Study on the hydrodynamics of a twin floating breakwater by using SPH method

Numerical and experimental studies are performed on the hydrodynamics including wave-attenuation perfor-mances measured by the transmission and reflection coefficients and dynamic responses of a twin floating breakwater. In the present work, the twin floating breakwater consists of two identical single pontoon-type floating breakwaters with independent identical mooring systems. Numerical simulations are performed with the delta-SPH, a Smoothed Particle Hydrodynamics model, after introducing a mooring line computation based on the catenary theory. The experimental tests are carried out in a wave flume at the Ocean University of China. The displacements of the twin floating breakwater and the water surface elevation are recorded in the experiment. Comparison of the numerical and experimental results demonstrates the reasonable accuracy of the present numerical model. Based on the numerical results, the wave-attenuation performances of the twin floating breakwater and a single pontoon floating breakwater are compared. Furthermore, the effects of the wave period and the horizontal spacing between the two pontoons on the hydrodynamics of the twin floating breakwater are studied, and in this process, Bragg resonance reflection of water waves by the twin floating breakwater is dis-cussed. The results reveal that the twin floating breakwater is superior to the single pontoon floating breakwater on wave-attenuation performances. Moreover, comparing with the horizontal spacing between two pontoons, the wave period has a more significant effect on the hydrodynamics of the twin floating breakwater. Furthermore, there could be Bragg resonance reflection between waves and the twin floating breakwater. However, this phenomenon can be significantly weakened by the movement of the twin floating breakwater.