LES Analysis of Turbulent Flow around a 3D Hill covered with Vegetation

Abstract

Large eddy simulation (LES) is carried out to investigate the turbulent boundary-layer type of flows over a hill-shaped model with a steep slope. Also, we focus on the surface condition of a hill, such as vegetation effects as well as curvature effects. In order to model the vegetation effects for LES, we employ the feedback forcing method proposed by Goldstein (1993). In this model, the equation of motion for trees or grasses is coupled with the Navier-stokes equation, so turbulence in the vegetation canopy can be numerically expressed. Instantaneous velocity profile of turbulent boundary layer on the corresponding surface is imposed at inflow boundary. Both the computed results over the hill with and without vegetation are in good agreement with Meng's (1998) experimental data for a rough and a smooth hill. Also, the effects of vegetation on turbulence statistics, including the coherent structures above the vegetation, are clarified.