Aquatic vegetation dramatically shifts the main flow, secondary flow and turbulent structures in a meandering channel. In this study, hydrodynamics in a bending channel with a vegetation patch (VP) has been numerically studied under the variation of curvature ratios (CRs=0.5, 1.0, 1.5, 2.0) and the vegetation density i.e. Solid Volume Fractions (SVF=1.13%, 4.86%). Both effects on vegetation shear flow, helical flow, bed shear stress and bulk drag coefficients are studied in twelve cases by using Ansys Fluent package. Unsteady Reynolds Averaging Navier-Stokes (URANS) framework coupled with the Reynolds Stress turbulence Model (RSM) and Volume Of Fluid (VOF) approach is successfully applied to predict the entire flow field including multi-circulation cells as well as the free surface. The conclusions are summarized as three points. Firstly, an increase of CR moves the main circulation cell and thalweg's location towards the outer bank, while decreasing the drag coefficients in streamwise and spanwise. However, the CR weakly affects the normalised shear flow velocity profiles and dominant eddy frequencies downstream of the VP. Secondly, the trend of the dominant shedding frequency to fall with the increase of SVF that has been known only for SVF<3.4% is extended up to 10.4%. Furthermore, an opposite trend is found between the frequency and SVF for 10.4%<SVF<20%. Thirdly, a newly proposed patch dimensionless frequency number, $S{t}_p\frac{\sqrt{\text{SVF}}}{\sqrt{N}}$, links St_p and SVF, where N is the number of stems in the patch. This number stays almost constant for each case series regardless of the variation of SVF (for SVF<10.4%). We also conclude that $S{t}_p\frac{\sqrt{\text{SVF}}}{\sqrt{N}}$ is strongly determined by the patch shape factor, mildly influenced by the patch Reynolds number, but it excludes the influence of the SVF and N. The insights from the present study unveil the complicated eco-hydro-morphic interactions among the bio-mass density, turbulent flow and channel meanders’ variation. It provides a better understanding of natural bending river systems’ development and fundamentals for the recovery of urban channel ecosystems by vegetated re-meandering.

水生植被在蜿蜒的河道中极大地改变了主要水流，次要水流和湍流结构。在这项研究中，在曲率比（CRs）变化的情况下，对带有植被斑块（VP）的弯曲通道中的流体动力学进行了数值研究。= 0.5、1.0、1.5、2.0）和植被密度，即固体体积分数（SVF = 1.13％，4.86％）。通过使用Ansys Fluent软件包，在12种情况下研究了对植被剪切流，螺旋流，床剪切应力和体积阻力系数的两种影响。非稳态雷诺平均Navier-Stokes（URANS）框架与雷诺应力湍流模型（RSM）和流体体积（VOF）方法相结合已成功应用于预测包括多循环单元以及自由表面在内的整个流场。结论归纳为三点。首先，CR的增加将主循环单元和thalweg的位置移向外岸，同时沿流向和跨向减小了阻力系数。但是，CR弱地影响归一化剪切流速分布和VP下游的主导涡频率。其次，仅SVF <3.4％的情况下，显着脱落频率随SVF的增加而下降的趋势扩展到了10.4％。此外，在频率和SVF之间发现相反的趋势，为10.4％<SVF <20％。第三，新提出的补丁无量纲频率数，$\mathrm{小号}{Ť}_p\frac{\sqrt{\text{SVF}}}{\sqrt{ñ}}$，链接St _p和SVF，其中N是补丁中的茎数。无论SVF的变化如何（对于SVF <10.4％），此数字对于每个病例系列几乎保持恒定。我们还得出结论：$\mathrm{小号}{Ť}_p\frac{\sqrt{\text{SVF}}}{\sqrt{ñ}}$是由贴片形状因子决定的，受贴片雷诺数的影响较小，但不包括SVF和N的影响。本研究的见解揭示了生物质密度，湍流和河道曲折变化之间复杂的生态-水-形态相互作用。它提供了对自然弯曲河流系统的发展以及通过植被重新过渡恢复城市河道生态系统的基本原理的更好理解。