Wind tunnel experiment on bulk scalar coefficient of urban-like roughness

The authors investigated bulk scalar coefficient (C_E) of the street in the 3-D canopy with various conditions of arrangement, plan area density (λ_p), frontal area index (λ_f), and variability of model height in a wind tunnel using salinity method. The results can be summarized as follows. 1) The relationships between C_E and lf of both staggered and normal arrayed canopy with uniform height shows different tendency. The C_E of 3-D canopy of staggered and normal pattern have similar value under the sparse (λ_f) and dense conditions, in contrast, C_E of staggered canopy is higher than that of normal canopy under the condition of λ_f = 17.4%. 2) C_E of uniform canopy is larger than that of canopy with height variation under the condition of λ_f < 17.4%. In contrast, C_E of uniform canopy is smaller than that of canopy with height variation under the condition of λ_f = 30.9%. Such a tendency is opposite to the result of drag force coefficient.