Individual violent wave-overtopping events: behaviour and estimation

Alison Raby*, Ravindra Jayaratne, Henrik Bredmose, Geoff Bullock

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

To better understand individual violent wave overtopping, of significance for coastal defence design, three breaking wave types (steep-fronted, plunging and broken) based on focused wave groups, were generated in laboratory and numerical models. High-speed video captured overtopping events and produced velocity vector maps by means of bubble image velocimetry (BIV). Results were compared with a numerical model based on a linear wave detection procedure and a two-phase incompressible Navier–Stokes-based solver. This novel approach revealed that the overtopping waves comprised an initial jet of 0.2 s duration, but dominated by quasi-steady flow. Whilst laboratory surface-elevation time-histories were highly repeatable, overtopping volume repeats were sensitive to the breaker type. Measured volumes were compared with: the numerical model (which over-predicted, but was reasonably accurate for steep-fronted waves); estimations based on BIV results (which provided very close agreement for the steep-fronted waves); and a weir-based analogy (which provided reasonable agreement, but always under-predicted).
Original languageEnglish
JournalJournal of Hydraulic Research
Number of pages13
ISSN0022-1686
DOIs
Publication statusAccepted/In press - 2019

Keywords

  • Breaking waves
  • Bubble image velocimetry
  • Coastal engineering
  • Flow visualization and imaging
  • Incompresible Navier-Stokes solver
  • Laboratory studies
  • Violent wave overtopping

Cite this

@article{8c8d26deed1e402eb930a713851383b2,
title = "Individual violent wave-overtopping events: behaviour and estimation",
abstract = "To better understand individual violent wave overtopping, of significance for coastal defence design, three breaking wave types (steep-fronted, plunging and broken) based on focused wave groups, were generated in laboratory and numerical models. High-speed video captured overtopping events and produced velocity vector maps by means of bubble image velocimetry (BIV). Results were compared with a numerical model based on a linear wave detection procedure and a two-phase incompressible Navier–Stokes-based solver. This novel approach revealed that the overtopping waves comprised an initial jet of 0.2 s duration, but dominated by quasi-steady flow. Whilst laboratory surface-elevation time-histories were highly repeatable, overtopping volume repeats were sensitive to the breaker type. Measured volumes were compared with: the numerical model (which over-predicted, but was reasonably accurate for steep-fronted waves); estimations based on BIV results (which provided very close agreement for the steep-fronted waves); and a weir-based analogy (which provided reasonable agreement, but always under-predicted).",
keywords = "Breaking waves, Bubble image velocimetry, Coastal engineering, Flow visualization and imaging, Incompresible Navier-Stokes solver, Laboratory studies, Violent wave overtopping",
author = "Alison Raby and Ravindra Jayaratne and Henrik Bredmose and Geoff Bullock",
year = "2019",
doi = "10.1080/00221686.2018.1555549",
language = "English",
journal = "Journal of Hydraulic Research",
issn = "0022-1686",
publisher = "CRC Press/Balkema",

}

Individual violent wave-overtopping events: behaviour and estimation. / Raby, Alison; Jayaratne, Ravindra; Bredmose, Henrik; Bullock, Geoff.

In: Journal of Hydraulic Research, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Individual violent wave-overtopping events: behaviour and estimation

AU - Raby, Alison

AU - Jayaratne, Ravindra

AU - Bredmose, Henrik

AU - Bullock, Geoff

PY - 2019

Y1 - 2019

N2 - To better understand individual violent wave overtopping, of significance for coastal defence design, three breaking wave types (steep-fronted, plunging and broken) based on focused wave groups, were generated in laboratory and numerical models. High-speed video captured overtopping events and produced velocity vector maps by means of bubble image velocimetry (BIV). Results were compared with a numerical model based on a linear wave detection procedure and a two-phase incompressible Navier–Stokes-based solver. This novel approach revealed that the overtopping waves comprised an initial jet of 0.2 s duration, but dominated by quasi-steady flow. Whilst laboratory surface-elevation time-histories were highly repeatable, overtopping volume repeats were sensitive to the breaker type. Measured volumes were compared with: the numerical model (which over-predicted, but was reasonably accurate for steep-fronted waves); estimations based on BIV results (which provided very close agreement for the steep-fronted waves); and a weir-based analogy (which provided reasonable agreement, but always under-predicted).

AB - To better understand individual violent wave overtopping, of significance for coastal defence design, three breaking wave types (steep-fronted, plunging and broken) based on focused wave groups, were generated in laboratory and numerical models. High-speed video captured overtopping events and produced velocity vector maps by means of bubble image velocimetry (BIV). Results were compared with a numerical model based on a linear wave detection procedure and a two-phase incompressible Navier–Stokes-based solver. This novel approach revealed that the overtopping waves comprised an initial jet of 0.2 s duration, but dominated by quasi-steady flow. Whilst laboratory surface-elevation time-histories were highly repeatable, overtopping volume repeats were sensitive to the breaker type. Measured volumes were compared with: the numerical model (which over-predicted, but was reasonably accurate for steep-fronted waves); estimations based on BIV results (which provided very close agreement for the steep-fronted waves); and a weir-based analogy (which provided reasonable agreement, but always under-predicted).

KW - Breaking waves

KW - Bubble image velocimetry

KW - Coastal engineering

KW - Flow visualization and imaging

KW - Incompresible Navier-Stokes solver

KW - Laboratory studies

KW - Violent wave overtopping

U2 - 10.1080/00221686.2018.1555549

DO - 10.1080/00221686.2018.1555549

M3 - Journal article

JO - Journal of Hydraulic Research

JF - Journal of Hydraulic Research

SN - 0022-1686

ER -