We review the efforts made by the scientific community in more than seventy years to elucidate the behaviour of concentration fluctuations arising from localized atmospheric releases of dynamically passive and non-reactive scalars. Concentration fluctuations are relevant in many fields including the evaluation of toxicity, flammability, and odour nuisance. Characterizing concentration fluctuations requires not just the mean concentration but also at least the variance of the concentration in the location of interest. However, for most purposes the characterization of the concentration fluctuations requires knowledge of the concentration probability density function (PDF) in the point of interest and even the time evolution of the concentration. We firstly review the experimental works made both in the field and in the laboratory, and cover both point sources and line sources. Regarding modelling approaches, we cover analytical, semi-analytical, and numerical methods. For clarity of presentation we subdivide the models in two groups, models linked to a transport equation, which usually require a numerical resolution, and models mainly based on phenomenological aspects of dispersion, often providing analytical or semi-analytical relations. The former group includes: large-eddy simulations, Reynolds-averaged Navier–Stokes methods, two-particle Lagrangian stochastic models, PDF transport equation methods, and heuristic Lagrangian single-particle methods. The latter group includes: fluctuating plume models, semi-empirical models for the concentration moments, analytical models for the concentration PDF, and concentration time-series models. We close the review with a brief discussion highlighting possible useful additions to experiments and improvements to models.

中文翻译：

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局部大气释放引起的浓度波动

我们回顾了科学界在 70 多年来为阐明动态被动和非反应标量的局部大气释放引起的浓度波动行为所做的努力。浓度波动与许多领域相关，包括毒性、可燃性和气味滋扰的评估。表征浓度波动不仅需要平均浓度，而且至少需要感兴趣位置的浓度方差。然而，在大多数情况下，浓度波动的表征需要了解感兴趣点的浓度概率密度函数 (PDF) 甚至浓度的时间演变。我们首先回顾了在现场和实验室中所做的实验工作，并涵盖点源和线源。关于建模方法，我们涵盖了分析、半分析和数值方法。为清楚起见，我们将模型细分为两组，与传输方程相关的模型，通常需要数值分辨率，以及主要基于色散现象学方面的模型，通常提供分析或半分析关系。前一组包括：大涡模拟、雷诺平均 Navier-Stokes 方法、二粒子拉格朗日随机模型、PDF 输运方程方法和启发式拉格朗日单粒子方法。后一组包括：波动羽流模型、浓度矩的半经验模型、浓度 PDF 的分析模型和浓度时间序列模型。