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MEK 4450Marine OperationsKvrner ASA / DNV, Fall 2013

Lesson 2/3

Lift phases

Load out

Transportation

Over boarding

Splash-zone

LoweringSofter system,- resonance

Landing

Recovery

Deck layout

Initial phases

Deck layoutHigh utilizationDeck strengthStrong seafastening, simple to removeSimple lifting routeCrane capacity

OverboardingClearance / clashesPendulum motionsHeeling of vesselRotation. Vessel sides

Systems for controlSet-down on deckGuiding structuresTugger winches

Lifting from deck of vessel

Lifting from deck of vessel

Lifting from deck of vessel

Splash zone

Splash zone

Often dimensioning for crane force

Buoyancy reduces mass of objectCrane wire tension

Sufficient time for air to evacuate

Stability of lifted objectInternal tanksAir filled compartment

Further lowering

Fatigue issues on the load

Effects on the crane and wire

Increased weight of the wire.

Generally no use of AHCDeep water resonance

Landing

Position control vs tolerancesGuiding structuresLines

Landing speedDamage moduleSoil damage (stiff clay)

Reduction of tension in crane wireVessel movement and ballasting

Capacity of AHC

Disconnection of rigging

Recovery

Recovery

Rigging connection points

Suction effects from seabed

Water escapation

No bouyancy+water filledMay be dimensioning for crane

Identical concerns as for deck lift-offGuidance and shock absorbers to be considered

Calculation model for lifting

Crane tip motion: Zc(t) Prescribed

Lifting wire: linear spring. K=EA/L

Lifted object. Z(t) Unknown

L

Calculation model for lifting

Crane wire load: Morison load: Static load:

Response:

Resonance

Solve numerically

Solve analytically: replace to equivalent linear damping

Resonance: neglect damping and loading

Solution,- no damping

Crane tip motion:

Assumed response

Numerical Tools / Analysis Software

Why numerical tools?

More accurate and detailed description

Why comercial tools:

Time consuming to produce inhouse

Better quality checks (?)

Clients acceptance

Typical numerical model

INPUTAB

OUTPUTABMODEL

AB

NotesAB

Disadvantages Advantages

Numerical models

Hydrostatic / stability models (e.g. AutoHydro, Hydro D)

Basic hydrodynamic analyses (e.g. WADAM, WAMIT)

Time domain coupeled analyses (e.g. SIMO)

CFD

Beam theory (e.g. Orcaflex, Riflex)

FEM

Hydrostatic Analysis

Hydrostatic model

INPUTWet hull

shapeMassCOG

OUTPUTFloating conditionStability margins

MODELGeometry: stripesMass and COGArchimedes Buoyancy and

moments

Use with care fornon- standard

aplications

Quick andsimple to use

Purpose madeFor normal shipHull and normal

operations

Hydrodynamic Analysis

Floating object in waves - standard theory

INPUTWet hull

shapeMass

distribution

OUTPUTMotion, pressure ++Transfer functionPostprocessing

MODELGeometry: panelsMass matrixInviscid

IncompressibleVessel: rigid bodyIncident waves

Viscous dampingneglected

Couplings andnonlinearity

neglected

Quick and accuratesolutions when

relevant

Purpose madeFor normal shipHull and normal

operations

Transfer function

Time domain simulationsCOMPLETE MODEL:

Fluid: CFDRigid bodiesElastic mediasInterfaces: Loads,

pressures, deflectionsToo time consuming!

CFD- approachKeep fluid model

accuratePure model

of marine system

Coefficient based approachPrescribed motion for

fluidsRigid bodies and

elastic couplingCoefficient based loading

Time domain simulation program

INPUT(Hydro)dynamic

characteristicsLinks, wires,

beams etcEnvironment

OUTPUTTime series for

motions, forces etcDesign values:post processing

MODELRigid body

motionsForces from

environments andlinks

Quality ofcoefficients?

Time consuming

Realistic modelingof marineoperations

Stepping forwardin time.

Runge Kutta etc

Time Domain Analysis

CFD

CFD

INPUTBoundary

geometry andconditions

Initial conditonsFluid andturbulenceparameters

OUTPUTFields for velocity,

pressure etc atdifferent time stepsIntegrated quantities

MODELViscous fluidTurbulenceBodies with

prescribed motion

Time consumingFloating bodies?

Realistic modelingof fluid flow

Accurate (?) calcs ofcoefficients

Stepping forwardin time.

Runge Kutta etc

Lifting analysis: what is relevant

Vessel Stability Wave

inducedmotions

Strength?

Wire Strength Flexibility

Module Weight & buoyancy Drag & added mass Stability & strength

Lifting analysis: which programs are relevant

Hydrostatic / stability modelsVessel using crane.Module flips around?

Basic hydrodynamic analysesVessel motion

Time domain coupled analysesSeparate rigid bodies equipped with drag coefficients etcEnvironmental condition => environmental responseForce- elongation coupling between vessel and module

CFD: improved quality of coefficients

Structural check

Global and local strength of vessel / deckTransport, storm condition

Module strengthTransportLowering

Wire strength

Edit this text for your titleLift phasesDeck layoutInitial phasesLifting from deck of vesselLifting from deck of vesselLifting from deck of vesselSplash zoneSplash zoneSlide Number 10Further loweringLandingRecoveryRecoveryCalculation model for liftingCalculation model for liftingResonanceSolution,- no dampingNumerical Tools / Analysis SoftwareTypical numerical modelNumerical modelsHydrostatic AnalysisHydrostatic modelHydrodynamic AnalysisFloating object in waves - standard theoryTransfer functionTime domain simulationsTime domain simulation programSlide Number 29CFDCFDLifting analysis: what is relevantLifting analysis: which programs are relevantStructural check