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.