Strong solutions for the Alber equation and stability of unidirectional wave spectra

Agissilaos G. Athanassoulis, Gerassimos A. Athanassoulis, Mariya Ptashnyk, Themistoklis Sapsis

Research output: Contribution to journalArticle

Abstract

The Alber equation is a moment equation for the nonlinear Schrodinger equation, formally used in ocean engineering to investigate the stability of stationary and homogeneous sea states in terms of their power spectra. In this work we present the first well-posedness theory for the Alber equation with the help of an appropriate equivalent reformulation. Moreover, we show linear Landau damping in the sense that, under a stability condition on the homogeneous background, any inhomogeneities disperse and decay in time. The proof exploits novel L2 space-time estimates to control the inhomogeneity and our result applies to any regular initial data (without a mean-zero restriction). Finally, the sufficient condition for stability is resolved, and the physical implications for ocean waves are discussed. Using a standard reference dataset (the \North Atlantic Scatter Diagram") it is found that the vast majority of sea states are stable, but modulationally unstable sea states do appear, with likelihood O(1/1000); these would be the prime breeding ground for rogue waves.

Original languageEnglish
Pages (from-to)703-737
Number of pages35
JournalKinetic and Related Models
Volume13
Issue number4
Early online date1 May 2020
DOIs
Publication statusE-pub ahead of print - 1 May 2020

Keywords

  • Alber equation
  • Landau damping
  • Modulation instability
  • Ocean wave spectra
  • Penrose condition
  • Wigner transform

ASJC Scopus subject areas

  • Numerical Analysis
  • Modelling and Simulation

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