Propwash Modeling for Contaminated Sediment Cap Design and Beyond
Vladimir Shepsis, PhD, PE, Coast & Harbor Engineering, IncTom Wang, PE, Anchor Environmental, QEA
November 06, 2009
Cap of contaminated sediment
Bottom and shoreline scour
Under pier slope protection
Eelgrass impact
Other
))((** 20 43.1578.2 0
Xz
XD
x ExpUV
2/10 )/(/6.1 pTDU p
= Jet velocity exiting propeller
Vx
(1949 )
Updated: June 8, 2007
))((** 20 43.1578.2 0
Xz
XD
x ExpUV
2/10 )/(/6.1 pTDU p
= Jet velocity exiting propeller
Vx
Velocity (feet/sec)
Steady Propwash – 2-Dimensional JETWASH Model
Distance propeller (feet)
Star "O" Class
Velocity (ft/s)
Distance from Propellers (ft)
Dep
th (ft
)Tractor Tug Garth Foss, Whatcom Waterway, Port of Bellingham
Steady Propwash – 2-Dimensional JETWASH Model
0
0.5
1
1.5
2
2.5
0 50 100 150 200
Distance aft, ft
Pro
pw
ash
vel
oci
ty,
ft/s
ecJETWASH; 500 r.p.m.JETWASH; 750 r.p.m.JETWASH; 1000 r.p.m.Measured; 500 r.p.m.Measured; 750 r.p.m.Measured; 1000 r.p.m.
Bottom slope = 0
JETWASH Model and measured velocities in
Vashon Field TestNear-Bottom Velocity
0
1
2
3
4
5
0 1 2 3 4 5
Measured Velocity (fps)
Ca
lcu
late
d V
elo
cit
y (
fps
)
Jay eqn 2-2 solutionJETWASH simulationSeries2
Line of perfect agreement
JETWASH Model and measured velocities in Kingston Field Test
Propwash Modeling Results
0 20 40 60 80 100 120
Distance (ft)
-40
-20
0
Ele
vatio
n (f
t, M
LLW
)
012345678910111213141516
Velocity (ft/sec)
0 20 40 60 80 100 120
Distance (ft)
-40
-20
0
Ele
vatio
n (f
t, M
LLW
)
Tug Boat
Bow Thruster
Bottom
Unsteady 3-Dimensional Model VH-PU, Plan view of bottom velocities
Section View of Velocities at Propeller Axis
Unsteady 3-Dimensional Model VH-PU, Cross sectional view of bottom velocities
VH-PU Model Verification with Lab DataExperimental Setup
Schokking (2002)
CHE Model Verification with Lab Data Verification Results
CHE Model Verification with Field DataField Test Setup
Test Propeller Rotation Rate (rpm)
Propeller Diameter (m)
Thrust(N)
Initial Velocity (m/s)
Depth(m)
Distance from Surface to Propeller Axis (m)
1 200 1.83 41,553 3.94 10.4 3.05
2 200 1.83 73,886 5.25 10.3 3.05
CHE Model Verification with Field Data
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
v (m/s)
Ele
vatio
n (m
)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
v (m/s)
Ele
vatio
n (m
)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
v (m/s)
Ele
vatio
n (m
)
t = 5 sec
t = 7 sec
t = 9 sec
Test 1
CHE Model Verification with Field Data
t = 1 sec
t = 3 sec
t = 5 sec
Test 2
0 0.5 1 1.5 2 2.5 3 3.5 4-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
v (m/s)
Ele
vatio
n (m
)
0 0.5 1 1.5 2 2.5 3 3.5 4-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
v (m/s)
Ele
vatio
n (m
)
0 0.5 1 1.5 2 2.5 3 3.5 4-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
v (m/s)
Ele
vatio
n (m
)
Capping Design, Lockheed Shipyard Project
Lockheed Shipyard ProjectSite Photos
Application to Environmental Impact Analysis Eelgrass Impacts
Plan View of Bottom Velocity during Ferry Landing
Application to Environmental Impact Analysis Eelgrass Impacts
Plan View of Bottom Velocity during Ferry LandingVessel is not moving
Updated: June 8, 2007
Bottom Velocity From Moving BoatStationary Vessel
Moving Vessel
Stationary Cruiser
Moving Cruiser
3-Dimensional VH-PU Coupled with FLOW 3D
Stationary Cruiser
Moving Cruiser
3-Dimensional VH-PU Coupled with FLOW 3D
Relative Bottom Velocity
Moving Vessel
0
1
2
3
4
5
6
7
8
9
10
0.00 0.50 1.00 1.50 2.00 2.50 3.00
Time (sec)
Ins
tan
tan
eo
us
Ne
arB
ott
om
Re
lati
ve
Flu
idV
elo
cit
y(f
t/s
)
T = 0.533 sec1(4 ft/s) T 2(4 ft/s) 1.16 sec
DT = 0.626 sec(4 ft/s)
V = 6.54 ft/seff
V = 9.07 ft/sx(peak)
V = 4.0 ft/sx
1.2”
1.9”
1.1”
Remedial Design Elements
76C
5B5A 2B
9
2C4
1C5C
3A3B2A
Log Pond
ASB
66-ft Motor Yacht
38-ft Sea Ray
Design Element
Source of Scour Bottom Velocities, ft/s
Sediment Size
inch
2B Propwash (Rec. cruiser) 3.2 0.3
2A Propwash (Puget Sound tug) 6.9 1.9
1C1 Propwash (Tractor tug) 9.4 4.0
1C1 Propwash (Star “O” – main) 6.6 2.6
1C1 Propwash (Star “O” – bow) 7.1 2.0
1C1 Propwash (Star “O” – stern) 5.7 1.2
6C Propwash (Puget Sound tug) and Waves 4.6 0.7
5B Propwash (Cruiser) and Waves 2.1 0.03
5C Propwash (Cruiser) 4.2 0.3
3B Propwash (Puget Sound tug), Waves, Creek Flow 2.8 0.08
4 Propwash (NOAA launch) 3.9 0.5
5A Prowpash (Cruiser) 0.8 0.001
1C1 Prowpash (Oscar Dyson – main) 2.0 0.2
1C1 Prowpash (Oscar Dyson – thruster) 10.2 4.9
Summary
• Propwash hydrodynamics and induced bottom sediment mobility physical processes are extremely complex and can not be accurately simulated, even with the most advanced computer software (models) available today.
• When designing a contaminated sediment cap or other responsible project effected by propwash, the Design Engineer should be thoughtful in his/her selection of modeling tools and methodologies. Rational decision on selection of the modeling tool would significantly reduce construction cost and provide sustainable environmental solution.
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