Numerical simulations of wave propagation over a vegetated platform

Abstract

Vegetated platforms have been constructed in recent years for the purpose of shore protection. This paper addresses some fundamental questions concerning the vegetated platform: (1) What is the difference in wave attenuation between a vegetated platform and a simple platform, and how much can vegetation increase the efficiency of reducing wave transmission? (2) Are there any differences between the effects of stems and roots on wave attenuation? (3) Does vegetation always reduce wave transmission? (4) Is it possible to develop an empirical formula for estimating the wave transmission of a vegetated platform? To answer the above questions, a numerical model solving the Navier-Stokes equations for wave propagation over a vegetated platform is established and validated by several existing laboratory experiments. A total of 244 numerical experiments based on this model have been carried out. The simulated results suggest that the platform plays a major role and the vegetation plays a supporting role in reducing wave transmission except for some special cases. Stems tend to have a larger influence than roots in reducing wave transmission with the same height. The roots always help reduce wave transmission, while the stems may increase wave transmission when the platform width is in the range of 37.5-62.5% of the incident wavelength. Based on our numerical experiments and existing laboratory data, the paper proposes a simple formula for predicting the wave transmission coefficient of a vegetated platform for engineering applications.

Wave scattering by a floating porous elastic plate of arbitrary shape: A semi-analytical study

“…Porous structures can be typically horizontal, vertical or inclined plates. A horizontal porous plate allows the free exchange of water or marine animals for the benefit of the environment; therefore, water-wave interaction with horizontal porous plates, in cases such as mobile offshore bases, floating breakwaters and floating vegetated platforms (see Chwang and Chan (1998); Wang et al (2010); Koley et al (2018); Chen et al (2016) for details), has been investigated by many researchers. Yu and Chwang (1994) used the boundary element method (BEM) to study wave diffraction by a horizontally submerged porous plate.…”

“…In most of these studies concerning a floating elastic plate, the plate was assumed to be either non-porous, or circular, and generally, free-floating, i.e., the shear force and the bending moment vanish at the edge of the plate. However, in practice the plates may be neither non-porous nor circular for artificial structures, e.g., artificial floating islands (Kamble and Patil, 2012), floating vegetation fields (Duncan, 2014;Chen et al, 2016) and floating breakwaters (Cheng et al, 2013). Furthermore, their edges are generally fixed by piles, anchors, or tension cables.…”

Three-Layer Analytical Solution for Wave Attenuation by Suspended and Nonsuspended Vegetation Canopy

“…Only recently did researchers start to pay attention to the wave attenuation by the suspended canopy (Plew 2005;Chen et al 2016). Theoretical work for the wave attenuation through suspended vegetation canopy is scarce in literature.…”

“…The vegetation canopy may be categorized as submerged or emerged, and rooted or suspended based on the its height relative to the water depth and vertical location in the water column (Plew, 2011;Huai et al, 2012;Chen et al, 2016).…”

Propagation and scattering of waves by dense arrays of impenetrable cylinders in a waveguide

“…Furthermore, wave transformation and attenuation in mangrove forests and marine vegetation is also a subject of interest in coastal engineering, taking into account their role in supporting local economy and stabilizing and protecting the coastal zone. In many studies mangrove trunks and roots are treated as vertical cylindrical elements located in the water column, [7]; see also [8]. Particular arrangements used in experiments and numerical models are regular arrays of vertical cylinders; see e.g., [9][10][11][12].…”