EXTENDED LINEAR REFRACTION-DIFFRACTION MODEL

An alternative derivation of the extended refraction-diffraction equat ion is presented. The bottom curvature and slope-squared terms ignored in the mild-slope equation are included to account for relatively ste ep and rapidly undulating bathymetry. The linear elliptic partial diff erential equation is solved by the hybrid element method and applied t o three-dimensional bedforms. Quadratic triangular elements are used i n the model so that the curvature can be calculated directly from the water depth defined at the nodes. The model is illustrated by simulati ng wave reflection from a ripple bed and wave transformation over a ci rcular shoal in which previous experimental and numerical results exis t. The relative effects of the additional terms and their significance in the model prediction are examined in a numerical experiment.