刚性沉水植物影响下波浪传播及泥沙悬浮数值模拟

Numerical Simulation of Wave Propagation and Sediment Suspension Affected by Submerged Rigid Vegetation

摘要:

由于植物引起的紊动作用，含刚性植物床面中悬浮泥沙浓度与无植物裸床相比显著增加，而通过平均流速计算底床切应力的传统泥沙模型无法模拟出该现象。因此，在含植物水流水沙运动物理模型试验的基础上，构建了基于Flow–3D的含刚性沉水植物条件下波浪传播的三维数学模型，模拟了植物影响下波浪动力特征和泥沙悬浮过程，同时从紊动能角度修正希尔兹数，对泥沙模块进行了改进。与实测数据相比，该模型可较精确地模拟出植物引起的整体水流流速减小和局部冠层顶部处的流速增大、水体紊动增强以及紊动能在波周期内出现两个峰值的现象。与原始泥沙模块相比，改进的模型考虑了植物尾流紊动对泥沙运动的影响，可提高含植物床面泥沙悬浮模拟的精度。

Abstract:

Due to the vegetation-induced turbulence， the suspended sediment concentration in the rigid vegetated bed increased significantly， relative to the bare bed. The traditional sediment model which calculates the bed shear stress by mean velocity cannot simulate the phenomenon. Therefore， based on the physical modelling experiment of hydro-sediment dynamics in vegetated flows， a three-dimensional mathematical model of wave propagation with submerged rigid vegetation was established using Flow–3D in this paper to simulate the hydrodynamic characteristics and sediment suspension process under the influence of vegetation. Meanwhile， the original sediment model in Flow–3D was improved by modifying Shields number using turbulent kinetic energy. Compared with the experimental data， the model could accurately reproduce the decrease of mean wave velocity in the entire water column and increase at the top of the canopy， the enhanced turbulence caused by vegetation， and the two peaks of turbulent kinetic energy in the wave period. Using the improved sediment model considering the influence of vegetation wake turbulence on sediment movement， the accuracy of sediment suspension simulation in vegetated bed was significantly higher than the results from the original sediment model.