Numerical study of water waves interacting with open comb-type caisson breakwaters

Abstract

The waves interacting with open comb-type caisson breakwaters was numerically investigated based on a three-dimensional numerical model by compiling a modified k-ω turbulence model. The numerical model can significantly supress nonphysical overestimation of turbulence kinetic energy. The numerical model was established in a specific strip of breakwater by introducing a periodic boundary condition to improve computational efficiency. The numerical model was validated against analytical and experimental results. Effects of wave and structural parameters on hydrodynamic performances, including wave reflection, wave transmission, wave forces, and energy dissipation, were investigated. The numerical results suggested the significance of the relative chamber width on hydrodynamic quantities. The hydrodynamic interaction, including the wave run-up on the superstructure and the eddy formation process, was illustrated by the time instants of the velocity and dynamic pressure, turbulence kinetic energy field and streamline. The energy dissipation was mainly due to wave breaking and vortex shedding and hence effectively reduced the wave transmission but had little influence on wave reflection. More wave energy went to higher frequency component as incident wave period increased. The investigation regarding the phase shift of wave forces acting on rectangular caisson and the side plates proved the advantage in mechanical characteristics of comb-type structure.