Exchange Flows through a Long Shallow Channel

Little Sodus Bay (LSB), a freshwater embayment along the coast of Lake Ontario (LO, North America), is used as a canonical lake–embayment system to investigate the effects of unsteadiness and viscosity on the generally assumed inviscid flow between two reservoirs through a topographic constriction. It is determined, through a scaling analysis based on field observations, that for this general class of embayments, frictional effects, vertical turbulent fluxes, and unsteadiness are all important processes in addition to baroclinic and barotropic forcing. A numerical model (Princeton Ocean Model) is used to explore the effects of these various processes on the exchange flow between LSB and LO. The results indicate a shift toward internal hydraulic dominated flows and layers become blocked (or arrested) earlier than inviscid internal hydraulic theory anticipates. An additional physical process, namely a surface wind stress, is also investigated with regards to the traditional hydraulic regimes and it is found that wind, while altering the exchange flow, does not change the fundamental character of the flow.