The Effect of a Muddy Bottom on Ship Control

1
The Effect of a Muddy Bottom on Ship Control
www.shallowwater.be

• Guillaume Delefortrie, jr. expert nautical
  research

2
Contents

• Nautical Bottom
• Experimental Research
• Simulations
• Conclusions

3
Contents

• Nautical Bottom
• Experimental Research
• Simulations
• Conclusions

4
Nautical Bottom confined conditions
deep
confined
muddy
5
Nautical Bottom general definitions
6
Nautical Bottom mud levels
Depth?
7
Nautical Bottom

• the level where physical characteristics of
  the bottom reach a critical limit
• beyond which contact with a ships keel causes
  either damage or unacceptable effects on
  controllability and manoeuvrability (PIANC)
• -gt applicable to any bottom

8
Nautical Bottom

• the level where physical characteristics of
  the bottom reach a critical limit
• beyond which contact with a ships keel causes
  either damage or unacceptable effects on
  controllability and manoeuvrability (PIANC)
• -gt applicable to any bottom

9
Nautical Bottom physical characteristics
Critical limit Mud rheology depends of many
time dependent factors and is difficult to
monitor
Water
Interface
210 kHz
Fluid mud
Consolidated mud
33 kHz
Bottom
10
Nautical Bottom density criterion
ZEEBRUGGE
Water
Interface
Fluid mud
occured at a density level of 1.15 ton/m³ or
more
Consolidated mud
Bottom
11
Nautical Bottom

• the level where physical characteristics of
  the bottom reach a critical limit
• beyond which contact with a ships keel causes
  either damage or unacceptable effects on
  controllability and manoeuvrability (PIANC)
• -gt applicable to any bottom

12
Contents

• Nautical Bottom
• Experimental Research
• Simulations
• Conclusions

13
Experimental Research overview
Choose relevant ship and bottom types (Zeebrugge
harbour)
Validate the critical limit with the pilots
Build mathematical model for ship manoeuvring
simulator
14
Experimental Research variables

• 3 ship models
• Bottom conditions
• Layer thickness 0.5 m - 1.5 m - 3.0 m
• Mud density 1100 - 1250 kg/m³
• Mud viscosity 0.04 0.33 Pa.s
• Under keel clearances -12 to 21 (interface)
• -gt artificial mud layer

15
Experimental Research towing tank
16
Contents

• Nautical Bottom
• Experimental Research
• Simulations
• Conclusions

17
Simulations mathematical model

• STEP 1 4 quadrants harbour manoeuvring model
  with a single set of coefficients for each bottom
  and ukc condition

• fast-time the computer performs calculations
  without human interaction
• real-time human interaction allows the user to
  perform a wide range of harbour manoeuvres

18
Simulations fast time

• Advance speed at harbour full (66 rpm)

19
Simulations real time trajectories
Arrival at Zeebrugge, OCHZ Terminal
Starboardside berthing
Portside berthing
20
Simulations real time trajectories
Arrival at Zeebrugge APM Terminal
Departure from Zeebrugge, OCHZ Terminal, portside
berthed
21
Simulations real time evaluation
Criterion controllability of 6000 TEU with 2x45
ton bollard pull
22
Simulations mathematical model

• STEP 2 Include the under keel clearance effect
  above a solid bottom
• STEP 3 Extend this effect to take the muddy
  bottom into account using a fluidization
  parameter F

h
F 1
F 1
F 0
23
Simulations fast time

• Advance speed at harbour full (66 rpm)

Under keel clearance
Speed (m/s)
Mud layer thickness (m)

• Real time to be performed (bow thruster effect)

24
Contents

• Nautical Bottom
• Experimental Research
• Simulations
• Conclusions

25
Conclusions

• Muddy areas the nautical bottom is the level
  where physical characteristics of the bottom
  reach a critical limit beyond which contact with
  a ships keel causes either damage or
  unacceptable effects on controllability and
  manoeuvrability (PIANC)
• Advantages
• Optimised dredging
• Admittance of deep drafted vessels
• Without jeopardizing the safety

26
QUESTIONS AND ANSWERS ONThe Effect of a Muddy
Bottom on Ship Control
www.shallowwater.be

• Guillaume Delefortrie, jr. expert nautical
  research
• THANK YOU FOR YOUR ATTENTION