Barge Roll Motions Slideshow

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A Reanalysis of Barge RollMotion Data

Allen H. Magnuson Ph. D., P. E.

Naval Architect

J. F. Moore International


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Introduction

Accurate prediction of roll motions for heavy-lift barges and ships, launchbarges, deck barges and the like are essential to assure the safety of thevessel and cargo in transit.

Accurate prediction of roll motions for heavy-lift ships and barges isnecessary for designing sea fastenings and leg stresses on jackups.

Existing commercially-available ship motions programs are generally knownto over-predict roll motion of loaded barge hullforms due to under-predictionof roll damping.

In addition existing motions programs do not appear to have been validatedfor loaded barge hullforms with their high VCGs and large radii of gyration inroll.

Ship model motions test data is almost always proprietary, so very little datais generally available.

November 13, 2006 All Rights Reserved, J. F. Moore

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Introduction

Purposes of Investigation:

To illustrate the unique relationships between bargeroll motions and barge design/loading parameters.

To present model test data on barge roll motions foruse by Naval Architects in developing and validating

in-house motions programs.


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Introduction 2

Data Sources:

S. Andos Data (ref: Trans. West Japan Soc. OfNav. Archs., 1975 - Translation from Japanese by

R. LaTorre: (ref) N.A.M.E. Dept. Report, U. of

Michigan, 1980)

Noble Denton & Assocs. (NDA) Barge Motion

Research Project (JIP): Summary Report, 1984.


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Outline

Intro: Definition of barge-type hullforms

Presentation of Andos Data: Roll Angle RAOs for various hulldesign/loading parameters Comparison with strip-theory computations

Presentation of NDA JIP Data:

NDA Standard Barge

Roll Angle RAOs for variations in L/B, B/d, and Roll Period (Tn)

Data on nonlinear effects on Roll Motion due to waveheight

Discussion: Comparison with predictions from strip theory program

Effect of hydrodynamic inertia in roll motion (a44)

Effect of location of roll center


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Heavy Lift Semi-Submersible Barges

and Transport Vessels


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Other applicable barge types:

Deck barges Jacket-launch barges

Hopper barges


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Definition of Barge -Type Hullforms

High B/d > 4

Block Coefficient > 0.85

Flat Bottom, rectangular sections

amidships, extensive parallel mid-body,

small bilge radius

When loaded:

Large Roll Radius of Gyration (Kxx/B) > .4 High KG (KG/d > 3)


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Roll Motion Analogy to

Mass-Spring-Damper System

(RAO as a Frequency-Response Function)

Damped Harmonic Oscillator - Magnitude Response:

Various Percent Critical Damping Ratios

0.1

1.0

10.0

0.10 1.00 10.00

Frequency Ratio (w/wn) (Log Scale)

MagnificationFactor(lo

gscal

5%

10%

20%

70%

Subcritical

Supercritical

Resonant DampingRatios


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Roll Motion Analogy to

Mass-Spring-Damper System

(RAO as Frequency-Response Function)

Roll NaturalPeriod:

n = 2 /n


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Roll Natural Period

Ixx + A44

M g GMT

= 2

A44 Is Added Hydrodynamic Moment of Inertia in Roll

GMT Is Transverse Metacentric Height

A44 can be computed from RAO data using the followingrelation:

A44 = M g GMT/ n2

Ixx


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Roll RAOs Based on Wave Slope

w= k

0, k = 2/g

w = Wave Slope

0 = Wave Amplitude

k = Wave number


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The RAO in Wave Spectral Theory

(Random Waves)

RMS = (RAO)2 Sw() d

0

oo

Sw ) = Wave Spectrum

Note that roll angle varies with the square of the roll RAO


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From Andos Paper:

Original Faired Roll Motion Data


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Andos Data Sets 1,2 & 3: KG/d

and Kxx/B Variation

Japanese Work Barge Rectangular hull, zero bilge radius

L/B = 2.2, B/d = 10

L = 50 m (164 ft) Regular Waves: Waveheight = 2.5 m (est.)

Note: OG = distance from W. L to CG

(KG/d = OG/d +1)


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Andos Data Set 1: KG Variation 1

Roll Motion For Ando's Barge: VCG Variation:

Kxx/B = 0.65

0

2

4

6

8

10

0.40 0.50 0.60 0.70 0.80

Wave Frequency (rad/sec)

RollR

AO(deg/deg

OG/d=3

OG/d=4

OG/d=5

OG/d=6


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Andos Data Set 1:

Correlation With Computed Values

Commercially- Available Ship Motions Program

Uses Strip Theory (Valid for High L/B ratio)

Motions Equations Based on Schmitkes Paper: Trans. SNAME1978.

Linear 2-D Wave-Making Roll Damping

Used Tanakas (1960 JSNAJ) Empirical Eddy Making RollDamping Model

Developed for destroyer type hull-forms, conventional ships


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Andos Data Set 1: Correlation With Computed Values

Roll Motion For Ando's Barge: OG/d = 4:

Kxx/B = 0.65

0

2

4

6

8

10

0.3 0.4 0.5 0.6 0.7 0.8


RollRAO(

deg/deg

Model Test

Strip Theory

Roll Motion For Ando's Barge:OG/d = 3, Kxx/B = 0.65

0

2

4

6

8

10

0.40 0.50 0.60 0.70 0.80


RollRAO(

deg/deg)

Model Test

Strip Theory

Roll Motion For Ando's Barge: OG/d = 5 :

Kx x/B = 0.65

0

2

4

6

8

10

0.3 0.4 0.5 0.6 0.7 0.8


RollRAO(

de

g/deg

Model Data

Strip Theory

Ro l l Mo t ion Fo r Ando ' s Ba rge : OG/d = 6 :

Kx x /B = 0.65

0

2

4

6

8

10

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

W av e F r e q u e n c y ( r a d /s e c )

RollRAO(

deg/deg

Model Data

Strip Theory


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Andos Data Set 2: KG Variation 2

Ando's Barge OG Var: Fig. 21a

Kxx/B = 0.4

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollR

AO(d

eg/deg

OG/d=1OG/d=2

OG/d=3


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Andos Data Set 2: Correlation with Computed Values

An do's Barg e OG/d = 1 Com pari son,

Kxx /B = 0.4

0

1

2

3

4

0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollRAO(

deg/deg)

Model Test

Strip Theory

Ando's Barge OG/d = 2 Comparison

Kxx /B = 0.4

0

1

2

3

4

0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollRAO

(deg/deg)

Model Test

Strip Theory

An do's Ba rg e OG/d =3: Com pari son of Mo del Data

w ith Com puted Values, Kxx /B = 0.4

0

1

2

3

4

0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollRAO(d

eg/deg)

Model Test

StripTheory


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A d D t S t 2 C l ti f RAO S d (P ti l t


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Andos Data Set 2: Correlation of RAO Squared (Proportional to

Motion) Model Data with Computed Values

Ando's Barge OG/d = 2 Comparison: RAO Squared

Kxx /B = 0.4

0

2

4

6

8

10

12

0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

Ro

llRAO^2(deg/deg

)^

Model Test

Strip Theory

Note approximate 2/1 difference in RAO^2 near natural frequency.

This would result in a 2/1 difference in roll angle, with the

computed roll angle being about twice that of the model test data.


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Andos Data Set 3: Kxx/B Variation

Ando's Barge Roll Data for Varying Kxx: OG/d = 2.13

0.0

1.0

2.0

3.0

4.0

0.6 0.7 0.8 0.9 1.0 1.1 1.2


RollRAO

(de

g/deg

Kxx/B=.5

Kxx/B=.55


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Andos Kxx/B Variation:

Comparison with Motions ProgramAndo's Barge Roll Data Comparison with

Strip Theory Motion Program, OG/d = 2.13

0

1

2

3

4

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2


RollRAO

(deg/deg

Model Data Kxx/B=.55Strip Theory Kxx/B = .52

Model Data Kxx/B = .50


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Andos Data Sets 4&5:

Bottom Bevel (Rake Angle) and DraftVariation

Rectangular Barge with Bottom Bevel (Rake)Measured from Horizontal

Bilge Radius = 0

L/B = 3

B/d = 5

KG/d = 1.67

Kxx/B = 0.45 L = 75 m (246 ft) Full Scale


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Andos Data Sets 4&5:

Bottom Bevel (Rake Angle) and Draft Variation

Bev. Angle

W. L.

Draft


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Andos Faired Data Set 4: Bottom Bevel (Rake Angle)


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Andos Data Set 4:

Bottom Bevel (Rake) Variation

Ando's Bevel- Bottom Barge Series:

Kxx/B = .35, KG/d = 1.67

0

1

2

3

4

5

6

7

0.50 0.60 0.70 0.80 0.90 1.00

Frequency (rad/sec)

RollR

AO(d

eg/deg

Bev=20

Bev=30Bev=40

Bev=50


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Andos Data Set 4: Bottom Bevel (Rake) Variation

Roll RAO Comparison: Ando's Data vs. Strip

Theory for B ottom B evel of 20 deg

0

2

4

6

0.2 0.4 0.6 0.8 1

Frequenc y (rad/sec)

RollRA

O(

deg/deg

Strip Theory

Ando

Roll RAO Comparison : Ando's Data vs. Strip

Theory for Bottom Bevel of 30 deg

0

2

4

6

8

0.2 0.4 0.6 0.8 1

Frequency (rad/sec)

RollRAO

(deg/deg

Strip Theory

Ando

Roll RAO Comparison: Ando's Data vs. Strip Theory

for Bottom Bevel of 40 deg

0

2

4

6

8

0.2 0.4 0.6 0.8 1

Frequency (rad/sec)

RollRA

O(

deg/deg

Strip Theory

Ando

Roll Angle Correl. for 50 deg Beveled Barge

0

2

4

6

8

0.2 0.4 0.6 0.8 1

Frequency (rad/sec)

RollR

AO(

deg/deg

Strip Theory

Model Data


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Andos Barge Data Set 5: Variable Draft:

Bottom Bevel = 20 deg.

Ando's Barge, Variable Draft

0

1

2

3

4

5

0.5 0.6 0.7 0.8 0.9 1.0

Frequency (rad/sec)

RollR

AO(d

eg/deg

.5 draft

.75 draft

full draft


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Part 2: NDA JIP: Roll Motions of the

Standard Barge


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Part 2:


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Part 2:

NDA JIP Data : Based on NDA

Standard Barge

Full Scale:

L = 300

B = 90

d = 9

Rectangular hull with 30 deg rake at bow, 28

long

Bilge radius 1.48 ftScale ratio = 1 / 30


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Part 2: Typical NDA JIP Model Test Data Plot for Regular Waves


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NDA JIP Roll Motions Data:


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NDA JIP Roll Motions Data:

Barge Model Series

NDE JIP Barge Characteristics

Case L/B B/d Tn sec KG/B Kxx/B

Vary L/B 1 4.5 10 10 0.356 0.576

Vary L/B 2 2.5 10 10 0.356 0.576

Std. Barge 3 3.33 10 10 0.356 0.576

Vary B/d 4 3.33 6 10 0.234 0.477 * Data N. G.

Vary B/d 5 3.33 12.9 10 0.423 0.661

Vary Tn 6 3.33 10 6 0.178 0.309

Vary Tn 7 3.33 10 14 0.445 0.803


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NDA JIP Data Set #1: L/B Variation

Roll RAOs, Length/Beam Variation:

3m W. H., B/D = 10, Kxx/B = 0.575, KG/d = 3.56

0

1

2

3

4

5

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollR

AO

(deg/deg

L/B=4.5

L/B=2.5L/B=3.3


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L/B Variation: Computed Roll RAO Data

Roll RAO Comparison: NDA Barge: L/B Variation,

Computed Values from Strip Theory

0

1

2

3

4

5

6

7

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollRAO(d

eg/deg

L/B = 2.5

L/B = 3.33

L/B = 4.5


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NDA JIP Data Set #2: B/d Variation

NDA B/d (Beam/Draft) Variation Series

0

1

2

3

4

5

6

4 6 8 10 12 14

Beam/Draft (B/d)

Kg/B,K

xx/B

KG/dKxx/B


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NDA JIP Data Set #2: B/d Variation

Roll RAOs, Beam/Draft (B/d) Variation:

3m W. H., Tn = 10 sec,: Kxx/B, KG/B Vary

0

1

2

3

4

5

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollR

AO(

deg/deg

B/d=10

B/d=6

B/d=12.9

B/D = 6 N. G.


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NDA JIP Data Set #3:


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Tn (Roll Period) Variation

NDA Tn (Roll Period) Variation Series

0

1

2

3

4

5

4 6 8 10 12 14 16

Roll Natural Period (sec)

Kg/B,K

xx/B

KG/dKxx/B


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Tn (Roll Period) Variation

Roll RAOs, Roll Period (Tn) Variation:

3m W. H.,B/d = 10

0

2

4

6

8

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Frequency (rad/sec)

RollRAO

(deg/deg

T=10 secT=6 sec

T=14 sec

T=6

T=14

T=10


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Comparison of NDA JIP Model Test Data with


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Computed Data -1

Roll RAO Comparison: NDA Standard Barge,

Model Test Data vs. Computed Values from Strip Theory

0

1

2

3

4

5

6

7

0.0 0.2 0.4 0.6 0.8 1.0

Frequency (rad/sec)

RollRAO

(deg/deg

Model Test

Strip Theory


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Comparison of NDA JIP RAO-Squared for


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Comparison of NDA JIP RAO Squared for

Standard Barge Model Test Data with Computed Data -1

Rol l RAO^2 Comparison: NDA Standard Barge, L/B = 3.33

Model Test Data vs. Computed Values from Str ip Theory

0

5

10

15

20

25

30

35

0.0 0.2 0.4 0.6 0.8 1.0

Frequency (rad/sec)

RAO^ Model Test

Strip Theory

Note approximate 2.5/1 difference in RAO^2 near natural frequency.

This would result in a 2.5/1 difference in roll angle, with the computed roll angle

being 2.5 times that of the model test data.


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Computed Data -2

Roll RAO Comparison: NDA Standard Barge,

Case 7: Tn = 14 sec

Model Test Data vs. Computed Values from Strip Theory

0

2

4

6

8

10

0.0 0.2 0.4 0.6 0.8 1.0

Frequency (rad/sec)

RollRAO(d

eg/deg

Model Test

Strip Theory


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NDA JIP Data 4: Nonlinear Effect on


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Roll Angle Peak Due to Wave Height

Effect of Waveheight on Peak Roll Angles

0

3

6

9

12

15

18

0.0 1.5 3.0 4.5 6.0 7.5 9.0

Waveheight (m)

RollAngle

Peak(deg)

Tn=14 sec

B/d=12.9

Std Barge

B/d=6

L/B=2.5


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R ll A l RAO P k D t W Sl


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Roll Angle RAO Peak Due to Wave Slope

(Max Wave Slope for Stable Wave = 8 deg)

Effect of Wave Slope on Peak RAOs

0

3

6

9

12

0 1 2 3 4 5 6 7 8 9 10

Wave Slope (deg)

RollRAOPeak(deg/deg

Tn=14 sec

B/d=12.9Std Barge

B/d=6

L/B=2.5


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Summary


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Summary

Roll RAO model test data for barge hullforms waspresented for a wide range of hull/loading parameters:

L/B

B/d Tn

KG (VCG/d),

Roll Radius of Gyration (Kxx/B),

Bottom Rake Angle,

Draft (B/d)

Roll RAO model test data was compared to predictionsfrom a ship motions program based on Strip Theory.


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Results

Generally, the computer RAO predictions agreed surprisingly well withthe reanalyzed model test data, even for very low L/B values.

The computed values generally underpredicted the roll dampingconsiderably.

However, if the RAOs are used to compute roll angles in randomwaves using spectral representation, the computer predictions cantypically be twice the value obtained from the model test data.

The computer program used in the study uses Tanakas (1960) eddy-making roll damping, which is well known to underpredict viscous rolldamping, thus overpredicting roll motion.

Accurate means to predict roll damping for these barge-type hullformsdo not exist at present.


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Results: Nonlinear (Waveheight) effect


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from NDA Data

1. RAO Model test data shows that roll

damping increases with waveheigt- RAO peak decreases with waveheight

- Roll angle peaks vs. waveheight tend

to level off as waveheight increases2. These are all nonlinear effects

3. Nonlinear effects can be treated using

frequency-domain spectral analysis by usingleast squares approach and appropriate

amplitude-dependent RAO.


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Summary, Conclusions


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y

The parametric RAO data presented here provides:

a. Useful insight into how roll motion is affected byvarious hull and hull loading parameters

b. Data for use in validating ship motions programs

c. Guidance and direction for future studies


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Recommendations


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Recommendations

Further Work: (Possibly form a JIP) Purpose: Reduce risks for ocean transport of platforms, other

large cargo on barges and barge-like transport ships Conduct new model test programs for typical modern barge /

semi-submersible heavy lift ship designs

Perform model tests in regular waves, random waves

Examine effects of bilge radius, bilge keels on roll motion, esp.nonlinear damping

Examine effects of quartering seas as well as beam seas

Acquire full-scale trials data for validation of model test data

Validate/evaluate current ship motions programs


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Barge Roll Motions Slideshow

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