Hydrodynamic characteristics of a free-surface semicircular breakwater exposed to irregular waves

A free-surface semicircular breakwater (SCB) has been developed for protecting coastal and marine infrastructures against ocean waves. The hydrodynamic characteristics of the breakwater are investigated in irregular seas through an experimental program. A test model of the semicircular breakwater has been constructed with front wall porosity varied at 0 (i.e., no perforations), 9, 18, and 27%. The wave surface elevations are measured at different locations upstream and downstream of the models, and the coefficients of wave transmission, reflection, and energy dissipation are evaluated. Wave climate in the vicinity of the breakwater models and horizontal wave force on them are
also measured. On the basis of the measured data, empirical models are proposed to provide design formulas for wave transmission, wave reflection, and horizontal wave force. The proposed empirical models show good agreement with the measured data; however, sensible engineering judgment must be taken while using these because the equations proposed are based on small-scale laboratory tests. The overall
results indicate that the impermeable SCB model is an effective wave reflector, and the permeable SCB models are good energy dissipaters.