Investigation on wave attenuation characteristics and mechanism of oyster castles under regular waves

Abstract

Oyster reefs protect coastal areas by reducing wave intensity and erosion, and their hydrodynamic behavior deserves further study. This paper delves into the wave attenuation characteristics and mechanism of oyster castles under regular waves through a combination of experimental and numerical approaches. The effects of relative reef submergence d_s/H_i, relative crest width B/H_i, and oyster density ρ₀ on wave attenuation are analyzed, the spatial variation of flow field and turbulent kinetic energy around oyster castles are investigated, and the wave attenuation mechanism are revealed. Overall, the transmission coefficient increased nonlinearly with growing relative reef submergence. When 1.0≤d_s/H_i ≤ 2.0, the effects of relative crest width and oyster density on the transmission coefficient are significant, and the transmission coefficient decreases with the enlarge of relative crest width or oyster density. When d_s/H_i = 1.0 and B/H_i = 5.0, the transmission coefficient of ρ₀ = 600 ind/m² decreases by about 13% in contrast to ρ₀ = 0 ind/m². In terms of wave attenuation mechanism, wave breaking and frictional dissipation dominate the wave attenuation when d_s/H_i = 1.0. When 2.0≤d_s/H_i ≤ 4.0, frictional dissipation dominates, and it steadily decreases with the extend of relative reef submergence. The findings could be instrumental for evaluating the disaster mitigation potential of oyster castles.