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MEASUREMENTS OF FREAK WAVES IN NORWAY AND RELATED SHIP ACCIDENTS.

MEASUREMENTS OF FREAK WAVES IN NORWAY AND RELATED SHIP ACCIDENTS. Søren Peter Kjeldsen Trondheim Maritime Academy Norway. BASIS FOR DESIGN :. The accident with the semisubmersible platform OCEAN RANGER , started this investigation.

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MEASUREMENTS OF FREAK WAVES IN NORWAY AND RELATED SHIP ACCIDENTS.

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  1. MEASUREMENTS OF FREAK WAVES IN NORWAY AND RELATED SHIP ACCIDENTS. Søren PeterKjeldsen Trondheim Maritime Academy Norway. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  2. BASIS FOR DESIGN : • The accident with the semisubmersible platform OCEAN RANGER , started this investigation. • A World Data Bank with ship and offshore installation accidents caused by extreme waves is established. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  3. Fig. 4. Example of extreme bow acceleration and stress mea AREAS WITH FREAK WAVES 1 New Foundland Banks 20. 21. 2 The Sea south of Greenland 3 Coastal areas near Iceland 4 Coastal areas near Færø Islands 5 Coastal areason the Norwegian coast 6 The North sea 7 The Baltic Sea 15 The South China Sea 16 The Japan Sea 17 The Pacific Sea east of Japan 18 Coastal areas near Australia 19 Areas south of 40 degr. South 20 Mediterranean Sea 21 Great Lakes 8 The Biscay Bay 9 Gulf Stream on the east coast of USA. 10 The Mexican Gulf 11 The Sea west of British Columbia. 12 The Sea near Cap Horn 13 Aghulhas current east of South Africa 14 The Bengal Sea Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  4. FIG 1. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  5. BREAKING CRITERIA • A Breaking Criteria for extreme irregular waves is based on : • CREST FRONT STEPNESS Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  6. Breaking Freak Wave Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  7. Time history of bow acceleration Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  8. Experiments with freak waves: • ·The “Tsunami Wave Model reversed in the time domain was found to be a succesfull mathematical technique for modeling of a 3-dimensional freak wave. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  9. A 3-dimensional freak wave Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  10. BASIS FOR DESIGN FULL SCALE MEASUREMENTS OF IMPACT FORCES ON A PLATFORM. • Drag and lift forces in extremes waves mapped from measurements in a : Large research programme with segmented pile structure. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  11. CONCLUSION 1: • The basis for computation of forces caused by extreme waves • Is an analysis in the time domain • Of the wave crest front steepness Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  12. CONCLUSION 2: • The experimental programs clearly shows that extreme wave load intensities are associated with transient 2– or 3-dimensional breaking waves and not with the highest waves. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  13. BREAKING CRITERIA: • The experiments show that irregular storm waves break when crest front steepness is in the range: • 0.32 – 0.78 measured in the synoptic domain. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  14. CONCLUSION 4: • Experiments show that wave crest particle velocities can reach values as high as 2.8 times the phase velocity. • Several mathematical models are now developed to predict crest kinematics. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  15. SCALE EFFECTS: • Green Water Impacts are measured on a platform at sea and stored in a data bank. • Impact forces did not follow Froudes Law for scaling of experiments. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

  16. Info: Peter.kjeldsen@c2i.netBooksVideo-Filmsand CD-romsare avaiable. Peter Kjeldsen: FREAK WAVES AND SHIP ACCIDENTS

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