Vortex Formation in Finite-length Shallow Flows

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0965293RockwellA large number of semi enclosed, cavity like configurations in the form of spur dikes (groynes), embayments, and jetties are located along rivers and in tidal regions around the world. The survival and maintenance of proper balances of living biomass and masses of nutrients, dissolved gases, vegetation, fish, and marine life, as well as the inadvertent or planned intrusion of a wide variety of pollutants and contaminants, are major concerns. The effectiveness with which water is drawn into, or purged from, these cavity like regions has important consequences for water quality. Such mass exchange involves shallow mixing layers, which have scales of instabilities and vortices much larger than the water depth. This program aims to fundamentally alter the approaches to, and our understanding of, shallow mixing layers of finite streamwise extent. Space time quantitative imaging will yield new representations of the flow structure of finite length shallow mixing layers, and thereby provide insight into the mass engulfment/exchange between the cavity and the region exterior to it. Such imaging will account for stabilization and destabilization of instabilities and vortex formation within the shallow mixing layer, arising from the effects of finite length scale and a standing gravity wave within the cavity. This approach will lead to a new, physics based framework for mass exchange between the cavity and its surroundings, in contrast to exchange coefficients empirically determined from flushing or purging times, and eventually contribute to enhanced water accessibility and quality, which is of increasing concern to nearly all developed and underdeveloped countries. An outreach program for underrepresented students will involve an integrated program, with several different initiatives, for a middle school and a community college having high percentages of minorities, in anticipation of the increasingly important role of community colleges.