Computational modeling of flow and morphodynamics through rigid-emergent vegetation

• LES coupled with sediment transport and morphodynamic models reproduces scour and transport processes through and around vegetation.
• Vegetation density affects morphodynamics through and around vegetation.
• Morphodynamic behavior in an infinitely long patch is significantly different from that in a small patch.

The flow and bed morphodynamics through rigid, emergent cylinders which are regarded as vegetation are computed using a three-dimensional numerical model by employing a large-eddy simulation approach with a ghost-cell immersed-boundary method. The scour and transport processes are solved using sophisticated sediment transport and morphodynamic models in a physics-based manner. In an infinitely long patch, the vegetation density significantly influences the flow and morphodynamic behavior. Under a low vegetation density, the scour and deposition are similar to those of an isolated cylinder, while there are significant variations at a higher vegetation density. The cylinder-interval variation has a negligible impact on the maximum scour depth, which is similar to that in an isolated cylinder case. In the high-vegetation-density case, a decrease in cylinders in a selected domain decreases the physical realism of the morphodynamic process. The scour and transport processes in a partly vegetated small patch show a significant difference, compared to the long patch. In this case, local and global scours are observed around the small patch and the maximum scour always occurs around the front cylinders (i.e., leading edge). The scour depth increases with a decrease in the cylinder interval, and the computed scour depths and trends agree well with the measured data in the literature.