Applicability of Multi-layer Wave Model for Prediction of Circulating Current Field Around a Submerged Breakwater

Abstract

 Submerged breakwaters have become an appealing alternative for conventional shore protection structures due to their lower impact on the coastal landscape. These structures however cause more complicated wave-induced circulation currents and, as a result, often fail to meet the expected coastal protective functions. Although previous studies have applied two-dimensional-horizontal (2DH) nearshore current models and quasi-three-dimensional (Q3D) models with different wave-breaking and surface roller models for prediction of the circulation currents around submerged breakwaters, most of these models have failed to reproduce the observed circulation current patterns accurately. The objective of this study is therefore to investigate the applicability of multilayer nonlinear dispersive model to predict circulation current patterns under different incident wave conditions. The recently developed SWASH model was applied to a unique set of laboratory experiments, and the effect of the multilayer model was investigated. According to the experimental observations both near-bottom and near-surface mean current patterns are highly sensitive to the incident wavelength. The two-layer mode was able to reasonably capture the variation in current patterns for different wave periods, while the one-layer mode significantly underestimated the current velocities and failed to represent the dependency of the circulation current patterns on incident wavelengths.