Aerodynamic Parameters of Urban Building Arrays with Random Geometries |
| |
Authors: | Sheikh Ahmad Zaki Aya Hagishima Jun Tanimoto Naoki Ikegaya |
| |
Institution: | (1) Forest Resources Utilization Laboratory, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya Aichi, 464-8601, Japan;(2) Data Integration and Analyses Group, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan;(3) Japan Science and Technology Agency, CREST, Kawaguchi, Japan;(4) Laboratory of Forest Meteorology and Hydrology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan;(5) The Japan Society for the Promotion of Science, Tokyo, Japan |
| |
Abstract: | It is difficult to describe the flow characteristics within and above urban canopies using only geometrical parameters such
as plan area index (λ
p
) and frontal area index (λ
f
) because urban surfaces comprise buildings with random layouts, shapes, and heights. Furthermore, two types of ‘randomness’
are associated with the geometry of building arrays: the randomness of element heights (vertical) and that of the rotation
angles of each block (horizontal). In this study, wind-tunnel experiments were conducted on seven types of urban building
arrays with various roughness packing densities to measure the bulk drag coefficient (C
d
) and mean wind profile; aerodynamic parameters such as roughness length (z
o
) and displacement height (d) were also estimated. The results are compared with previous results from regular arrays having neither ‘vertical’ nor ‘horizontal’
randomness. In vertical random arrays, the plot of C
d
and z
o
versus λ
f
exhibited a monotonic increase, and z
o
increased by a factor of almost two for λ
f
= 48–70%. C
d
was strongly influenced by the standard deviation of the height of blocks (σ) when λ
p
≥ 17%, whereas C
d
was independent of σ when λ
p
= 7%. In the case of horizontal random arrays, the plot of the estimated C
d
against λ
f
showed a peak. The effect of both vertical and horizontal randomness of the layout on aerodynamic parameters can be explained
by the structure of the vortices around the blocks; the aspect ratio of the block is an appropriate index for the estimation
of such features. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|