Upload
sybil-nunez
View
47
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Ultrasonic Scattering to Measure Dispersed Oil Droplet Size and Sediment Particle Size. Paul D. Panetta 1,4 , Leslie G. Bland 1,2 , Domi Paxton 3 , Grace Cartwright 4 , and Carl Friedrichs 4 1 Applied Research Associates, Inc. 2 University of Virginia - PowerPoint PPT Presentation
Citation preview
Paul D. Panetta1,4, Leslie G. Bland1,2, Domi Paxton3, Grace Cartwright4, and Carl Friedrichs4
1Applied Research Associates, Inc.2University of Virginia
3Department of Geology, College of William & Mary4Virginia Institute of Marine Science, College of William & Mary
Oceans ’12October 18, 2012
Ultrasonic Scattering to Measure Dispersed Oil Droplet Size and Sediment Particle Size
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
2
Outline Motivation and background Lab tests Field tests at Ohmsett wave
tank with Canadian Hebron crude
Sediment measurements SINTEF Tower Tank tests Conclusions and Future Work
U.S. Air Force chemical dispersing aircraft drops an oil dispersing chemical into the Gulf of Mexico as part of the Deepwater Horizon Response effort, May 5, 2010. U.S. Air Force Photo by Tech. Sgt. Adrian Cadiz; RestoreTheGulf.govDeepwater Horizon oil spill
Subsea blow out from the Deepwater Horizon leakDeepwater Horizon fire
Deepwater Horizon fire
Subsea blow out from the Deepwater Horizon leakAerial application of dispersant
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
3
MotivationDeepwater Horizon Incident• 4.9 million barrels of oil released• 1.1 million gallons of dispersants
used subsea for the first time• No subsea methods to assess
dispersants effectiveness exist
Motivation: Develop acoustic methods to measure dispersant effectiveness subsea and transfer technology to sonar and marine acoustic instruments.
Images courtesy of Alun Lewis
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
4
Dispersant effects on oil
0
20
40
60
80
100
120
140
160
180
200
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 100 200 300 400 500
Conc
entr
ation
(PPM
)
Conc
entr
ation
(PPM
)
Average Droplet Size (microns)
Crude oilCrude oil with Corexit 9500
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
5
Stokes law
Dh/t = D2(rw - ro)g18hw
• Dh/t is the oil droplets rising velocity (m/s),
• D is the oil droplet diameter (m)
• ρw is the density of the water (kg/m3), and
• ρo is the density of the oil (kg/m3)
• g is the gravitational acceleration (m/s2),
• hw is the viscosity of the water
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
6
Lab measurements 15 mL Canadian Hebron crude 15 mL Canadian Hebron Crude DOR 1:10 Corexit 9500
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
7
Ohmsett Facility, NJ
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
8
Various views from the Tow Bridge
Towards wave maker Canadian Hebron crude slick
Dispersant application After breaking waves
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
9
Laser In-situ Scattering Transmissometer (LISST) with acoustic sensor attached
Installation from Tow Bridge
Acoustic sensor
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
10
Acoustic results from Ohmsett testing as bridge is moved
Background DOR 1:20 No breakers0.
51.
0D
epth
(met
ers)
Ping number
(a) Background - prior to addition of oil (b) After Adding Corexit 9500, DOR 1:20 – no breakers
% Screen Height
012
Ultrasonic transducer
Ping number
Dep
th (m
eter
s)0.
51.
0
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
11
Acoustic signals at Ohmsett of partial dispersion and full dispersion
Partial Dispersion Full Dispersion0.
51.
0D
epth
(met
ers)
(a) Just Breaking Waves
0.5
1.0
Dep
th (m
eter
s)
(b) Heavy Breaking Waves
% Screen Height
012
Ultrasonic transducer
Ping number Ping number
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
12
Acoustic test chamber
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
13
Acoustic signals in the lab of dispersed crude oil
Hebron Crude Oil
Hebron Crude Oiland Corexit 9500 dispersant
Time (seconds)0 20 40 60 80 100 120
0 20 40 60 80 100 120
Time (seconds)
Dep
th (
cm)
Dep
th (
cm)
0.0
9.0
12.0
4.5
0.0
9.0
12.0
4.5
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
14
Attenuation of isolated droplets
se = extinction cross section• sum of the scattering cross
section and the absorption cross section
a = droplet radius f = frequency fr = resonance frequency d = damping constant at fr c0 = speed of sound
𝑘𝑟=2𝜋 𝑎 𝑓 𝑟𝑐0
𝑎𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 ( 𝑓 ,𝑎) 𝜎𝑒=
4𝜋 𝑎2𝛿𝑘𝑟 𝑎
( 𝑓 𝑟2
𝑓 2−1)
2
+𝛿2
𝑓𝑟 = 12𝜋𝑎ඨ3𝛾𝑃𝜌
g = ratio of specific heat at constant pressure and volumeP = hydrostatic pressurer = density of water
At 5 MHz, Attenuation ~ a
For 100 micron oil droplet , fr = 55 kHz
Robert J. Urick, “Principles of underwater sound”, 3e, Mc Graw Hill 1983
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
15
Acoustic determination of oil droplet size
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300 350
Lase
r Ave
rage
Dro
plet
Siz
e (m
icro
ns)
Acoustic Average Droplet Size (microns)
Laboratory testing
Ohmsett DOR 1:20
0
20
40
60
80
100
120
140
160
180
200
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 100 200 300 400 500
Conc
entr
ation
(PPM
)
Conc
entr
ation
(PPM
)
Average Droplet Size (microns)
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
16
Motivation for high frequency acoustic sediment characterization
• In the water column there is a need to determine grain size and sediment type.
• In the seafloor the properties of the top ~5cm control erodibility and sediment transport.
• Typically measurements are performed on cores in the lab.• There is a need to determine these properties in the water
without disturbing the sediment by coring and transporting to the lab.• Ideally we want to measure sediment properties in-situ over time
• Knowledge of the sediment properties will also help wave propagation models that include seafloor reflections
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
17
Sand and mud
Sand
Mud
Acoustic Transducer
Acoustic Transducer
Sand ~63 mm
Acoustic Imaging of Sediment Dynamics (5 MHz)
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
18
Seabed Sediment Characterization
Acoustic scan of sediment core Placement of
X-ray subcore Subsampling for grain size and %moisture
measurements (every 1 cm)
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
19
Sediment characterization of York River Ferry Point (5035)X-ray 2.25 MHz Acoustic Backscattering
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
20
Sonar, marine acoustic, and portable ultrasonic tools
Marine Sonic 900 kHz Side Scan Sonar
Imagenex 881 rotary sonar Edgetech SB-216S Chirp
Acoustic Doppler Current Profiler
Acoustic Doppler Velocimeter and Laser In-Situ Scattering Transmissometer (LISST)
Portable acoustics 50 kHz to 25 MHz
Cop
yrig
ht 2
009.
All
right
s re
serv
ed. A
pplie
d R
esea
rch
Ass
ocia
tes,
Inc
.
21
Conclusions Acoustic images can be used to qualitatively characterize oil slick
dispersion and plume size. We developed acoustic measurements to size oil droplets for surface
dispersant applications at Ohmsett and in the lab. Additional measurements of subsurface releases of oil and
dispersant are needed. Initial measurements on suspended and consolidated sediment
show promise for in-situ characterization.
Acknowledgements This work is supported by the Department of Interior, Bureau of Safety and
Environmental Enforcement (BSEE) under project number E12PC00011. Student funding was provided by National Science Foundation grant OCE-1061781.
Special Thanks to Randy Belore from SL Ross and Tim Nedwed from ExxonMobil during the work at Ohmsett and Per Johan Brandvik during the work at SINTEF and Kyle Winfield for his help with laboratory measurements.