Numerical study of turbulent flow fields around of a row of trees and an isolated building by using modified k-ε model and LES model

Turbulent flow fields over two typical urban elements, a row of trees with low packing density and an isolated building with high packing density, are investigated by a modified k−ε model and a LES model. The applicability of these two models is evaluated by the validation metrics. Instantaneous flow fields are visualized by vortex cores and examined by quadrant analysis. In the wake region of the row of trees, predicted mean wind speed by the modified k−ε model shows favourable agreement with the measured data, but turbulent kinetic energy is underestimated since the modified k−ε model is not capable of simulating organized motions. In the wake region of the isolated building, both predicted mean wind speed and turbulent kinetic energy by the modified k−ε model are slightly underestimated due to lack of the vortex shedding in the simulation. On the other hand, LES model well predicts both mean wind speed and turbulent kinetic energy since all large vortices are directly resolved by LES model.