Hydrodynamics and Morphology of Equilibrium Tidal Freshwater Channels
Friedrichs, Carl
Friedrichs, Carl
Abstract
This presentation addresses the dynamics and morphology of near-equilibrium tidal freshwater channels. The dynamics considered are based on sectionally-averaged current velocity and a barotropic momentum balance. A series of geometries are examined which attempt to encompass generic, reasonably realistic scenarios for tidal fresh water channels found in nature. This work presents and scales the governing equations of mass and momentum conservation. An essential step in this process is the identification of key length scales, corresponding inverse length scales (or "spatial rates of change"), and dimensionless ratios to be used subsequently to determine when and where to keep or neglect various dynamic or kinematic terms. The order of presentation proceeds from cases that are dynamically the most simple, yet still observationally useful, toward somewhat more complicated but naturally common "equilibrium" and "near-equilibrium" channels. Along the way, controls on tidal asymmetries are specifically considered in the context of relatively short and/or shallow channels. A key aspect of near-equilibrium, freshwater tidal channels is that variations in morphologically controlling total velocity amplitude (tidal velocity plus fresh river velocity) along such channels tends to be relatively small, and prominent reflected waves are uncommon. A theme common to all cases is the potential role of the full system width (including tidal storage in marsh, flats, shoals and tributaries) relative to the width of the momentum transporting channel in affecting the tidal dynamics
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2012-11-13
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Virginia Institute of Marine Science