Wind environment (1)

[11] LES ANALYSIS FOCUS ON THE THERMAL EFFECT WHICH INFLUENCES THE DISPERSION BEHAVIOR AND VORTEX STRUCTURE IN URBAN CANOPY AREA

○Yuto Sakuma¹, Tetsuro Tamura², Hidenori Kawai², Tomotaka Hosoi (1.Department of Environmental Science and Technology Tokyo Institute of Technology, 2.School of Environment and Society-Department of Architecture and Building Engineering)

Keywords:LES, Dispersion behavior, Atmospheric stability, Local thermal condition, Vortex structure

In order to realize the accurate LES prediction of near-ground high concentrations for atmospheric dispersion in urban area, we performed LES analysis considering atmospheric stability and constructed an urban model using simple roughness block, which has various types of local thermal condition on building wall and roof. For LES validation in the wide range, the results are compared with the reference data in neutral condition and the thermal effects on dispersion characteristics within urban canopy are investigated. Analysis on the obtained results focuses on the turbulent energy exchange between above and within the unban canopy, in order to clarify the generating, the developing or the decaying process of coherent structures such as stream wise vortices over urban canopy and the intensity of updraft or downdraft inside canopy. Also, the flow visualization can exhibit roles of coherent structures for occurrence of high concentration.