Passing Ship Seelig

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NAVAL FACILITIES ENGINEERING SERVICE CENTERPort Hueneme, California 93043-4370

TechnicalReportTR-6027-OCN

PASSING SHIP EFFECTS ON MOORED SHIPS

by

William N. Seelig, P.E.

NFESC East Coast Detachment

Washington Navy Yard

1435 10TH

STREET SE Suite 3000

Washington Navy Yard DC 20374-5063

20 November 2001

Prepared for:

Commander, Naval Facilities Engineering Command

Engineering Innovation & Criteria Office

NAV

AL

FAC ILITIE

S

E

N

G

I

NEE

RIN

GS E R V

I CE

C

EN

T

E

R


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TR-6027-OCN PASSING SHIP EFFECTS ON MOORED SHIPS i

EXECUTIVE SUMMARY

If a moving ship passes a moored ship too close or too fast, then themoored ship can be subjected to high forces and moments ( Wang, 1975,Flory, 2001 and many other references). The resulting moored shipresponse to the passing ship can cause serious accidents.

Therefore, the Commander, Naval Facilities Engineering Command,Engineering Innovation & Criteria Office tasked the Naval FacilitiesEngineering Command (NFESC) to develop methods for analyzingpassing ship effects on moored ships. These methods can be used toimprove mooring safety and aid in developing rules-of-the-road for U.S.ports.

The approach taken in this report is to use the deepwater numerical results

of Wang (1975) to evaluate passing ship forces and moments on a mooredship. Shallow water correction factors are then applied. The shallow watercorrection factors are developed by empirically re-analyzing results from anumber of scale physical model studies. The resulting information can beused in a number of engineering tools including:

PASS-MOOR.xls An engineering spread sheet was developed as part ofthis project. This spread sheet uses the mooring efficiency approach(Seelig, NFESC Report TR-6005-OCN, Rev B May 1998) to staticallyestimate the number of mooring lines needed to safely secure a ship in

passing ship events. This spread sheet also estimates peak forces andmoments on a moored ship due to a passing ship that can be used in staticanalyses. Finally, this spread sheet produces applied force and momenttime histories that can be used in full dynamic analyses.

STATIC ANALYSES. The peak forces and moments on the moored shipcomputed by PASS-MOOR can be input into various static mooringsoftware packages (FIXMOOR, OPTIMOOR, AQWA LIBRIUM, etc.).These programs can be used to estimate static tensions in variousmooring lines and static offset of the ship from a given position for passing

ship events.

DYNAMIC ANALYSES. The force and moment time histories on themoored ship computed by PASS-MOOR can be input into various dynamicmooring software packages (AQWA DRIFT, etc.) to evaluate moored shipresponse to passing ships.


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TR-6027-OCN PASSING SHIP EFFECTS ON MOORED SHIPS ii

TABLE OF CONTENTS

Section Pg.

EXECUTIVE SUMMARY ......................................................................................i

TABLE OF CONTENTS........................................................................................ ii

LIST OF APPENDICES ........................................................................................ ii

1.0 INTRODUCTION/PURPOSE .....................................................................11.1 Far-Field Ship-Generated Waves........................................................11.2 Near-Field Effects................................................................................11.3 Moored Ship Coordinate System.........................................................41.4 Definition of the Problem .....................................................................5

1.5 Typical Channel Water Depths in the U.S. ........................................11

2.0 FORCES AND MOMENTS APPLIED TO THE MOORED SHIPBY THE PASSING SHIP ........................................................................142.1 Forces and Moments in Deepwater...................................................142.2 Shallow Water Correction Factors.....................................................24

3.0 COMPUTATIONS ....................................................................................313.1 The PASS-MOOR Spread Sheet and an Example ..........................313.2 The Influence of Parameters .........................................................35

4.0 SUMMARY AND CONCLUSIONS ..........................................................38

5.0 POINTS OF CONTACT............................................................................40

6.0 REFERENCES AND BIBLIOGRAPHY.....................................................41

LIST OF APPENDICES

A. NOTATION USEDB. PREVIOUS WORK


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TR-6027-OCN PASSING SHIP EFFECTS ON MOORED SHIPS 1

PASSING SHIP EFFECTS ON MOORED SHIPS

By

Will iam N. Seelig, P.E.

1.0 INTRODUCTION/PURPOSE

As vessels move through the water they generate waves and otherphenomena that may influence moored vessels, contribute to coastalerosion, etc.. Therefore, Commander, Naval Facilities EngineeringCommand (NAVFACENGCOM) Engineering Innovation and Criteria Officetasked the Naval Facilities Engineering Service Center (NFESC) todevelop criteria for ship-generated waves.

Two key phenomena of practical interest to engineers are investigated inrecent efforts: far-field wave effects and near-field effects.

1.1 FAR-FIELD SHIP-GENERATED WAVES

As a vessel moves through the water it produces water waves. Detailedinformation on how to predict characteristics of these water waves at somedistance from the vessel is presented in Seelig, W. and Kriebel, D., ShipGenerated Waves, NFESC TR-6022-OCN, (draft in prep).

1.2 NEAR-FIELD EFFECTS

As a vessel moves through the water there is a pressure field developed inthe vicinity of the moving ship. If the moving ship passes close to amoored ship, then high temporary forcing on the moored ship may occur.For example, the moored ship can be violently pulled off the pier or wharfdue to a combination of wave and Bernoulli effects. This problem occurseven for low passing-ship Froude numbers. In these cases there may beno obvious surface wave produced by the moving ship. In other cases thesurface wave can be relatively large.

A number of very serious mooring accidents have occurred due to passingships. Examples are provided in Table 1. Figure 1 shows the tankerJUPITER, which was totally destroyed by fire. A passing ship caused themooring to fail, fuel hoses broke and unleaded gasoline caught on firecausing death, injury, total loss of the ship and damage to the pier.


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Table 1. SAMPLE ACCIDENTS/EVENTS CAUSED BY PASSING SHIPS

CASE NOTES

Two battleships (BB-62class) moored at thePhiladelphia NavalShipyard drydock wharf

1990s

These battleships were moored side-by-sidewith over twenty legs of 2.5-inch chain andsinkers. The two battleships would surge 12to 15 feet as larger commercial ships passedthe site causing accelerated wear onmooring hardware.

USNS REGULUS andUSNS POLLUS;

13 June 1998

Two MSC ships were moored side-by-side atBerth #5, Violet Dock Port at Violet, LA withUSNS REGULUS the inboard ship next tothe pier. A woman and child visiting this U.S.Navy ship were both seriously hurt whenthey were run over by a rolling 3,000 poundgangway. The gangways sudden motionoccurred when both of the moored shipssurged as large cargo ships passed nearbyin the Mississippi River.

Tanker U.S. JUPITER10,900 DWT Length 382feet;

16 Sep 1990

U.S JUPITER was moored and unloadingunleaded gasoline when BUFFALO (17,500DWT and 635 feet long) traveling at about4.2 knots passed with a gap between thevessels of 60 to 65 feet. JUPITER had

mooring lines break, the discharge hosebroke and the resulting fire caused 1 death,18 injuries, JUPITER was a total loss and thepier was damaged.

QUEEN ELIZABETH IILength 963 feet, Width 105feet and Draft 32.6 feet;and AFDM-7

7 Jan 1976 at 2 pm

QUEEN ELIZABETH II passedapproximately 1,600 feet from the Norfolk,VA waterfront at an estimated speed of 15 to20 knots. AFDM-7 parted three 3.5-inchmooring chains; the ship in dock shifted onits blocks. All up and down the waterfrontnumerous Navy ships broke mooring lines,shore cables broke, utilities failed, browsfailed and pier pilings were broken.


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Figure 1. TANKER JUPITER TOTALLY DESTROYED IN A FIRECAUSED BY A PASSING SHIP

Near-field effects are highly complex, so the work of several investigators

is compiled and re-analyzed in this report. The methods developed in thisreport are then used to systematically show the importance of typicalconditions on moored ships in an easy-to-use form.

Appendix A summarizes notation used in this report. Appendix Bsummarizes previous work on this topic and provides laboratorymeasurements made by various researchers.

An spreadsheet PASS-MOOR.xls is provided to perform preliminaryanalyses. This spread sheet can also be used to develop input for static

analyses (using tools such as FIXMOOR, OPTIMOOR, AQWA LIBRIUM,etc.). The spread sheet also provides force and moment time histories forinput into full dynamic analyses (AQWA DRIFT, etc.).


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1.3 MOORED SHIP COORDINATE SYSTEM

The moored ship, designated as Ship 1, is the primary ship of interest inthis study. The coordinate system assigned to the initial position of themoored ship is a local right-handed coordinate system (see Figure 1.3-1)with:

X= distance forward from midships

Y= distance towards port from ship centerline

Z= distance upwards from the ship baseline (i.e. keel) and

L1= length of the moored ship

Angles are measured positive in a counter-clockwise direction.

See Appendix A for notation used in this report.


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Figure 1.3-1. COORDINATE SYSTEM FOR FORCES/MOMENTS ON THE MOORED SHIP DUE TO THE PASSING SHIP AT AN INSTANT IN TIME

1.4 DEFINITION OF THE PROBLEM

In this report we take for simplicity the case of a ship moored on its

starboard in still water, as shown in Figure 1.4-1 (moored ship is on theright). This moored ship can be described as moored in the upstreamdirection.

A moving ship with a speed, V, relative to the world fixed coordinatesystem is traveling upstream. If the moving ship passes too close to themoored ship or at too high of a speed, then moored ship transient motionsand resulting high dynamic mooring forces may occur.

Ship 1

Moored

Y+

M+

L1

X+

Wharf

Pier orF

F


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At any instant in time the longitudinal distance between ship midships is x,

the lateral distance between ship centerlines is and the lateral gapbetween the ships is G. In the case shown in Figure 1.4-1, xis negativebecause the passing ship is behind the moored ship. As the midships of

the passing ship moves forward of the moored ship, then xbecomespositive.

The relative speed, VR, between the ship and current speed, VC, (if any)is:

VR= V VC Eq (1)

For the case shown in Figure 1.4-2 the ship and current speeds are thesame magnitude and direction (i.e. current is flood and the passing ship ismoving upstream). In this case the relative ship speed is zero, so thepassing ship effects will be minimal. In the case of the passing shiptraveling at the same speed and direction as the current, the passing shiphas little effect on the moored ship because the passing ship effectivelyacts like a slug of water moving by the moored ship.

If on the other hand the passing ship is moving upstream and the current isebbing down stream in the opposite direction of the ship motion, as shown

in Figure 1.4-3, then the relative ship speed, VR, effects may be verysignificant on the moored ship. In this case the relative ship speed throughthe water is higher than the world ship speed, V.

The special case of the passing ship moving upstream at a slower speedthan a flooding current (i.e. the ship has reverse thrust, but still movingupstream) is not covered in this report, since this case is not likely to be aproblem.

For other cases, such as the moored ship with its port side to the pier, the

passing ship moving in the downstream direction, etc., the engineer canuse methods in this report and change signs and coordinate systems tomeet his particular situation.

Note that the ship speed, V, relative to the world fixed coordinate system isthe velocity that determines how quickly the passing ship encounters themoored ship.


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In this report the surge, sway and yaw degrees-of-freedom are considered.Heave, roll and pitch are not addressed, because they are believed to beless important.

In this study it is assumed that a vessel of interest is moving at a constant

velocity in constant water depth. The passing ship is assumed to beparallel to the moored ship.


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Figure 1.4-1 SAMPLE CONDITION FOR THE CASE OF NO CURRENT( x is negative at this time because the moving ship is

behind the moored ship)

x

G

V

Ship 1

MooredMoving

Ship 2


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Figure 1.4-2 SAMPLE CONDITION FOR THE CASE OF A SHIP TRAVELINGAT THE SAME VELOCITY AS THE CURRENT(In this case there is little passing ship effect)

Moving

Ship 2

Moored

Ship 1

V

V = currentc

V = V - V = 0R c


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Figure 1.4-3 SAMPLE CONDITION FOR THE CASE OF A SHIP TRAVELINGIN AN OPPOSING CURRENT

(In this case there may be significant passing ship effects)

Moored

Ship 1

V = current

Moving

Ship 2

c

V = V - V

V

R c(V is negative in this case)c


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1.5 TYPICAL CHANNEL WATER DEPTHS IN THE U.S.

The ratio of ship draft to water depth is an important parameter in passingship processes. A list of typical water depths of U.S. navigation channelsis shown in Table 1.5-1. The median navigation channel depth is 12 m (40feet) for this list. However, there is considerable variation in depth, asshown in Table 1.5-1 and Figure 1.5-1.


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Table 1.5-1. WATER DEPTHS OF REPRESENTATIVE MAJOR CHANNELS

Dmin (m) Dmax (m) Dmin (ft) Dmax (f t) DATUM

Port Location State

Port of Anchorage AK 9.14 21.34 30 70 MLLWCanaveral Port Authority FL 11.89 39 MLW

Port of Coos Bay OR 11.28 37 MLLW

Port of Everett WA 12.19 40 *

Port Everglades FL 14.33 47 MLW

Port of Galveston TX 12.19 40

Port Authority of Guam 10.36 34.14 34 112 *

Port of Gulfport MS 10.97 36 *

Port of Houston TX 10.97 13.72 36 45 *

Port of Hueneme CA 10.67 35 MLLW

Jacksonville Port Authority FL 11.58 38 *

Port of Kalama WA 12.19 40 *

Port of Long Beach CA 23.16 76 *

Port of Los Angeles CA 13.72 15.24 45 50 *

Port Manatee/Tampa Bay FL 12.19 40 MLWMaryland Port Administration MD 15.24 50 *

Massachusetts (Boston) Port Authority MA 12.19 40 MLW

Port of Miami FL 12.80 42 *

Port of New Orleans LA 10.97 13.72 36 45 *

Port Authority of NY and NJ (New York) NY 10.67 13.72 35 45 *

North Carolina State Ports Authority (Wilmington) NC 12.19 13.72 40 45 *

Port of Oakland CA 12.80 42 *

Port of Olympia WA 9.14 30 MLLW

Port of Orange TX 9.14 30 *

Port of Palm Beach District FL 10.06 33 *

Panama City Port Authority FL 9.75 32 *

Port of Pascagoula MS 11.58 38 *

Port of Pensacola FL 10.06 33 MLW

Port of Philadelphia/Camden PA 12.19 40 *Port of Portland OR 12.19 40 *

Port of Richmond CA 11.58 38 *

Port of Richmond VA 7.62 25 *

Port of Sacramento CA 9.30 30.5 *

San Diego Unified Port District CA 12.50 41 MLLW

Port of San Francisco CA 16.76 55 *

Port of Seattle WA 16.76 55 *

South Carolina State Ports Authority (Charleston) SC 12.19 13.72 40 45 MLW

Port of Stockton CA 10.67 35 MLLW

Port of Tacoma WA 13.72 16.76 45 55 MLLW

Tampa Port Authority FL 13.11 43 *

Port of Vancouver WA 12.19 40 MLW

Virginia Port Authority (Norfolk) VA 15.24 50 *

Port of Wilmington DE 11.58 38 MLW* DATUM NOT GIVEN

Reference: American Association of PortAuthorities, 1999 AAPA Directory, "Seaports of theAmericas", Compass North America, Inc., 1999


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Figure 1.5-2. CUMULATIVE DISTRIBUTION OF MINIMUMCHANNEL DEPTHS

(Major Channels in the U.S.)

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90 100

CUMULATIVE PROBABILITY (%)

DEPTH (ft)

25

30

35

40

45

50

55

60


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2.0 FORCES AND MOMENTS APPLIED TO THE MOORED SHIPBY THE PASSING SHIP

Deepwater: For the deepwater case (i.e. T/dis small for both the passingand the moored ship) forces and moments applied to the moored ship bythe passing ship are computed using the method of Wang (1975).

Shallow Water: Most cases of interest to designers are for relativelyshallow water (i.e. T/dlarge). Wang (1975) provides a method fordetermining shallow water correction factors. However, the Wang methoddoes not cover the zone of interest to most design situations. Therefore,physical scale model laboratory test results from previously conductedstudies are re-analyzed to develop shallow water correction factors. These

correction factors are applied to the predicted deepwater forces andmoments to determine values used for realistic shallow water cases.

2.1 FORCES AND MOMENTS IN DEEPWATER

Wang (1975) develops a numerical method for determining forces andmoments applied to the moored ship by a passing ship in deepwater (i.e.T/d= 0). Figure 2.1-1 shows the results of Wangs work in dimensionlessform.

Physical model tests show a pattern very similar to that of Figure 2.1-1.Also, physical model and other numerical model simulation methods giveresults similar to Wang (1975) for cases of small T/d, so Wang (1975) isused for deepwater.

In this report Ship 1 is taken as the moored ship and Ship 2 is taken as thepassing ship (see Appendix A for notation used).


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Figure 2.1-1 DIMENSIONLESS PASSING SHIP FORCING ON MOORED SHIPS FOR DEEP WATER

(after Wang, 1975)

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

x / L

DIMENSIONLE

SSFORCE/MOMENT

.

X

Y

M

after Wang (1975)

Fig. 2

X+ = ship f orward

Y+ = ship to port

M+ = ship counterclockw ise

X- = ship backward

Y- = ship to starboard

M- = ship clockwis e


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Figure 2.1-2 shows the effect of a passing ship (Ship 2) moving upstreamon a moored ship (Ship 1), where Lis the average of the two ship lengths

L1and L2. The forces and moments on the moored ship at various stagesof ship passage are discussed below.

a) At a distance of 2 ship lengths (i.e. x/ L< -2 ) there is littlepassing ship effect (Figure 2.1-2).

b) At a distance of approximately negative one-third a ship length(i.e. x/ L= -0.35 ) there is maximum negative longitudinal forceand negative moment on the moored ship (Figure 2.1-3).

c) There is maximum positive Yforce on the ship when the shipsare adjacent (i.e. x/ L= 0.0 ) (Figure 2.1-4).

d) At a distance of approximately positive one-third a ship length(i.e. x/ L= +0.35 ) there is maximum positive longitudinal forceand positive moment on the moored ship (Figure 2.1-5).

e) The passing ship effect on the moored ship is once againnegligible by the time the moving ship is two ship lengths past themoored ship (i.e. x/ L> 2 ).

Note that distance, x, between the passing and moored ships can also beexpressed in terms of time, t, since the passing ship has a velocity, V,relative to the world fixed coordinate system.


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Figure 2.1-2. APPROACHING SHIP(Little Passing Ship Effect at this Point)

Ship 2

Moving

V

L2

xMoored

Ship 1

Wharf

L1

Pier or

L< - 2.0


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Figure 2.1-3. APPROACHING SHIP AT x/L = -0.35(Maximum Negative X Force at this Position)

Ship 2Moving

= -0.35L

V

x

Moored

Ship 1

Pier orWharf

x

X-F

FY+

M-


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Figure 2.1-4. APPROACHING SHIP AT x/L = 0.0(Maximum Posit ive Y Force at this Posit ion)

= 0.0x

L

Ship 2

Moving

Moored

FY+

V

Pier orWharf

Ship 1


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Figure 2.1-5. APPROACHING SHIP AT x/L = 0.35 (Maximum Positive X Force and Moment at this Point)

= 0.35L

x

Ship 2

Moving

X+

Moored

F

V

M+

WharfPier or

Ship 1

x

FY-


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Wangs numerical work shows that in deepwater with no current the

magnitudes of the peak forces and moment on the moored ship arefunctions of the ship sizes, relative distance between the ship centerlinesand speed of the passing ship.

Figures 2.1-6, -7 and 8 show predicted peak non-dimension forces andmoments in deepwater. Note that these values have been made non-dimensional by Wang (1975) using the parameter, Q, where:

Q= V2(L1)2(S1/L1

2)(S2/L22) Eq (2)

Figures 2.1-6, -7, 8 and Eq (2) are used to find peak forces and momentson moored ships due to passing ships in deepwater for the case of nocurrent. The computed peak values are then applied to the curves shownin Figure 2.1-1 to calculate time histories of forces and moments acting ona moored ship due to a passing ship.


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Figure 2.1-6. NON-DIMENSIONAL PEAK FORCE IN THE SURGEDIRECTION ON THE MOORED SHIP (after Wang, 1975)

FOR DEEPWATER

0

1

2

3

4

5

6

7

8

9

10

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

/L1

Fx

/Q

L2/L1

After WANG (1975) Fig. 3 Left

pass-wang.xls

0.5

0.7

0.8

0.9

0.6

1.0

1.2

1.6

2.0


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Figure 2.1-7. NON-DIMENSIONAL PEAK FORCE IN THE SWAYDIRECTION ON THE MOORED SHIP (after Wang, 1975)

FOR DEEPWATER

0

5

10

15

20

25

30

35

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

/L1

Fy

/Q

After WANG (1975) Fig. 3 Middle

pass-wang.xls

L2/L1

2.0

1.6

1.2

1.0

0.9

0.8

0.7

0.6

0.5


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Figure 2.2-1. SAMPLE OF A SHIP IN SHALLOW WATER

The approach taken in this report is:

Use Wangs (1975) method for deepwater. A shallow water correctionfactor is then defined as the ratio of a force or moment measured in thelaboratory, (Fx)lab, in finite water depth to the value predicted by Wang

(1975) in deepwater, (Fx)0. For example the shallow water correctionfactor for the peak force in the X-direction is defined as:

CFx= (Fx)lab/ (Fx)0 Eq (3)

The shallow water correction factor is defined in a similar manner for theforce in the Y-direction and moment, M, in the yaw direction.

Appendix B, Table B-2, includes the correction factors determined fromeach laboratory experiment. Note that some researchers performed alarge number of experiments. However, all efforts to find a complete dataset have failed suggesting that the detailed results are no longer available.Only those tests with complete information known are used in this report.

T/B = 0.245

End View

d

LHA-1


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Fortunately there are some with numerous parameters fixed. Then a keyparameter was systematically varied. This allows detailed study of theeffects of a single parameter. For example Remery (1974), Muga andFang (1975) and Cohen (1983) performed certain tests over a common setof parameters where (T/d ) was the key parameter varied.

Figure 2.2-2, for example, shows the shallow water correction factor for theforce in the sway direction. Laboratory data is shown as points. A curvehas been fit through the data showing that the ratio of ship draft to waterdepth (T/d ) has a strong influence on passing ship peak sway force. Notethat the curve fit to the data was selected to have a value of 1.0 at (T/d ) =0.0, so the peak sway force approaches the deep water value as (T/d )becomes small.

Figure 2.2-2. SAMPLE SHALLOW WATER CORRECTION FACTORFOR THE PEAK SWAY FORCE

0

5

10

15

20

25

30

35

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

T/d

CF

Y

EXPERIMENTAL RESULTS

Remery (1974), Muga and Fang (1975) &

Cohen (1983)

with:

G/B = 1.5

T/B = 0.4

CFY= 1 + 30 * (T/d)4

PASS.XLS


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Unfortunately, several of the researchers did not report the peak forcemeasured in the surge direction, so the range of conditions tested is not aswide. Inspection of the data suggests that the finite water depth surgeforce correction is not as strongly dependant on the ratio of ship draft towater depth, (T/d ), as shown in Figure 2.2-3.

Figure 2.2-3. SAMPLE SHALLOW WATER CORRECTION FACTORFOR THE PEAK SURGE FORCE

0

2

4

6

8

10

12

14

16

18

20

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

T/d

CF

X

REMERY

MUGA

EXPERIMENTAL RESULTS

Remery (1974), Muga and Fang (1975)

PASS.XLS


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Inspection of available data suggests that the correction factor shown inFigure 2.2-4 is reasonable for the maximum surge force. This figureshows that as the gap between the passing ship and moored shipbecomes large and as (T/d ) becomes small, the surge force approachesthe value in deepwater.

Figure 2.2-4. SHALLOW WATER CORRECTION FACTORFOR THE PEAK SURGE FORCE

0

2

4

6

8

10

12

14

16

18

0 1 2 3 4 5 6 7 8 9 10 11 12

G/B

CF

X

T/d =

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

CFX=1 + 16 * (T/d) * EXP(-0.08 * ((G/B) - 3.5)2)

PASS.XLS


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The shallow water correction factors found for peak sway force andmoment are similar, so the recommended values are shown in Figure 2.2-5. This figure illustrates the case for T/B= 0.4. The sway and momentcorrections are very sensitive in shallow water, as was shown in Figure2.2-2, so two versions of Figure 2.2-5 are provided to cover the range of

interest.

Figure 2.2-5. SHALLOW WATER CORRECTION FACTORFOR THE MAXIMUM SWAY FORCE AND MAXIMUM YAW MOMENT

FOR T/B = 0.4

0

5

10

15

20

25

30

35

40

45

0 1 2 3 4 5 6 7 8 9 10 11 12

G/B

CF

Yan

dCF

M

CFY= CFM= 1 + 25 * (T/B)-0.35

* (T/d)4* EXP(-0.08 * ((G/B) - 3.3)

2)

T/d =

1.0

0.9

0.8

0.7

0.6

0.5

0.0

T/B = 0.4


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Figure 2.2-5. cont. SHALLOW WATER CORRECTION FACTOR FOR THE MAXIMUM SWAY FORCE AND MAXIMUM YAW MOMENT FOR T/B = 0.4

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

0 1 2 3 4 5 6 7 8 9 10 11 12

G/B

CF

Yan

dCF

M

CFY= CFM= 1 + 25 * (T/B)

-0.35

* (T/d)

4

* EXP(-0.08 * ((G/B) - 3.3)

2

)

T/d =

0.6

0.5

0.4

0.3

0.2

0.0

T/B = 0.4


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3.0 COMPUTATIONS

3.1 THE PASS-MOOR SPREADSHEET AND AN EXAMPLE

A spread sheet is provided that performs the computations described in

this report. The spread sheet:

(1) Has an input section.(2) Calculates peak forces and moments for deepwater using Wang

(1975).(3) Determines shallow water correction factors using methods

presented in this report.(4) Calculates peak forces and moments for finite water depth.(5) Uses the mooring efficiency approach (Seelig, 1998) to estimate

the number of mooring lines required.

(6) Outputs time histories of applied forces and moments on themoored ship.

The peak forces and moments in Item (4) can be used with varioussoftware packages (FIXMOOR, OPTIMOOR, AQWA LIBRIUM, etc.) toperform static mooring analyses. These static programs can be used toestimate line tensions and moored ship offsets from initial position.

The force and moment time histories applied to the moored ship, Item (6),can be used as input to dynamic simulation software packages (AQWA

DRIFT, etc.) to calculate dynamic response of a moored ship to a passingship.

EXAMPLE

The use of this spread sheet is illustrated with the example shown inFigure 3.1-1.

INPUT

Figure 3.1-2 shows the input screen. Cells in yellow are for input. Cells ingreen are output. Totally black cells are blank.

Note that the methods described in this report were developed for aspecific range of conditions. If a user inputs a value that results in a caseoutside the valid range, then the message Error !!! is displayed in theError Flag column E. For example, if the length of Ship 1 is input as a


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Figure 3.1-1. EXAMPLE

negative number then the message Error !!! is displayed, as shown inFigure 3.1-3.

The user should not proceed if any of the Error !!! flags are turned on,because output results will be incorrect.

Ship 2

Passing

V = 7 knots Moored

Ship 1

Pier orWharf

223'

L=843'B=121'T=52'd=59'

L=991'B=153'T=52'.5d=59'

NO CURRENT


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Figure 3.1-2. PASS-MOOR INPUT FOR THE EXAMPLE OF A MOOREDTANKER AND PASS TANKER MOVING AT 7 KNOTS

(Note that Input Cells are Yellow)

Figure 3.1-3. ILLUSTRATION OF AN INPUT ERROR,A SHIP LENGTH OF NEGATIVE 100 FEET IS INPUT FOR SHIP 1


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OUTPUT

Figure 3.1-4 shows a sample output screen. Output is shown in green.For the sample problem the predicted peak loads are:

Longitudinal Peak Force = 232,800 pounds force

Lateral Peak Force = 1,295,700 pounds force

Peak Yaw Moment = 200,731,000 foot*pounds

Figure 3.1-4. OUTPUT FOR THE EXAMPLE

The quick mooring efficiency analysis for this example, Figure 3.1-5,suggests that on the order of 16 parts of breasting line and 6 parts ofspring line would be required for this case to maintain a factor of safety of2 on mooring lines.


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Figure 3.1-5. MOORING EFFICIENCY OUTPUT

The PASS-MOOR spread sheet also provides plots of force and momenttime histories, as illustrated in Figure 3.1-6. In this spread sheet time 0 isthe point where the passing ship just starts to have an influence on the

moored ship (i.e. at x/L = -2).

For this example the moored ship is pushed onto the pier with maximumforces (negative) at times of 100 and 210 seconds. The highest forcepulling the ship off the pier occurs at 155 seconds. The maximum forcepulling the moored ship in the aft direction occurs at 130 seconds and themaximum force pushing the moored ship in the forward direction occurs at180 seconds. The highest moments also occur at times of 130 and 180seconds.

3.2 THE INFLUENCE OF PARAMETERS

Parameters can by systematically varied in PASS-MOOR to show theirvarious effects.

SHIP VELOCITY

Figure 3.2-1 shows that as the passing ship velocity increases, the peaksway force dramatically increases for the example.

WATER DEPTH

Figure 3.2-2 shows that a small decrease in the water depth causes alarge increase in peak sway force for the example.


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Figure 3.1-6. APPLIED FORCES/MOMENTS ON THE MOORED SHIP FORTHE EXAMPLE

-1000

-500

0

500

1000

1500

0 50 100 150 200 250 300 350

TIME (sec)

Fx (kips)Fy (kips)

APPLIEDFORCESTOTHEMOOR

EDSHIP(kips

)

-250000

-200000

-150000

-100000

-50000

0

50000

100000

150000

200000

250000

0 50 100 150 200 250 300 350

TIME (sec)

APPLIEDMOMENTTOTHEMOOREDSHIP(fo

ot*kips

)

M (ft*kips)


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Figure 3.2-1. INFLUENCE OF PASSING SHIP VELOCITYON PEAK SWAY FORCE FOR THE EXAMPLE

Figure 3.2-2. INFLUENCE OF WATER DEPTH ONPEAK SWAY FORCE FOR THE EXAMPLE

0

200

400

600

800

1000

1200

1400

0 1 2 3 4 5 6 7

PASSING SHIP VELOCITY (knots )

PEAKSWAYFORCE(thou

san

dspoun

ds

)

PASS.XLS

0

200

400

600

800

1000

1200

1400

1600

1800

2000

50 55 60 65 70 75

WATER DEPTH (ft)

PEAKSWAYFORCE(thousan

dspoun

ds

)

PASS.XLS


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CURRENT SPEED

Figure 3.2-3 shows that an ebb current opposing a passing ship causes a

dramatic increase in peak sway force on the moored ship. A flood current,on the other hand, causes the peak sway force on the moored ship todecrease.

DISTANCE BETWEEN SHIPS

Figure 3.2-4 shows that the peak sway force increases as the passing shipgets closer to the moored ship.

4.0 SUMMARY AND CONCLUSIONS

A passing ship may have a major influence on a nearby moored ship dueto a combination of wave, pressure, Bernoulli and other effects. Themoored ship may be pushed in the fore and aft directions, pushed into thepier, pulled off the pier and forced to yaw in response to the passing ship.

In this report forces and moments on the moored ship due to the passingship are estimated by:

(a) Using the method of Wang (1975) to estimate values for the deepwatercase.

(b) Correcting for realistic finite depth effects using correction factorsdeveloped from re-analyses of scale model laboratory data.

(c) Using the spreadsheet PASS-MOOR.xls to estimate the peak forcesand moments. These forces vary as a function of time, so the spreadsheet outputs time series.

The mooring efficiency approach (Seelig, 1998) is incorporated into thespread sheet to give a preliminary estimate of the number of mooring linesthat would be required to secure the moored ship in a passing ship event.


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Figure 3.2-3. INFLUENCE OF CURRENT VELOCITY ONPEAK SWAY FORCE FOR THE EXAMPLE

Figure 3.2-4. INFLUENCE OF SHIP SPACING ONPEAK SWAY FORCE FOR THE EXAMPLE

0

500

1000

1500

2000

2500

3000

-4 -3 -2 -1 0 1 2 3 4CURRENT VELOCITY (knots )

PEAKSWAYFORCE(thousands

poun

ds

)

PASS.XLS

EBB FLOW FLOOD FLOW

0

500

1000

1500

2000

2500

0 50 100 150 200 250 300 350 400 450 500

DISTANCE BETWEEN SHIP CENTERLINES (ft)

PEAKSWAYFORCE(thousan

dspounds

)

PASS.XLS


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Some of the methods that can be used to estimate passing ship forces andmoments on moored ships are:

The PASS-MOOR spread sheet discussed in this report.

The reader can perform his own inspection of previous model testresults summarized in Appendix B, Figures 2.2-2 and -3, etc.

Flory (2001) provides an empirical method.

Wang (1975) provides a method based on computations.

Pinkster (2000) provides a computational numerical model.

Specific laboratory scale models can be conducted.

Full-scale tests can be conducted.

Forces and moments on moored ships can then be used as input tovarious mooring software packages, such as FIXMOOR, OPTIMOOR,

AQWA LIBRIUM, AQWA DRIFT, etc., to determine ship offsets from itsinitial position, mooring line tensions, moored ship motions, velocities,accelerations, etc.

5.0 POINTS OF CONTACT

Points of contact are provided in Table 5.

TABLE 5. POINTS OF CONTACT

NAME PHONE EMAIL

Frank Cole (NAVFAC) 757-322-4203 [email protected]

Bill Seelig (NFESC) 202-433-2396

fax -5089

[email protected]


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6.0 REFERENCES AND BIBLIOGRAPHY

Cohen, S. and Beck, R., "Experimental and Theoretical Hydrodynamic Forces ona Mathematical Model in Confined Waters", Journal of Ship Research, Vol. 27,

No. 2, June 1983.

De-bo, Huang and Yunbo, Li, Ship Wave Resistance Based on NoblessesSlender Ship Theory and Wave-Steepness Restriction, Ship TechnologyResearch, Vol. 44, pp. 198-202, 1977.

Flory, J., A Method for Estimating Passing Ship Forces, ASCE, ProceedingsPorts 2001, 2001.

Grollius, W., Muller, E., Lochte-Holtgreven, H., and Guesnet, Th., Results ofModel Tests with Fast Unconventional Ships in Shallow Water, Proceedings, 3rd

Int. Conf. On Fast Sea Transport, FAST 95, Vol. 2, SchiffbautechnischeGesellschaft (STG), Berlin, 1995.

Husig, A., Linke, T. and Zimmermann, C., Effects from Supercritical ShipOperation on Inland Canals, ASCE, Journal of Waterway, Port, Coastal, andOcean Engineering, Vol. 126, No. 3, May/June 2000, pp. 130-135.

King, G.W., "Unsteady Hydrodynamic Interactions Between Ships", Journal ofShip Research, Vol. 21, No. 3, Sep 1977.

Kizakkevariath, S., Hydrodynamic Analysis and Computer Simulation Applied to

Ship Interaction During Maneuvering in Shallow Water, Ph.D. Dissertation,VPISU, May, 1989.

Kurata, K. and Oda, K., Ship Waves in Shallow Water and Their Effects onMoored Small Vessel, Proceedings Coastal Engineering Conference, pp. 3258-3273, 1984.

Lean, G.H., and Price, W.A., "The Effect of Passing Vessels on a Moored Ship",The Dock and Harbour Authority, Nov. 1977.

Muga, B. and Fang S.,Passing Ship Effects from Theory and Experiment,

Proceedings Offshore Technology Conference, Paper No. 2368, 1975.

Muga, B., Overton, M. and Sidiropoulos, Effects Induced by Passing Ships onWaterfront Facilities, Dept. of CE, Duke University, Report for NAVFAC,Contract No. N00025-76-C-0026, March, 1978.


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National Transportation Safety Board, Explosion and Fire Aboard the U.S.Tankship Jupiter, Bay City, Michigan, September 16, 1990, Marine AccidentReport, PB91-916404, NSTB/MAR-91/04, Adopted Oct. 29, 1991.

Occasion, L. K., The Analysis of Passing Vessel Effects on Moored Tankers,

Directed Research PTE-490x, 616-03-8123, Dec. 10, 1996.

Pinkster, J. (description of the program DELPASS provided by email), MARIN,2000.

Remery, G.F.M., Mooring Forces Induced by Passing Ships, OTC 2066, 1974.

Seelig, W., EMOOR - A Quick and Easy Method of Evaluating Ship Mooring atPiers and Wharves, NFESC Report TR-6005-OCN, Rev B May 1998.

Seelig, W. (ed.), Mooring Design, MIL-HDBK-1026/4, 1999.

Spencer, J., McBride, M., Beresford, P. and Goldberg, D., Modeling the Effectsof Passing Ships, Proceedings, International Colloquium on Computer

Applications in Coastal and Offshore Engineering, Kuala Lumpa, June 1993.

Wang, Shen, Dynamic Effects of Ship Passage on Moored Vessels, ASCE,Journal of the Waterways, Harbors and Coastal Engineering Division, WW3, pp.247-258, Aug. 1975.


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APPENDIX A - NOTATION USED

The following notation is used in this report:

Variable Description Units

B Ship width L

Cb Ship block coefficient -

Cm Mid-ships coefficient, Cm = maximum ship end-onsubmerged cross-sectional area divided by shipwidth times draft

-

CFX, CFY, CFM Finite depth correction factors for peak forces inthe X direction, Y direction and yawing moment.

-

d Water depth L

fx, fy, m Dimensionless forces and moments on themoored ship

-

Fx, Fy, M Forces and moments on the moored ship F, F*L

G Gap distance between ships L

g Acceleration due to gravity L/T2

L Mean ship length = 0.5 *(L1+ L2) L

L1, L2 Lengths of ships 1 and 2 at waterline L

Q Demonimator Q= V2(L1)2(S1/L1

2)(S2/L22) F

S1, S2 Cross-sectional midship submerged areas ofShips 1 and 2

L2

T Ship draft of moored Ship 1 L

t Time T

VR Passing ship velocity relative to the water L/T

V Passing ship velocity relative to the world L/T

VC Current velocity L/T

X X-coordinate L

Y Y-coordinate L

Lateral distance between ship centerlines L

Subscripts

0 Deepwater (i.e. T/d = 0)


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1 Moored ship (the subscript may be omitted) -

2 Moving ship -

Lab Experimental measurement in the laboratory

x Peak force in the x-direction

y Peak force in the y-direction

M Peak moment in the yaw direction

UNITS:

- = dimensionlessL = lengthT = time

ANG = angF = force


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APPENDIX B - PREVIOUS WORK

The interactions between a moored and a moving ship nearby can behighly complex. Therefore, several investigators have used scale modelstudies and/or theoretical calculations to examine these phenomena. Thevarious studies are discussed below.

REMERY (1974)

Remery (1974) performed a systematic set of laboratory studies. He fixedthe ship draft to water depth ratio at T/ d= 0.87 for the moored ship.Moving ships were tests at three speeds. Three different moving shipswere tested, which had masses 30%, 110% and 160% of the mass of themoored ship.

The moored ship was initially held rigidly and forces/moments on the

moored ship were measured. Then linear mooring systems with variousamounts of stiffness were installed on the moored ship and experimentsre-run.

Remery (1974) concluded:

The loads induced by a passing ship on a moored vessel are proportionalto the square of the speed of the passing vessel for no current and arerelated to the relative position between both vessels.

The stiffness of the mooring system has a considerable effect on themooring forces. When only small excursions are allowable, a stiff systemtends to result in the smallest mooring forces.

Muga and Fang (1975)

Muga and Fang (1975) performed 47 laboratory tests with identical mooredand passing ships (250 000 DWT tankers). Tests were conducted over arange of conditions with and without a current. Most of the data from thisresearch appear to be lost. Some data can be taken from figures in this

paper. However, it appears the data was plotted with an error of 2 or they-axes of the figures were mis-labeled. Corrected data is used in thisreport.


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Lean and Price (1977)

Lean and Price (1977) performed 135 laboratory tests. Only a fraction ofthe data are reported. These authors concluded that pressure gradientsassociated with the passing ship are important because the observedwaves had small height at low ship speed and the length of the observed

surface waves were short in comparison with the size of the moored ship.

The authors conclude that slack lines are to be avoided and that somerelief in maximum line loads can be achieved by increasing the linepretension.

King (1977)

King developed a numerical model and performed selected model tests.Only sway force and yaw moment were measured. The surge force wasnot reported.

Cohen and Beck (1983)

These authors developed a numerical model and performed selectedmodel tests. Only sway force and yaw moment were measured. Thesurge force was not reported.

Kizakkevariath, S. (1989)

Kizakkevariath, S. (1989) performed various numerical simulations ofpassing ship and other effects.

Flory, J. (2001)

Flory developed an empirical method for estimating passing ship forcesand moments on a moored ship based on a re-analysis of existing

information.

Table B-1 summarizes the previous model tests reanalyzed in this report.


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Table B-1. SHALLOW WATER CORRECTION FACTORS DETERMINEDFROM LABORATORY SCALE MODEL STUDIES OF PASSING SHIP

EFFECTS ON MOORED SHIPS

Data Pt # d/L L2/L1 eta/L1 T/d CFX CFY CFM GAP/B1 T/B Source

1 0.07 0.712 0.239 0.870 8.027 10.675 9.308 0.815 0.402 REMERY (1974)2 0.07 0.712 0.356 0.870 10.274 14.694 14.762 1.630 0.402 REMERY (1974)

3 0.07 0.712 0.589 0.870 12.75 20.345 23.220 3.261 0.402 REMERY (1974)

4 0.07 0.973 0.267 0.870 8.871 12.075 10.261 0.815 0.374 REMERY (1974)

5 0.07 0.973 0.384 0.870 11.348 15.469 10.787 1.630 0.374 REMERY (1974)

6 0.07 0.973 0.617 0.870 13.190 9.584 3.261 0.374 REMERY (1974)

7 0.07 0.973 0.928 0.870 9.699 10.355 7.604 5.435 0.374 REMERY (1974)

8 0.07 1.175 0.279 0.870 9.636 11.910 11.899 0.815 0.344 REMERY (1974)

9 0.07 1.175 0.396 0.870 15.530 15.386 1.630 0.344 REMERY (1974)

10 0.07 1.175 0.629 0.870 11.146 16.306 14.550 3.261 0.344 REMERY (1974)

11 0.07 1.175 0.94 0.870 9.308 10.908 9.592 5.435 0.344 REMERY (1974)

12 0.068 1.000 0.292 0.909 10.9245 18.865 11.580 0.900 0.402 MUGA (1975)*

13 0.068 1.000 0.385 0.909 13.623 24.364 15.248 1.500 0.402 MUGA (1975)*

14 0.068 1.000 0.477 0.909 17.4565 24.737 18.278 2.100 0.402 MUGA (1975)*

15 0.08 1.000 0.385 0.769 9.9455 11.666 21.046 1.500 0.402 MUGA (1975)*

16 0.068 1.000 0.385 0.909 13.623 24.364 15.248 1.500 0.402 MUGA (1975)*

17 0.066 1.000 0.385 0.943 15.009 27.707 33.184 1.500 0.402 MUGA (1975)*18 0.066 1.000 0.292 0.943 11.831 20.608 25.158 0.900 0.402 MUGA (1975)*

19 0.062 1.000 0.292 1.000 10.179 29.903 32.067 0.900 0.402 MUGA (1975)*

20 0.075 1.000 0.167 0.833 6.736 6.415 0.336 0.500 COHEN (1983)

21 0.075 1.000 0.229 0.833 8.157 8.879 0.832 0.500 COHEN (1983)

22 0.075 1.000 0.292 0.833 10.595 8.618 1.336 0.500 COHEN (1983)

23 0.075 1.000 0.354 0.833 12.450 10.114 1.832 0.500 COHEN (1983)

24 0.05 1.000 0.167 0.833 8.412 9.661 0.336 0.333 COHEN (1983)

25 0.05 1.000 0.229 0.833 11.057 11.303 0.832 0.333 COHEN (1983)

26 0.05 1.000 0.292 0.833 15.666 11.350 1.336 0.333 COHEN (1983)

27 0.05 1.000 0.354 0.833 16.357 13.663 1.832 0.333 COHEN (1983)

28 0.094 1.000 0.167 0.667 4.272 4.311 0.336 0.500 COHEN (1983)

29 0.094 1.000 0.229 0.667 5.220 5.223 0.832 0.500 COHEN (1983)

30 0.094 1.000 0.292 0.667 6.248 6.601 1.336 0.500 COHEN (1983)

31 0.094 1.000 0.354 0.667 6.874 6.616 1.832 0.500 COHEN (1983)

32 0.063 1.000 0.167 0.667 4.663 4.402 0.336 0.333 COHEN (1983)33 0.063 1.000 0.229 0.667 5.928 5.911 0.832 0.333 COHEN (1983)

34 0.063 1.000 0.292 0.667 7.478 6.674 1.336 0.333 COHEN (1983)

35 0.063 1.000 0.354 0.667 8.950 8.831 1.832 0.333 COHEN (1983)

36 0.1 2.000 0.625 1.000 10.246 1.500 0.400 KING (1977)

37 0.1 1.333 0.417 1.000 14.408 1.500 0.600 KING (1977)

38 0.1 1.000 0.313 1.000 16.176 7.687 1.500 0.800 KING (1977)

39 0.1 0.667 0.208 1.000 18.038 1.500 1.200 KING (1977)

40 0.1 0.500 0.156 1.000 25.098 1.500 1.600 KING (1977)

* AUTHOR MADE AN ERROR OF 2.0 WHEN PLOTTING


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Figure B-1. MEASURED VS. PREDICTED CFX

Figure B-2. MEASURED VS. PREDICTED CFY

0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 18

MEASURED CFX

PREDICTEDCF

X

.

CFX=1 + 16 * (T/d) * EXP(-0.08 * ((G/B) - 3.5)2)

PASS.XLS

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

MEASURED CFY

PREDICTEDCF

Y

.

CFY= 1 + 25 * (T/B)-0.35

* (T/d)4

* EXP(-0.08 * ((G/B) - 3.3)2

)

PASS.XLS


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Figure B-3. MEASURED VS. PREDICTED CFM

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

MEASURED CFM

PREDIC

TEDCF

M

.

CFM= 1 + 25 * (T/B)-0.35

* (T/d)4* EXP(-0.08 * ((G/B) - 3.3)

2)

PASS.XLS

Documents

Passing Ship Seelig