热分层对空腔内示踪气体扩散影响的大涡模拟

IF 1.3 4区 工程技术 Q3 MECHANICS
W A McMullan, J Mifsud
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引用次数: 0

摘要

摘要采用大涡模拟方法,评价了热分层对固定长径比为1.0 m空腔内惰性示踪气体扩散预测的影响。空腔流动的雷诺数为67 000。热分层是通过加热或冷却腔内的一个或多个壁来实现的。与等温(中性)情况相比,除了迎风壁被加热的情况外,表面加热产生的不稳定分层通常对初级再循环腔涡的影响较弱。对于迎风壁面加热,在迎风壁面和空腔底部的角落出现一个较大的二次涡。不稳定分层对空腔中污染物团块的去除无显著影响。通过表面冷却形成的稳定分层极大地改变了腔内的流动模式,将腔涡推向腔的上象限。因此,在空腔内存在大面积的停滞流体,降低了剪切层从空腔中去除污染物浓度的有效性。与中性情况相比,一些稳定的分层配置可以使腔内的污染物质量增加五倍以上。污染物浓度通量图显示,在稳定分层的情况下,大部分污染物从空腔输送是夹带到初级空腔涡的结果。研究结果表明,城市街道峡谷型水流中的污染物浓度随昼夜冷暖变化而发生显著变化,这可能会影响城市环境中行人管理策略。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Large eddy simulation of thermal stratification effects on tracer gas dispersion in a cavity
Abstract This paper assesses the effect of thermal stratification on the prediction of inert tracer gas dispersion within a cavity of height ( H ) 1.0 m, and unity aspect ratio, using large eddy simulation. The Reynolds number of the cavity flow, was 67 000. Thermal stratification was achieved through the heating or cooling of one or more of the walls within the cavity. When compared to an isothermal (neutral) case, unstable stratification from surface heating generally has a weak influence on the primary recirculating cavity vortex, except in the case where the windward wall is heated. For windward wall heating, a large secondary vortex appears at the corner of the windward wall and cavity floor. Unstable stratification has no significant influence on the removal of pollutant mass from the cavity. Stable stratification through surface cooling drastically alters the flow pattern within the cavity, pushing the cavity vortex towards the upper quadrant of the cavity. As a result, large regions of stagnant fluid are present within the cavity, reducing the effectiveness of the shear layer at removing pollutant concentration from the cavity. Some stable stratification configurations can increase the pollutant mass within the cavity by over a factor of five, when compared to the neutral case. Pollutant concentration flux maps show that, in stably stratified cases, the majority of pollutant transport from the cavity is the result of entrainment into the primary cavity vortex. The results show that pollutant concentrations in urban street canyon-type flows are substantially altered by diurnal heating and cooling, which may influence pedestrian management strategies in urban environments.
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来源期刊
Fluid Dynamics Research
Fluid Dynamics Research 物理-力学
CiteScore
2.90
自引率
6.70%
发文量
37
审稿时长
5 months
期刊介绍: Fluid Dynamics Research publishes original and creative works in all fields of fluid dynamics. The scope includes theoretical, numerical and experimental studies that contribute to the fundamental understanding and/or application of fluid phenomena.
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