Wave nonlinearity

The nonlinearity of surface gravity waves refers to their deviations from a sinusoidal shape. In the fields of physical oceanography and coastal engineering, the two categories of nonlinearity are skewness and asymmetry. Wave skewness and asymmetry occur when waves encounter an opposing current or a shallow area.[1][2] As waves shoal in the nearshore zone, in addition to their wavelength and height changing, their asymmetry and skewness also change.[3] Wave skewness and asymmetry are often implicated in ocean engineering and coastal engineering for the modelling of random sea states, in particular regarding the distribution of wave height, wavelength and crest length. For practical engineering purposes, it is important to know the probability of these wave characteristics in seas and oceans at a given place and time. This knowledge is crucial for the prediction of extreme waves, which are a danger for ships and offshore structures. Satellite altimeter Envisat RA-2 data shows geographically coherent skewness fields in the ocean and from the data has been concluded that large values of skewness occur primarily in regions of large significant wave height.[4]

At the nearshore zone, skewness and asymmetry of surface gravity waves are the main drivers for sediment transport.[5]

  1. ^ Elgar, Steve, and R. T. Guza. "Observations of bispectra of shoaling surface gravity waves." Journal of Fluid Mechanics 161.1 (1985): 425-448.
  2. ^ van de Ven, Maartje (2018). "The effects of currents on wave nonlinearities". {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ Doering, J.C.; Bowen, A.J. (1995-09-01). "Parametrization of orbital velocity asymmetries of shoaling and breaking waves using bispectral analysis". Coastal Engineering. 26 (1–2): 15–33. doi:10.1016/0378-3839(95)00007-X. ISSN 0378-3839.
  4. ^ Gómez-Enri, J.; Gommenginger, C. P.; Srokosz, M. A.; Challenor, P. G.; Benveniste, J. (2007-06-01). "Measuring Global Ocean Wave Skewness by Retracking RA-2 Envisat Waveforms". Journal of Atmospheric and Oceanic Technology. 24 (6): 1102–1116. Bibcode:2007JAtOT..24.1102G. doi:10.1175/JTECH2014.1. ISSN 0739-0572.
  5. ^ Ruessink, B. G.; Berg, T. J. J. van den; Rijn, L. C. van (2009). "Modeling sediment transport beneath skewed asymmetric waves above a plane bed". Journal of Geophysical Research: Oceans. 114 (C11). Bibcode:2009JGRC..11411021R. doi:10.1029/2009JC005416. ISSN 2156-2202. S2CID 129854001.