Author(s): Shu Kai Ng; Bobby Minola Ginting; Tatsuhiko Uchida
Linked Author(s): Tatsuhiko Uchida
Keywords: Detached breakwater; Near-bed hydrodynamics; Non-hydrostatic model; Wave-structure interaction
Abstract: Predicting sediment dynamics around detached breakwaters remains challenging due to highly three-dimensional near-bed flows that are often simplified in intermediate-complexity numerical models. This study presents new laboratory measurements designed to investigate the performances of advanced-depth-integrated models which can consider non-hydrostatic (NH) pressure and non-equilibrium velocity profiles induced by boundary layer and three-dimensional vortex motions. Experiments were conducted with regular waves acting on a fixed slope with a layer of coloured sand. A dense grid of Acoustic Doppler Velocimeter (ADV) measurements provided time-averaged near-bed velocity fields, while overhead images documented the movement of the sand layer during the first 6 minutes of wave action. Results show a strong correspondence between circulation patterns, zones of elevated near-bed velocity, and the initial redistribution of the coloured sand, with most changes occurring in the first 2–3 minutes. The dataset isolates the incipient sediment-response stage, offering a controlled benchmark for evaluating how differences in non-hydrostatic pressure treatment influence predictions of near-bed flow and erosion/deposition tendencies. Numerical comparisons using the advanced depth integrated models including BVC and linear-NH models are conducted and compared with experiment and the conventional 2D model.
Year: 2026