Trimaran Motion and Load Assessment - viking-systems.net · Trimaran Assessment Presentation Topics: 1. Development of Tool for Motions and Structural Loading Assessment 2. Design

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ASNE High Speed Craft Conference, Annapolis, Jan 24, 2007

Seakeeping Assessment of Large Trimaran for Naval Aircraft Operations

Presented by Mr. Boyden Williams, Mr. Lars Henriksen (Viking Systems), Dr. Igor Mizine (CSC/Advanced Marine Center), and Dr. Nils Salvesen (Viking Systems)

Seakeeping Assessment of Large Trimaran for Naval Aircraft Operations

Trimaran Assessment Presentation Topics:Trimaran Assessment Presentation Topics:1. Development of Tool for Motions and Structural Loading Assessment2. Design of Hulls by Advanced Fully 3D Hydrodynamic Assessment3. Application to HALSS Trimaran Concept for Sealift Missions4. Evaluation to NATO Seakeeping Criteria for Naval Aircraft Operations5. Evaluation to NATO Seakeeping Criteria for Sealift Transit Operations6. Presentation of Trimaran Systematic Series Seakeeping Results7. Interesting Findings, Conclusions, and Future Studies

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Sponsored by CCDOTT 1999-2006 High Speed Trimaran Technology Development Program

Background of Selected Vessel Background of Selected Vessel -- HALSSHALSSHALSS helps Early Insertion & Logistic Support:

Deploys at High Speed (35 Knots) Operate fixed wing aircraft between advanced base and sea base

HALSS helps Force Deployment:Operate fixed wing aircraft for theater operationsArrange and Configure military loads in preparation for early entry to the Theater operations

Heavy Air Lift Sea Basing Ship (HALSS)

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HALSS Principal CharacteristicsHALSS Principal CharacteristicsFlight Deck Length 1,100 FTFlight Deck Width / Docking Hull Beam 274 FT / 180 FTDraft 37.9 FTDepth 100 FTPayload:

Combat forces sustainment 8,900 STAircraft Fuel Supply 2,650 ST

Fixed Wing Aircraft Six C-130JStowage Factor

Main (Flight) Deck 185,900 SQFTII Cargo Deck 141,000 SQFTIII (Crossover) & IV Decks 51,100 SQFT

HALSS Stowage Factor 46.7 SQFT/MT

Unrefueled Range of Sea Voyage - CONUS to Advanced Base or to JOA10,000 NM at 35 knots>15,000 NM at 25 knots Followed by 10 days endurance in JOA

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High Speed Trimaran Seakeeping Study High Speed Trimaran Seakeeping Study -- ObjectivesObjectives

Establish Reliable Trimaran Analysis Procedure:Displacement, Velocities, Accelerations; Relative Motions for Slamming and Emergence; Hull Girder Loads and Local Pressures; Interaction between Main and Side Hulls.

Determine Criteria for Assessment: Naval Air Operations (NATO STANAG 4154, 1997) Transit (NATO Generic Frigate)

Assess Motion, Slamming, Emergence & Hull Girder Loads:Sea States 4 through 7; Vessel Speeds of 15, 25, 35 knots; Vessel Headings of 0, 45, 90, 135, 180 degrees;Multiple Hull Configurations

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Design Variables Design Variables -- Trimaran Synthesis Model Trimaran Synthesis Model

a

b

L*sidehull

Lcenterhull

b

X (Centerhull)Y (centerhull)

X* (sidehull)

Y* (sidehull)

MHBeamClearanceSeparation =

( )SHMH

SHSH

LOALOA

LOAMS

Stagger−

⎟⎠⎞

⎜⎝⎛ −

=2

MSSH - Distance from AP to Midship of Side HullLOASH – Overall Length of the Side HullLOAMH – Overall Length of the Main Hull

Clearance - Distance between the Outside of the Main Hull and the Inside of the Outer Hull at the waterlineBeamMH - Maximum Beam of the Main Hull

Stagger of side hulls 0.00, 0.24, 0.40 & 0.80Separation of side hulls 0.36, 0.75, 1.25Overall vessel size 150m, 200m, 250m & 300m

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Method and Software Method and Software -- Selection Criteria :Selection Criteria :

Ability to Handle Trimaran Type HullTime-Domain Hydrodynamic AnalysisTransformation to Frequency Domain for RAOs / Scaling Non-Linear Capability for Detailed InvestigationAbility to Assess NATO CriteriaExtendable to FEA Structural AnalysisAbility to Rapidly Model Geometric VariationsAbility to Work with Existing Software

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Selection of Hydrodynamic SoftwareSelection of Hydrodynamic Software

Codes Considered LAMP (SAIC)SWAN (MIT)WASIM (DNV implementation of SWAN)

WASIM is Chosen as Project SoftwareWASIM is advanced fully 3-D ship motion assessment toolAssessment in Time DomainCapable of Non-Linear Hydrostatics WASIM previously used for trimaran type hull (M/V Triton)Viking Systems has extensive experience with DNV SoftwareWASIM is integrated with SAGA Software

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Seakeeping Criteria Seakeeping Criteria –– Naval Air OperationsNaval Air OperationsNATO STANAG 4154 (Edition 3, 1997)Single Amplitude RMS Values:

Motion Limit Location

Aircraft Handling Roll

Sink off bow and OLS limits Pitch

Ramp Clearance Vertical Displacement 0.8 m Stern Ramp at

Flight Deck

Landing Line-up Lateral Displacement 2.3 m Stern Ramp at

Flight Deck

Landing Gear Vertical Velocity 0.7 m/sec Touchdown Point

Crosswinds and Landing loads Relative Wind

35 to 40 knots envelope, +/- 15 degrees from the bow

Governing Factors Performance Limitations

Period > 20s, 1 Deg.; Period > 20s, 1.5 Deg

Period > 10s, 0.5 Deg.; Period > 15s, 1 Deg

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Naval Air Naval Air Operations Operations

--Environment Environment Conditions

Wind Speed Over Deck for Flight Operations

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7Sea State

Win

d Sp

eed

(Kno

Wind Speed

Minimum Required Speed Over Deck

Maximum Required Speed Over Deck

Wind - Sea State

Wind - Vessel

Conditions

Wind Speed Minimum Vessel Speed

Maximum Vessel Speed

(Knots) (Knots) (Knots)0 0.0 35.0 40.01 3.0 32.0 37.02 8.5 26.5 31.53 13.5 21.5 26.54 19.0 16.0 21.05 24.5 10.5 15.5

5.5 30.0 5.0 10.06 37.5 -2.5 2.57 51.5 -16.5 -11.5

Head Sea Cases used for AnalysisInsufficient Forward Speed to Maintain Maneuverability

Sea State Using Wind Speed Criteria:

The wind associated with a Sea State defines the required vessel speed to maintain 35 -40 knot apparent wind speed over flight deck

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Seakeeping Criteria Seakeeping Criteria -- TransitTransitNATO Generic Frigate Criteria (Pattison & Sheridan, 2004)Single Amplitude RMS Values:

Parameter Limit Value Roll Angle 4.0 deg Pitch Angle 1.5 deg Vertical Acceleration 0.2 g Lateral Acceleration 0.1 g Bottom Slamming Index 20 per hour Propeller Emergence Index 90 per hour

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Comparison to Rule Hull Girder Loads

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Hydrodynamic AnalysisHydrodynamic Analysis

Define Vessel and Incoming WavesPanel and Mass Models defined to Represent Vessel Wave Elevation for Time Domain Analysis as Fourier Series

of Cosine Waves with Amplitude According to PM Spectrum

Recording Output & ResultsTime Series Recorded for 6 DOF Motions, Velocities & Accelerations Relative Wave Elevations Recorded for Series of 30 Locations Along

the Length of Main and Side HullsHull Girder Shear Force & Bending Moments Recorded at Stations

Result Processing Result Processing -- Time vs. FrequencyTime vs. FrequencyHydrodynamic Analysis is Performed in the Time Domain, Results can be Transformed into Frequency Domain.

Result Processing in the Time Domain - BenefitsStatistical Analysis of Time Series for Result VariablesAbility to Track Occurrence of Individual PhenomenonUnique Analysis Run for Each Sea State, Heading & Speed

Result Processing in the Frequency Domain - BenefitsResults Transformed into Response Amplitude Operators (RAO)Response to Unit Wave (RAO) Combined with Sea SpectrumRequires Fewer Analysis Runs – Saves Computational TimeResults can be Scaled for Vessels of Varying Length

Reliable and Repeatable Post-Processing of Data is Essential13


Result Processing Result Processing –– Method ValidationMethod ValidationHALSS is evaluated in both Time and Frequency Domains

Roll Motion Results Compared for Sea State 5, 6 & 7Pitch Motion Results Compared for Sea State 5, 6 & 7

15 Knot Pitch Angle

0

0.5

1

1.5

2

2.5

3Head Sea

45

90

135

Following Sea

225

270

315

15 Knot Roll Angle

0

2

4

6

8

10

12Head Sea

45

90

135

Following Sea

225

270

315

Time & Frequency Domain Calculations Provide Nearly Identical Results14


Result Processing Result Processing -- Time vs. FrequencyTime vs. Frequency

Frequency Domain Analysis using RAO’s possible for Motion, Velocity, Acceleration, Shear and Bending Loads – saves calculation time

Time Domain Analysis needed for Slamming and Emergence Assessment – Head Sea Governs – saves calculation time

Frequency Domain:

Pitch & Roll MotionHeave & Sway Acceleration Vertical Bending MomentVertical Shear Force

Time Domain:

Slamming Occurrence Center HullSlamming Occurrence Side HullBridge Deck Slamming OccurrencePropeller Emergence Occurrence

0

0.5

1

1.5

2

2.5

3

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Frequency (Rad/s)

Am

plitu

d

00.511.522.533.544.55

Wave Spectrum - SS6

Pitch RAO - L = 300m




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Results Summary for HALSSResults Summary for HALSS

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HALSS Trimaran Hull Configuration – 35 knots in SS7 – Head Seas

Results Summary for HALSSResults Summary for HALSSComparison of Hydrodynamic Results to NATO Criteria for Naval Air Operations

Vertical Displacement at Stern

10.0

15.5

21.026.531.5

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 1 2 3 4 5 6 7Sea State

(Vessel Speed Shown in Labels)

Ver

t. D

ispl

acem

ent (

RMS ResponseDisplacement Limit

Pitch Motion

10.0

15.5

21.026.531.5

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7Sea State


Pitc

h A

ngle

(Deg

ree RMS Response

Pitch Limit

Vertical Velocity at Touchdown Point

10.0

15.5

21.026.531.5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1 2 3 4 5 6 7Sea State


Vert.

Vel

ocity

(m/

RMS ResponseVelocity Limit

Vertical Acceleration at Bridge

31.5 26.5 21.015.5 10.0

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7Sea State


Ver

t. Ac

cele

ratio

n (m

/s

RMS ResponseAcceleration Limit

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Results Summary for HALSSResults Summary for HALSSComparison of Results to NATO Criteria for Transit

Polar Plots to Facilitate Comparisons, 150 m vs. 300 m:

RMS Pitch Angle

0

0.5

1

1.5

2

2.5

3

3.5

4Head Sea

45

90

135

Follow ing Sea

225

270

315

150 m TrimaranSeparation = 0.36

Stagger = 0.24Speed = 10.6 Kts

300 m Trimaran

Separation = 0.36Stagger = 0.24

Speed = 15.0 Kts

SS 5

Pitch Criteria

SS 6

SS 7

SS 6

SS 7

SS 5

RMS Roll Angle

-1

4

9

14

19

24Head Sea

45

90

135

Following Sea

225

270

315



Roll Criteria



SS 6

SS 7

SS 5

SS 6

SS 7

SS 5

Results for 150 m Vessel Created by Length Scaling RAOs

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Results Summary for HALSSResults Summary for HALSSComparison of Results to NATO Criteria for Transit

Center Hull Propeller Emergence - 25 Knot Vessel Speed

0

50

100

150

200

250

300

350

400

0 45 90 135 180Wave Heading

Emer

genc

es P

er H

our

SS4 - 25KnotsSS5 - 25KnotsSS6 - 25KnotsSS7 - 25KnotsCriteria

Center Hull Propeller Emergence - 35 Knot Vessel Speed

0

50

100

150

200

250

300

350

400

450


Emer

genc

es P

er H

our


Side Hull Propeller Emergence - 25 Knot Vessel Speed

0

100

200

300

400

500

600

700


Emer

genc

es P

er H

our



0

50

100

150

200

250

300

350

400


Emer

genc

es P

er H

our



0

100

200

300

400

500

600

700


Emer

genc

es P

er H

our


Center Hull Propellers Side Hull Propellers

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HALSS Transit Slamming and Hull Girder LoadsHALSS Transit Slamming and Hull Girder Loads

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Center Hull Bottom Slamming

0

50

100

150

200

250

300


Emer

genc

es P

er H

our

SS7 - 15KnotsSS7 - 25KnotsSS7 - 35KnotsCriteria

No Slamming below Sea State 7

Head Sea is the worst wave heading for slamming

ABS Rule Shear for equivalent monohull = 4.18 x 107 N

ABS Rule Bending Moment for equivalent monohull = 4.60 x 109 N-m

Vertical Shear Force Envelope - All Directions - 35 Knots

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

3.00E+07

3.50E+07

4.00E+07

4.50E+07

0 50 100 150 200 250 300Longitudinal Location (m)

Shea

r For

ce (N

)

SeaState4 SeaState5 SeaState6 SeaState7 ABS Rule Shear

Vertical Bending Moment Envelope - All Directions - 35 Knots

0.00E+00

5.00E+08

1.00E+09

1.50E+09

2.00E+09

2.50E+09

3.00E+09

3.50E+09

4.00E+09

4.50E+09

5.00E+09

0 50 100 150 200 250 300Longitudinal Location (m)

Ben

ding

Mom

ent (

N-m

)

SeaState4 SeaState5 SeaState6 SeaState7 ABS Rule Bending

Comparison of Results to NATO Transit Criteria and ABS Rule Loads

HALSS Transit Acceleration ResultsHALSS Transit Acceleration ResultsComparison of Results to NATO Criteria for Transit

35 Knot Vertical Acceleration

0

1

2

3

4

5

6Head Sea

45

90

135

Following Sea

225

270

315

SS7 - Bow

SS6 - Bow

SS5 - Bow

SS4 - Bow

Criteria

SS7 - MidShips

SS7 - Stern

SS6 - MidShips

SS6 - Stern

SS5 - MidShips

SS5 - Stern

SS4 - MidShips

SS4 - Stern

SS7 - Bow

SS7 - MidShips

SS7 - Stern

SS6 - Bow

SS6 - MidShips

SS6 - Stern

SS5 - Bow

SS5 - MidShips

SS5 - Stern

SS4 - Bow

SS4 - MidShips

SS4 - Stern

Acceleration at CL

Acceleration at Max Beam

Vertical Acceleration

Criteria

35 Knot Horizontal Acceleration

0

0.2

0.4

0.6

0.8

1Head Sea

45

90

135

Following Sea

225

270

315

SS7 - Bow

SS6 - Bow

SS5 - Bow

SS4 - Bow

Criteria

SS7 - MidShips

SS7 - Stern

SS6 - MidShips

SS6 - Stern

SS5 - MidShips

SS5 - Stern

SS4 - MidShips

SS4 - Stern

SS7 - Bow

SS7 - MidShips

SS7 - Stern

SS6 - Bow

SS6 - MidShips

SS6 - Stern

SS5 - Bow

SS5 - MidShips

SS5 - Stern

SS4 - Bow

SS4 - MidShips

SS4 - Stern

Acceleration at CL

Acceleration at Max Beam

Horizontal Acceleration

Trimaran meets vertical acceleration criteria up to sea state 6

Trimaran meets horizontal acceleration criteria up to sea state 7

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Result Highlights for Other Hull ConfigurationsResult Highlights for Other Hull ConfigurationsResult Data Sheet for Each Stagger, Separation, Length, Speed & Sea State

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Stagger InfluenceStagger Influence15 knots – Maximum Response from All Headings

Pitch Angle

0

0.5

1

1.5

2

2.5

SS4 SS5 SS6 SS7

Stagger = 0.00Stagger = 0.24Stagger = 0.40Stagger = 0.80

Roll Angle

0

1

2

3

4

5

6

7

8

9

10

SS4 SS5 SS6 SS7


Vertical Acceleration at Bow - Centerline

0

0.5

1

1.5

2

2.5

3

SS4 SS5 SS6 SS7


Vertical Acceleration at Stern - Centerline

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

SS4 SS5 SS6 SS7


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Pitch Angle

0

0.5

1

1.5

2

2.5

SS4 SS5 SS6 SS7

Separation = 0.36Separation = 0.75Separation = 1.25

Roll Angle

0

1

2

3

4

5

6

7

8

9

SS4 SS5 SS6 SS7


Vertical Acceleration at Bow - Centerline

0

0.5

1

1.5

2

2.5

3

SS4 SS5 SS6 SS7


Vertical Acceleration at Stern - Centerline

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

SS4 SS5 SS6 SS7

Separation = 0.36

Separation = 0.75

Separation = 1.25

Separation InfluenceSeparation Influence15 knots – Maximum Response from All Headings

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Wave Train Interaction Wave Train Interaction vs. Trimaran Configurationvs. Trimaran ConfigurationEffect of Separation along the Center Hull Effect of Stagger along the Center Hull

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The wave train interaction between the hulls increases the amplitude of the standing wave along the length of the center hull for certain hull configurations. This amplification of center hull waves leads to additional bending moment in the hull girder loads and a wave trough in way of the props, which can induce excessive amounts of propeller emergences.

Wave Train Interaction can have large impact on trimarans performance

Phenomenon can guide the choice

of trimaran hull configuration

More studies are needed to fully

comprehend the impact on design

Wave Train Interaction PhenomenonWave Train Interaction PhenomenonVessel Configuration with 0.8 Stagger Ratio / 0.75 Separation Ratio –

35 knots in Sea State 5

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Structural Design as a Criteria for Structural Design as a Criteria for Seakeeping AssessmentSeakeeping Assessment

The impact of the vessel configurations and hydrodynamic loads on the structural requirements of the vessel are considered in the selection of the optimal design

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Structural Optimization Structural Optimization –– Ongoing Work Ongoing Work The design pressures and accelerations developed with the

hydrodynamic analysis can be translated directly to Finite Element Analysis (FEA) models.

FEA provides a direct assessment of the variations in motions and loads on the structural requirements of the vessel.

Based on present results, a structural optimization routine isbeing developed

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ConclusionsConclusionsSystematic Seakeeping Database Established for Trimarans

Valuable for synthesis level of design

Useful as concept evaluation tools

Will be expanded with future work to include structural optimization

WASIM / SAGA is a reliable and expandable design tool

Strong Wave Train Interaction Phenomenon Identified

Early detection allows problem to be addressed at the hull form development stage

HALSS Provides Favorable Seakeeping Performance

Side hull propeller emergence – limiting factor

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Documents

Trimaran Motion and Load Assessment - viking-systems.net · Trimaran Assessment Presentation Topics: 1. Development of Tool for Motions and Structural Loading Assessment 2. Design