Edit this text for your title MEK 4450 Marine Operations Edit this text for your sub-title Presenter name, location, date etc. Kværner ASA / DNV, Fall 2013 Lesson 2/3
Lift phases Load out Transportation Over boarding Splash-zone Lowering Softer system,- resonance Landing Recovery
Deck layout
Initial phases Deck layout High utilization Deck strength Strong seafastening, simple to remove Simple lifting route Crane capacity Overboarding Clearance / clashes Pendulum motions Heeling of vessel Rotation. Vessel sides Systems for control Set-down on deck Guiding structures Tugger 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 object Crane wire tension Sufficient time for air to evacuate Stability of lifted object Internal tanks Air filled compartment
Further lowering Fatigue issues on the load Effects on the crane and wire Increased weight of the wire. Generally no use of AHC Deep water resonance
Landing Position control vs tolerances Guiding structures Lines Landing speed Damage module Soil damage (stiff clay) Reduction of tension in crane wire Vessel movement and ballasting Capacity of AHC Disconnection of rigging
Recovery
Recovery Rigging connection points Suction effects from seabed Water escapation No bouyancy+water filled May be dimensioning for crane Identical concerns as for deck lift-off Guidance and shock absorbers to be considered
Calculation model for lifting Crane tip motion: Zc(t) Prescribed L Lifting wire: linear spring. K=EA/L Lifted object. Z(t) Unknown
Calculation model for lifting Crane wire load: Morison load: Static load: Response: ಳ ష
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 INPUT A B Disadvantages MODEL A B Notes A B OUTPUT A B 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 INPUT Wet hull shape Mass COG Use with care for non- standard aplications MODEL Geometry: stripes Mass and COG Archimedes Buoyancy and moments Purpose made For normal ship Hull and normal operations OUTPUT Floating condition Stability margins Quick and simple to use
Hydrodynamic Analysis
Floating object in waves - standard theory INPUT Wet hull shape Mass distribution Viscous damping neglected Couplings and nonlinearity neglected MODEL Geometry: panels Mass matrix Inviscid Incompressible Vessel: rigid body Incident waves Purpose made For normal ship Hull and normal operations OUTPUT Motion, pressure ++ Transfer function Postprocessing Quick and accurate solutions when relevant
Transfer function
Time domain simulations COMPLETE MODEL: Fluid: CFD Rigid bodies Elastic medias Interfaces: Loads, pressures, deflections Too time consuming! CFD- approach Keep fluid model accurate Pure model of marine system Coefficient based approach Prescribed motion for fluids Rigid bodies and elastic coupling Coefficient based loading
Time domain simulation program INPUT (Hydro)dynamic characteristics Links, wires, beams etc Environment Quality of coefficients? Time consuming MODEL Rigid body motions Forces from environments and links Stepping forward in time. Runge Kutta etc OUTPUT Time series for motions, forces etc Design values: post processing Realistic modeling of marine operations
Time Domain Analysis
CFD
CFD INPUT Boundary geometry and conditions Initial conditons Fluid and turbulence parameters Time consuming Floating bodies? MODEL Viscous fluid Turbulence Bodies with prescribed motion Stepping forward in time. Runge Kutta etc OUTPUT Fields for velocity, pressure etc at different time steps Integrated quantities Realistic modeling of fluid flow Accurate (?) calcs of coefficients
Lifting analysis: what is relevant Wire Strength Flexibility Vessel Stability Wave induced motions Strength? Module Weight & buoyancy Drag & added mass Stability & strength
Lifting analysis: which programs are relevant Hydrostatic / stability models Vessel using crane. Module flips around? Basic hydrodynamic analyses Vessel motion Time domain coupled analyses Separate rigid bodies equipped with drag coefficients etc Environmental condition => environmental response Force- elongation coupling between vessel and module CFD: improved quality of coefficients
Structural check Global and local strength of vessel / deck Transport, storm condition Module strength Transport Lowering Wire strength