Exploring thermal buoyant flow in urban street canyons: Influence of approaching turbulent boundary layer

IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Experimental Thermal and Fluid Science Pub Date : 2024-06-18 DOI:10.1016/j.expthermflusci.2024.111255
Yunpeng Xue , Yongling Zhao , Shuo-Jun Mei , Yuan Chao , Jan Carmeliet
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Abstract

Turbulent boundary layer inflow is a critical factor in urban climate research, shaping canyon flow dynamics, air ventilation patterns, and heat flux distribution. In numerical simulation studies, it serves as a fundamental inflow boundary condition, profoundly influencing overall results. In this study, simultaneous Particle Image Velocimetry and Laser-Induced Fluorescence (PIV-LIF) measurements are utilized within a large closed-circuit water tunnel. This approach allows comprehensive flow data to be gathered under varied flow and thermal conditions, encompassing a spectrum of Richardson numbers ranging from 0.01 to 1.34. The investigation aims to elucidate the effects of turbulent boundary layer flows on heat transfer mechanisms and flow behaviours within a two-dimensional street canyon model with a unit aspect ratio. The analysis reveals distinct heat and fluid flow characteristics, highlighting the interplay between thermal conditions and flow dynamics. The three chosen turbulent boundary layer flows demonstrate unique influences on flow characteristics and heat removal capacity. Significant variations in ventilation rates are observed, with a maximum difference of 80% among the tested boundary layer flows. Additionally, the most pronounced variation in heat removal capacity is approximately 45%. Thicker boundary layers with lower velocities near the canyon exhibit reduced ventilation and heat removal capabilities. Furthermore, the investigation reveals that varied turbulence inlet profiles result in diverse fluctuating features at the canyon roof level, with a comparatively lesser impact on the deeper regions of the canyon.

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探索城市街道峡谷中的热浮力流:接近湍流边界层的影响
湍流边界层流入是城市气候研究中的一个关键因素,它影响着峡谷流动动力学、空气通风模式和热通量分布。在数值模拟研究中,它是一个基本的流入边界条件,对整体结果影响深远。在本研究中,在一个大型闭路水隧道内同时进行了粒子图像测速仪和激光诱导荧光(PIV-LIF)测量。通过这种方法,可以在不同的流动和热条件下收集全面的流动数据,包括从 0.01 到 1.34 的理查德森数谱。这项研究旨在阐明湍流边界层流动对具有单位长宽比的二维街道峡谷模型中传热机制和流动行为的影响。分析揭示了不同的热量和流体流动特征,突出了热量条件和流动动力学之间的相互作用。所选的三种湍流边界层流对流动特性和热量去除能力产生了独特的影响。在测试的边界层流动中,通风率存在显著差异,最大差异达 80%。此外,散热能力的最大差异约为 45%。峡谷附近较厚、速度较低的边界层显示出较低的通风和散热能力。此外,研究还发现,不同的湍流入口剖面会导致峡谷顶层出现不同的波动特征,而对峡谷深层区域的影响相对较小。
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来源期刊
Experimental Thermal and Fluid Science
Experimental Thermal and Fluid Science 工程技术-工程:机械
CiteScore
6.70
自引率
3.10%
发文量
159
审稿时长
34 days
期刊介绍: Experimental Thermal and Fluid Science provides a forum for research emphasizing experimental work that enhances fundamental understanding of heat transfer, thermodynamics, and fluid mechanics. In addition to the principal areas of research, the journal covers research results in related fields, including combined heat and mass transfer, flows with phase transition, micro- and nano-scale systems, multiphase flow, combustion, radiative transfer, porous media, cryogenics, turbulence, and novel experimental techniques.
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