Flow Characteristics Around Step-Up Street Canyons with Various Building Aspect Ratios

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Title
Flow Characteristics Around Step-Up Street Canyons with Various Building Aspect Ratios
Author
Park, Soo-JinKim, Jae-JinChoi, WonsikKim, Eun-RyoungSong, Chang-KeunPardyjak, Eric R.
Issue Date
2020-03
Publisher
Kluwer Academic Publishers
Citation
BOUNDARY-LAYER METEOROLOGY, v.174, no.3, pp.411 - 431
Abstract
We investigate the flow characteristics around step-up street canyons with various building aspect ratios (ratio of along-canyon building length to street-canyon width, and upwind building height to downwind building height) using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations as those in the wind-tunnel experiments. The CFD model reproduces the measured in-canyon vortex, rooftop recirculation zone above the downwind building, and stagnation point position reasonably well. We analyze the flow characteristics, focusing on the structural change of the in-canyon flows and the interaction between the in- and around-canyon flows with the increase of building-length ratio. The in-canyon flows undergo development and mature stages as the building-length ratio increases. In the development stage (i.e., small building-length ratios), the position of the primary vortex wanders, and the incoming flow closely follows both the upstream and downstream building sidewalls. As a result, increasing momentum transfer from the upper layer contributes to a momentum increase in the in-canyon region, and the vorticity in the in-canyon region also increases. In the mature stage (i.e., large building-length ratios), the primary vortex stabilizes in position, and the incoming flow no longer follows the building sidewalls. This causes momentum loss through the street-canyon lateral boundaries. As the building-length ratio increases, momentum transfer from the upper layer slightly decreases, and the reverse flow, updraft, and streamwise flow in the in-canyon region also slightly decrease, resulting in vorticity reduction.
URI
https://scholarworks.unist.ac.kr/handle/201301/31138
URL
https://link.springer.com/article/10.1007/s10546-019-00494-9
DOI
10.1007/s10546-019-00494-9
ISSN
0006-8314
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