Wave propagation through dense vertical cylinder arrays: Interference process and specific surface effects on damping

Arnaud, G.; Rey, Vincent; Touboul, Julien; Sous, Damien; Molin, Bernard; Gouaud, Fabrice

doi:10.1016/j.apor.2017.04.011

Cited by 30 publications

(59 citation statements)

References 23 publications

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“…Following the general understanding of turbulent boundary layers in open channel flows (Rosman & Hench, ; Tachie et al, ) or recent works on wave dynamics over coral reefs (Monismith et al, ; Pomeroy et al, ; Van Dongeren et al, ), the bottom roughness is expected to enhance energy dissipation, and this effect increases with the height of roughness elements relative to the local water depth. Furthermore, when the physical roughness height increases to more than few percents of the water depth, the concept of bottom roughness itself becomes irrelevant, and the flow and wave dynamics must be discussed in the framework of porous media (Arnaud et al, ; Monismith, ). The quantitative comparison between runup over coral reefs and rocky cliff is not directly relevant, as shorelines in coral reef systems are separated from the steep forereef by a reef flat and/or lagoon.…”

Section: Discussionmentioning

confidence: 99%

Wave Runup Over Steep Rocky Cliffs

et al. 2018

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Wave runup is known to depend on offshore wave conditions and coastal morphology.While most field studies on wave runup have focused on low-to-mild-sloping sandy beaches, runup measurements on steep and irregular rocky cliff profiles are still very scarce. Here we investigate the physical processes controlling wave runup in such environments and the range of applicability of empirical runup formula. This study focuses on the steep rocky cliffs (0.1 < tan < 0.4) of Banneg Island, a small island located in the Molène archipelago, Brittany, France, occasionally flooded during extreme water level events. A statistical parameter for extreme runup is derived from the measurements of pressure sensors deployed in the intertidal zone. Deep water wave parameters are used to force a high-resolution wave model, and nearshore wave parameters and high-resolution topographic data are analyzed concurrently with runup time series in order to assess the dependence of the runup on hydrodynamic conditions and morphological parameters. The wave runup is shown to be strongly related to the square root of the offshore significant wave height times the offshore wavelength. The measurements also reveal the depth dependence of the runup, which is mainly attributed to the curvature of the foreshore profile. In comparison to empirical relation obtained for a mild-sloping beach, the present data show a significant reduction in normalized wave runup, that is attributed to enhanced bottom friction over the rocky bottom. Plain Language SummaryWhen waves reach the shores, they travel up and down the beach before being reflected seaward. The maximum vertical excursion of the waterline relative to the still water level, called the wave runup, is a key parameter for the design of coastal structures and the prediction of overtopping volumes during storm events. Most runup studies in natural environments have focused on smooth and mild-sloping sandy beaches, and empirical formula to predict the wave runup has been derived for these environments. Here we study the process of wave runup over steep rocky cliffs. Using pressure sensors deployed in the intertidal zone of Banneg Island-a small island located west of Brittany, France, exposed to very high waves-we measured runup events. Then we investigated the link between these runup data, offshore wave parameters, and cliff slopes. Our results reveal that the wave runup is linearly dependent to the square root of the offshore wave height times the offshore wavelength. In addition, a significant reduction of the runup is found compared to sandy environments, which is attributed to the frictional effect exerted by the rocky bottom on the flow.

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Section: Discussionmentioning

confidence: 99%

Wave Runup Over Steep Rocky Cliffs

et al. 2018

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“…These axes form a 45 • angle with the longitudinal axis of the structure. A detailed study of such structure is presented in Arnaud et al (2017) in the 2D case. In the present study, the cylinder diameter is D = 0.032 m. The length of the structure is L = 0.30 m and the width is 2d p = 1.20 m. The distances between cylinders along horizontal axis are dx = 0.0384 m and dy = 0.0365 m, respectively (see Fig.…”

Section: Porous Mediummentioning

confidence: 99%

“…In the present study, the porous medium is considered as a homogeneous structure at the wave scale since both the size and spacing of the cylinders remain small compared to the wavelength. This assumption allows to define an equivalent wavelength within the porous medium as described in the 2D case by Arnaud et al (2017). Numerical resolution at the macroscale using boundary integral matching method between the different domains is then consid-March 18, 2019 14:39 WSPC/INSTRUCTION FILE Arnaud-et-al˙IJOCE˙Review Wave propagation through dense vertical cylinder arrays: 3D experimental study 3 ered.…”

Section: Introductionmentioning

confidence: 99%

“…For dense arrays of vertical emerging cylinders, both cylinder diameter and spacing are small compared to the wavelength. With this approximation, the cylinder array can be considered as a porous medium, as done by Arnaud et al (2017) in a one-dimensional case.…”

Section: Introductionmentioning

confidence: 99%

“…Since the porous media is considered as homogeneous at the wave scale a linear damping approach is used to take into account wave dissipation inside the porous media. Wave damping parametrization takes advantage of the careful experiments including various wave steepnesses and periods carried out in the 2D case by Arnaud et al (2017) for similar structure.. The problem solution is obtained by integral matching method resolving continuity equations of velocity and pressure at vertical boundaries between domains.…”

Section: Introductionmentioning

confidence: 99%

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Wave Propagation Through Dense Vertical Cylinder Arrays: 3D Experimental Study

Arnaud

Rey

Touboul

et al. 2019

International Journal of Ocean and Coastal Engineering

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The purpose of this research work is to study the diffraction of surface gravity waves propagating through rectangular porous medium in three dimensions. The considered porous structure consists of dense arrays of surface piercing vertical cylinders. Experiments for different regular wave conditions have been carried out, especially for three-wave frequencies. The experimental data of wave refraction–diffraction and reflection have been compared to computed results from potential linear theory solved with an integral matching method. Comparison with a previous 2D study about wave propagation through porous medium in a 10 m long wave flume is also discussed in order to highlight the refraction–diffraction effect due to the porous structure.

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On the small‐scale fractal geometrical structure of a living coral reef barrier

Sous

Bouchette

Doerflinger

et al. 2020

Earth Surf Processes Landf

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Summary The topographical complexity of coral reefs is of primary importance for a number of hydrodynamical and ecological processes. The present study is based on a series of high‐resolution seabottom elevation measurements along the Maupiti Barrier Reef, French Polynesia. Several statistical metrics and spectral analysis are used to characterize the spatial evolution of the coral geometrical structure from the reef crest to the backreef. A consistent fractal‐like power law exists in the spectral density of bottom elevation for length scales between 0.1 and 7 m, while at larger scale, the reef structure shows a different pattern. Such a fine characterization of the reef geometrical structure provides key elements to reconstruct the reef history, to improve the representation of reef roughness in hydrodynamical models and to monitor the evolution of coral reef systems in the context of global change. © 2020 John Wiley & Sons, Ltd.

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Wave propagation through dense vertical cylinder arrays: Interference process and specific surface effects on damping

Cited by 30 publications

References 23 publications

Wave Runup Over Steep Rocky Cliffs

Wave Runup Over Steep Rocky Cliffs

Wave Propagation Through Dense Vertical Cylinder Arrays: 3D Experimental Study

On the small‐scale fractal geometrical structure of a living coral reef barrier

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