Influence of urban configuration on the structure of kinetic energy transport and the energy dissipation rate

The urban configuration, which pertains to the arrangement and height of buildings, has strong relationships not only with pedestrian wind environment within the focused urban district but also with that in areas leeward of the focused area. Therefore, such influences on leeward areas should be considered concurrently when improving the wind environment within the focused area. In this study, a large-eddy simulation (LES) was applied to four types of flow field over urban-like roughness using two different building layouts: regular and staggered, and two different building height conditions: uniform and non-uniform. Periodic boundary conditions are imposed laterally and streamwise directions to simulate an infinite array in equilibrium flow field. Based on LES data, the vertical structures of the transport and dissipation of kinetic energy were analyzed. Negative effects of the increase the wind velocity and enhancement the outdoor ventilation at pedestrian-level within the focused area on the wind environment of the leeward area were evaluated quantitatively with respect to the energy dissipation rate of the kinetic energy within the focused area. Additionally, the normalized airflow rate was defined for evaluating the relationship between the total amount of kinetic energy dissipation and outdoor ventilation performance, and the relationship was investigated.