Surface Roller Effect Affecting on Shear Fluctuations of a SandyDuck Experiment under a Random Wave Environment

Surface roller effect affecting on shear fluctuations of a SandyDuck experiment was investigated under a random wave environment by using the combination of SHORECIRC and SWAN. The surface roller, which is a strong turbulent region of waves that break and tumble shoreward, has been known to be significant for modelling of nearshore wave-induced motions. The surface roller forces to move the maximum of the cross-shore profile of the mean longshore current toward the shore, and it increases longshore current velocity in the sandbar trough region. Consequently its effect improves the predictions of mean nearshore circulations and surface elevation. The surface roller effect, which gives the corrections to surfzone dynamics, plays a significant role on the shear fluctuations of longshore current. In this study, shear fluctuation changes depending on the surface roller effect were numerically analyzed. As a result, since the surface roller effect moves the maximum of the cross-shore profile of the mean longshore current toward the shore, the location of shear fluctuations was moved toward the shore. And the surface roller effect suppressed rapid rip currents or separation of vortices due to shear fluctuation out of the surfzone, and decreased its fluctuation energy.