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Modelling and Computer Animation of Damage Stability. K. Hasegawa, K. Ishibashi, Y. Yasuda. Presentation: Marcel van den Elst. Presentation Outline. Historical background damage stability issues Osaka University and Strathclyde University joint research on damage stability

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modelling and computer animation of damage stability

Modellingand Computer Animation of Damage Stability

K. Hasegawa, K. Ishibashi, Y. Yasuda

Presentation: Marcel van den Elst

presentation outline
Presentation Outline
  • Historical background
      • damage stability issues
      • Osaka University and Strathclyde University joint research on damage stability
  • Mathematical Model
      • vectorial Equations of Motion for a damaged ship
      • scalar equations for sway, heave and roll
      • modelling the water ingress
      • residual stability and its calculation
slide3
Simulation of a damaged ship
      • selected ship model and capsizing scenario
      • simulation results
      • steady states
      • possible explanation
  • Computer animation of a damaged ship
      • animation software structure
      • animation software specifications
      • animation video
  • Conclusions
historical background
Historical Background
  • Damage stability issues
      • capsizing of Ro-Ro passenger ferries
      • prediction of (the effects of) water accumulation on bulkhead decks
      • both hydrostatic and hydrodynamic effects
      • need for simulations
  • Osaka University and Strathclyde University
      • Hasegawa’s stay at Strathclyde in 1996 resulted in joint research on damage stability
      • focus on model expansion, simulation and visualisation of simulation results
mathematical model
Mathematical Model
  • General vector Equations of Motion for a damaged ship
  • Scalar equations for sway, heave and roll
  • Modelling the water ingress
  • Residual Stability and its calculation
equations of motion
Equations of Motion
  • General vector Equations of Motion for a damaged ship
slide7
Damaged ship with progressive flooding
      • can be regarded as a single dynamic system
      • 3 dominant motions in beam seas are considered: sway, heave and roll
  • Radiation and Diffraction forces
      • calculated based on Ursell and Tasai method for sectional Lewis forms in still water
  • Froude-Krylov forces
      • calculated based on the Hamamoto method to account for variations of hull submersion in waves
water ingress
Water Ingress
  • water ingress influenced by configuration of the opening area, position of the opening area, wave condition, etc.
  • CFD techniques not yet well enough developed to describe such a highly complex phenomenon
  • Vassalos e.a. proposed a simplified method based on interior and exterior water level difference, with complexities concentrated in flooding coefficient K
residual stability
Residual Stability
  • static stability affected by flooding
  • important because it is used as a standard in stability regulations
  • calculated using an added mass method
slide13
center of each section of the ship hull calculated by the Hamamoto method
      • considers heave and pitch in balance so that
      • heave displacement and pitch angle calculated numerically using the Newton-Raphson method
slide14
GZ(m)

GZ(m)

GZ(m)

Roll (deg)

Roll (deg)

Roll (deg)

  • resulting residual stability curves (Gzdamage)
      • wall sided Ro-Ro passenger ship
      • flooding into two compartments under bulkhead deck

GM=1.5m GM=1.76m GM=2.0m

slide15
GZ(m)

GZ(m)

GZ(m)

Roll (deg)

Roll (deg)

Roll (deg)

  • resulting residual stability curves (Gzdamage)
      • wall sided Ro-Ro passenger ship
      • flooding into the car deck

GM=1.5m GM=1.76m GM=2.0m

simulation of a damaged ship
Simulation of a Damaged Ship
  • ship model and capsizing scenario
  • simulation results
  • steady states
  • possible explanation
slide17
Ship model and capsizing scenario
      • a wall sided Ro-Ro passenger ship like the Estonia
      • a capsizing scenario conform IMO regulations for ship safety:flooding occurring simultaneously into watertight compartments under the bulkhead deck and onto a car deck above the bulkhead deck
      • different compartment layouts have been simulated to show general applicability of the method to ships other than Ro-Ro passenger ships
slide20
capsize

Time(sec)

slide21
H/

Wave period (sec)

  • simulation results show 3 steady states
      • heel to lee side
      • heel to weather side without capsize
      • heel to weather side with capsize
slide22
possible explanation for these states to occur

heel to lee side

      • damage opening above water surface

heel to weather side resulting in capsizing

      • roll moment of the waves larger than the restoring moment of the ship

heel to weather side without capsizing

      • heel moment of accumulated water in phase with the moment of inclination of the ship
      • accumulated water level equals the wave surface
computer animation
Computer Animation
  • important for qualitative understanding of the combined motions in case of flooding
  • two programs produce time-series data for respectively wave and ship motion
  • third program visualizes the scene
      • programmed in OpenInventor, a top layer on OpenGL
slide24
3D animation software program structure

Wave

Generator

Ship Motion

Generator

Ship

Data

3D Simulator

slide25
3D animation simulator specifications
      • simultaneously shows ship motions, waves, and accumulated water inside the flooded compartments
      • video output at 10 frames/second
      • viewpoint and zoom can be adjusted freely with a mouse during the animation to be able to view every part of the ship during the animation
conclusions
Conclusions
  • A mathematical model that accounts for large rolling motions of damaged (passenger) ships in waves has been realised and simulated
  • Three steady state conditions of the damaged ship could be identified
  • A 3D animation software tool has been implemented to visualise the simulations
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