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Ship motion in waves prediction of dynamic stability

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**1. **TUMST Ship Manoeuvrability - Theory and Assessment- 1 Ship motion in waves ? prediction of dynamic stability ? Toshio Iseki
Tokyo University of Marine Science and Technology

**2. **TUMST Ship Manoeuvrability - Theory and Assessment- 2 IMO (International Maritime Organization) IS Code
(Code on Intact Stability for All Types of Ships Covered by IMO Instruments)
3.1 General intact stability criteria for all ships
3.2 Severe wind and rolling criterion (weather criterion)
To be revised in 2007
Weather criterion (SLF 47)
Guidance to the Master for Avoiding Dangerous Situations in Following and Quartering Seas (MSC Circ.707)
Dynamic phenomena in seaways
Restoring arm variation problems
Dead ship condition (beam sea resonance)
Manoeuvring related problems (broaching-to) As you well know, all ships require to be controllable in direction in the horizontal plane in order to prevent marine casualties happening. In 1993, the Maritime safety committee established the interim standards for ship manoeuvrability and, in 2002, the MSC adopted resolution MSC.137 on Standards for ship manoeuvrability. The main aim of the resolution is to exclude the ships that were built with very poor manoeuvring qualities. Therefore, understanding the theory and assessment of ship manoeuvring performance is still very important.As you well know, all ships require to be controllable in direction in the horizontal plane in order to prevent marine casualties happening. In 1993, the Maritime safety committee established the interim standards for ship manoeuvrability and, in 2002, the MSC adopted resolution MSC.137 on Standards for ship manoeuvrability. The main aim of the resolution is to exclude the ships that were built with very poor manoeuvring qualities. Therefore, understanding the theory and assessment of ship manoeuvring performance is still very important.

**3. **TUMST Ship Manoeuvrability - Theory and Assessment- 3 IMO (International Maritime Organization) Restoring arm variation problems
Parametric oscillation
Pure loss of stability
Stability problems occurring for any ship having large righting arm variations between trough and crest condition.
As you well know, all ships require to be controllable in direction in the horizontal plane in order to prevent marine casualties happening. In 1993, the Maritime safety committee established the interim standards for ship manoeuvrability and, in 2002, the MSC adopted resolution MSC.137 on Standards for ship manoeuvrability. The main aim of the resolution is to exclude the ships that were built with very poor manoeuvring qualities. Therefore, understanding the theory and assessment of ship manoeuvring performance is still very important.As you well know, all ships require to be controllable in direction in the horizontal plane in order to prevent marine casualties happening. In 1993, the Maritime safety committee established the interim standards for ship manoeuvrability and, in 2002, the MSC adopted resolution MSC.137 on Standards for ship manoeuvrability. The main aim of the resolution is to exclude the ships that were built with very poor manoeuvring qualities. Therefore, understanding the theory and assessment of ship manoeuvring performance is still very important.

**4. **TUMST Ship Manoeuvrability - Theory and Assessment- 4 Contents Basic theory of ship stability
Meta-centric height
Stability curve
Dynamic stability in waves
Wetted surface & dynamic pressure
Instability of rolling motion in waves
Simple simulation program
Short presentation This lecture is devoted mainly to the conventional rudder steered ship.This lecture is devoted mainly to the conventional rudder steered ship.

**5. **TUMST Ship Manoeuvrability - Theory and Assessment- 5 Meta-centric height “GM”

**6. **TUMST Ship Manoeuvrability - Theory and Assessment- 6 Meta-centric height “GM”

**7. **TUMST Ship Manoeuvrability - Theory and Assessment- 7 Evaluation of GM

**8. **TUMST Ship Manoeuvrability - Theory and Assessment- 8 Actual ship configuration

**9. **TUMST Ship Manoeuvrability - Theory and Assessment- 9 Righting lever GZ (Restoring arm)

**10. **TUMST Ship Manoeuvrability - Theory and Assessment- 10 GZ Curve

**11. **TUMST Ship Manoeuvrability - Theory and Assessment- 11 Dynamic stability

**12. **TUMST Ship Manoeuvrability - Theory and Assessment- 12 Underwater configuration in waves

**13. **TUMST Ship Manoeuvrability - Theory and Assessment- 13 Underwater configuration in waves

**14. **TUMST Ship Manoeuvrability - Theory and Assessment- 14 GZ curves in waves

**15. **TUMST Ship Manoeuvrability - Theory and Assessment- 15 Displacement of the center of buoyancy

**16. **TUMST Ship Manoeuvrability - Theory and Assessment- 16 Displacement of the center of buoyancy

**17. **TUMST Ship Manoeuvrability - Theory and Assessment- 17 Dangerous condition Deep water

**18. **TUMST Ship Manoeuvrability - Theory and Assessment- 18 Container ship (Lpp=300m)

**19. **TUMST Ship Manoeuvrability - Theory and Assessment- 19 Estimation of ship stability in waves

**20. **TUMST Ship Manoeuvrability - Theory and Assessment- 20 Co-ordinate systems First of all, we have to define the co-ordinate systems to make up the equations of motion. Let’s consider a ship with constant speed vector U.First of all, we have to define the co-ordinate systems to make up the equations of motion. Let’s consider a ship with constant speed vector U.

**21. **TUMST Ship Manoeuvrability - Theory and Assessment- 21 Co-ordinate system

**22. **TUMST Ship Manoeuvrability - Theory and Assessment- 22 Equations of waves In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.

**23. **TUMST Ship Manoeuvrability - Theory and Assessment- 23 Equations of waves In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.

**24. **TUMST Ship Manoeuvrability - Theory and Assessment- 24 Equations of waves In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.

**25. **TUMST Ship Manoeuvrability - Theory and Assessment- 25 Equations of pressure In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.In general case, we need only consider equations of motion along the x and y axes and angular motion about the z axis for a surface ship.
It should be noted that the equations are based on the body axes not on the space axes.

**26. **TUMST Ship Manoeuvrability - Theory and Assessment- 26 Simple Simulation of rolling motion in waves

**27. **TUMST Ship Manoeuvrability - Theory and Assessment- 27 Simulation of rolling motion in waves

**28. **TUMST Ship Manoeuvrability - Theory and Assessment- 28 GZ curves of the ship

**29. **TUMST Ship Manoeuvrability - Theory and Assessment- 29 Summary Basic theory of ship stability
Dynamic phenomena in seaways
Restoring arm variation problems
Simple simulation of roll in waves

**30. **TUMST Ship Manoeuvrability - Theory and Assessment- 30 Ship motion in waves ? prediction of dynamic stability ? The end

**31. **TUMST Ship Manoeuvrability - Theory and Assessment- 31 Assignment Suppose that a ship is traveling at the speed of 20 knots in following seas and the ship’s length is 200 (m). From the viewpoint of the restoring arm variation problem,
Estimate the speed of the most dangerous wave.
Calculate the encounter period.