily on exper-
imental work and the development of empirical data-
bases [2, 3]. Some computational efforts have been un-
* Associate Professor, Member AIAA.
Research Associate, currently at NASA Jet Propulsion Lab
Professor and Chairman, Associate Fellow AIAA.
[
]
wDoctoral Student, Member AIAA.
Copyright E 1996 by M. Keith Hudson. Published by theAmerican Institute of Aeronautics and Astronautics, Inc.with permission.
dertaken [4, 5, 6] but have been limited primarily to
large caliber gun systems.
In the case of small caliber guns, suppressors have been
widely used as clandestine devices in sniper and other
roles in warfare to avoid detection of the shooter. While
this role has been widely accepted for many years other
applications of suppression are being sought, particular-
ly to reduce the acoustic pressure levels from small arms
firing to address hearing loss disability. Interestingly,
while suppression for hearing loss reduction has re-
ceived some study, there has been little reported in the
open literature over the many years that these devices
have seen use. This is most likely due to strict US regu-
lation of these devices in civilian applications.
As in the case of the large caliber suppressors, the design
process for the suppressors has depended heavily on ex-
periments and a cutandtry procedure. Unlike the large
caliber work, no significant computational effort has
been undertaken. Therefore, the goal of the currentstudy is to determine the applicability of computational
tools developed for the large caliber suppressors to the
small caliber suppressors. Of primary concern is the
scaling of the blast phenomena and the identification of
the driving physics which dictates the peak overpressur-
es and pressure signals. These two factors are key to the
acoustic signature of the suppressor and need to be cap-
tured by any computational code to be used for suppres-
sor design.
This report summarizes the initial experimental and
computational investigation into suppressors for 22 and
38 caliber / 9 mm guns. The experimental effort tested
a commercial suppressor as well as a cylindrical baffledesign used to evaluate the computational code. The re-
mainder of this document first discusses the experimen-
tal details and highlights some of the predominate
physical occurrences identified. Next the computational
model is reviewed and the simulations for the cylindri-
cal baffle suppressor are presented and discussed. Con-
clusions are then drawn as to the utility of computational
codes in small caliber suppressor design and the driving
physics behind the acoustic signal.
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Experimental Investigation
1. Experimental Setup and Description
Firearms suppressor data collection requires that the re-
searcher have a sound insulated laboratory with ade-
quate backdrop for projectile containment, or have the
ability to set up on an outdoor range which has adequate
facilities to support the planned experiment. A suitable
range has been located which offerers a sheltered area
with utilities, but provides an adequate acoustic envi-
ronment to make sound measurements. All testing has
been performed with the instrumentation sheltered from
direct sunlight, but with the firearms muzzle and micro-
phone located just outside of the shelter to avoid direct
sound reflection effects on the collected data.
Figure 1 shows the general layout of the equipment and
tested firearm for all experimental trials. The equip-
ment used includes a Competitor Corp. 38 Special cali-
ber action for all nominally 38 caliber / 9 mm testing anda AMT Lightning rifle for all 22 LR testing. Both ac-
tions have been modified to allow fitting of a commer-
cial suppressor shell, utilizing a GEMTECH Model Vor-
tec 9 for 38 / 9 mm and a Vortec 2 for all 22 LR testing.
Barrel length on the Competitor action is 10 inches
while the 22 rifle has a length of 20 inches. The cylindri-
cal baffle suppressor dimensions are given in figure 2.
Handloaded ammunition has been used in the 38 / 9 mm
unit consisting of a 160 grain Speer jacketed bullet in a
38 Special casing, over 8.6 grains of Alliance Blue Dot
Powder. The 22 LR has used commercially available
CCI Blazer brand ammunition. During firing, the 38 /
9 mm unit is held on a sandbag, while the 22 rifle is
shoulder fired in the normal manner. Care is taken to en-
sure the same relative alignment of the pressure gages
for each firing.
Acoustic data is collected using a Bruel and Kjaer 4135
condenser microphone powered by a 2801 power sup-
ply. Calibration data indicated that this unit is accurate
to 100 KHz and provides an output of 3.39 mV/Pa. The
microphone is positioned upright (pointed up) on a tri-
pod and positioned between 3 and 20 inches from the
muzzle. The firearm is then positioned to a point paral-
lel to the microphone, and then pulled back up to 10 in-
ches from the microphone to establish a grid of measure-
ments (Table 1). The microphone is read by a LeCroyModel 9400A, 175 MHz 8bit digital storage scope.
Computer readouts of the sound tracings during firings
are not available so peak data is recorded by hand. If
there appeared to be two major sound peaks, each peak
is recorded. Measurements from three firings are made
at each gage position. Firings are made with the bare
muzzle in all positions, followed by a similar set of fir-
ings with the suppressor attached. For all experimental
firings, the suppressors consisted of a right circular cyl-
inder body with one copper baffle held in place one third
of the distance down the suppressor body by aluminum
spacers (Figure 3). Limiting firing has been carried out
using the commercial suppressor on the 22 to show the
cylindrical suppressor to be used in the computational
code evaluation produce similar pressure reductions.
2. Experimental Results and Discussion
All the experimental measurements are presented in
Table 2 where Sup denotes the cylindrical baffled
suppressor and Com the commercial suppressor.
Scope traces from the unsuppressed firearms show a
single highintensity peak with only minimal ringing
type peaks seen over the rest of the measurement period.
This of course correlates with the sharp, highintensity
crack heard by the ear upon firearms discharge. For the
positions further from the muzzle the sound is seen to di-
minish with distance from the microphone, as would be
expected, and the tracing pattern remains essentially the
same except for the overall intensity changes.Scope traces for the firearm firings using the cylindrical
baffle suppressor show a characteristic intensity spread-
ing. The large single peak seen with the bare muzzle is
gone, replaced typically by a set of peaks of similar in-
tensity, often by two peaks of almost the same amplitude
especially in the 38 / 9 mm data. The values of the two
peaks are given in Table 2 and are denoted with the 1 and
2 following the suppressor designation. Also for the sup-
pressor configuration, the smaller peaks which appear
as ringing type peaks in the bare muzzle tests are rela-
tively larger when compared to the peak signals. This
is in agreement with the suppressor acting to spread
the discharge sound out over a larger time scale, mini-mizing the peak value, but giving a longer duration to
the overall sound. Audibly, this is heard by the authors
as a change in the characteristics of the sounds to less of
a crack and more of a loud hissing noise. Also, audibly,
the sound is suppressed to a level where it is not objec-
tionable to the unprotected ear. The control firings
made using the full commercial set of baffles is noted to
be very quiet, although still sounding like a firearm in
general. Another distinct acoustic signal noted during
testing is the sonic crack generated by the supersonic
bullet. This is especially true in the 22 LR trials.
Computational Model
1. Governing Equations
The computational model used for the current study is
a finite volume based computational fluid dynamics
(CFD) code developed to aid in the design of gun
muzzle devices. The governing equations for the gun
blast problem are the full NavierStokes equations for
a multispecies chemically reacting flow. The current
study focuses on the inviscid and real gas aspects of the
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problem to determine their relative role in the genera-
tion of the acoustic signature. Therefore, the equations
to be solved are the Euler equations for a multispecies
flow with variable specific heats. When discretized, the
equations take the form
J Qt )
J F
c ) J G
h ) J H + 0 (1)
where the dependent variable and flux vectors are
Q +
rrurv
rEra1
LraNS*1
, F +
rU
ruU ) cxPrvU ) cyPUrE ) Pra1U
LraNS*1U
,
G +
rVruV ) hxPrvV ) hyPVrE ) Pra1V
LraNS*1V
, H + 1y
rvruv
rv2
vrE ) Pra1v
LraNS*1v
.
(2)
The dependent variable ai is the mass fraction ofith spe-cies with the fluid being defined by NS total species.
Note that the mass fraction of the NSth species is not ex-
plicitly modeled since the total density is included and
the relationship r + NS
i+1
rai holds.
The suppressor design to be simulated are axisymmetric
and therefore the axisymmetric form of the equations is
used and the effects of the third dimension are included
by incorporating the source term H.
The grid Jacobian J and the contravariant velocities are
defined as
J + xcyh * xhycU + cxu ) cyvV + hxu ) hyv
. (3)
The effects of the projectile are included in the simula-
tion by making a constant velocity assumption and de-
termining at each time interval the appropriate location
of the projectile. The cells which contain the projectile
are identified and an additional source term is added to
denote the appropriate volumetric change and imperme-
able surface boundary conditions are applied to model
the projectiles surface.
2. Gas Properties
The equation of state is derived by assuming the ideal
gas equation is valid for each species and has the form
[7]
P + rRuTNS
i+1
aiMi
(4)
The temperature during the calculations must be ex-
tracted from the conserved quantity of internal energy
using the relationship
e + NS
i+1
aihi *Pr
hi + ho
fi ) T
TR
CpidT
(5)
where TR is the reference temperature for the gas prop-
erties. The specific heat, Cpi, of each species is a known
function of temperature. The representation of specific
heats can vary from assuming they remain constant to
a quadratic dependence on T. If a high order function is
used for Cpi then an iterative procedure must be used to
extract the temperature in each cell at each time level.
Here, a compromise between efficiency and sophistica-
tion is made by representing Cp as a linear function of
T over the temperature range to be encountered during
the simulations. By using the linear relationship, thetemperatures at each point in the field can be extracted
by solving a simple equation while introducing the ef-
fects of varying specific heats.
3. Fluid Dynamics Operator
The fluid dynamics aspects of the problem are modeled
using an explicit schemes. To maintain secondorder
accuracy, the fluid dynamics operator must be second
order and here a predictioncorrection scheme is used
of the form [8]
Q* + Qn * Dt2 cF(1) ) hG(1) ) Hi , jn
Qn)1 + Qn * DtcF(2) ) hG(2) ) Hi , j* (6)
with
cF + Fi)12
, j* F
i*12
, j
hG + Gi , j)1
2
* Gi , j*1
2
(7)
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and where the superscripts * and n denote the time level
at which the fluxes are computed and the superscripts
(1) and (2) denote the spatial order of the numerical
fluxes. Note the fluxes in c and h are computed at thecell faces and the axisymmetric source term is com-
puted based on the cell average.
The scheme used to define the inviscid numerical fluxesis the StegerWarming flux vector splitting algorithm
which has been extended to model multispecies flows
[9]. The flux vector splitting algorithm decomposes the
inviscid fluxes into nonnegative (K+) and nonpositive
(K) components based on the eigenvalues of the Jaco-
bian A + FQ and likewise for G. The split fluxes take
the form
K" + l"1K1 ) l"
2K2 ) l"
3K3 (8)
where the eigenvalues are
l"k+ 12lk" |lk|
l1 + bkl2 + bk) c|k|l3 + bk* c|k|
(9)
with
qk+ k~
xu ) k~
yv
k~
x +kx
|k| k~
y +ky
|k|
|k| k2
x ) k2
y+
(10)
The split flux components are
K1 +g* 1g
rrurv
rht * c2g* 1ra1L
raNS*1
K2,3 +12g
r
ru " k~ xcrv " k~ ycrht " qkc
ra1L
raNS*1
(11)
The above formulation gives K=F when k=c and K=Gwhen k=h. For the multispecies chemically reactingflow, c is the frozen speed of sound where
c2 + g Pr and g is the effective specific heat ra-tion.
As indicated in equation 7, the fluxes are evaluated at
the cell faces and are either 1st or 2nd order representa-tions. The flux at the face is a function of the states in
the neighboring cells and can be symbolically repre-
sented by
Fi)1
2, j+ F)QL
i)12
, j) F*QR
i)12
, j (12)
If a 1st order spatial representation is used, then
QLi)1
2, j+ Qi , j , Q
R
i)12
, j+ Qi)1 , j . To achieve
2nd order accuracy, a MUSCL approached is used in
which cellcenter values are extrapolated to the inter-
faces [10]. Also, to guard against the interpolation
introducing any nonphysical extremes into the field in
the region of large gradients, a limiter must be used. The
formula for the neighboring states takes the form
QLi)1
2, j+ Qi , j )F
*i)1
2, j
QRi)1
2, j+ Qi)1 , j *F
)i)1
2, j
(13)
where the limiting function is
F)i)1
2, j+
li)1 , j
2mmodDQ)i)1 , j,DQ*i)1 , j
F*i)1
2, j+ li , j
2mmodDQ*i , j,DQ)i , j
(14)
with
DQ)i , j +2Qi)1 , j * Qi , j
li)1 , j ) li , j
DQ*i , j +2Qi , j * Qi*1 , j
li , j ) li*1 , j
(15)
Here the popular minmod limiter is used where
mmod [X, Y] +sign(X) max[0.,min(|X|, Ysign(X))] . (16)
Note li,j, the celllength, is used to provide weighting
for nonuniform grid spacing. The same extrapolation
procedure is carried out for the fluxes in h and can beperformed on either the dependent or primitive vari-
ables. Previous investigations have shown that using
primitive variables gives better performance for flows
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with strong shocks and this is the method used here [10].
4. Boundary Conditions
The present predictive code has been designed to model
the launch phase of the ballistics problem and therefore,
it is assumed that boundary conditions near the muzzleexit are known. This alleviates the need to recompute
the interior ballistics phase for each computations
which reduces the computational time when conducting
design studies for muzzle devices. Typical boundary
condition information needed includes temperature,
pressure, and velocity time histories near the muzzle
exit as well as the gun propellant used. This information
can be obtained either from an interior ballistic code or
from experimental measurements. For the current study,
the simulations were carried out in parallel to the experi-
ments so some assumptions had to be made as to the
boundary conditions. The exact boundary conditions
achieved during the experiments may vary somewhatfrom those assumed, however, the relative effects of the
muzzle device should be evident in the simulations.
The particular boundary conditions used for the simula-
tions of the 38 / 9 mm are a peak pressure of 6,000 psi,
peak velocity of 1000 fps, and a peak temperature of
2400 F. It is assumed that all quantities decayed to atmo-
spheric conditions over a time period of approximately
4 ms. For the 22, the peak pressure is lowered to 2,000
psi but the remaining variables were kept the same.
The simulations presented here model the flow field as
a combination of three species, these being the O2 and
N2found in the ambient air and the gun propellant gas.
The properties for oxygen and nitrogen are available in
various sources [11]. The gun propellant is known to be
composed primarily of the active agents CO and H2 as
well as the inert N2 and to a smaller extent the combus-
tion products H2O and CO2 resulting from the interior
ballistic process. Therefore, the properties used for the
gun propellant (F) are formulated to represent a mixture
of CO and H2 and the boundary conditions imposed near
the muzzle exit specify the mass fraction to be
aF+ .64 and aN2+ .36. These assumptions which
simplify the gun gas composition are done to reduce the
number of governing equations. Similar processes have
been used previously with good results even when fur-
ther combustion is included in the modeling [6].
5. Results and Discussions
The only experimental data available for code evalua-
tion is the peak pressures measured in the experiments.
Therefore, the only judgement as to the utility of the
computational code that can be made is whether the
code correctly simulates the general effect of the sup-
pressors in reducing the pressure levels and in turn the
acoustic signal. This data can also be used to determine
if the inviscid and real gas effects being modeled are
dominate players in the determination of the peak pres-
sures and the acoustic signals. The data from the experi-
ments and simulations are presented with respect to the
gage location. The locations of the gages are given in
table 1. The distances are measured from the exit of the
muzzle in the cases with no suppressor and from the exit
of the suppressor when it is used.
A comparison between the simulated and measured
pressures for the bare muzzle 38 / 9 mm is presented in
figure 4 as well as data for the 38 / 9 mm with the sup-
pressor present. The curves denoting the experimental
measurements are fit to the average of the three firings
made for each configuration and gage location. During
the firing with the suppressor, two distinct peaks were
measured by the gages and these are denoted wave 1 and
wave 2 with wave 1 being the peak which arrived first.
Likewise, the simulations showed the initial peak to be
accompanied by a second peak or plateau (figure 5).However, in the simulations the larger of the two peaks
always arrived first where as in the experiments the larg-
er of the two peaks arrived second. This discrepancy
may results from the assumptions about the projectile
flight velocity since the interaction of the projectile with
the pressure field as it is evolving in the suppressor can
effect the resulting pressures. Previous studies [6] have
shown that neglecting the projectile can affect the pre-
dicted overpressures and the same results would be ex-
pected if there is error in the projectile velocity. Howev-
er, the simulated pressure levels agree quite well with
the experiments and do indeed convey the effect of the
suppressor in reducing the pressure and in turn the level
of sound generated.
The peak pressures from the simulation for the 22 cali-
ber case are presented in figure 6 with the nomenclatural
the same as earlier. The first observation is that even
though the simulation captures the trend in overpressur-
es for the bare muzzle case, the values are lower than
those measured at all gage locations. This indicates ei-
ther the pressure assumed for the boundary conditions
in the simulation was somewhat lower than those
achieved during the experiments or the inviscid non
reacting flow model is not capturing some of the driving
physics. It has been shown that by including the chemi-
cal reaction processes higher overpressures are seen insimulations for gun blast [6]. However, before adding
reaction for the cases in the current study, a closer as-
sessment of the true boundary conditions should be
made.
The simulations of the 22 with suppressor do capture the
general trend of the baffle design producing lower pres-
sures and in turn lower sound levels. However, the simu-
lated peak pressure values are somewhat larger than the
measurements for gages 3 and 6. Again it is believed
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that some of the discrepancy is due to the assumed pro-
jectile velocity but further investigation is needed. Even
given these regions of over prediction, the simulation
does capture the effects of the baffle design in reducing
the pressure levels and in turn the sounds generated.
As in the case of the 38 / 9 mm with suppressor, the mea-
surements for the 22 also showed a coupling of highpressure peaks. But here the variation in the magnitudes
were much less and the larger of the two was not always
the peak which arrived first. In the simulations, the pre-
dominate peak was followed by a lower peak or plateau
in pressure (figure 7) much as the case for the 38 simula-
tions. As mentioned earlier, when fired the baffle design
generates a sequence of pressure waves emitted from
the suppressor with magnitudes larger than the ringing
noted in the bare muzzle case. This phenomena is also
seen in the simulations and can be seen in Figure 8 which
shows a pressure contour at one instance in time during
the firing of the 22 with suppressor. The contour levels
have been set to highlight the pressure spectrum around1 atmosphere. Evident in the figure is a sequence of
pressure pulses emitted from the suppressor. Points A,B,
and C denote the peaks of the pulses where A is a pulse
just being emitted while B and C are pulses which have
traveled outward into the field. If the time evolution of
the suppressors internal flow field is viewed, it is evi-
dent that shocks are continuously reflecting off the face
of the suppressor walls normal to the line of fire. This is
most likely the driving force behind the pulsating pres-
sure signature.
Conclusions
Many types of muzzle devices are used to reduce theoverpressures generated during the gun firing process.
An example of these type devices is the baffle configu-
ration tested here. Both the experiments and simulations
show such a design reduces the level of overpressures.
The fact that the current simulations captures this phe-
nomena infers that the reduction in sound by muzzle de-
vices such as the baffle design are due in a large part to
the inviscid aspects of the flow. This as well as the good
comparisons with the measured peak pressures is en-
couraging to the engineer tasked to design muzzle de-
vices since all these simulations have been carried out
modeling only the inviscid and real gas aspects of the
problem. Further accuracy can be achieved by includingthe chemical reactions and turbulence and this would be
required to model muzzle flash. Also, phenomenon such
as suppressor erosion would require some accounting
for the particle loading and heat transfer to the walls.
Any investigation into these phenomena should be ac-
companied with a more detailed model of the internal
flow field to include the modeling of the turbulence.
Further investigation is needed to determine to what lev-
el these aspects need to be modeled for engineering ap-
plications. To correct some of the discrepancies identi-
fied here in the prediction of pressure and sound
generation, more attention should be paid to the projec-
tile flight parameters with one option being to use the
simulated pressures on the projectile to dictate its flight
velocity. However, any increase to the model sophis-
tication should be weighed against its robustness and ef-
ficiency for the task at hand. The current study does
show the utility of computational modeling in the design
process of suppressors which is needed to reduce the
reliability on empirical databases and the expensive
cutandtry procedure.
Acknowledgements
The authors wish to thank Armond Tomany for work in
modifying the firearms to accept the suppressor units
and to Philip H. Dater, M.D., of GemTech Division of
Gemini Technologies and Antares Technologies for
supplying the suppressors used in this study.
References[1] E.C. Ezell, Small Arms of the World, 12th Ed.,
Barnes and Noble, New York, 1993.
[2] L. Stiefel, Gun Propulsion Technology, Vol 109Progress in Astronautics and Aeronautics, AIAA,Washington D.C., 1988 pp. 183259.
[3] G Klingenberg, J.M.Heimerl, Gun Muzzle Blastand Flash, Vol 139 Progress in Astronautics and Aero-nautics, AIAA, Washington D.C., 1992 pp. 197338.
[4] G.C. Carofano, Blast Field Contouring UsingUpstream Venting, ARCCBTR93009, US ArmyArmament Research, Development and EngineeringCenter, March 1993.
[5] G.C. Carofano, A Note On The Blast Signatureof a Cannon, ARCCBTR92014, US Army Arma-ment Research, Development and Engineering Cen-ter, March 1992.
[6] J.K. Clutter, G. Abate, W. Shyy, & C. Segal StudyOf Fast Transient Flow Phenomenon For MunitionApplication, AIAA Paper 960829.
[7] J. Anderson, Hypersonic and High Temperature
Gas Dynamics, McGrawHill New York, 1989.
[8] R.J. LeVeque and H.C. Yee, A Study of Numeri-cal Methods for Hyperbolic Conservation Laws withStiff Source Terms, Journal of Computational Phys-
ics, Vol 86, 1990, pp 187210.[9] M.S. Liou, B. Van Leer, and J.S. Shuen, Splitting
of Inviscid Flues for Real Gases, Journal of Com-putational Physics, Vol. 87, 1990 pp 124.
[10] J.S. Shuen Upwind Differencing and LU Factor-ization for Chemical Nonequilibrium NavierStokesEquations, Journal of Computational Physics, Vol99, 1992, pp 233250.
[11] Stull, D.R. and Prophet, H., JANAF Thermo-chemical Tables, NSRDSNBS 37, June 1971.
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Caliber Gage X (in) Y (in)
22 1 0 7.5
22 2 3.5 7.5
22 3 7 7.5
22 4 0 1022 5 5 10
22 6 10 10
38 1 0 10
38 2 5 10
38 3 10 10
Table 1. Placement of pressure gages for the experiments and simulations.
Table 2. Experimental measured peak pressures in atmospheres for all configurations.
Cal Y X Bare Sup (1) Sup (2) Com (1) Com (2)
22 7.5 0.0 1.0505 1.0074
22 7.5 3.5 1.0604 1.0098 1.0125
22 7.5 3.5 1.0658 1.0119 1.0113
22 7.5 3.5 1.0621 1.0106 1.0135
22 7.5 7.0 1.0757 1.0123 1.0169 1.0082 1.0061
22 7.5 7.0 1.0749 1.0124 1.0130 1.0071 1.0053
22 7.5 7.0 1.0782 1.0124 1.0139
22 10.0 0.0 1.0387 1.0048 1.0056
22 10.0 0.0 1.0391 1.0055 1.0053
22 10.0 0.0 1.0366 1.0051 1.0043
22 10.0 5.0 1.0511 1.0092 1.0097
22 10.0 5.0 1.0532 1.0087 1.0098
22 10.0 5.0 1.0536 1.0075 1.0094
22 10.0 10.0 1.0501
22 10.0 10.0 1.0583 1.0128
22 10.0 10.0 1.0600 1.0109
22 10.0 10.0 1.0565 1.0128
38 10.0 0.0 1.1500 1.0300 1.0416
38 10.0 0.0 1.1636 1.0266 1.0281
38 10.0 0.0 1.1670 1.0203 1.0237
38 10.0 5.0 1.1936 1.0479 1.0542
38 10.0 5.0 1.2105 1.0392 1.0532
38 10.0 5.0 1.1922 1.0489 1.0523
38 10.0 10.0 1.1704 1.0610 1.0987
38 10.0 10.0 1.1554 1.0629 1.0799
38 10.0 10.0 1.1626 1.0658 1.0842
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Figure 1. Schematic of experimental layout.
Oscopepreamp
y distance
x distance
Microphone
(vertical)
suppressorsandbagfirearm
table
Figure 2. Schematic of cylindrical baffle suppressors cross section and specific distances.
L
L / 3
Center Line / Line of Fire
Di
DeDe
WeWi
L = 4.316 6.373
Di = .749 .995
De = .263
.22 .38
.442
Wi = .25 .25
We = .36 .36
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Figure 3. Picture of the cylindrical baffle suppressor and 38 action used in the tests.
Figure 4. Comparison of peak pressures from the experiments and the simulations for the 38 / 9 mmwith and without suppressor.
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1 2 3
P(atm)
gage
38_bare.dat38_sup_wave_1.dat38_sup_wave_2.dat
38.sim38_sup_wave_1.sim38_sup_wave_2.sim
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Figure 5. Simulated pressure time history at gage location 3 for the 38 with and without suppressor.
0.95
1
1.05
1.1
1.15
1.2
1.25
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
P(atm)
time (~ms)
38_bare38_sup
Figure 6. Comparison of peak pressures from the experiments and the simulations for the 22with and without suppressor.
1
1.02
1.04
1.06
1.08
1.1
1.12
1 2 3 4 5 6
P(atm)
gage
22_bare.dat22_sup_wave_1.dat22_sup_wave_2.dat
22.sim22_sup.sim
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Figure 7. Simulated pressure time history at gage location 2 for the 22 with and without sup-pressor.
0.98
0.99
1
1.01
1.02
1.03
1.04
1.05
1.06
1.07
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
P(atm)
time (~ms)
22_bare22_sup
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Figure 8. Simulated pressure contour at one instant in time for the 22 with suppressor. In (b) the scale hasbeen set to highlight the pressure spectrum around 1 atm. Pressure peaks are denoted with A, B, and C.
(b)
(a)
Scale : .5 3. atm