High‐Resolution Large Eddy Simulations of Vortex Dynamics Over Ripple Defects Under Oscillatory Flow

Abstract

We carried out high‐resolution Large Eddy Simulations to study the three‐dimensional hydrodynamic characteristics over regular and irregular wave‐generated ripples. Two types of irregularities in ripple crestlines are considered, namely ripples with a termination defect and with a bifurcation defect. Over regular ripples, the flow and vortex structures vary in the spanwise direction, displaying evident three‐dimensional vortex structures. Compared to regular ripples, the presence of a bifurcation or a termination defect implies local variations in ripple height and spacing. As a result, the maximum velocity, vortex strength and the position of the vortex center over ripples neighboring a defect are all affected by the presence of the defect. The maximum velocity at the ripple crest neighboring a defect is linearly related to the position of the vortex center. The presence of defects induces an asymmetric distribution of shear stress and sediment flux that will ultimately affect bedform evolution.

Discontinuity in Equilibrium Wave‐Current Ripple Size and Shape and Deep Cleaning Associated With Cohesive Sand‐Clay Beds

“…Storm‐induced waves combined with currents cause particularly dynamic ripple behavior and thus large and rapidly changing sediment transport rates (e.g., Li & Amos, 1999 ; Wengrove et al., 2018 ). The understanding of how hydrodynamics control ripple dimensions is therefore essential for ensuring the improved performance of coastal morphodynamic models through well‐parameterized bed roughness and for process‐scale models of ripple development and stability (Jin et al., 2022 ; Marieu et al., 2008 ). This may also be beneficial for the improvement of estuarine and coastal management within the broader context of climate change and sea level rise in coastal systems.…”

“…morphodynamic models through well-parameterized bed roughness and for process-scale models of ripple development and stability (Jin et al, 2022;Marieu et al, 2008). This may also be beneficial for the improvement of estuarine and coastal management within the broader context of climate change and sea level rise in coastal systems.…”

Medium-term observations of salt marsh morphodynamics

“…The morphology of tidal flats is continuously modulated by the interactions between hydrodynamics (e.g., tidal currents, waves, storm events), sediment supply, global climate change (i.e. storm events and sea level rise), and biological factors (e.g., salt marshes, biofilms) (Le Hir et al, 2000;D'Alpaos et al, 2007;Green and Coco, 2007;Kirwan et al, 2010;Friedrichs, 2011;Fagherazzi et al, 2012;Chen et al, 2019;Zhao et al, 2021;Jin et al, 2022). Salt marshes in front of coastal infrastructure provide important ecological services in attenuating wave and current energy, trapping sediment and accelerating sedimentation (Temmerman et al, 2003;van de Koppel et al, 2005;Anderson and Smith, 2014;Gong et al, 2017).…”