PREDICTING THE BREAKING STRENGTH OF GRAVITY WATER WAVES FROM DEEP TO SHALLOW WATER

James T Kirby,Michael L Banner,Stephan Grilli,Morteza Derakhti

doi:10.9753/icce.v36.waves.9

Abstract

We revisit the classical but as yet unresolved problem of predicting the breaking strength of 2-D and 3-D gravity water waves.Our goal is to find a robust and local parameterization to predict the breaking strength of 2-D and 3-D gravity water waves. We use a LES/VOF model described by Derakhti & Kirby (2014) to simulate nonlinear wave evolution, breaking onset and post-breaking behavior for representative cases of focused wave packets or modulated wave trains. Using these numerical results, we investigate the relationship between the breaking strength parameter b and the breaking onset parameter B proposed by Barthelemy et al. (2018). While the results are potentially applicable more generally, in this paper we concentrate on breaking events due to focusing or modulational instability in wave packets over flat bottom topography and for conditions ranging from deep to intermediate depth, with depth to wavelength ratios ranging from 0.68 to 0.13.

Highlights

Phillips/Duncan spectral framework for the mean breaking crest length per unit area, combined with a scaling argument for the wave energy dissipation rate per unit length of breaking crest, giving a total dissipation written as
WORK The results shown here show a systematic collapse of the proposed breaking strength predictor G for a diverse range of representative 2D and 3D water wave trains
The success of the parameterization for predicting breaking strength found here would make it possible to better describe breaking events in codes based on potential flow theory, such as high-order spectral (HOS) codes, where breaking is not predicted by the model itself

Summary

Introduction

Phillips/Duncan spectral framework for the mean breaking crest length per unit area, combined with a scaling argument for the wave energy dissipation rate per unit length of breaking crest, giving a total dissipation written as. Further targeted study of representative cases of the most severe laterally-focused 3-D wave packets in deep and intermediate depth water shows that the threshold remains robust. These numerical findings for 2-D and 3-D cases have since been supported by laboratory observations. We use a LES/VOF model described by Derakhti & Kirby (2014) to simulate nonlinear wave evolution, breaking onset and post-breaking behavior for representative cases of focused wave packets or modulated wave trains Using these numerical results, we investigate the relationship between the breaking strength parameter b and the breaking onset parameter B proposed by Barthelemy et al (2018). While the results are potentially applicable more generally, in this paper we concentrate on breaking events due to focusing or modulational instability in wave packets over flat bottom topography and for conditions ranging from deep to intermediate depth, with depth to wavelength ratios ranging from 0.68 to 0.13

Objectives

Findings

Conclusion