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Challenges in Hydrodynamic Analysis of VLFS

Join the workshop on Very Large Floating Structures for the Future to explore the challenges in hydrodynamic analysis of VLFS. Topics include non-uniformity, station-keeping, consequences of small failures, local phenomena, and small global rigidity. Learn about plate vibrations, wave resonance, deflection in oblique waves, and more. Don't miss this opportunity to engage with experts in the field.

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Challenges in Hydrodynamic Analysis of VLFS

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  1. Workshop on Very Large Floating Structures for the Future Trondheim 28-29 October 2004 Challenges in Hydrodynamic Analysis of VLFS M.Ohkusu ohkusu@jamstec.go.jp

  2. Challenges • Non-uniformity • Station-keeping • Consequence of small failure • Local phenomena • Small global rigidity

  3. Thin plate type: Y Fluid without the platform above X h d Fluid beneath the platform

  4. Thin plate type: Frequency of resonance of 1D vibration: Eqs of vibration Eq. of wave number -b b x

  5. Complex frequency of resonance for a plate (Meylan 2003)

  6. Energy of plate vibration (Meylan 2003)

  7. Transmission T and reflection R coefficients of a plate (Meylan 2003)

  8. Reflection coefficient is zero at

  9. Thin plate type: Frequency of resonance of 2D vibration Periodic in Y direction y x b -b

  10. y x b -b : progressive wave impossible : trapped-mode no incident wave

  11. y x b -b : progressive wave impossible : trapped-mode no incident wave

  12. Complex frequency of resonance (2nd symmetric mode) (Tkhacheva 2000 )

  13. Complex frequency of resonance (2nd asymmetric mode) (Tkhacheva 2000 )

  14. Geometrical optics approach water plate Parabolic approximation

  15. Deflection of a Plate in Oblique Waves at 65.2deg Less Than the Critical Angle (shallow water)

  16. Comparison of Analytical and Numerical Solutions Analytical Numerical

  17. Deflection: Analytical Numerical

  18. Oblique incidence ( Takagi ) Ray approach Full numerical ( Ohmatsu )

  19. Float array Hierarchical Interaction Theory (Kashiwagi) A trouble: Fictitious bodies must not penetrate each other

  20. Wave Pattern around a column-supported VLFS N=32X160(d/a=2) N=16X80(d/a=1) In a wave of L/λ=32.59 coming from upper right

  21. Experiment (Kashiwagi)

  22. Wave elevation between floats

  23. Wave exciting surge & heave forces

  24. Wave exciting surge & heave forces

  25. Steady Wave Drift Force ; inside(left) & outside (right)

  26. y x b -b : progressive wave impossible : trapped-mode no incident wave

  27. Complex frequency of resonance (2nd symmetric mode) (Tkhacheva 2000 )

  28. Complex frequency of resonance (2nd asymmetric mode) (Tkhacheva 2000 )

  29. Geometrical optics approach water plate Parabolic approximation

  30. Deflection of a Plate in Oblique Waves at 65.2deg Less Than the Critical Angle (shallow water)

  31. Comparison of Analytical and Numerical Solutions Analytical Numerical

  32. Deflection: Analytical Numerical

  33. Oblique incidence ( Takagi ) Ray approach Full numerical ( Ohmatsu )

  34. Float array Hierarchical Interaction Theory (Kashiwagi) A trouble: Fictitious bodies must not penetrate each other

  35. Wave Pattern around a column-supported VLFS N=32X160(d/a=2) N=16X80(d/a=1) In a wave of L/λ=32.59 coming from upper right

  36. Experiment (Kashiwagi)

  37. Wave elevation between floats

  38. Wave exciting surge & heave forces

  39. Wave exciting surge & heave forces

  40. Steady Wave Drift Force ; inside(left) & outside (right)

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