Articles | Volume 11, issue 3
Nat. Hazards Earth Syst. Sci., 11, 895–903, 2011

Special issue: Extreme and rogue waves

Nat. Hazards Earth Syst. Sci., 11, 895–903, 2011

Research article 22 Mar 2011

Research article | 22 Mar 2011

Occurrence of extreme waves in three-dimensional mechanically generated wave fields propagating over an oblique current

A. Toffoli1,2, L. Cavaleri3, A. V. Babanin1, M. Benoit4, E. M. Bitner-Gregersen5, J. Monbaliu2, M. Onorato6, A. R. Osborne6, and C. T. Stansberg7 A. Toffoli et al.
  • 1Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, P.O. Box 218, Hawthorn, 3122 Vic., Australia
  • 2K.U.Leuven, Kasteelpark Arenberg 40, 3001 Heverlee, Belgium
  • 3Institute of Marine Sciences, Castello 1364/A, 30122 Venice, Italy
  • 4Saint-Venant Laboratory for Hydraulics, Université Paris-Est (joint research unit EDF R&D, CETMEF, Ecole des Ponts ParisTech), 6 quai Watier, BP 49, 78401 Chatou, France
  • 5Det Norske Veritas, Veritasveien 1, 1322 Høvik, Norway
  • 6Dipartimento di Fisica Generale, Università di Torino, Via P. Giuria 1, 10125 Torino, Italy
  • 7Marintek, P.O. Box 4125 Valentinlyst, 7450 Trondheim, Norway

Abstract. Laboratory experiments were performed to study the dynamics of three- dimensional mechanically generated waves propagating over an oblique current in partial opposition. The flow velocity varied along the mean wave direction of propagation with an increasing trend between the wave-maker and the centre of the tank. Tests with regular wave packets traversing the area of positive current gradient showed that the concurrent increase of wave steepness triggered modulational instability on otherwise stable wave trains and hence induced the development of very large amplitude waves. In random directional wave fields, the presence of the oblique current resulted in a weak reinforcement of wave instability with a subsequent increase of the probability of occurrence of extreme events. This seems to partially compensate the suppression of strongly non-Gaussian properties due to directional energy distribution.

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