DATABASE OF TURBULENT FLOW STATISTICS IN URBAN DISTRICT CREATED BY NUMERICAL SIMULATION

Abstract

 This study aims to create a database of turbulent flow statistics within the urban district based on an urban turbulent boundary layer simulation. The inflow turbulence gradually loses its characteristics while progressing and developing the turbulent boundary layer. Turbulence finally becomes well-adjusted to the local surface conditions that are generally represented by massive obstacles in urban districts. This concept allows for the decomposition of a huge computational domain and a reconstruction of the simulation results of the decomposed simulation pieces. We apply this to create a mean flow database in the urban canopy layer of the Tokyo 23 wards. The simulation domain was decomposed in spanwise and streamwise directions. This resulted in the mean wind speed distributions being generally reconstructable after friction velocity normalization without any additional adjustments. On the other hand, if organized turbulent structures develop and stay for significant time above the building canopy, the mean flow structure is disturbed, and the quality of the reconstruction worsen.