Scholarlink

<p>Introducing a vegetation barrier in place of one building obstacle within a canonical street canyon of identical geometry yields a coupled vegetation-building (V–B) or building–vegetation (B–V) configuration, depending on whether the vegetation is located on the upwind or downwind side of the canyon, whose flow structure and turbulence characteristics remain less explored compared with the canonical building-building (B–B) case. The extent to which results in V–B and B–V canyons deviate from or converge with those of a generic B–B canyon remains unclear. Using large-eddy simulation across a range of leaf area densities (<i>LAD</i>), this study examines how vegetation placement and porosity modulate canyon-scale vortex geometry, turbulence structure, and air exchange. The zero-<i>w</i> trace delineating the primary canyon vortex, which aligns approximately with the vertical axis in a unit-aspect-ratio B–B canyon, exhibits a monotonic tilt toward the vegetation side as <i>LAD</i> decreases, reflecting progressive deformation and weakening of the mean circulation. Within V–B canyons, turbulence intensity and vertical momentum flux show little dependence on <i>LAD</i>, implying that upwind vegetation primarily acts as a momentum sink that suppresses near-wall shear. In contrast, these turbulence statistics in B–V canyons exhibit stronger sensitivity to <i>LAD</i> (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(R^2\sim 0.81\)</EquationSource> </InlineEquation> and 0.65, respectively), suggesting enhanced turbulence generation through canopy-wake interaction. Both mean and fluctuating air-exchange rates increase smoothly with <i>LAD</i> for vegetated canopies but decline sharply as the system approaches the impermeable B–B limit. This non-monotonic behaviour demonstrates that the <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(LAD\to\infty\)</EquationSource> </InlineEquation> limit is dynamically distinct from an impermeable wall, as dense vegetation retains finite permeability and sustains shear-layer instabilities absent in solid obstacles.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Turbulent Flow and Air Exchange Within Alternating Building-Vegetation-Constrained Canyons: Evaluation of Leaf-Area-Density Impacts

  • 期刊论文

  • 发表日期：

    2026年3月9日

查看全文
  • G. Duan,
  • Z. Bi,
  • H. Wang,
  • L. Zhao,
  • X. Zheng,
  • T. Takemi

摘要

Introducing a vegetation barrier in place of one building obstacle within a canonical street canyon of identical geometry yields a coupled vegetation-building (V–B) or building–vegetation (B–V) configuration, depending on whether the vegetation is located on the upwind or downwind side of the canyon, whose flow structure and turbulence characteristics remain less explored compared with the canonical building-building (B–B) case. The extent to which results in V–B and B–V canyons deviate from or converge with those of a generic B–B canyon remains unclear. Using large-eddy simulation across a range of leaf area densities (LAD), this study examines how vegetation placement and porosity modulate canyon-scale vortex geometry, turbulence structure, and air exchange. The zero-w trace delineating the primary canyon vortex, which aligns approximately with the vertical axis in a unit-aspect-ratio B–B canyon, exhibits a monotonic tilt toward the vegetation side as LAD decreases, reflecting progressive deformation and weakening of the mean circulation. Within V–B canyons, turbulence intensity and vertical momentum flux show little dependence on LAD, implying that upwind vegetation primarily acts as a momentum sink that suppresses near-wall shear. In contrast, these turbulence statistics in B–V canyons exhibit stronger sensitivity to LAD ( \(R^2\sim 0.81\) and 0.65, respectively), suggesting enhanced turbulence generation through canopy-wake interaction. Both mean and fluctuating air-exchange rates increase smoothly with LAD for vegetated canopies but decline sharply as the system approaches the impermeable B–B limit. This non-monotonic behaviour demonstrates that the \(LAD\to\infty\) limit is dynamically distinct from an impermeable wall, as dense vegetation retains finite permeability and sustains shear-layer instabilities absent in solid obstacles.