A PHYSICAL AND NUMERICAL MODEL OF WAVES AND NEAR-BED VELOCITIES UNDER BICHROMATIC CONDITIONS OVER A STEEPLY SLOPING BEACH FACE

摘要

This study aims to further the understanding of cross-shore flows, sediment transport and beach evolution by combining physical model results with numerical predictions. The wave and morphological numerical model XBeach will be compared with laboratory results for a variety of erosive conditions, bed shear stresses and near bed velocities to understand bottom boundary layer processes. Physical model tests were performed in a 22.75 m long by 1.7 m wide by 0.4 m deep channel in a wave basin with a 0.165 mm sand beach. Detailed acoustic bottom velocity measurements along the beach profile were made in combination with wave measurements at an array of 8 capacitance wave gauges. Measurements were made under bichromatic wave conditions with a peak period of 2.15 seconds and a wave group period of 21 seconds. Velocity observations indicate an increased zone of near bed velocities 20-30cm from the dune face in the region of most intense breaking. XBeach simulations of breaking wave profiles do not agree with laboratory observations in the breaker zone and future tests will allow for more detailed comparisons.