Wave-Current Turbulence over Nature Rough Seabeds (Iv)

Understanding the hydrodynamics and turbulent flows is crucial in modeling and monitoring thegeological, biogeochemical, and biological processes in nearshore environments. It is difficult to have aquantitative study due to the complex process of wave-current interaction and three-dimensional topographyinteraction. Based on the up-to-date literature review and our recent efforts, wave-current turbulence in naturerough seabed of coastal environments are largely unexplored. As a result, we propose to study the wavecurrentturbulence over nature rough seabed in fields. In the recent published and submitted works, we haveshown the ability and experiences to perform high-quality field experiments to observe turbulent mixing inshallow waters in the challenging coastal zone where waves and currents coexist. We have conducted severalfield experiments; several research topics have been studied, published, or in preparation for submission: (1)vertical structure of turbulence within the Hobihu coral-reef colonies; (2) dissipation of colony-scale turbulentwakes in a shallow coral reef, (3) vertical structures of flow and turbulence in sparse coral bommies in DongShaatoll. In this proposal, field experiments and data analysis will be conducted to explore the mechanismsdriving the turbulent mixing over the nature rough seabed over coral reefs at Hobihu and DongSha atoll. Theresults from the two field sites will be compared. A suite of instruments including pressure sensor,velocimetry, wind sensor, and video camera will be deployed along a line in the cross-shore direction tomeasure the wind, waves, currents, turbulence, and wave breaking over these reefs. Field experimental dataobserved from the coral-reef experiments at Hobihu and DongSha atoll will be analyzed. In summary, thisproposal is seeking to investigate the following questions: (1) flow structure and drag parameterization aboveand within coral-reef colonies; (2) effects of heterogeneous distribution of coral colonies on form-dragdissipation. The final goal is to connect the bulk drag coefficient with turbulent mixing around coral-reefcolonies under currents and waves. This study has been promoted as international collaboration research withscientists in WHOI.