Vegetation exerts notable influences on urban microenvironment through biophysical processes. Studying the flow over urban vegetated region requires a proper treatment of the vegetation canopy. A large eddy simulation (LES) method is developed in the present work, which can well simulate the canopy flow. Using LES the turbulent flow over a model vegetation canopy is investigated under the neutral atmospheric condition. Each vegetation element consisting of a sphere-shaped tree crown and a cylindrical trunk is fully resolved. The resulting turbulence statistics and the drag force on vegetation agree well with the measurements from the corresponding wind-tunnel experiment. Two other numerical representations of vegetation canopies, referred to as drag element approach and drag crown approach, have also been developed to assess their performances. The drag crown approach yields better agreement between numerical results and experimental measurements than the traditional drag element approach, thus providing a promising numerical model for simulating canopy turbulence.

vegetation canopies  /  large eddy simulation  /  environmental flow  /  canopy representation