A numerical study on the influence of curvature ratio and vegetation density on a partially vegetated U-bend channel flow

Aquatic vegetation dramatically shifts the main flow, secondary flow and turbulent structures in a meandering channel. In this study, hydrodynamics bending channel with patch (VP) has been numerically studied under variation of curvature ratios (CRs=0.5, 1.0, 1.5, 2.0) density i.e. Solid Volume Fractions (SVF=1.13%, 4.86%). Both effects on shear helical bed stress bulk drag coefficients are twelve cases by using Ansys Fluent package. Unsteady Reynolds Averaging Navier-Stokes (URANS) framework coupled Stress turbulence Model (RSM) Of Fluid (VOF) approach is successfully applied to predict entire field including multi-circulation cells as well free surface. The conclusions summarized three points. Firstly, an increase CR moves circulation cell thalweg's location towards outer bank, while decreasing streamwise spanwise. However, weakly affects normalised velocity profiles dominant eddy frequencies downstream VP. Secondly, trend shedding frequency fall SVF that known only for SVF<3.4% extended up 10.4%. Furthermore, opposite found between 10.4%<SVF<20%. Thirdly, newly proposed dimensionless number, StpSVFN, links Stp SVF, where N number stems patch. This stays almost constant each case series regardless (for SVF<10.4%). We also conclude StpSVFN strongly determined shape factor, mildly influenced but it excludes influence N. insights from present study unveil complicated eco-hydro-morphic interactions among bio-mass density, meanders’ variation. It provides better understanding natural river systems’ development fundamentals recovery urban ecosystems vegetated re-meandering.