Abstract

This study carried out extensive numerical studies on a refined “One dimensional (1-D) Reynolds Averaging Navier-Stokes (RANS) Model” for vegetated open channel flow. In the 1-D RANS model, the Spalart Allmaras closure model was used to model the turbulence caused by eddies within the vegetation zone and the interface between the top of the vegetation and the clear water zone. In this work, numerical simulations using 1-D RANS model are carried out using dataset obtained from the laboratory under different hydraulic conditions of varying areal vegetation densities. Three classes of highly flexible vegetation densities were simulated: low, medium and highly dense vegetation. The model predictions in terms of mean vertical stream-wise velocity profile and Reynolds Shear Stresses were compared with the laboratory flume experimental results. The 1-D RANS model performances were satisfactory for low and medium densities. However, discrepancies were seen in the model prediction for highly dense vegetation. Hence, the hydraulic roughness parameters in the numerical model has been modified for model re-calibration to capture the position of zero-displacement of velocities. Using the modified parameters, the velocity profiles and the Reynolds Shear Stresses were predicted with very low uncertainty.