Improving modeling of submerged canopy flows with a vortex-based Spalart–Allmaras model

Abstract

Accurately modeling the hydrodynamics of submerged canopies is crucial for predicting sediment dynamics and geomorphodynamics. This paper introduces vortex-based Spalart–Allmaras (VBSA) models, considering the spatial structure of canopy-scale vortices and stem wakes. The VBSA models are innovative in incorporating the physics of canopy-overflow interaction. They were validated using experimental data across a wide range of velocities and canopy densities, and their performance was compared with other turbulence models (i.e., previous SA models and k-ε model). Despite lacking high-order numerical schemes, the VBSA models outperform other turbulence models, exhibiting less numerical dissipation and better replication of mean velocity and Reynolds shear stress profiles in the vortex penetration space and below the surface. A sensitivity analysis was conducted to identify optimal values for new model parameters. Analyses suggest that the porous canopy layer suppresses the mixing efficiency by reducing the turbulence length scale. The analysis of eddy viscosity flux balance reveals that the eddy viscosity is transferred to the canopy layer from the overflow by the canopy-scale vortices and is destructed in the canopy, with production being less important, particularly in large submergence scenarios.