Large-eddy simulation of the Mississippi River under base-flow condition: hydrodynamics of a natural diffluence-confluence region

We conduct large-eddy simulation (LES) to investigate the turbulent flow in a 3.2 km long reach of the Mississippi River. The digital elevation model of the study reach was reconstructed from remote sensing data (light detection and ranging; LiDAR) and field measurements. Flow depth and velocity profile measurements were carried out in five field campaigns in 2009, 2014 and 2015 under base-flow condition using acoustic Doppler current profiler. The detailed geometry of the river bathymetry, islands, and hydraulic structures were incorporated in the numerical simulation using the curvilinear immersed boundary approach. LES results are used to demonstrate and gain insight into the complexity of the river flow dynamics induced by the interaction of shear-layers developing along the intricate geometry of the islands and bar within the study area. Our results also show the long-range impacts of hydraulic structures on the downstream flow structures. This study demonstrates the feasibility of high-resolution LES for large-scale rivers by taking into account the detailed bathymetry and submerged hydraulic structures.