不規則波による沿岸流速に及ぼす砕波モデル選択の影響

Abstract

Various factors affecting the velocities of longshore currents induced by obliquely incident random waves are examined through numerical calculation and literature review. Several models of the random breaking process are used for mutual comparison. These models produce some differences in the estimate of wave height decay in the surf zone, and the differences cause large changes in the longshore velocities. Efficiency of horizontal mixing also depends on the wave breaking model employed. The eddy viscosity formulation by Larson and Kraus (1991) is found better suited to random waves than those by Longuet-Higgins (1970) and Battjes (1975). Introduction of surface rollers in numerical models is necessary in shifting the longshore current profile toward the shoreline and brings forth appreciable strength of longshore currents at the trough of a barred beach. Compared to significant consequence of the selection of wave breaking models, eddy viscosity, and surface roller strength, a questionof linear or nonlinear formulation of shear stress along the seabed seems trivial.