Mathematical model of estuarial sediment transport. Final report.
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A 2-dimensional finite element model that simulates erosion, transport, and deposition of suspended sediments is presented. The breadth-averaged or depth-averaged equations may be used depending on the problem to be solved. The governing equations for two phase transport are derived and then solved by the finite element method using isoparametric quadrilateral elements in which a quadratic approximation is made for the suspended sediment concentrations. Expressions used for the rates and conditions under which erosion and deposition occur are from previous experimental studies. Continuing aggregation is accounted for by specifying the settling velocity of the flocs in each element at each time step. The bed is considered to be formed of a number of layers of sediment whose physical properties change with overburdened pressure. The model provides suspended sediment concentrations and bed profile at each time step. Numerical stability and convergence tests were conducted by comparing simulated results with analytic solutions and actual measurements. The original model, SEDIMENT I, was verified by comparison with measurements in a recirculating flume. The modified model, SEDIMENT II, developed for this project was verified by comparison with field measurements in the Savannah Estuary, Georgia.