Analytical Model for Graded Sediment Transport in Velocity‐ and Acceleration‐Skewed Oscillatory Sheet Flow

Abstract

At high sediment transport intensities, the oscillatory ripple loses its height and the bed becomes flat, and sediment motion then occurs as a sheet within a few centimeters near the bottom (Hassan & Ribberink, 2010). Sheet flow study is of considerable importance to coastal processes, as it can cause substantial morphological evolutions during severe hydrodynamic conditions over a short time scale (Tan & Yuan, 2021). Sheet flow transport in the coastal area is mainly influenced by the intensity of hydrodynamic forcing and the sediment properties (i.e., size, density, and shape) (Durafour et al., 2015). The heterogeneity of sediment properties is important to sheet flow transport (de Meijer et al., 2002), and this paper only focuses on the heterogeneity of sediment size. Many sediment beds have wide-size distributions, and the distributions may not be lognormal and tend to be negatively or positively skewed (Mohtar et al., 2016). Non-uniform sediments are also generally found in nearshore projects that involve the mixing of multiple types of sediment (e.g., beach nourishment and dredged material disposal) . The non-uniformity of grain size plays a very important role in the sediment movement caused by wave motion (Holland & Elmore, 2008). Massive sediment transport occurs in the surf zone and the swash zone, where graded sediment bed moves primarily under the sheet flow regime (Harada et al., 2015;van der Zanden et al., 2019). Hence, ascertaining the mechanism of oscillatory sheet flow for graded sediment is essential in coastal sediment dynamics.

Cross-Shore Sediment Transport in the Coastal Zone: A Review

“…The first two terms on the right side of Equation (84) correspond to bedload transport, while the third term corresponds to transport by suspension. Hu and Chen [37] proposed an analytical model for graded sediment transport in velocity and acceleration skewed oscillatory sheet flow. The composition of transported sediment is shown to be different from the initial bed composition.…”