Abstract Gravity currents, driven by density differences, are widely observed in natural environments and engineering applications. However, their interactions with bed forms such as ripples remain insufficiently understood. In this study, three‐dimensional Large‐Eddy Simulation, validated against lock‐exchange experiments, is employed to explore the kinematic and dynamic evolution of gravity currents over rippled beds. The geometric parameters of ripples (including wave height, wavelength, and lee‐side slope angle) are found to exert significant influences on flow characteristics, mixing efficiency and sediment transport capacity through their coupled effects on flow separation, energy redistribution and bed shear stress. A key result is the identification of a dual‐layer vortex structure: ripple‐induced separation vortices in the lower layer and Kelvin‐Helmholtz (K‐H) instability vortices at the upper density interface. Ripples regulate current motion by mediating potential and kinetic energy conversion and dissipation redistribution, producing stepwise variations in potential energy and accelerating kinetic energy decay by a factor of 2.3. A steep lee‐side slope enhances the bulk entrainment coefficient by 35%–50%, while ripples systematically reduce bed shear stress by 20%–35%, leading to deposition on the lee‐side and erosion on the stoss‐side. The results also indicate that internal density‐driven forces primarily govern entrainment intensity. This study advances the theoretical understanding of coupled gravity current‐ripple interactions and provides insights for practical applications in reservoir sediment management and estuarine regulation.
Lin et al. (Wed,) studied this question.