Field measurement of nonlinear changes to large gravity wave groups. (25th August 2019)

• Record Type: Journal Article
• Authors: Tang, Tianning; Tromans, Peter S.; Adcock, Thomas A. A.
• Is Part Of: Journal of fluid mechanics. Volume 873(2019)
• Page Start: 1158
• Page End: 1178
• Publication Date: 2019-08-25
• Subjects: surface gravity waves; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2019.454
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : The dynamics of large gravity waves are known to be modified from the linear model by nonlinear physics. In this paper we analyse Eulerian surface elevation time histories measured from two sites, Lake George (Australia) and the North Sea, to examine how weak nonlinearity has modified the shape of extreme wave groups relative to linear theory. We analyse the asymmetry of the extreme wave groups and find that, on average, the wave in front of an extreme wave is smaller than the wave following it. We also observe a contraction in the envelope width of the wave group relative to linear theory. The departures from linear theory are strongly correlated with the steepness of the underlying sea state and are generally consistent with theoretical expectations, providing strong evidence that such nonlinear phenomena arise in naturally occurring water waves.