Numerical Modelling and Analysis of Turbulent Flow in an Open Channel with Submerged Vegetation

Abstract

Turbulent flow in an open channel whose bed is covered with vegetation is studied. Vegetation has been modeled by a series of small diameter rigid cylinders protruded vertically from the channel bed. 3-D computations were performed using the ANSYS-CFX computer program which uses a finite volume method to solve the partial differential equations describing fluid flow. In order to reduce the computational burden, periodic boundary conditions in the direction of the channel axis have been used. The computational domain has been discretized using tetrahedral elements. Six mesh designs were evaluated in order to choose the optimal/suboptimal mesh and ensure that the solution is independent of the mesh used. The mesh finally chosen provides a good balance between the stability of the solution and the flow field resolution. However, achieving mesh-independent solutions for a complex geometry problem, such as the one studied in this work, requires tremendous computational resourses. The connection of the hydrodynamic model to the study of contaminant transport and sedimentation processes in aquatic environments is also discussed.