Numerical simulation of fluid-vegetation coupled dynamic using a promoted semi-resolved coupling model

Abstract

Flexible vegetation is an important component of riverine and coastal ecosystems. The numerical simulation is difficult due to the complex motions of flexible vegetation and fluid. In this work, a semi-resolved numerical model coupling the computational fluid dynamics (CFD) and flexible rod dynamics (FRD) using a promoted two-way domain expansion method was proposed with the accuracy of the resolved model and the efficiency of the unresolved model. The governing equations of the flexible rod dynamics are solved by the finite element method (FEM). The effect of vegetation is added as source terms to the Reynolds-averaged Navier-Stokes equations, which are discretized and solved by the finite volume method (FVM). The anisotropic Gaussian kernel function is adopted to calculate the interactive forces between the fluid and the flexible rod with an anisotropic cross-section. The model was first validated by simulating the flow passing through a single flexible rod with a rectangular cross-section. Meanwhile, the main factors were calibrated. The engineering application of the model was further validated by simulating the flow passing through a finite patch of flexible vegetation. These results indicate that the proposed model could well simulate the open channel flows with the flexible vegetation.