行道树对城市峡谷湍流波动和传输过程的影响:风洞研究

IF 2.3 3区 地球科学 Q3 METEOROLOGY & ATMOSPHERIC SCIENCES
Annika Vittoria Del Ponte, Sofia Fellini, Massimo Marro, Maarten van Reeuwijk, Luca Ridolfi, Pietro Salizzoni
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引用次数: 0

摘要

由于速度场的复杂结构,城市峡谷中植被的存在会导致空气中污染物浓度的非微妙模式。为了研究浓度、速度场和植被密度之间的关系,我们在一个缩小尺度的街道峡谷中进行了风洞实验,峡谷的方向与外部风流垂直,我们在峡谷中放置了一个稳定的地面被动示踪线源。通过在峡谷的两个长边插入塑料微型树,按照三种不同的密度,再现了植被的空气动力学行为。通过对峡谷内密集网格点的浓度和速度进行单点同步统计,研究了峡谷通风情况。结果表明,树木的存在阻碍了屋顶平均垂直速度的上升,导致峡谷内的湍流动能减少,并降低了大尺度的能量含量。相反,标量集中的特点是湍流波动水平增强,其幅度不会随着树木密度的增加而减弱。在峡谷内,高树木密度抑制了湍流质量通量,而在屋顶层,湍流质量通量反而增强了,但标量通量的平均分量却受到了阻碍。对浓度时间序列的统计分析显示,对数正态分布适用于模拟线性源排放的分散羽流中的浓度波动和极端事件。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Influence of Street Trees on Turbulent Fluctuations and Transport Processes in an Urban Canyon: A Wind Tunnel Study

Influence of Street Trees on Turbulent Fluctuations and Transport Processes in an Urban Canyon: A Wind Tunnel Study

The presence of vegetation within urban canyons leads to non-trivial patterns of the concentration of airborne pollutants, as a result of the complex structure of the velocity field. To investigate the relationship between concentration, velocity fields and vegetation density, we have performed wind-tunnel experiments in a reduced-scale street canyon, oriented perpendicular to the external wind flow, within which we placed a steady ground-level line source of a passive tracer. The aerodynamic behavior of vegetation was reproduced by inserting plastic miniatures of trees along the two long sides of the canyon, according to three different densities. The canyon ventilation was investigated by acquiring one-point simultaneous statistics of concentration and velocity over a dense grid of points within the canyon. The results show that the presence of trees hinders the upward mean vertical velocity at the rooftop, causes a reduction of the turbulent kinetic energy inside the canyon, and reduces the energy content of the large scales. The scalar concentration is conversely characterized by an enhanced level of turbulent fluctuations, whose magnitude is not dampened increasing the tree density. Within the canyon, high tree density inhibits turbulent mass fluxes, which are instead enhanced at roof level, where the mean component of the scalar flux is however hindered. A statistical analysis of concentration time series reveals that the lognormal distribution is suitable to model concentration fluctuations and extreme events, in dispersing plumes emitted by a linear source.

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来源期刊
Boundary-Layer Meteorology
Boundary-Layer Meteorology 地学-气象与大气科学
CiteScore
7.50
自引率
14.00%
发文量
72
审稿时长
12 months
期刊介绍: Boundary-Layer Meteorology offers several publishing options: Research Letters, Research Articles, and Notes and Comments. The Research Letters section is designed to allow quick dissemination of new scientific findings, with an initial review period of no longer than one month. The Research Articles section offers traditional scientific papers that present results and interpretations based on substantial research studies or critical reviews of ongoing research. The Notes and Comments section comprises occasional notes and comments on specific topics with no requirement for rapid publication. Research Letters are limited in size to five journal pages, including no more than three figures, and cannot contain supplementary online material; Research Articles are generally fifteen to twenty pages in length with no more than fifteen figures; Notes and Comments are limited to ten journal pages and five figures. Authors submitting Research Letters should include within their cover letter an explanation of the need for rapid publication. More information regarding all publication formats can be found in the recent Editorial ‘Introducing Research Letters to Boundary-Layer Meteorology’.
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