Wave Energy Dissipation by Permeable and Impermeable Submerged Breakwaters

Abstract

The purpose of this study was to investigate the effect of the porosity of a submerged breakwater on wave fields, including snapshots of the wave, velocity profiles of the water over the structure, and the kinetic energy of the wave. Two-dimensional experiments were conducted for submerged trapezoidal breakwaters with impermeable and permeable layers in a two-dimensional wave tank. The flow fields obtained by the particle image velocimetry (PIV) technique are presented to understand the flow characteristics due to the waves' interactions with the submerged impermeable and permeable breakwaters, and these characteristics showed that the vertical velocity dominant flow occurred under the crest of the wave. In addition, the kinetic energies were compared for different porosities and wave conditions. The comparisons of the wave flow fields and kinetic energy distributions showed that the different pattern of the dissipated kinetic energy was dependent on the porosity. The dissipation of kinetic energy also was observed to increase as the wave period increased. The comparisons indicated that greater amounts of energy were dissipated for longer wave periods.

Hydrodynamic performance of submerged breakwater in tandem with thin-walled as submerged reef structure

“…The induced wave breaking increases the dissipation coefficient K D of a coastal structure, lowering its transmission coefficient K T and improving its hydrodynamic performance. The experimental investigations by Ryu et al 32 used particle image trajectories to get the flow field in order to study the flow characteristics and energy dissipation capacities K D of impermeable and permeable submerged breakwaters. Khan and Behera 25 found that when series of porous structures are considered, the wave transmission K T in the lee side of the structures is greatly reduced when compared to that obtained for a single structure due to increased wave energy dissipation K D .…”