On estimating extremes in an evolving wave field

A. K. Magnusson, M. A. Donelan, W. M. Drennan

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

Observations of waves as a time series from a fixed or moored sensor are shown to underestimate the extreme waves occurring in the vicinity. The underestimate arises because of the difference in phase and envelope propagation of surface water waves so that the highest crest, for example, is recorded only when the crest coincides with the envelope maximum at the location of the wave recorder. In addition, the dispersive nature of water waves can lead to the coalescence of groups of waves as longer waves catch up to shorter slower waves, so that the group shape changes markedly as the waves propagate. Moored accelerometer buoys introduce another error that exacerbates the underestimate of the highest crest-the quasi-Lagrangian motion of the buoy leads to flattening of the crests and sharpening of the troughts so that apparent mean water level is raised and thus the height of crests above it is reduced. An analysis approach to correct these underestimates is outlined and tested with observed data against the predictions of extreme values based on narrow-banded random wave theory.

Original languageEnglish (US)
Pages (from-to)147-163
Number of pages17
JournalCoastal Engineering
Volume36
Issue number2
DOIs
StatePublished - Mar 1 1999

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Keywords

  • Buoy measurements
  • Extreme waves
  • Rayleigh distribution
  • Wave evolution
  • Wave forces on structures
  • Wave groups

ASJC Scopus subject areas

  • Environmental Engineering
  • Ocean Engineering

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