Flow and Turbulence at Rubble-Mound Breakwater Armor Layers under Solitary Wave

Bjarne Jensen, Erik Damgaard Christensen, B. Mutlu Sumer, Martin Vistisen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

This paper presents the results of an experimental investigation of the flow and turbulence at the armor layer of rubble-mound breakwaters during wave action. The study focused on the details of the flow and turbulence in the armor layer and on the effect of the porous core on flow and stability. To isolate the processes involved with the flow in the porous core, experiments were conducted with increasing complexity. Specifically, three parallel experiments were performed including (1) an impermeable smooth breakwater slope, (2) an impermeable breakwater slope with large roughness elements added to the breakwater, and (3) a porous breakwater where the porous core was added below the breakwater front. One breakwater slope of 1:1.5 was applied. In this paper the focus is on the details of a single sequence of wave approach, run-up, and rundown. To isolate this sequence the experiments were performed applying a solitary wave. The individual sources of turbulence generation were distinguished using Laser Doppler anemometry measurements, and the effect of the armor layer and porous core was described in terms of a reduced impact of the rundown process, production of lee wake turbulence, and less transport of turbulence above the armor layer. The shear stresses were evaluated from the measurements of turbulence, and they were associated with the run-up and rundown phases. The Shields parameter, determined from the shear stresses, was found to be reduced by 30% as a result of the porous core material.
Original languageEnglish
Article number04015006
JournalJournal of Waterway, Port, Coastal, and Ocean Engineering
Volume141
Issue number6
Number of pages14
ISSN0733-950X
DOIs
Publication statusPublished - 2015

Keywords

  • Wave-structure interaction
  • Rubble-mound breakwaters
  • Porous flow
  • Turbulence
  • Shear stresses
  • Breakwater stability
  • Model scale experiments

Cite this

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title = "Flow and Turbulence at Rubble-Mound Breakwater Armor Layers under Solitary Wave",
abstract = "This paper presents the results of an experimental investigation of the flow and turbulence at the armor layer of rubble-mound breakwaters during wave action. The study focused on the details of the flow and turbulence in the armor layer and on the effect of the porous core on flow and stability. To isolate the processes involved with the flow in the porous core, experiments were conducted with increasing complexity. Specifically, three parallel experiments were performed including (1) an impermeable smooth breakwater slope, (2) an impermeable breakwater slope with large roughness elements added to the breakwater, and (3) a porous breakwater where the porous core was added below the breakwater front. One breakwater slope of 1:1.5 was applied. In this paper the focus is on the details of a single sequence of wave approach, run-up, and rundown. To isolate this sequence the experiments were performed applying a solitary wave. The individual sources of turbulence generation were distinguished using Laser Doppler anemometry measurements, and the effect of the armor layer and porous core was described in terms of a reduced impact of the rundown process, production of lee wake turbulence, and less transport of turbulence above the armor layer. The shear stresses were evaluated from the measurements of turbulence, and they were associated with the run-up and rundown phases. The Shields parameter, determined from the shear stresses, was found to be reduced by 30{\%} as a result of the porous core material.",
keywords = "Wave-structure interaction, Rubble-mound breakwaters, Porous flow, Turbulence, Shear stresses, Breakwater stability, Model scale experiments",
author = "Bjarne Jensen and Christensen, {Erik Damgaard} and Sumer, {B. Mutlu} and Martin Vistisen",
year = "2015",
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journal = "Journal of Waterway, Port, Coastal, and Ocean Engineering",
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Flow and Turbulence at Rubble-Mound Breakwater Armor Layers under Solitary Wave. / Jensen, Bjarne; Christensen, Erik Damgaard; Sumer, B. Mutlu; Vistisen, Martin.

In: Journal of Waterway, Port, Coastal, and Ocean Engineering, Vol. 141, No. 6, 04015006, 2015.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Flow and Turbulence at Rubble-Mound Breakwater Armor Layers under Solitary Wave

AU - Jensen, Bjarne

AU - Christensen, Erik Damgaard

AU - Sumer, B. Mutlu

AU - Vistisen, Martin

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AB - This paper presents the results of an experimental investigation of the flow and turbulence at the armor layer of rubble-mound breakwaters during wave action. The study focused on the details of the flow and turbulence in the armor layer and on the effect of the porous core on flow and stability. To isolate the processes involved with the flow in the porous core, experiments were conducted with increasing complexity. Specifically, three parallel experiments were performed including (1) an impermeable smooth breakwater slope, (2) an impermeable breakwater slope with large roughness elements added to the breakwater, and (3) a porous breakwater where the porous core was added below the breakwater front. One breakwater slope of 1:1.5 was applied. In this paper the focus is on the details of a single sequence of wave approach, run-up, and rundown. To isolate this sequence the experiments were performed applying a solitary wave. The individual sources of turbulence generation were distinguished using Laser Doppler anemometry measurements, and the effect of the armor layer and porous core was described in terms of a reduced impact of the rundown process, production of lee wake turbulence, and less transport of turbulence above the armor layer. The shear stresses were evaluated from the measurements of turbulence, and they were associated with the run-up and rundown phases. The Shields parameter, determined from the shear stresses, was found to be reduced by 30% as a result of the porous core material.

KW - Wave-structure interaction

KW - Rubble-mound breakwaters

KW - Porous flow

KW - Turbulence

KW - Shear stresses

KW - Breakwater stability

KW - Model scale experiments

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DO - 10.1061/(asce)ww.1943-5460.0000306

M3 - Journal article

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JF - Journal of Waterway, Port, Coastal, and Ocean Engineering

SN - 0733-950X

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M1 - 04015006

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