Atmospheric Boundary Layer Experiment-1

Project Description
Flow structures and scalar dispersions in urban boundary layers are analyzed, using large eddy simulation with an explicitly resolved urban geometry. Two types of urban surface geometry have been investigated. One is large square/staggered arrays of uniform building with various areal densities (Experiment-1), and the other is a real 3-D building geometry using GIS-data of Tokyo Metropolitan area (Experiment-2).

The purpose of the Experiment-1 is to obtain basic knowledge for making simple urban canopy models for meso-scale simulations. First, a passive scalar was released at a constant flux from all constituent surfaces under fully-developed turbulent flows, and then a dataset of relative value of local transfer coefficients of each constituent surface was constructed for a wide range of simple building arrays. Second, simulations with a constant heat flux to one of the constituent surfaces (four vertical walls, roof, and floor, respectively) were performed. The results revealed that the heating of windward-wall generates significantly larger Reynolds stress than the heating of the other surfaces even though the heat fluxes per unit lot area are all the same.

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