Energy dissipation characteristics in vegetation belt due to mono-chromatic and bi-chromatic waves

Abstract

The present experimental scaled model (1:40) study investigates the energy attenuation process occurring due to the presence of the vegetation belt and the importance of vegetation patch length considering mono-chromatic and bi-chromatic waves interacting with four different vegetation patch lengths. The energy attenuation process in the vegetation takes place in two stages. Initially, the energy is re-distributed within the different frequency components and later, the dissipation occurs at the higher harmonics. The front rows of vegetation belts are observed to initiate the former process, and the rear rows of vegetation attenuate the energy from the higher harmonics. The vegetation patch corresponding to 225 mm in length along the wave direction (shortest among the four vegetation patches) was observed to show negative impacts. The transmission coefficient for the array of cylinders (vegetation belt) correlates with the inertial (Cm) and drag (Cd) coefficient of a single cylinder. Further, the energy attenuation trend is observed to be non-uniform within a wave cycle. The vortex shedding breakdown at various instances of a wave cycle was reported using IITM-RANS3D. The intensity of the vortex shedding breakdown was observed to be significant during the crest phase of the wave cycle which aligned with the experimental observations of higher attenuation at the crest.