A numerical model predicting lenticular sedimentary structures formed by breaking waves over antidunes

A numerical model that computes the vertical distribution of different sediment sizes in riverbeds has been used to predict the formation of lenticular sedimentary structures in a flume with antidunes. The Navier–Stokes equations were solved to find the water velocities and the turbulence, and convection‐diffusion equations for five different sediment sizes were used to predict the sediment concentrations. Changes in the elevations of the water surface and bed due to erosion and deposition were also included. The model includes algorithms that divide the bed into 1,000 adaptive vertical layers, each with its unique grain size distribution. The spatial resolution of the bedding and the resulting lenticular structures was thereby computed directly. The model predicted the formation of stationary and downstream‐moving antidunes that occasionally would move upstream, leading to the formation of the lenticular structures. The numerical model explained the different physical processes with high spatial and temporal variation in velocity, turbulence, pressure, changes in bed sediment size fractions, together with water surface and bed movements. This is documented by detailed figures and animations in the current study.