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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union

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Nat. Hazards Earth Syst. Sci., 11, 895-903, 2011
http://www.nat-hazards-earth-syst-sci.net/11/895/2011/
doi:10.5194/nhess-11-895-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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 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.

Citation: Toffoli, A., Cavaleri, L., Babanin, A. V., Benoit, M., Bitner-Gregersen, E. M., Monbaliu, J., Onorato, M., Osborne, A. R., and Stansberg, C. T.: Occurrence of extreme waves in three-dimensional mechanically generated wave fields propagating over an oblique current, Nat. Hazards Earth Syst. Sci., 11, 895-903, doi:10.5194/nhess-11-895-2011, 2011.
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