Numéro : 2380 - Year : 2001
Rogue waves and damages at sea
Michel. HUTHER, BUREAU VERITAS - Division Marine
Jean Claude. LE HIRE, BUREAU VERITAS - Division Marine
Michel OLAGNON, IFREMER - Cellule Océano Météo
Recent accidents at sea, including the loss of the Derbyshire, have brought back to the attention of marine engineers the phenomenon named 'Freak wave' that caused many losses in the seventies along the shores of South Africa. A workshop organized in Brest by Ifremer in November 2000 has allowed to assess the state of the art on that topic. The paper intends, after a short historical reminder, to describe the phenomenon and to detail its most probable causes according to present studies. Observations and acceleration and strain measurements on a ship are presented to illustrate the phenomenon and the ship structural response. The consequences of the encounter between a ship and a rogue wave are analysed with reference to observed damage. It may be concluded that if one is entitled to qualify the phenomenon as exceptional, it is not by its existence but because of the unpredictable and giant nature of the corresponding waves. Engineers are thus faced with a dilemna: although it is unrealistic to design ships able to withstand such waves, it is unacceptable that human lives should be lost as a consequence. A direction of action might be taking into account the survival capacity of the ship after she has encountered such a giant wave, as it is the case for stability in damaged condition.