CCS Monthly Forum

Abstract: Multiscale bottom topography is ubiquitous in coastal systems. Interactions of surface waves with this topography cause bottom drag, drive mixing, and dissipate wave energy. We investigate how different topography length scales act together in multiscale topography to determine dynamics of oscillatory flow, and dissipation of wave energy using CFD simulations. High-relief topographies consisting of hemispheres of different diameters were used to study the wave energy dissipation. The hydrodynamic interactions between hemispheres strongly depend on the ratio of diameters of the large hemisphere to the small hemisphere (R). When R is close to unity, the drag reduction due to flow sheltering is negligible unless the gap distance is much smaller than the diameter. When R is large, the drag force on the small hemisphere is greatly enhanced when the gap distance is small and the small hemisphere is on the side of the large hemisphere, suggesting small-scale roughness elements can significantly contribute to energy dissipation. The small-scale morphology features on reefs play important roles on wave energy dissipation and turbulent mixing processes and should be considered in artificial reef design.

Bio: Xiao Yu, Ph.D., obtained a doctorate in Ocean Engineering from University of Delaware in 2012. He worked as a postdoctoral researcher at the Center for Applied Coastal Research at University of Delaware between 2012 and 2015, and postdoc at Institute of Marine Sciences at the University of North Carolina at Chapel Hill between 2015 and 2017. He joined University of Florida in 2017 and now is an associate professor in the Department of Civil and Coastal Engineering (2024-present).