Unsteady Wave-Driven Circulation Cells Relevant to Rip Tides and Coastal Engineering

点击翻译按钮获取中文摘要

PROPOSAL NO.: CTS-0423877PRINCIPAL INVESTIGATOR: ANDREW B. KENNEDYINSTITUTION: UNIVERSITY OF FLORIDAUNSTEADY WAVE-DRIVEN CIRCULATION CELLS RELEVANT TO RIP TIDES AND COASTAL ENGINEERING This grant is to study wave forcing and fluctuations in irrotational and rotational wave-driven near-shore flows. The approach is primarily theoretical and numerical, but will make use of existing laboratory and field results. Field and laboratory observations have recorded significant unsteadiness in wave-driven near-shore flows with time scales much larger than a typical wave period, such a those occurring with rip tides. These fluctuations are known to be driven by some combination of unsteadiness in incident wave forcing and free instabilities of the mean flow but the relative importance of free and forced motions remains unknown. Even the relative importance of forced rotational versus irrotational fluctuations is wholly unknown. Three major tasks are stated for the study: Analytical study of wave-forced forced irrotational and rotational fluctuations; Numerical study of free and forced hydrodynamic unsteadiness in the near-shore; and Analytical study of circulation cell stability.Broader impacts of the technical proposal include understanding of near shore phenomena that lead to rip currents, which kill people every year. Besides drowning due to rip currents, understanding how flows near beaches/the shore work is important in a variety of contexts, namely beach erosion (a large sub-field of coastal engineering), transport of larval organisms (many implications for recreational and commercial fishing), and wave-driven circulation over coral reefs. Strictly focusing on beaches, there is the issue of transport of contaminants like fecal indicator bacteria that can lead to beach closures costing hundreds of millions of dollars or more every year in the US. The societal broader impacts of the proposal include wide dissemination of the results to the community and educational components, which include training of graduate students and integration of the research results into courses. This grant co-funded by the Office of Naval Research, Coastal Geosciences Program, Code 321CG.