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The Effect of a Muddy Bottom on Ship Control

www.shallowwater.be. The Effect of a Muddy Bottom on Ship Control. Guillaume Delefortrie, jr. expert nautical research. Contents. Nautical Bottom Experimental Research Simulations Conclusions. Contents. Nautical Bottom Experimental Research Simulations Conclusions.

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The Effect of a Muddy Bottom on Ship Control

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  1. www.shallowwater.be The Effect of a Muddy Bottom on Ship Control 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. Draft T Depth h Under keel clearance (h-T)/T Nautical Bottom: general definitions

  6. Nautical Bottom: mud levels Depth? 210 kHz 33 kHz 1150 kg/m3 1200 kg/m3

  7. Nautical Bottom =the level where physical characteristics of the bottom reach a critical limit beyond which contact with a ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability (PIANC) -> applicable to any bottom

  8. Nautical Bottom =the level where physical characteristics of the bottom reach a critical limit beyond which contact with a ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability (PIANC) -> 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 ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability (PIANC) -> 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) -> 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. Speed (kn) Under keel clearance (interface) 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. h1(N) h1(N) h2(N) h1(N) h 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 ship’s 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. www.shallowwater.be QUESTIONS AND ANSWERS ONThe Effect of a Muddy Bottom on Ship Control Guillaume Delefortrie, jr. expert nautical research THANK YOU FOR YOUR ATTENTION

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