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Water tank modelling of variations in inversion breakup over a circular city

机译：圆形城市中反演破裂的水箱建模

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Air pollution and extreme heat waves are among the major environmental challenges faced by modern cities. Stable stratification and temperature inversion help to trap urban airborne pollutants and produce a strong urban heat island intensity. Such adverse effects can disappear when the buoyancy flows introduced by the city heat is sufficiently strong to break up the inversion. This paper investigates the possible mechanisms of the inversion breakup process and their effects. A lack of time-saving and cost-effective techniques with high temporal and spatial resolution in the field study has been the main limiting factor to a systematic investigation of the physical process of inversion breakup. In this study, water tank experiments were conducted to study the characteristics of the mean and turbulent flow structures of the inversion breakup process. Four cases with different background density profiles are simulated. Three stages of inversion breakup were identified, the two-dome stage, the wing-shrinking stage and the perforative-plume stage. During the two-dome stage, shear instability and buoyancy instability (Fig. 3d) are both important for heat and mass transfer between the lower-level dome in the stable layer near the surface and the upper-level dome in the neutral residual layer aloft. The vertical dimension of the lower-level dome begins to grow, whilst the horizontal extent shrinks at the wing-shrinking stage. Finally, in the perforative-plume stage, the stable layer is destroyed, and the plume extends from the surface to the top of the residual layer. The pollutants and heat dispersion are both enhanced significantly during this stage.
机译：空气污染和极端热浪是现代城市面临的主要环境挑战。稳定的分层和温度反转有助于捕获城市空气中的污染物，并产生强烈的城市热岛强度。当城市热量引入的浮力足够强大以破坏反演时，这种不利影响就会消失。本文研究了反演破裂过程的可能机制及其影响。在野外研究中缺乏时间和空间分辨率高，节省时间和成本效益的技术已成为系统研究反演破裂物理过程的主要限制因素。在这项研究中，进行了水箱实验以研究反演破裂过程的均值和湍流结构的特征。模拟了具有不同背景密度分布的四种情况。确定了三个阶段的反转破裂，即两穹顶阶段，机翼收缩阶段和射孔软化阶段。在两穹顶阶段，剪切不稳定性和浮力不稳定性（图3d）对于表面附近稳定层中的下层穹顶与中性残余层中的上层穹顶之间的传热和传质都很重要。 。下层圆顶的垂直尺寸开始增大，而水平范围在机翼收缩阶段收缩。最后，在打孔阶段，稳定层被破坏，羽流从表面延伸到残留层的顶部。在此阶段，污染物和热扩散都得到了显着提高。

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