Hydrodynamic and water quality modelling of Chicago Area Waterway System (CAWS)

Illinois Environmental Fluid Dynamics Code (I-EFDC);Chicago River;Hydrodynamic Modeling;Water Quality Modeling;TELEMAC

Sinha, Sumit

关键词: Illinois Environmental Fluid Dynamics Code (I-EFDC);    Chicago River;    Hydrodynamic Modeling;    Water Quality Modeling;    TELEMAC;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/42172/Sumit_Sinha.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Chicago Area Waterway System (CAWS) is a highly branched network of natural rivers and man-made canals. The total length of CAWS including rivers and canals is about 250 kms (156 miles). Although not very long CAWS is famous for the engineering feat that reversed the flow of Chicago River (CR), an integral part of CAWS, westward away from lake Michigan into which it previously drained. The flow in CAWS is regulated with the help of controlling structures existing at the extremities of the system. Also present at the banks of CAWS are four waste water treatment plants (WWTP's). Discharge from these four WWTP's account for the 75 percent of the flow in CAWS. CAWS also serve as an important link between Mississippi River basin and the Great Lakes. Although the dry-weather flow discharge in CAWS is as low as 15-20 m3/s; the wet-weather flow discharge can be as high as 400 m3/s. The normal dry-weather flow pattern in CAWS is from north to south and quite unidirectional. During the wet-weather condition with inflows from numerous CSO outlets, pumping station and WWTP's the flow becomes entirely three-dimensional.In this research two and three dimensional numerical models are developed and applied to gain insights into the flow structure of CAWS under both dry and wet weather conditions. Numerical models based on different methodologies are used to study the flow physics in CAWS. For the two dimensional modelling two different models are used. A finite-difference model capable of solving shallow water equations (SWE) on generalised curvilinear coordinates on structured mesh is developed and applied to a portion of CAWS. Also used for the two dimensional modelling is a finite-element model, TELEMAC-2D, for the same portion of the river. TELEMAC suite of models are open-source and freely downloadable and have been developed by EDF (Laboratoire National D'hydraulique Et Environment). Furthermore the parallelized version of TELEMAC-2D is used for larger spatial domain of CAWS and temporally longer simulations are conducted. The results from hydrodynamic simulations are validated with the help of observed data obtained from the United States Geological Survey (USGS) located inside the computational domain.As regards to three-dimensional modelling again combination of numerical models are used. EPA (Environmental Protection Agency) approved three-dimensional model EFDC (Environmental Fluid Dynamics Code) is used for the three-dimensional modelling of CAWS. For longer term simulation of CAWS, EFDC model has been parallelized using Open-MP paradigm leading to {I-EFDC} model. EFDC model solves the three dimensional vertically hydrostatic, free surface, turbulent averaged equations of motions for a variable density fluid. EFDC uses a stretched sigma or vertical coordinates and curvilinear orthogonal horizontal coordinates and is applied on structured mesh. The results obtained by the EFDC model were again validated with the help of observed data from various USGS gauging stations. After having applied and calibrated the hydrodynamic model; the water quality modelling of CAWS as a whole and it's various portions are conducted in a piecewise manner. For the water quality simulation simplistic DO-BOD (dissolved oxygen - biochemical oxygen demand) models is developed under Open-MP paradigm and joined with the hydrodynamic kernel of EFDC. Furthermore for portions of CAWS another three-dimensional model TELEMAC-3D is used. Once again for simulating range of flow conditions on a fine mesh, the MPI (message passing interface) parallelized version of TELEMAC-3D is used. Both with 2D and 3D models very good agreement between the observed and modelling results are obtained.As CAWS criss-crosses through the city of Chicago and adjoining areas; its importance from aesthetic, environmental, social and economic point of view can not be over emphasized. The insights gained from the numerical modelling effort presented here will finally help in better management and upkeep of CAWS.