Development of a DYNASWIRL - Dynaflow, Inc.

Appears in 50th AIAA Aerospace Sciences Meeting Online Proceedings including the New Horizons Forum and
Aerospace Exposition (2012)
Development of a DYNASWIRL ® Phase Separator
for Space Applications
Xiongjun Wu and Georges L. Chahine
DYNAFLOW, INC., Jessup, MD, 20794
This paper describes the development of a new passive phase separator based on
imparting swirl to the flow using a DYNAFLOW patented nozzle. By combining swirl,
cavitation, and rectified gas diffusion, the DYNASWIRL ® phase separator is able to force even
very low void fraction gas out of the liquid into the central core of the vortex, and the extract
it from the core. A prototype that was tested on a NASA reduced gravity flight in August
2009 successfully reduced the void fraction down to 10 -8 . Data analysis and flow visualization
indicated that a steady vortex core was maintained and that the gas was continuously
removed from the vortex core under the reduced-gravity conditions. Development of the
phase separator was guided by 3D Numerical simulations using 3DYNAFS © , which couples
an incompressible Navier-Stokes flow solver and a bubble tracking and dynamics code.
Nomenclature
= void fraction
= dynamic viscosity
= kinetic viscosity
= medium density
= rotational speed
= swirl parameter
= vortex strength
a c = vortex core radius
a g = gas extraction orifice radius
c = sound speed
d ij, d kl, d lk = deformation tensors
dt = time step
h = height
p c = pressure at vortex core
p e = ambient pressure at exit
p g0 = initial gas bubble pressure
p o = pressure at chamber boundary
p v = liquid vapor pressure
v a = exit velocity
v t = tangential inlet velocity
r = radial distance
A t = area of tangential slots
A o = area of exit orifice
C d = discharge coefficient
D 1 = chamber diameter
F D = drag force coefficient
P enc = average pressure over bubble surface
Q t = inlet flow rate
R = bubble radius
u = velocity vector
u enc = average velocity vector over bubble surface
Subscripts:

g
l
m
= bubble
= gas
= liquid
= mixture
I. Introduction and Background
HE limits on the amount of liquids and gases that can be carried to space make it imperative to recycle and
T reuse these fluids. On earth, bubbles in a liquid are easily separable by buoyancy. In microgravity, other
external forces, such as a centrifugal force, must be utilized to separate bubbles from liquids. Two categories of
centrifugal force separators exist: one uses active rotation by mechanically spinning the tank. This is very efficient
but requires shaft, bearings, and motor. In the second, the tank is fixed, and the rotation is induced by eccentric
injection of the mixture. This method requires little power, is much simpler than active separators, and consumes
less energy. McQuillen et al. [1,2] at NASA Glenn Research center has been developing the Cascade Cyclonic
Separation Device (CSD-C) since the mid 90’s. This separator has been proven to be very efficient for mid-range
void fraction (from 50 to 80% of gas) with an efficiency approaching 100%. However, it is not as efficient for lower
void fraction, where there is a need for further research [3,4].
A. DYNASWIRL ® Vortex Chamber
Under on-going support from NASA, DYNAFLOW INC. has been developing a phase separator for gas-liquid
mixtures based on its efficient swirling flow generation DYNASWIRL ® technology. The DYNASWIRL ® was
extensively tested for various applications in previous studies and was shown to be able to simultaneously
accomplish several water reclamation functions: liquid
oxidation, TOC reduction, disinfection, and
oxygenation [5-9]. This type of vortex generator has
also been extensively used in applications such as algae
removal, underwater painting and surface preparation
[10]. The DYNASWIRL ® has also been used to develop a
fine bubble generator [11]. The mechanisms enabling
the accomplishment of each of these functions are
different while all arise from induced cavitation bubble
dynamics, growth, and collapse.
The phase separation DYNASWIRL ® consists of two
concentric cylinders as shown in Figure 1. The fluid is
introduced in the space between the two cylinders and
exits through orifices on the cylinder axis, with area,
A o . The swirling flow inside the inner cylinder is
generated with tangential slots which enable flow from
outer to inner cylinder. This configuration makes the
vortex core very stable even at low flow rates. The ratio
between axial and tangential velocities, ,
or the swirl Figure 1. Cross section of a DYNASWIRL ® Chamber.
parameter, can be controlled by changing the relative
areas of the slots, A t , and the orifice, A o , respectively. With high tangential velocities, the pressure on the axis can be
made low enough to make microbubbles grow on the axis and collect into a line vortex bubble. At even higher
tangential velocities cavitation occurs and further enhances gas diffusion and gas transfer into the central vortex
core. The main idea of the DYNASWIRL ® separator is to use swirl, cavitation, and rectified gas diffusion to force low
void fraction gas out of the liquid into the central core of the vortex and extract the gas from the central cavitation
core.
The pressure drop at the center of a vortex flow is a direct function of the vortex strength, Γ, and of the radius of
the vortex viscous core, a c . The flow field of a rotating fluid or vortex, can be considered with reasonable accuracy
to be composed of two regions. In the innermost region, of radius a c , the fluid viscosity is predominant, and the
fluid rotates en masse as a solid body. In that region the tangential velocity of the fluid increases linearly with the
distance from the vortex axis where the tangential velocity is zero. At a distance r from the vortex axis the tangential
velocity in this viscous region can be related to the angular velocity, , as
v r
(0)
1
.

In the outermost region of the vortex, the flow is that of an ideal inviscid fluid. In that region, the circulation,
which is equal to the integral of the velocity along a closed line encircling the vortex center, is everywhere constant
and equal to the vortex strength, Γ. The velocity at a point located at a distance r from the vortex center in this
outermost region is related to Γ by
v2 / 2 r.
(1)
At the transition between the viscous and inviscid regions, where r = a c and v 1 = v 2 , the following relationship
can be derived:
2
2 a c
.
(2)
Let p o be the ambient pressure at the inner chamber boundary, the pressure at the vortex center, p c , can be
determined knowing Γ , and the liquid density, ρ. By applying Bernoulli's equation in the inviscid region and
solving the equations of conservation of mass and momentum in the viscous region one finds:
2
pc po ( / 2 ac
) .
(3)
Cavitation in the vortex occurs when p c drops locally below the liquid critical pressure, p c , or for simility the
vapor pressure, p v , of the liquid at the considered temperature [12]. In order to increase the pressure drop or the
degree of cavitation it is necessary to either increase Γ or decrease a c . In order to extract the gas from the central
core, the core size has to be larger than the gas extraction orifice size, a g , therefore
2
p p ( / 2 a
) .
(4)
v o g
With DYNASWIRL ® , the swirling vortex is generated by tangentially directing fluid about the longitudinal axis of
a cylindrical swirl chamber positioned within a nozzle. If v t is defined as the fluid tangential injection velocity into
the swirl chamber, and D 1 is the diameter of the swirl chamber, Γ is directly related to v t and D 1 by the simple
relation:
Dv
1 t
.
(5)
Since D 1 is a fixed geometric dimension of the swirl chamber, v t can be varied and is directly determined by the
total tangential flow rate, Q t and the total tangential injection area, A t with the following relation:
vt Qt / At
.
(6)
The axial velocity component of the liquid coming out of the orifice has an average value, v a , directly related to
Q t and the area, A o , of the exit orifice, by the relation:
va Qt / Ao
.
(7)
Since p o is the driving pressure that push the liquid out of the chamber through the axial orifice, it can be written
as
1 2
po pe va
,
(8)
2
where p e is the ambient pressure outside of the DYNASWIRL ® chamber liquid exit. And Q t and V t can be related by
the relation:
Qt C , d
Ao va (9)
where C d is the discharge coefficient of the liquid exit orifice. Combining the above equations, the following
relationship is satisfied:
2
2
Q
t
D1Q
t
Cd A
0
ag A
t
1
pv
pe
2 2
This equation defines what is needed to obtain a stable cavitating core.
B. 3D Coupled Numerical Simulations
Numerical simulations were conducted to to gain insight of the separation process and to assist the design of an
efficient separator. The bubbly mixture flow inside the swirl chamber was treated from the following two
perspectives:
Microscopic level: Individual bubbles are tracked in a Lagrangian fashion, and their dynamics are followed by
solving the surface averaged pressure Rayleigh-Plesset equation. The bubble responds to its surrounding
medium described by its mixture density, pressure, velocity, etc.
Macroscopic level: Bubbles are considered collectively and define a void fraction space distribution. The
mixture medium has a time and space dependant local density which is related to the local void fraction. The
mixture density is provided by the microscale tracking of the bubbles and the determination of their local
volume fraction.
(10)

The two levels are fully coupled: the bubble dynamics are in response to the variations of the mixture flow field
characteristics, and the flow field depends directly on the bubble density variations. This is achieved through a twoway
coupling between the unsteady Navier Stokes solver 3DYNAFS-VIS © and the bubble dynamics code
3DYNAFS-DSM © .
3DYNAFS-VIS © is an incompressible Navier-Stokes flow solver, it can includes bubbles, cavities, and large free
surface deformation effects and uses moving overset grids and dynamic grid generation schemes. 3DYNAFS-VIS ©
enables direct numerical solution in addition to RANS. The code is based on the artificial-compressibility method.
The mixture medium satisfies the following general continuity and momentum equations:
m
mu m 0 , (11)
t
Dum
2
m pm 2mij m u m , (12)
Dt
3
where, the subscript m represents the mixture medium, and
ij
is the Kronecker delta. The mixture density and the
mixture viscosity for a void volume fraction can be expressed as:
1 , (13)
m
g
1 , (14)
m
where the subscript represents the liquid and the subscript g represents the gaseous bubbles. The medium has a
variable density because the void fraction varies in space and in time.
Lagrangian bubble tracking is accomplished by 3DYNAFS-DSM © . It is a multi-bubble dynamics code for tracking
and describing the dynamics of bubble nuclei present in a flow field. The user can select a bubble dynamics model;
either the incompressible Rayleigh-Plesset equation [13] or the compressible Keller-Herring equation [14-16]. In the
first option, the bubble dynamics is solved by using a modified Rayleigh-Plesset equation improved with a Surface-
Averaged Pressure (SAP) scheme:
3k
2
3 | |
2 1 R0
2
4mR uenc
ub
RR R pv pg 0
Penc
,
2
m
R
(15)
R R
4
where R is the bubble radius at time t, R 0 is the initial or reference bubble radius, is the surface tension parameter,
µ m is the medium viscosity, m is the density, p v is the liquid vapor pressure, p g0 is the initial gas pressure inside the
bubble, k is the polytropic compression law constant, u enc is the liquid convection velocity vector and u b is the
bubble travel velocity vector, and P enc is the ambient pressure “seen” by the bubble during its travel. With the
Surface Averaged Pressure (SAP) model, P enc and u enc are the average of the pressure over the surface of the bubble.
If the second option is adopted, the effect of liquid compressibility is accounted for by using the following
Keller-Herring equation.
3k
2
R 3 R
2 1 R R d
R0
2
4 mR
| uenc ub
|
1 RR 1 R 1 pv pg 0
Penc
,
cm 2 3cm
m
cm cm
dt
R
(16)
R R
4
where c m is the speed of sound in the mixture medium.
The bubble trajectory is obtained from the bubble motion equation derived by Johnson and Hsieh [17]:
1/2
du
( )
b
m 3R
m u
1 m du
dub
b m Kv mdij
FD u ub u ub ub g 1/4
b .
dt 2R x 2
dt dt
u u (17)
R( d d )
b b b b b
The first term in Equation (17) accounts for the drag force effect on the bubble trajectory. The drag coefficient
F D is determined by the empirical equation of Haberman and Morton [18]. The second and third term in Equation
(17) account for the effect of change in added mass on the bubble trajectory. The fourth term accounts for the effect
of pressure gradient, and the fifth term accounts for the effect of gravity. The last term in Equation (17) is the
Saffman [19] lift force due to shear as generalized by Li & Ahmadi [20]. The coefficient K is 2.594, is the
kinematic viscosity, and d ij is the deformation tensor.
The unsteady two-way interactions can be described as follows:
The bubbles in the flow field are influenced by the local densities, velocities, pressures, and pressure gradients
of the mixture medium. The dynamics of individual bubbles and Lagrangian tracking of them are based on
these local flow variables as described in Equations (15) to (17).
g
lk
kl

The mixture flow field is influenced by the presence of the bubbles. The local void fraction, and accordingly
the local mixture density, is modified by the migration and size change of the bubbles, i.e., the bubble
population and size. The flow field is adjusted according to the modified mixture density distribution in such a
way that the continuity and momentum are conserved through Equations (11) and (12).
Void fractions based on -cells were used in the 3-D space to compute the void fraction [21].
II. Reduced Gravity Flight Test
A prototype of the DYNASWIRL ® Free Vortex Phase Separator (FVS) was selected to be tested at a reduced
gravity flight test under the NASA FAST program (The Facilitated Access to the Space Environment for
Technology Development and Training) in August, 2009. This prototype consisted of 3 chambers connected in
series as shown in Figure 2. In the center was the DYNASWIRL ® chamber where the gas-liquid mixture was
introduced in the space between the two cylinders. The side chambers were a vacuum chamber and a mixing
chamber. An orifice between the vacuum chamber and the DYNASWIRL ® chamber acted as a “gas finder” orifice.
Once the core was generated in the vortex chamber, the “gas finder” orifice started to extract gas from the vortex
core into the vacuum chamber. This chamber was connected to a vacuum pump to insure gas removal at a faster
speed. The “mixing” chamber was also connected to the “vortex” chamber, but through a larger orifice. It was used
to receive a gas-liquid mixture obtained with a DYNASWIRL ® bubble generator before the test. During the test it was
used as a reservoir to collect the gas reduced mixture (which exited from the larger orifice of the “vortex” chamber).
This mixture of gas and liquid was then pumped back to the “vortex” chamber for further gas-liquid separation.
Figure 2. Schematic of the prototype of the DYNASWIRL ® Phase Separator, which was tested at a reduced
gravity flight test under the NASA FAST program in August, 2009.
A. Experiment Setup
The DYNASWIRL ® phase separator prototype was setup for the reduced gravity flight test in a loop sketched in
Figure 3. A ¾ HP centrifugal pump was used to supply the mixture to the phase separator and a vacuum/air supply
pump was used to provide vacuum during the phase separation process. A vacuum breaker was installed at the gas
extraction port of the vacuum chamber to prevent liquid from getting into the gas extaction line. Additionally, a
“liquid catcher” chamber was installed to store the water escaped from the vacuum chamber under microgravity
when vacuum was applied to prevent the water from entering the vacuum pump. This water from the liquid catcher
chamber was recycled back into the FVS periodically.
An ABS ACOUSTIC BUBBLE SPECTROMETER ®© [22-26] with two hydrophones setup in the mixing chamber was
used to monitor the void fraction during the whole flight. A high definition video camera was also used for flow
visualization of the gas extraction process. In addition, the pressures in all the three chambers, as well as the
accelerometer signals from the airplane, were recorded during the flight. The entire setup had a secondary
confinement to prevent any possible leaks during the reduced gravity flight. The DYNASWIRL ® phase separator was
confined in a Plexiglas box and all pipes were equipped with a secondary hose to capture any potential leaks. Table
1 shows a list of the components used in the experiment setup as shown in Figure 3.

Figure 3. Experimental setup for the bubble generation and air separation experiments conducted in a
reduced gravity flight test under FAST program in August, 2009.
Item
Description
Dimensions
(in)
Weight
(lbs)
Pump Water pump, 3/4HP, 115V, 9 Amps. 1789 41
FVS DYNASWIRL ® Chamber: Free Vortex Separator 181010 25
Vacuum/ Air
Pump
Vacuum/air pump, 115V, 4.2 Amps 8611 16
Bubble
Generator
DYNASWIRL ® Bubble Generator 611 1
Laptop Dell Inspiron laptop 14101.5 6
ABS ABS ACOUSTIC BUBBLE SPECTROMETER® box 168.52 3
Frame
Aluminum tubing frame with aluminum bottom and
top
483620 46
Camcorder HD digital camcorder 2
Misc. PVC piping, valves, tubing, water… - ~115
Table 1. List of Equipment used in the Free Vortex Separator Experiment on the reduced gravity flight
test under the FAST program in August, 2009.
B. Numerical Simulations
3DYNAFS-VIS © was used to characterize the DYNASWIRL ® phase separator prototype. A multi-block grid, as
shown in Figure 4, was generated to represent the DYNASWIRL ® chamber with two orifices connecting to the two
external chambers. A larger orifice connected with the mixing chamber and a smaller one connected with the
vacuum chamber. Figure 5 shows a sample pressure distribution at an inlet flow rate of 20 GPM, the pressure was
normalized with the high pressure at the injection slot of the inner DYNASWIRL ® chamber. A low pressure vortex
core region can be clearly observed in the swirl chamber from Figure 5.
The flow field in the phase separator was unsteady
and the flow near the two orifices behaved quite
differently from each other. Figure 6 and Figure 7 show
some details of the flow field at two time steps near the
liquid extraction and gas extracton orifices respectively.
Figure 4. Multi-block grid used for 3DYNAFS-
VIS © simulation of the DYNASWIRL ® phase

Animation with time show more significant fluctuations near the smaller orifice, where the flow can come in and
out of the swirl chamber through the orifice. 3D coupled numerical simulations on the DYNASWIRL © phase separator
by coupling 3DYNAFS-VIS © and 3DYNAFS-DSM © were also performed to study the bubble dynamics in the flow
field. Figure 8 shows a snapshot of the bubbles in the flow field obtained from the coupled run. Bubbles were
injected from the slot of the DYNASWIRL © inner chamver, as shown in the figure, bubbles were concentrated into the
vortex core region and escaped into the vacuum chamber through the gas extraction orifice.
Figure 5. Normalized pressure distribution in the DYNASWIRL ® phase separatorat flow rate of 8.5 GPM.
SC
MC
SC
MC
Figure 6. Flow field near the larger orifice that connects swirl chamber (VC) and mixing chamber (MC) at
two different time steps.
VC
SC
VC
SC
Figure 7. Flow field near the smaller orifice that connects vacuum chamber (VC) and swirl chamber (SC) at
two different time steps

Figure 8. A snapshot of the results from 3DYNAFS-DSM © using background flow provided by 3DYNAFS-VIS © .
C. Flight Test Results
The reduced gravity test was performed in a Zero-
G Boeing 727 airplane on August 12, 2009. The
bubbly medium was generated before the parabolic
maneuvers started. Once the void fraction reached a
preset 1% value, the bubble generator was turned off
and the bubbly medium were kept circulating
throught the mxing chamber without going through
the DYNASWIRL ® chamber to maintain a
homogeneous bubbly medium until right before the
parabolic maneuvers began. Then the bubbly medium
was directed into the phase separator to remove the
injected air, the phase separation process was
monitored during the complete flight duration with
parabolic maneuvers.
The total flight time during which there were
parabolic maneuvers was about 55 minutes. The
DYNASWIRL ® phase separator was run at a flow rate
of 15 GPM for the first 25 minutes for initial gas
extraction, and then at an increased flow rate of 20
GPM for the final gas extraction. Data analysis and
flow visualizations indicated that a steady vortex core
was maintained and that the gas was continuously
removed from the vortex core during the zero-gravity
condition.
Figure 9 shows the gas bubbles being extracted
from the vortex core under zero-gravity. As the gas
extraction progressed, the vortex core shrunk and the
number of visible bubbles kept decreasing. It was also
observed during the test that the bubbles in the vortex
chamber moved towards the core as shown in Figure
10.
Figure 11 shows the images of the mixing
chamber taken during the initial and the final stages
of the flight. As seen from these images clarity was
much improved at the end as the visible amount of
bubbles significantly reduced.
Similar results were observed from the images of
the vortex chamber and the vacuum chamber during
the initial and final stages of the test. These images are
shown in Figure 12. The number of visible bubbles
Figure 9. Gas extraction under zero gravity.
Vacuum Chamber
Vortex Chamber
Vortex Core
Figure 10. bubbles in the vortex chamber moving
towards the vortex core.
Figure 11. Sanp shots of the mixing chamber during
the initial (left) and final (right) stages of the flight.

was significantly reduced in the final stages of the flight when compared to the initial stages. These images also
show that vortex core size had shrunk in the final stage when compared to that at initial stage.
Figure 12. Snap shots of the vortex chamber and the vacuum chamber during the initial stage (left) and final
stage (right) of the reduced gravity flight.
Figure 14. Sample signals of the Pressure
signal and gravity in the z-direction during
the flight.
Figure 13. Void fraction as a function of time.
Figure 15. Comparisons of test raw signals (red ) measured by the hydrophones during the initial stage of the
flight, i.e high void fraction (left) and final stage of the flight, i.e. low void fraction (right).
Figure 14 shows the pressure signal amplitudes in the mixing, vacuum, and vortex chambers along with the
acceleration of gravity in the z direction on the second y axis. As seen in the figure, the pressure was highest in the
vortex chamber and lowest in the vacuum chamber. Since the vacuum pump was turned off to avoid water fouling
the vacuum line during the reduced gravity phases, under the microgravity condition the pressure in all three
chambers was higher, compared to the case when there was gravity present, however this change had no effects on
the smooth operation of the phase separator.

Figure 13 shows the void fraction in the mixing chamber during the flight as measured by the ABS . Note that
the hydrophones deployed in this test were designed to measure only very low void fractions. In the initial stage, the
void faction was above the upper limit of the measurement range, the reading was saturated at around 2 x 10 -5 . As
the phase separation progressed, the void fraction decreased continuously with time, proving that the DYNASWIRL ®
phase separator was working under microgravity. At the end of the test, the void fraction measured by the ABS was
of the order of 10 -8 , while is started at the beginning of the flight over 10 -2 . Figure 15 shows a comparison of a
sample ABS raw signals at the initial and final stage, the received test signals are in red. At the beginning, the
received signals were very weak due to the large amount of bubbles. With the DYNASWIRL ® phase separator
continuously removing bubbles, the void fraction decreased, and the received test signals became very significantly
stronger.
From the above described reduced gravity test results, identified areas for improvement included:
Improve gas extraction efficiency.
Reduce or eliminate the remixing of liquid and gas
Expand the operation ranges of void fraction and flow rate
Enable a continuous feed of two-phase content
We are addressing these identified areas for improvement through ground based tests and numerical simulations
prior to the next scheduled zero gravity flight tests in 2012.
III. Conclusion
A new phase separator based on DYNAFLOW patented DYNASWIRL ® technology was developed and tested during
a NASA reduced gravity flight. During the test, the phase separator successfully reduced the mixture void fraction
down to 10 -8 . Data analysis and flow visualization indicated that a steady vortex core was maintained and that the
gas was continuously removed from the vortex core under the reduced-gravity conditions. 3D Numerical simulations
using a Navier-Stokes flow solver, 3DYNAFS-VIS © , coupled with a bubble dynamics solver, 3DYNAFS-DSM © were
used to guide the design. 3DYNAFS © provided us with a powerful numerical tool to help optimize the design and
ultimately develop a fully operational DYNASWIRL ® Phase Separator to be tested by NASA on the International
Space Station (ISS).
Acknowledgments
This work is supported by NASA under Grant No. NNX09AI35G, the authors would like to thank Mr.
McQuillen, program monitor, for his support and advice.
References
1 McQuillen, J. B., Neumann, E. S., “Two-Phase Flow Research Using the Laserjet Apparatus,” NASA Technical
Memorandum, NASA, Cleveland, OH 106814, 1995, pp. 1-14.
2 Hoyt, N. C., Kamotani, Y., McQuilen, J. B., Sankovics, J. M., “Computational Investigation of the NASA Cascade Cyclonic
Separation Device,” 46 th AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 2008.
3 Shoemaker, J. M., Schrage, D. S., “Microgravity Fluid Separation Physics – Experimental and Analytical Results,” 35 th AIAA
Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 1997.
4 Schrage, D. S., Shoemaker, J. M., McQuillen, J., “Passove Two-phase Fluid Separation – A Dynamic Simulation Model,”
36 th AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 1998.
5 Chahine, G. L., Hsiao, C. T., Choi, J. K., Kalumuck, K. M., Loraine, G., Aley, P. D., Frederick, G. S., “Development of a
DYNAJETS Cavitation System for High Rate Disinfection of Combined Sewer Overflows,” DYNAFLOW, INC, Report 2M3032-1,
2005.
6 Chahine, G. L., Kalumuck, K. M., Hsiao, C. T., Choi, J. K., Loraine, G., Aley, P. D., Frederick, G. S., “Water Reclamation
Using the DYNAJETS Cavitating Jets for the Advanced Life Support System,” DYNAFLOW, INC, Report 2M2001-1-NASA,2005.
7 Loraine, G., Chahine, G. L., Hsiao, T. T., Choi, J. K., Jain, A., Aley, P. D., Frederick, G. S., “ Cavitating Jets for Aquaculture
Wastewater Treatment and Recycling,” DYNAFLOW, INC, Report 2M5016-NOAA-01, 2005.
8 Chahine, G. L., Hsiao, C. T., Choi, J. K., Loraine, G., Frederick, G. S., Aley, P. D., “Reduction of Chemical and Biological
Containments Using the DYNAJETS Cavitating Jets: Post-or Pre treatment for Desalination,” DYNAFLOW, INC, Report 2M3038-1-
ONR, 2005.
9 Loraine, G., Choi, J. K., “Seawater Remediation Technology Using DynaJets,” DYNAFLOW, INC, Report 2M6022-1-
NSWC,2007.
10 Chahine, G. L., Choi, J. K., Loraine, G., Aley, P., “Development of a DYNASWIRL Cavitating Jet Nozzle for Underwater
Hull Grooming” DYNAFLOW, INC, Report 2M7036-NSWCCD-1,2009.
11 Chahine, G. L., Barbier, C., Loraine, G., Choi, J. K., "Development of a Bubble Generator Suitable for Spallation Neutron
Source Shock Mitigation Applications", DYNAFLOW, INC, Report 2M7022-DOE-Bub-1, May 2008.

12 Chahine, G. L., “A Numerical Model for Three-Dimensional Bubble Dynamics in Complex Geometries”, 22nd American
Towing Tank Conference, St. Johns, Newfoundland, Canada, August 1989.
13 Plesset, M. S., “Dynamics of Cavitation Bubbles”, Journal of Applied Mechanics, Vol. 16, 1948, pp. 228-231.
14 Gilmore, F. R., “The Collapse and Growth of a Spherical Bubble in a Viscous Compressible Liquid”, Div. Rep. 26-4,
California Institute of Technology Hydrodynamics Laboratory, Pasadena, CA, 1952.
15 Knapp, R. T., Daily, J. W., Hammit, F. G., “Cavitation”, McGraw-Hill, New York, 1970.
16 Vokurka, K., “Comparison of Rayleigh’s, Herring’s, and Gilmore’s Models of Gas Bubbles”, Acustica, Vol. 59, No. 3, 1986,
pp. 214-219.
17 Johnson, V. E. and Hsieh, T., “The Influence of the Trajectories of Gas Nuclei on Cavitation Inception”, Proc. Sixth
Symposium on Naval Hydrodynamics, Washington, DC, 1966, pp. 163-179.
18 Haberman, W. L. and Morton, R. K., “An Experimental Investigation of the Drag and Shape of Air Bubbles Rising in
Various Liquids”, Report 802, David Taylor Model Basin, Washington, DC, 1953.
19 Saffman, P. G., “The Lift on a Small Sphere in a Slow Shear Flow”, Journal of Fluid Mechanics, Vol. 22, 1965, pp. 385-400.
20 Li, A. and Ahmadi, G., “Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow”,
Aerosol Science and Technology, Vol. 16, 1992, pp. 209-226.
21 Chahine, G. L., Hsiao, C. T., Choi, J. K., Wu, X., “Bubble Augmented Waterjet Propulsion: Two-Phase Model Development
and Experimental Validation”, 27th Symposium on Naval Hydrodynamics, Seoul, Korea, October, 2008.
22 Duraiswami, R., Prabhukumar, S., Chahine, G. L., "Bubble Counting Using an Inverse acoustic Scattering Method",
Journal of Acoustical. Society of America, 104 (5), November 1998, pp.2699-2717.
23 Chahine, G. L., Kalumuck, K. M., Cheng, J. Y., Frederick, G. S., “Validation of Bubble Distribution Measurements of the
ABS Acoustic Bubble Spectrometer with High Speed Video Photography,” 4th International Symposium on Cavitation,
California Institute of Technology, Pasadena, California, June 2001.
24 Chahine, G. L. and Kalumuck, K.M., “Development of Near Real Time Instrument for Nuclei Measurements: The ABS
ACOUSTIC BUBBLE SPECTROMETER ®© ,” 4th Joint ASME-JSME Joint Fluids Engineering Conference, Honolulu, HI, July 2003.
25 Chahine, G. L., Hsiao, C. T., Tanguay, M., Loraine, G., “Acoustic Measurements of Bubbles in Biological Tissue,”
Cavitation: Turbo-machinery & Medical Applications, WIMRC Forum, Warwick University, U.K, July 2008.
26 Wu X. and Chahine, G. L., “Development of an Acoustic Instrument for Bubble Size Distribution Measurement”, Journal of
Hydrodynamics, Ser. B, Vol. 22, Issue 5, Supplement 1, October 2010, PP. 330 – 336.