Evaluation of fast atmospheric dispersion models in a regular street network
Evaluation of fast atmospheric dispersion models in a regular street network
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常规街道网络中快速大气扩散模型的评估
DOI：
10.1007/s10652-018-9587-7
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发表时间：
2018
影响因子：
2.2
通讯作者：
Hertwig D
中科院分区：
文献类型：
--
作者：
Hertwig D
平衡计算速度和模拟精度的需要是设计可用于需要近实时灾害预测的情景的大气扩散模型的一个关键挑战。这一挑战在城市中加剧，模型需要具有一定程度的建筑意识，以及捕捉主导城市流过程影响的能力。我们使用高分辨率的大涡模拟（LES）和风洞数据的流动和分散在一个理想化的，等高的城市冠层突出重要的分散过程，并评估这些是如何再现的最流行的建模方法的代表：（1）高斯烟羽模型，（2）拉格朗日随机模型和（3）街道网络分散模型。从LES的浓度数据，验证对风洞数据，平均超过街道的体积，以提供一个高保真度的参考，适合于评估不同的模型在同一个立足点。对于这里研究的强迫风向和源位置的特定组合，LES参考的最强偏差与浓度的平均过度预测有关，约为2倍，相对分散度大于平均值的4倍，对应于平均羽流中心线也明显偏离LES的情况。这与底层流动模型/参数的低准确性有关，导致污染物沿沿着流动和在交叉口观察到的不均匀羽流分支的错误表述。模型预测与LES（明确解决湍流和分散过程）的协议大大提高了建设引起的驱动流场的修改的准确性。当提供一组有限的代表性速度参数时，相对简单的街道网络模型与在全三维风场上运行的拉格朗日模型相比表现同样好或更好。研究表明，街道网络模型捕获的主导建筑引起的扩散过程中的冠层通过参数化的水平平流和垂直交换过程的规模的实际利益。与此同时，与网络方法相关的计算成本和计算时间非常适合紧急响应应用。
The need to balance computational speed and simulation accuracy is a key challenge in designing atmospheric dispersion models that can be used in scenarios where near real-time hazard predictions are needed. This challenge is aggravated in cities, where models need to have some degree of building-awareness, alongside the ability to capture effects of dominant urban flow processes. We use a combination of high-resolution large-eddy simulation (LES) and wind-tunnel data of flow and dispersion in an idealised, equal-height urban canopy to highlight important dispersion processes and evaluate how these are reproduced by representatives of the most prevalent modelling approaches: (1) a Gaussian plume model, (2) a Lagrangian stochastic model and (3) street-network dispersion models. Concentration data from the LES, validated against the wind-tunnel data, were averaged over the volumes of streets in order to provide a high-fidelity reference suitable for evaluating the different models on the same footing. For the particular combination of forcing wind direction and source location studied here, the strongest deviations from the LES reference were associated with mean over-predictions of concentrations by approximately a factor of 2 and with a relative scatter larger than a factor of 4 of the mean, corresponding to cases where the mean plume centreline also deviated significantly from the LES. This was linked to low accuracy of the underlying flow models/parameters that resulted in a misrepresentation of pollutant channelling along streets and of the uneven plume branching observed in intersections. The agreement of model predictions with the LES (which explicitly resolves the turbulent flow and dispersion processes) greatly improved by increasing the accuracy of building-induced modifications of the driving flow field. When provided with a limited set of representative velocity parameters, the comparatively simple street-network models performed equally well or better compared to the Lagrangian model run on full 3D wind fields. The study showed that street-network models capture the dominant building-induced dispersion processes in the canopy layer through parametrisations of horizontal advection and vertical exchange processes at scales of practical interest. At the same time, computational costs and computing times associated with the network approach are ideally suited for emergency-response applications.
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城市空气质量：测量、建模和管理：第二届国际城市空气质量会议：测量、建模和管理，1999 年 3 月 3-5 日在马德里技术大学计算机科学学院举行
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发表时间：
2000
期刊：
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作者：
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2001
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DOI：
--
发表时间：
2007
期刊：
影响因子：
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作者：
P. Klein;B. Leitl;M. Schatzmann
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DOI：
--
发表时间：
2002
期刊：
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