Applications of Immersed Boundary Methods in Hydrodynamic Simulations

Ning Zhang, Department of Chemical, Civil and Mechanical Engineering, McNeese State University, Xiao Han, Department of Chemical, Civil and Mechanical Engineering, McNeese State University; and Susan Regmi, Department of Chemical, Civil and Mechanical Engineering, McNeese State University

Two immersed boundary methods (IBM) have been developed previously by the authors for implementing levees/floodgates and 1-D rivers/streams in hydrodynamic simulations. In this study, the IBM levees and streams were implemented in a regional-scale hydrodynamic model for Calcasieu Lake and surrounding areas in southwest Louisiana. Calcasieu Lake and ship channel connect the port of Lake Charles to the Gulf, which is the major water system in southwest Louisiana and the critical to the environmental system in the area. There are two wild life refuges in the west and east sides of the lake, which are covered by coastal wetlands. There is a levee system on the coast of the lake to prevent salt water intrusion to the wetlands. There are multiple streams connecting the lake to the surrounding wetlands. In the previous studies, hydrodynamics, sediment transport and salinity transport have been simulated in the target area, and the in-house code was validated. The levees and rivers/channels were implemented by changing the topographic data. Since the grid resolution is much greater than the thickness of the levee and the width of some of the streams, there are inaccuracies for the levee implementation by placing higher or lower elevations on the grid points to represent the levee and streams. Thanks to the IBM, the structure in-between the grid points can be realized, therefore, the new implementation presents some advantages over the traditional implementation. In addition, the IBM implementation also makes it possible to simulation scenario such as the levee collapsing and breaching during the floods, which the traditional approach is difficult to achieve. In this paper, the levee and one stream were implemented using the IBMs, and the simulation results were compared to the results from traditional method and measured data for validation. Several flooding scenario were simulated to investigate the flood damages to the wetlands.

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