Wave Attenuation and Turbulence Driven by Submerged Vegetation Under Current-Wave Flow

A set of laboratory experiments are carried out to investigate the effect of following/opposing currents on wave attenuation. Rigid vegetation canopies with aligned and staggered configurations were tested under the condition of various regular wave heights and current velocities, with the constant water depth being 0.60 m to create the desired submerged scenarios. Results show that the vegetation-induced wave dissipation is enhanced with the increasing incident wave height. A larger velocity magnititude leads to a greater wave height attenuation for both following and opposing current conditions. Moreover, there is a strong positive linear correlation between the damping coefficient β and the relative wave height H₀/h, especially for pure wave conditions. For the velocity profile, the distributions of U_min and U_max show different patterns under combined wave and current. The time-averaged turbulent kinetic energy (TKE) vary little under pure wave and U_c = ±0.05 m/s conditions. With the increase of flow velocity amplitude, the time-averaged TKE shows a particularly pronounced increase trend at the top of the canopy. The vegetation drag coefficients are obtained by a calibration approach. The empirical relations of drag coefficient with Reynolds and Keulegane-Carpenter numbers are proposed to further understand the wave-current-vegetation interaction mechanism.