Near Field Behavior of a Far Field Circulation Model

by Xueyong Zhang, Massachusetts Inst of Technology, Cambridge, United States,
Eric Adams, Massachusetts Inst of Technology, Cambridge, United States,
Alan Blumberg, Massachusetts Inst of Technology, Cambridge, United States,
Z. G. Ji, Massachusetts Inst of Technology, Cambridge, United States,
Kirk Ziegler, Massachusetts Inst of Technology, Cambridge, United States,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

Output from the 3-D far field circulation model ECOMsi was compared with output from EPA initial mixing models in two simulations of coastal sewage outfalls - an idealization with steady flow and a continuous application in Massachusetts Bay. In both simulations trap heights and thicknesses from the two models agreed reasonably well. However, plume widths and dilutions showed greater discrepancies: relative to the initial mixing model, predictions for both variables from ECOMsi were generally greater in the idealized domain and less in the Mass Bay simulation. The agreement in vertical behavior gives confidence to far field water quality simulations which require realistic vertical distributions of plume properties such as light and nutrient level. The discrepancies in plume widths and dilutions result from insufficient grid resolution and suggest the desirability of using hybrid models combining random-walk particle tracking in the near field with concentration-based models in the far field.

Subject Headings: Water quality | Water circulation | Three-dimensional models | Simulation models | Mathematical models | Water pollution | Sewage | Massachusetts | United States

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